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  • Traversing Java Object Arrays [migrated]

    - by Sundi
    Please Help. Program does not read Array rentBooks[] in the for() loop this option is selected when choosing option 2 then option 4 in the menu The Array reads perfectly when reading the items after the setBook() Method import java.io.File; import java.io.FileNotFoundException; import java.util.Scanner; import java.io.*; import java.util.Locale; import java.text.SimpleDateFormat ; class Library { protected static String Author; protected static String Title; SimpleDateFormat PublicationDate; int itemCode; int available = 1; } class Book extends Library { protected static String PublisherName; protected static String Edition; static Book[] rentBooks = new Book[5]; //Book[] rentBooks = new Book[5]; int count = 0; public Book() { String start= "start"; showBook.main(anza); } public void setBook( String Auth, String Titl, String PublishName) { this.Author = Auth; this.Title = Titl; this.PublisherName = PublishName; } public void getBook() { //System.out.println("*************BOOKS*************************"); System.out.println( "\n\nThe Author of the first Book is "+ this.Author ); System.out.println( "The Title of the book is "+ this.Title); System.out.println( "The Publisher of the book is "+ this.PublisherName ); // System.out.println( "The Edition of the book is "+ Edition ); } } class showBook{ static Book[] rentBooks = new Book[5]; static Book[] rentBooks2 = new Book[5]; static int a,b; //for ( a=0; a < 5; a++ ) //rentBooks2[a] = new Book(); public static void main(String[] args) { File file = new File("Book2.txt"); //Book libraryBooks = new Book(); int j; //initialise Array Class Objects for( j = 0; j < 5; j++) { rentBooks[j] = new Book(); } int i = 0; try{ Scanner scanner = new Scanner(file); scanner.useDelimiter(","); String loan=""; int loan2; while( scanner.hasNextLine()) { //Should the Books be Stored in An Array? // At the moment you have separate objects stored in unknown location String Author = scanner.next(); String Title = scanner.next(); String PublisherName = scanner.next(); if ( i < 4) { System.out.println(i); rentBooks[i].setBook(Author, Title, PublisherName); rentBooks[i].getBook(); // MEMBERS SHOWN i++; } public class readBook4{ public static void main(String[] args) { int number =0; System.out.println( "Please select one of the choices below " ); System.out.println( "Select option 1 to list all items in the library "); System.out.println( "Select option 2 to list the items by category"); System.out.println( "Select option 3 to choose item available in the library "); System.out.println( "Select option 7 to exit " ); InputStreamReader isr = new InputStreamReader( System.in); BufferedReader buffer = new BufferedReader( isr); String input = ""; try { input = buffer.readLine(); number = Integer.parseInt(input); //int number = Integer.parseInt( Edition); if ( number == 1 ) { System.out.println( " \nThanks you are reading "+ input); //showStudent.main(args); showPeriodical.main(args); showDVD.main(args); // showBook.main(args); } if ( number == 2 ) { //jht.cls(); int number2; System.out.println( "Please select one of the choices below " ); System.out.println( "Select option 4 to list Books only "); System.out.println( "Select option 5 to list the Periodicals only"); System.out.println( "Select option 6 to list DVDs only"); InputStreamReader isr2 = new InputStreamReader(System.in); BufferedReader buffer2 = new BufferedReader(isr2); String input2 = ""; try { input2 = buffer2.readLine(); buffer.close(); } catch(IOException e) { System.out.println("An input error has occured"); } //System.out.println("Thanks, you are reading" + input2); number2 = Integer.parseInt(input2); if ( number2 == 4 ) { showBook.main(args); } if ( number2 == 5 ) { showPeriodical.main(args); } if ( number2 == 6 ) { showDVD.main(args); } // readBook4.main(args); } if( number == 3 ) { //showBook.main(args); showBook.availableBooks(); showDVD.availableDVD(); showPeriodical.availablePeriodical(); } if ( number == 7 ) { showStudent.main(args); } buffer.close(); } catch( IOException e ) { System.out.println( " An input error has occured "); } //System.out.println( " \nThanks you are reading "+ input); } } } //buffer.close(); scanner.close(); } catch( FileNotFoundException e) { System.out.println("File not Found"); } for ( i=0; i < 5; i++ ) rentBooks[i].getBook(); //ARRAY NOT SHOWN } }

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  • Adding a second table in a database

    - by MB
    Hi everyone. I used the code provided by the NoteExample from the developers doc to create a database. Now I want to add a second table to store different data. I simply "copied" the given code, but when I try to insert into the new table I get an error saying: "0ERROR/Database(370): android.database.sqlite.SQLiteException: no such table: routes: , while compiling: INSERT INTO routes(line, arrival, duration, start) VALUES(?, ?, ?, ?);" Can someone please take quick look at my DbAdapter class and give me a hint or a solution? I really don't see any problem. my code compiles without any errors.. thanks in advance! CODE: import static android.provider.BaseColumns._ID; import android.content.ContentValues; import android.content.Context; import android.database.Cursor; import android.database.SQLException; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteOpenHelper; import android.util.Log; public class DbAdapter { public static final String KEY_FROM = "title"; public static final String KEY_TO = "body"; public static final String KEY_ROWID = "_id"; public static final String KEY_START = "start"; public static final String KEY_ARRIVAL = "arrival"; public static final String KEY_LINE = "line"; public static final String KEY_DURATION = "duration"; private static final String DATABASE_NAME = "data"; private static final String DATABASE_NOTESTABLE = "notes"; private static final String DATABASE_ROUTESTABLE = "routes"; private static final String TAG = "DbAdapter"; private DatabaseHelper mDbHelper; private SQLiteDatabase mDb; /** * Database creation sql statement */ private static final String DATABASE_CREATE_NOTES = "create table notes (_id integer primary key autoincrement, " + "title text not null, body text not null)"; private static final String DATABASE_CREATE_ROUTES = "create table routes (_id integer primary key autoincrement, " + "start text not null, arrival text not null, " + "line text not null, duration text not null);"; private static final int DATABASE_VERSION = 2; private final Context mCtx; private static class DatabaseHelper extends SQLiteOpenHelper { DatabaseHelper(Context context) { super(context, DATABASE_NAME, null, DATABASE_VERSION); } @Override public void onCreate(SQLiteDatabase db) { db.execSQL(DATABASE_CREATE_NOTES); Log.d(TAG, "created notes table"); db.execSQL(DATABASE_CREATE_ROUTES); //CREATE LOKALTABLE db.execSQL("CREATE TABLE " + DATABASE_ROUTESTABLE + " " + "(" + _ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " + KEY_START + " TEXT NOT NULL, " + KEY_ARRIVAL + " TEXT NOT NULL, " + KEY_LINE + " TEXT NOT NULL, " + KEY_DURATION + " TEXT NOT NULL"); Log.d(TAG, "created routes table"); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { Log.w(TAG, "Upgrading database from version " + oldVersion + " to " + newVersion + ", which will destroy all old data"); db.execSQL("DROP TABLE IF EXISTS notes"); onCreate(db); } } /** * Constructor - takes the context to allow the database to be * opened/created * * @param ctx the Context within which to work */ public DbAdapter(Context ctx) { this.mCtx = ctx; } /** * Open the notes database. If it cannot be opened, try to create a new * instance of the database. If it cannot be created, throw an exception to * signal the failure * * @return this (self reference, allowing this to be chained in an * initialization call) * @throws SQLException if the database could be neither opened or created */ public DbAdapter open() throws SQLException { mDbHelper = new DatabaseHelper(mCtx); mDb = mDbHelper.getWritableDatabase(); return this; } public void close() { mDbHelper.close(); } /** * Create a new note using the title and body provided. If the note is * successfully created return the new rowId for that note, otherwise return * a -1 to indicate failure. * * @param title the title of the note * @param body the body of the note * @return rowId or -1 if failed */ public long createNote(String title, String body) { ContentValues initialValues = new ContentValues(); initialValues.put(KEY_FROM, title); initialValues.put(KEY_TO, body); return mDb.insert(DATABASE_NOTESTABLE, null, initialValues); } /** * Create a new route using the title and body provided. If the route is * successfully created return the new rowId for that route, otherwise return * a -1 to indicate failure. * * @param start the start time of the route * @param arrival the arrival time of the route * @param line the line number of the route * @param duration the routes duration * @return rowId or -1 if failed */ public long createRoute(String start, String arrival, String line, String duration){ ContentValues initialValues = new ContentValues(); initialValues.put(KEY_START, start); initialValues.put(KEY_ARRIVAL, arrival); initialValues.put(KEY_LINE, line); initialValues.put(KEY_DURATION, duration); return mDb.insert(DATABASE_ROUTESTABLE, null, initialValues); } /** * Delete the note with the given rowId * * @param rowId id of note to delete * @return true if deleted, false otherwise */ public boolean deleteNote(long rowId) { return mDb.delete(DATABASE_NOTESTABLE, KEY_ROWID + "=" + rowId, null) > 0; } /** * Return a Cursor over the list of all notes in the database * * @return Cursor over all notes */ public Cursor fetchAllNotes() { return mDb.query(DATABASE_NOTESTABLE, new String[] {KEY_ROWID, KEY_FROM, KEY_TO}, null, null, null, null, null); } /** * Return a Cursor over the list of all routes in the database * * @return Cursor over all routes */ public Cursor fetchAllRoutes() { return mDb.query(DATABASE_ROUTESTABLE, new String[] {KEY_ROWID, KEY_START, KEY_ARRIVAL, KEY_LINE, KEY_DURATION}, null, null, null, null, null); } /** * Return a Cursor positioned at the note that matches the given rowId * * @param rowId id of note to retrieve * @return Cursor positioned to matching note, if found * @throws SQLException if note could not be found/retrieved */ public Cursor fetchNote(long rowId) throws SQLException { Cursor mCursor = mDb.query(true, DATABASE_NOTESTABLE, new String[] {KEY_ROWID, KEY_FROM, KEY_TO}, KEY_ROWID + "=" + rowId, null, null, null, null, null); if (mCursor != null) { mCursor.moveToFirst(); } return mCursor; } /** * Return a Cursor positioned at the route that matches the given rowId * * @param rowId id of route to retrieve * @return Cursor positioned to matching route * @throws SQLException if note could not be found/retrieved */ public Cursor fetchRoute(long rowId) throws SQLException { Cursor mCursor = mDb.query(true, DATABASE_ROUTESTABLE, new String[] {KEY_ROWID, KEY_START, KEY_ARRIVAL, KEY_LINE, KEY_DURATION}, KEY_ROWID + "=" + rowId, null, null, null, null, null); if (mCursor != null) { mCursor.moveToFirst(); } return mCursor; } /** * Update the note using the details provided. The note to be updated is * specified using the rowId, and it is altered to use the title and body * values passed in * * @param rowId id of note to update * @param title value to set note title to * @param body value to set note body to * @return true if the note was successfully updated, false otherwise */ public boolean updateNote(long rowId, String title, String body) { ContentValues args = new ContentValues(); args.put(KEY_FROM, title); args.put(KEY_TO, body); return mDb.update(DATABASE_NOTESTABLE, args, KEY_ROWID + "=" + rowId, null) > 0; } }

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  • Trouble calling a method from an external class

    - by Bradley Hobbs
    Here is my employee database program: import java.util.*; import java.io.*; import java.io.File; import java.io.FileReader; import java.util.ArrayList; public class P { //Instance Variables private static String empName; private static String wage; private static double wages; private static double salary; private static double numHours; private static double increase; // static ArrayList<String> ARempName = new ArrayList<String>(); // static ArrayList<Double> ARwages = new ArrayList<Double>(); // static ArrayList<Double> ARsalary = new ArrayList<Double>(); static ArrayList<Employee> emp = new ArrayList<Employee>(); public static void main(String[] args) throws Exception { clearScreen(); printMenu(); question(); exit(); } public static void printArrayList(ArrayList<Employee> emp) { for (int i = 0; i < emp.size(); i++){ System.out.println(emp.get(i)); } } public static void clearScreen() { System.out.println("\u001b[H\u001b[2J"); } private static void exit() { System.exit(0); } private static void printMenu() { System.out.println("\t------------------------------------"); System.out.println("\t|Commands: n - New employee |"); System.out.println("\t| c - Compute paychecks |"); System.out.println("\t| r - Raise wages |"); System.out.println("\t| p - Print records |"); System.out.println("\t| d - Download data |"); System.out.println("\t| u - Upload data |"); System.out.println("\t| q - Quit |"); System.out.println("\t------------------------------------"); System.out.println(""); } public static void question() { System.out.print("Enter command: "); Scanner q = new Scanner(System.in); String input = q.nextLine(); input.replaceAll("\\s","").toLowerCase(); boolean valid = (input.equals("n") || input.equals("c") || input.equals("r") || input.equals("p") || input.equals("d") || input.equals("u") || input.equals("q")); if (!valid){ System.out.println("Command was not recognized; please try again."); printMenu(); question(); } else if (input.equals("n")){ System.out.print("Enter the name of new employee: "); Scanner stdin = new Scanner(System.in); empName = stdin.nextLine(); System.out.print("Hourly (h) or salaried (s): "); Scanner stdin2 = new Scanner(System.in); wage = stdin2.nextLine(); wage.replaceAll("\\s","").toLowerCase(); if (!(wage.equals("h") || wage.equals("s"))){ System.out.println("Input was not h or s; please try again"); } else if (wage.equals("h")){ System.out.print("Enter hourly wage: "); Scanner stdin4 = new Scanner(System.in); wages = stdin4.nextDouble(); Employee emp1 = new HourlyEmployee(empName, wages); emp.add(emp1); printMenu(); question();} else if (wage.equals("s")){ System.out.print("Enter annual salary: "); Scanner stdin5 = new Scanner(System.in); salary = stdin5.nextDouble(); Employee emp1 = new SalariedEmployee(empName, salary); printMenu(); question();}} else if (input.equals("c")){ for (int i = 0; i < emp.size(); i++){ System.out.println("Enter number of hours worked by " + emp.get(i) + ":"); } Scanner stdin = new Scanner(System.in); numHours = stdin.nextInt(); System.out.println("Pay: " + emp1.computePay(numHours)); System.out.print("Enter number of hours worked by " + empName); Scanner stdin2 = new Scanner(System.in); numHours = stdin2.nextInt(); System.out.println("Pay: " + emp1.computePay(numHours)); printMenu(); question();} else if (input.equals("r")){ System.out.print("Enter percentage increase: "); Scanner stdin = new Scanner(System.in); increase = stdin.nextDouble(); System.out.println("\nNew Wages"); System.out.println("---------"); // System.out.println(Employee.toString()); printMenu(); question(); } else if (input.equals("p")){ printArrayList(emp); printMenu(); question(); } else if (input.equals("q")){ exit(); } } } Here is one of the class files: public abstract class Employee { private String name; private double wage; protected Employee(String name, double wage){ this.name = name; this.wage = wage; } public String getName() { return name; } public double getWage() { return wage; } public void setName(String name) { this.name = name; } public void setWage(double wage) { this.wage = wage; } public void percent(double wage, double percent) { wage *= percent; } } And here are the errors: P.java:108: cannot find symbol symbol : variable emp1 location: class P System.out.println("Pay: " + emp1.computePay(numHours)); ^ P.java:112: cannot find symbol symbol : variable emp1 location: class P System.out.println("Pay: " + emp1.computePay(numHours)); ^ 2 errors I'm trying to the get paycheck to print out but i'm having trouble with how to call the method. It should take the user inputed numHours and calculate it then print on the paycheck for each employee. Thanks!

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  • Multiple routers, subnets, gateways etc

    - by allentown
    My current setup is: Cable modem dishes out 13 static IP's (/28), a GB switch is plugged into the cable modem, and has access to those 13 static IP's, I have about 6 "servers" in use right now. The cable modem is also a firewall, DHCP server, and 3 port 10/100 switch. I am using it as a firewall, but not currently as a DHCP server. I have plugged into the cable modem, two network cables, one which goes to the WAN port of a Linksys Dual Band Wireless 10/100/1000 router/switch. Into the linksys are a few workstations, a few printers, and some laptops connecting to wifi. I set the Linksys to use take static IP, and enabled DHCP for the workstations, printers, etc in 192.168.1.1/24. The network for the Linksys is mostly self contained, backups go to a SAN, on that network, it all happens through that switch, over GB. But I also get internet access from it as well via the cable modem using one static IP. This all works, however, I can not "see" the static IP machines when I am on the Linksys. I can get to them via ssh and other protocols, and if I want to from "outside", I open holes, like 80, 25, 587, 143, 22, etc. The second wire, from the cable modem/fireall/switch just uplinks to the managed GB switch. What are the pros and cons of this? I do not like giving up the static IP to the Linksys. I basically have a mixed network of public servers, and internal workstations. I want the public servers on public IP's because I do not want to mess with port forwarding and mappings. Is it correct also, that if someone breaches the Linksys wifi, they still would have a hard time getting to the static IP range, just by nature of the network topology? Today, just for a test, I toggled on the DHCP in the firewall/cable modem at 10.1.10.1/24 range, the Linksys is n the 192.168.1.100/24 range. At that point, all the static IP machines still had in and out access, but Linksys was unreachable. The cable modem only has 10/100 ports, so I will not plug anything but the network drop into it, which is 50Mb/10Mb. Which makes me think this could be less than ideal, as transfers from the workstation network to the server network will be bottlenecked at 100Mb when I have 1000Mb available. I may not need to solve that, if isolation is better though. I do not move a lot of data, if any, from Linsys network to server network, so for it to pretend to be remote is ok. Should I approach this any different? I could enable DHCP on the cable modem/firewall, it should still send out the statics to the GB switch, but will also be a DHCP in 10.1.10.1/24 range? I can then plug the Linksys into the GB switch, which is now picking up statics and the 10.1.10.1/24 ranges, tell the Linksys to use 10.1.10.5 or so. Now, do I disable DHCP on the Linksys, and the cable modem/firewall will pass through the statics and 10.0.10.1/24 ranges as well? Or, could I open a second DHCP pool on the Linksys? I guess doing so gives me network isolation again, but it is just the reverse of what I have now. But I get out of the bottleneck, not that the Linksys could ever really touch real GB speeds anyway, but the managed switch certainly can. This is all because 13 statics are not that many. Right now, 6 "servers", the Linksys, a managed switch, a few SSL certs, and I am running out. I do not want to waste a static IP on the managed GB switch, or the Linksys, unless it provides me some type of benefit. Final question, under my current setup, if I am on a workstation, sitting at 192.168.1.109, the Linksys, with GB, and I send a file over ssh to the static IP machine, is that literally leaving the internet, and coming back in, or does it stay local? To me it seems like: Workstation (192.168.1.109) -> Linksys DHCP -> Linksys Static IP -> Cable Modem -> Server ( and it hits the 10/100 ports on the cable modem, slowing me down. But does it round trip the network, leave and come back in, limiting me to the 50/10 internet speeds? *These are all made up numbers, I do not use default router IP's as I will one day add a VPN, and do not want collisions. I need some recommendations, do I want one big network, or two isolated ones. Printers these days need an IP, everything does, I can not get autoconf/bonjour to be reliable on most printers. but I am also not sure I want the "server" side of my operation to be polluted by the workstation side of my operation. Unless there is some magic subetting I have not learned yet, here is what I am thinking: Cable modem 10/100, has 13 static IP, publicly accessible -> Enable DHCP on the cable modem -> Cable modem plugs into managed switch -> Managed switch gets 10.1.10.1 ssh, telnet, https admin management address -> Managed switch sends static IP's to to servers -> Plug Linksys into managed switch, giving it 10.1.10.2 static internally in Linksys admin -> Linksys gets assigned 10.1.10.x as its DHCP sending range -> Local printers, workstations, iPhones etc, connect to this -> ( Do I enable DHCP or disable it on the Linksys, just define a non over lapping range, or create an entirely new DHCP at 10.1.50.0/24, I think I am back isolated again with that method too? ) Thank you for any suggestions. This is the first time I have had to deal with less than a /24, and most are larger than that, but it is just a drop to a cabinet. Otherwise, it's a router, a few repeaters, and soho stuff that is simple, with one IP. I know a few may suggest going all DHCP on the servers, and I may one day, just not now, there has been too much moving of gear for me to be interested in that, and I would want something in the Catalyst series to deal with that.

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  • Singleton code linker errors in vc 9.0. Runs fine in linux compiled with gcc

    - by user306560
    I have a simple logger that is implemented as a singleton. It works like i want when I compile and run it with g++ in linux but when I compile in Visual Studio 9.0 with vc++ I get the following errors. Is there a way to fix this? I don't mind changing the logger class around, but I would like to avoid changing how it is called. 1>Linking... 1>loggerTest.obj : error LNK2005: "public: static class Logger * __cdecl Logger::getInstance(void)" (?getInstance@Logger@@SAPAV1@XZ) already defined in Logger.obj 1>loggerTest.obj : error LNK2005: "public: void __thiscall Logger::log(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > const &)" (?log@Logger@@QAEXABV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@Z) already defined in Logger.obj 1>loggerTest.obj : error LNK2005: "public: void __thiscall Logger::closeLog(void)" (?closeLog@Logger@@QAEXXZ) already defined in Logger.obj 1>loggerTest.obj : error LNK2005: "private: static class Logger * Logger::_instance" (?_instance@Logger@@0PAV1@A) already defined in Logger.obj 1>Logger.obj : error LNK2001: unresolved external symbol "private: static class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > Logger::_path" (?_path@Logger@@0V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@A) 1>loggerTest.obj : error LNK2001: unresolved external symbol "private: static class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > Logger::_path" (?_path@Logger@@0V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@A) 1>Logger.obj : error LNK2001: unresolved external symbol "private: static class boost::mutex Logger::_mutex" (?_mutex@Logger@@0Vmutex@boost@@A) 1>loggerTest.obj : error LNK2001: unresolved external symbol "private: static class boost::mutex Logger::_mutex" (?_mutex@Logger@@0Vmutex@boost@@A) 1>Logger.obj : error LNK2001: unresolved external symbol "private: static class std::basic_ofstream<char,struct std::char_traits<char> > Logger::_log" (?_log@Logger@@0V?$basic_ofstream@DU?$char_traits@D@std@@@std@@A) 1>loggerTest.obj : error LNK2001: unresolved external symbol "private: static class std::basic_ofstream<char,struct std::char_traits<char> > Logger::_log" (?_log@Logger@@0V?$basic_ofstream@DU?$char_traits@D@std@@@std@@A) The code, three files Logger.h Logger.cpp test.cpp #ifndef __LOGGER_CPP__ #define __LOGGER_CPP__ #include "Logger.h" Logger* Logger::_instance = 0; //string Logger::_path = "log"; //ofstream Logger::_log; //boost::mutex Logger::_mutex; Logger* Logger::getInstance(){ { boost::mutex::scoped_lock lock(_mutex); if(_instance == 0) { _instance = new Logger; _path = "log"; } } //mutex return _instance; } void Logger::log(const std::string& msg){ { boost::mutex::scoped_lock lock(_mutex); if(!_log.is_open()){ _log.open(_path.c_str()); } if(_log.is_open()){ _log << msg.c_str() << std::endl; } } } void Logger::closeLog(){ Logger::_log.close(); } #endif ` ... #ifndef __LOGGER_H__ #define __LOGGER_H__ #include <iostream> #include <string> #include <fstream> #include <boost/thread/mutex.hpp> #include <boost/thread.hpp> using namespace std; class Logger { public: static Logger* getInstance(); void log(const std::string& msg); void closeLog(); protected: Logger(){} private: static Logger* _instance; static string _path; static bool _logOpen; static ofstream _log; static boost::mutex _mutex; //check mutable }; #endif test.cpp ` #include <iostream> #include "Logger.cpp" using namespace std; int main(int argc, char *argv[]) { Logger* log = Logger::getInstance(); log->log("hello world\n"); return 0; }

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  • Grails: Querying Associations causes groovy.lang.MissingMethodException

    - by Paul
    Hi, I've got an issue with Grails where I have a test app with: class Artist { static constraints = { name() } static hasMany = [albums:Album] String name } class Album { static constraints = { name() } static hasMany = [ tracks : Track ] static belongsTo = [artist: Artist] String name } class Track { static constraints = { name() lyrics(nullable: true) } Lyrics lyrics static belongsTo = [album: Album] String name } The following query (and a more advanced, nested association query) works in the Grails Console but fails with a groovy.lang.MissingMethodException when running the app with 'run-app': def albumCriteria = tunehub.Album.createCriteria() def albumResults = albumCriteria.list { like("name", receivedAlbum) artist { like("name", receivedArtist) } // Fails here maxResults(1) } Stacktrace: groovy.lang.MissingMethodException: No signature of method: java.lang.String.call() is applicable for argument types: (tunehub.LyricsService$_getLyrics_closure1_closure2) values: [tunehub.LyricsService$_getLyrics_closure1_closure2@604106] Possible solutions: wait(), any(), wait(long), each(groovy.lang.Closure), any(groovy.lang.Closure), trim() at tunehub.LyricsService$_getLyrics_closure1.doCall(LyricsService.groovy:61) at tunehub.LyricsService$_getLyrics_closure1.doCall(LyricsService.groovy) (...truncated...) Any pointers?

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  • Sql Server as logging, best connection practise

    - by ozz
    I'm using SqlServer as logging. Yes this is wrong decision, there are better dbs for this requirement. But I have no other option for now. Logging interval is 3 logs per second. So I've static Logger class and it has static Log method. Using "Open Connection" as static member is better for performance. But what is the best implemantation of it? This is not that I know. public static class OzzLogger { static SqlConnection Con; static OzzLogger() { Con=ne SqlConnection(....); Con.Open(); } public static void Log(....) { Con.ExecuteSql(......); } } UPDATE I asked because of my old information. People say "connection pooling performance is enough". If there is no objection I'm closing the issue :)

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  • How do I replace "this" in Java with something that works.

    - by Luke Alderton
    I'm looking to get the showGUI() method work, the compiler says "this" is not a static variable and cannot be referenced from a static context, what would I use to replace "this"? I've tried test.main (test being the package it's in). The reason I'm using the static method showGUI() is because I need the method to be called from another static method, as well as the startup() method. Below are my two main classes. public class Main extends SingleFrameApplication { @Override protected void startup() { showGUI(); } @Override protected void configureWindow(java.awt.Window root) { } public static Main getApplication() { return Application.getInstance(Main.class); } public static void main(String[] args) { launch(Main.class, args); } public static void showGUI() { show(new GUI(this)); } } public class GUI extends FrameView { public GUI(SingleFrameApplication app) { super(app); initComponents(); } private void initComponents() { //all the GUI stuff is somehow defined here } }

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  • NLog Exception Details Renderer

    - by jtimperley
    Originally posted on: http://geekswithblogs.net/jtimperley/archive/2013/07/28/nlog-exception-details-renderer.aspxI recently switch from Microsoft's Enterprise Library Logging block to NLog.  In my opinion, NLog offers a simpler and much cleaner configuration section with better use of placeholders, complemented by custom variables. Despite this, I found one deficiency in my migration; I had lost the ability to simply render all details of an exception into our logs and notification emails. This is easily remedied by implementing a custom layout renderer. Start by extending 'NLog.LayoutRenderers.LayoutRenderer' and overriding the 'Append' method. using System.Text; using NLog; using NLog.Config; using NLog.LayoutRenderers;   [ThreadAgnostic] [LayoutRenderer(Name)] public class ExceptionDetailsRenderer : LayoutRenderer { public const string Name = "exceptiondetails";   protected override void Append(StringBuilder builder, LogEventInfo logEvent) { // Todo: Append details to StringBuilder } }   Now that we have a base layout renderer, we simply need to add the formatting logic to add exception details as well as inner exception details. This is done using reflection with some simple filtering for the properties that are already being rendered. I have added an additional 'Register' method, allowing the definition to be registered in code, rather than in configuration files. This complements by 'LogWrapper' class which standardizes writing log entries throughout my applications. using System; using System.Collections.Generic; using System.Linq; using System.Reflection; using System.Text; using NLog; using NLog.Config; using NLog.LayoutRenderers;   [ThreadAgnostic] [LayoutRenderer(Name)] public sealed class ExceptionDetailsRenderer : LayoutRenderer { public const string Name = "exceptiondetails"; private const string _Spacer = "======================================"; private List<string> _FilteredProperties;   private List<string> FilteredProperties { get { if (_FilteredProperties == null) { _FilteredProperties = new List<string> { "StackTrace", "HResult", "InnerException", "Data" }; }   return _FilteredProperties; } }   public bool LogNulls { get; set; }   protected override void Append(StringBuilder builder, LogEventInfo logEvent) { Append(builder, logEvent.Exception, false); }   private void Append(StringBuilder builder, Exception exception, bool isInnerException) { if (exception == null) { return; }   builder.AppendLine();   var type = exception.GetType(); if (isInnerException) { builder.Append("Inner "); }   builder.AppendLine("Exception Details:") .AppendLine(_Spacer) .Append("Exception Type: ") .AppendLine(type.ToString());   var bindingFlags = BindingFlags.Instance | BindingFlags.Public; var properties = type.GetProperties(bindingFlags); foreach (var property in properties) { var propertyName = property.Name; var isFiltered = FilteredProperties.Any(filter => String.Equals(propertyName, filter, StringComparison.InvariantCultureIgnoreCase)); if (isFiltered) { continue; }   var propertyValue = property.GetValue(exception, bindingFlags, null, null, null); if (propertyValue == null && !LogNulls) { continue; }   var valueText = propertyValue != null ? propertyValue.ToString() : "NULL"; builder.Append(propertyName) .Append(": ") .AppendLine(valueText); }   AppendStackTrace(builder, exception.StackTrace, isInnerException); Append(builder, exception.InnerException, true); }   private void AppendStackTrace(StringBuilder builder, string stackTrace, bool isInnerException) { if (String.IsNullOrEmpty(stackTrace)) { return; }   builder.AppendLine();   if (isInnerException) { builder.Append("Inner "); }   builder.AppendLine("Exception StackTrace:") .AppendLine(_Spacer) .AppendLine(stackTrace); }   public static void Register() { Type definitionType; var layoutRenderers = ConfigurationItemFactory.Default.LayoutRenderers; if (layoutRenderers.TryGetDefinition(Name, out definitionType)) { return; }   layoutRenderers.RegisterDefinition(Name, typeof(ExceptionDetailsRenderer)); LogManager.ReconfigExistingLoggers(); } } For brevity I have removed the Trace, Debug, Warn, and Fatal methods. They are modelled after the Info methods. As mentioned above, note how the log wrapper automatically registers our custom layout renderer reducing the amount of application configuration required. using System; using NLog;   public static class LogWrapper { static LogWrapper() { ExceptionDetailsRenderer.Register(); }   #region Log Methods   public static void Info(object toLog) { Log(toLog, LogLevel.Info); }   public static void Info(string messageFormat, params object[] parameters) { Log(messageFormat, parameters, LogLevel.Info); }   public static void Error(object toLog) { Log(toLog, LogLevel.Error); }   public static void Error(string message, Exception exception) { Log(message, exception, LogLevel.Error); }   private static void Log(string messageFormat, object[] parameters, LogLevel logLevel) { string message = parameters.Length == 0 ? messageFormat : string.Format(messageFormat, parameters); Log(message, (Exception)null, logLevel); }   private static void Log(object toLog, LogLevel logLevel, LogType logType = LogType.General) { if (toLog == null) { throw new ArgumentNullException("toLog"); }   if (toLog is Exception) { var exception = toLog as Exception; Log(exception.Message, exception, logLevel, logType); } else { var message = toLog.ToString(); Log(message, null, logLevel, logType); } }   private static void Log(string message, Exception exception, LogLevel logLevel, LogType logType = LogType.General) { if (exception == null && String.IsNullOrEmpty(message)) { return; }   var logger = GetLogger(logType); // Note: Using the default constructor doesn't set the current date/time var logInfo = new LogEventInfo(logLevel, logger.Name, message); logInfo.Exception = exception; logger.Log(logInfo); }   private static Logger GetLogger(LogType logType) { var loggerName = logType.ToString(); return LogManager.GetLogger(loggerName); }   #endregion   #region LogType private enum LogType { General } #endregion } The following configuration is similar to what is provided for each of my applications. The 'application' variable is all that differentiates the various applications in all of my environments, the rest has been standardized. Depending on your needs to tweak this configuration while developing and debugging, this section could easily be pushed back into code similar to the registering of our custom layout renderer.   <?xml version="1.0"?>   <configuration> <configSections> <section name="nlog" type="NLog.Config.ConfigSectionHandler, NLog"/> </configSections> <nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> <variable name="application" value="Example"/> <targets> <target type="EventLog" name="EventLog" source="${application}" log="${application}" layout="${message}${onexception: ${newline}${exceptiondetails}}"/> <target type="Mail" name="Email" smtpServer="smtp.example.local" from="[email protected]" to="[email protected]" subject="(${machinename}) ${application}: ${level}" body="Machine: ${machinename}${newline}Timestamp: ${longdate}${newline}Level: ${level}${newline}Message: ${message}${onexception: ${newline}${exceptiondetails}}"/> </targets> <rules> <logger name="*" minlevel="Debug" writeTo="EventLog" /> <logger name="*" minlevel="Error" writeTo="Email" /> </rules> </nlog> </configuration>   Now go forward, create your custom exceptions without concern for including their custom properties in your exception logs and notifications.

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  • C# Extension Methods - To Extend or Not To Extend...

    - by James Michael Hare
    I've been thinking a lot about extension methods lately, and I must admit I both love them and hate them. They are a lot like sugar, they taste so nice and sweet, but they'll rot your teeth if you eat them too much.   I can't deny that they aren't useful and very handy. One of the major components of the Shared Component library where I work is a set of useful extension methods. But, I also can't deny that they tend to be overused and abused to willy-nilly extend every living type.   So what constitutes a good extension method? Obviously, you can write an extension method for nearly anything whether it is a good idea or not. Many times, in fact, an idea seems like a good extension method but in retrospect really doesn't fit.   So what's the litmus test? To me, an extension method should be like in the movies when a person runs into their twin, separated at birth. You just know you're related. Obviously, that's hard to quantify, so let's try to put a few rules-of-thumb around them.   A good extension method should:     Apply to any possible instance of the type it extends.     Simplify logic and improve readability/maintainability.     Apply to the most specific type or interface applicable.     Be isolated in a namespace so that it does not pollute IntelliSense.     So let's look at a few examples in relation to these rules.   The first rule, to me, is the most important of all. Once again, it bears repeating, a good extension method should apply to all possible instances of the type it extends. It should feel like the long lost relative that should have been included in the original class but somehow was missing from the family tree.    Take this nifty little int extension, I saw this once in a blog and at first I really thought it was pretty cool, but then I started noticing a code smell I couldn't quite put my finger on. So let's look:       public static class IntExtensinos     {         public static int Seconds(int num)         {             return num * 1000;         }           public static int Minutes(int num)         {             return num * 60000;         }     }     This is so you could do things like:       ...     Thread.Sleep(5.Seconds());     ...     proxy.Timeout = 1.Minutes();     ...     Awww, you say, that's cute! Well, that's the problem, it's kitschy and it doesn't always apply (and incidentally you could achieve the same thing with TimeStamp.FromSeconds(5)). It's syntactical candy that looks cool, but tends to rot and pollute the code. It would allow things like:       total += numberOfTodaysOrders.Seconds();     which makes no sense and should never be allowed. The problem is you're applying an extension method to a logical domain, not a type domain. That is, the extension method Seconds() doesn't really apply to ALL ints, it applies to ints that are representative of time that you want to convert to milliseconds.    Do you see what I mean? The two problems, in a nutshell, are that a) Seconds() called off a non-time value makes no sense and b) calling Seconds() off something to pass to something that does not take milliseconds will be off by a factor of 1000 or worse.   Thus, in my mind, you should only ever have an extension method that applies to the whole domain of that type.   For example, this is one of my personal favorites:       public static bool IsBetween<T>(this T value, T low, T high)         where T : IComparable<T>     {         return value.CompareTo(low) >= 0 && value.CompareTo(high) <= 0;     }   This allows you to check if any IComparable<T> is within an upper and lower bound. Think of how many times you type something like:       if (response.Employee.Address.YearsAt >= 2         && response.Employee.Address.YearsAt <= 10)     {     ...     }     Now, you can instead type:       if(response.Employee.Address.YearsAt.IsBetween(2, 10))     {     ...     }     Note that this applies to all IComparable<T> -- that's ints, chars, strings, DateTime, etc -- and does not depend on any logical domain. In addition, it satisfies the second point and actually makes the code more readable and maintainable.   Let's look at the third point. In it we said that an extension method should fit the most specific interface or type possible. Now, I'm not saying if you have something that applies to enumerables, you create an extension for List, Array, Dictionary, etc (though you may have reasons for doing so), but that you should beware of making things TOO general.   For example, let's say we had an extension method like this:       public static T ConvertTo<T>(this object value)     {         return (T)Convert.ChangeType(value, typeof(T));     }         This lets you do more fluent conversions like:       double d = "5.0".ConvertTo<double>();     However, if you dig into Reflector (LOVE that tool) you will see that if the type you are calling on does not implement IConvertible, what you convert to MUST be the exact type or it will throw an InvalidCastException. Now this may or may not be what you want in this situation, and I leave that up to you. Things like this would fail:       object value = new Employee();     ...     // class cast exception because typeof(IEmployee) != typeof(Employee)     IEmployee emp = value.ConvertTo<IEmployee>();       Yes, that's a downfall of working with Convertible in general, but if you wanted your fluent interface to be more type-safe so that ConvertTo were only callable on IConvertibles (and let casting be a manual task), you could easily make it:         public static T ConvertTo<T>(this IConvertible value)     {         return (T)Convert.ChangeType(value, typeof(T));     }         This is what I mean by choosing the best type to extend. Consider that if we used the previous (object) version, every time we typed a dot ('.') on an instance we'd pull up ConvertTo() whether it was applicable or not. By filtering our extension method down to only valid types (those that implement IConvertible) we greatly reduce our IntelliSense pollution and apply a good level of compile-time correctness.   Now my fourth rule is just my general rule-of-thumb. Obviously, you can make extension methods as in-your-face as you want. I included all mine in my work libraries in its own sub-namespace, something akin to:       namespace Shared.Core.Extensions { ... }     This is in a library called Shared.Core, so just referencing the Core library doesn't pollute your IntelliSense, you have to actually do a using on Shared.Core.Extensions to bring the methods in. This is very similar to the way Microsoft puts its extension methods in System.Linq. This way, if you want 'em, you use the appropriate namespace. If you don't want 'em, they won't pollute your namespace.   To really make this work, however, that namespace should only include extension methods and subordinate types those extensions themselves may use. If you plant other useful classes in those namespaces, once a user includes it, they get all the extensions too.   Also, just as a personal preference, extension methods that aren't simply syntactical shortcuts, I like to put in a static utility class and then have extension methods for syntactical candy. For instance, I think it imaginable that any object could be converted to XML:       namespace Shared.Core     {         // A collection of XML Utility classes         public static class XmlUtility         {             ...             // Serialize an object into an xml string             public static string ToXml(object input)             {                 var xs = new XmlSerializer(input.GetType());                   // use new UTF8Encoding here, not Encoding.UTF8. The later includes                 // the BOM which screws up subsequent reads, the former does not.                 using (var memoryStream = new MemoryStream())                 using (var xmlTextWriter = new XmlTextWriter(memoryStream, new UTF8Encoding()))                 {                     xs.Serialize(xmlTextWriter, input);                     return Encoding.UTF8.GetString(memoryStream.ToArray());                 }             }             ...         }     }   I also wanted to be able to call this from an object like:       value.ToXml();     But here's the problem, if i made this an extension method from the start with that one little keyword "this", it would pop into IntelliSense for all objects which could be very polluting. Instead, I put the logic into a utility class so that users have the choice of whether or not they want to use it as just a class and not pollute IntelliSense, then in my extensions namespace, I add the syntactical candy:       namespace Shared.Core.Extensions     {         public static class XmlExtensions         {             public static string ToXml(this object value)             {                 return XmlUtility.ToXml(value);             }         }     }   So now it's the best of both worlds. On one hand, they can use the utility class if they don't want to pollute IntelliSense, and on the other hand they can include the Extensions namespace and use as an extension if they want. The neat thing is it also adheres to the Single Responsibility Principle. The XmlUtility is responsible for converting objects to XML, and the XmlExtensions is responsible for extending object's interface for ToXml().

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  • Creating a dynamic proxy generator with c# – Part 4 – Calling the base method

    - by SeanMcAlinden
    Creating a dynamic proxy generator with c# – Part 1 – Creating the Assembly builder, Module builder and caching mechanism Creating a dynamic proxy generator with c# – Part 2 – Interceptor Design Creating a dynamic proxy generator with c# – Part 3 – Creating the constructors   The plan for calling the base methods from the proxy is to create a private method for each overridden proxy method, this will allow the proxy to use a delegate to simply invoke the private method when required. Quite a few helper classes have been created to make this possible so as usual I would suggest download or viewing the code at http://rapidioc.codeplex.com/. In this post I’m just going to cover the main points for when creating methods. Getting the methods to override The first two notable methods are for getting the methods. private static MethodInfo[] GetMethodsToOverride<TBase>() where TBase : class {     return typeof(TBase).GetMethods().Where(x =>         !methodsToIgnore.Contains(x.Name) &&                              (x.Attributes & MethodAttributes.Final) == 0)         .ToArray(); } private static StringCollection GetMethodsToIgnore() {     return new StringCollection()     {         "ToString",         "GetHashCode",         "Equals",         "GetType"     }; } The GetMethodsToIgnore method string collection contains an array of methods that I don’t want to override. In the GetMethodsToOverride method, you’ll notice a binary AND which is basically saying not to include any methods marked final i.e. not virtual. Creating the MethodInfo for calling the base method This method should hopefully be fairly easy to follow, it’s only function is to create a MethodInfo which points to the correct base method, and with the correct parameters. private static MethodInfo CreateCallBaseMethodInfo<TBase>(MethodInfo method) where TBase : class {     Type[] baseMethodParameterTypes = ParameterHelper.GetParameterTypes(method, method.GetParameters());       return typeof(TBase).GetMethod(        method.Name,        BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic,        null,        baseMethodParameterTypes,        null     ); }   /// <summary> /// Get the parameter types. /// </summary> /// <param name="method">The method.</param> /// <param name="parameters">The parameters.</param> public static Type[] GetParameterTypes(MethodInfo method, ParameterInfo[] parameters) {     Type[] parameterTypesList = Type.EmptyTypes;       if (parameters.Length > 0)     {         parameterTypesList = CreateParametersList(parameters);     }     return parameterTypesList; }   Creating the new private methods for calling the base method The following method outline how I’ve created the private methods for calling the base class method. private static MethodBuilder CreateCallBaseMethodBuilder(TypeBuilder typeBuilder, MethodInfo method) {     string callBaseSuffix = "GetBaseMethod";       if (method.IsGenericMethod || method.IsGenericMethodDefinition)     {                         return MethodHelper.SetUpGenericMethod             (                 typeBuilder,                 method,                 method.Name + callBaseSuffix,                 MethodAttributes.Private | MethodAttributes.HideBySig             );     }     else     {         return MethodHelper.SetupNonGenericMethod             (                 typeBuilder,                 method,                 method.Name + callBaseSuffix,                 MethodAttributes.Private | MethodAttributes.HideBySig             );     } } The CreateCallBaseMethodBuilder is the entry point method for creating the call base method. I’ve added a suffix to the base classes method name to keep it unique. Non Generic Methods Creating a non generic method is fairly simple public static MethodBuilder SetupNonGenericMethod(     TypeBuilder typeBuilder,     MethodInfo method,     string methodName,     MethodAttributes methodAttributes) {     ParameterInfo[] parameters = method.GetParameters();       Type[] parameterTypes = ParameterHelper.GetParameterTypes(method, parameters);       Type returnType = method.ReturnType;       MethodBuilder methodBuilder = CreateMethodBuilder         (             typeBuilder,             method,             methodName,             methodAttributes,             parameterTypes,             returnType         );       ParameterHelper.SetUpParameters(parameterTypes, parameters, methodBuilder);       return methodBuilder; }   private static MethodBuilder CreateMethodBuilder (     TypeBuilder typeBuilder,     MethodInfo method,     string methodName,     MethodAttributes methodAttributes,     Type[] parameterTypes,     Type returnType ) { MethodBuilder methodBuilder = typeBuilder.DefineMethod(methodName, methodAttributes, returnType, parameterTypes); return methodBuilder; } As you can see, you simply have to declare a method builder, get the parameter types, and set the method attributes you want.   Generic Methods Creating generic methods takes a little bit more work. /// <summary> /// Sets up generic method. /// </summary> /// <param name="typeBuilder">The type builder.</param> /// <param name="method">The method.</param> /// <param name="methodName">Name of the method.</param> /// <param name="methodAttributes">The method attributes.</param> public static MethodBuilder SetUpGenericMethod     (         TypeBuilder typeBuilder,         MethodInfo method,         string methodName,         MethodAttributes methodAttributes     ) {     ParameterInfo[] parameters = method.GetParameters();       Type[] parameterTypes = ParameterHelper.GetParameterTypes(method, parameters);       MethodBuilder methodBuilder = typeBuilder.DefineMethod(methodName,         methodAttributes);       Type[] genericArguments = method.GetGenericArguments();       GenericTypeParameterBuilder[] genericTypeParameters =         GetGenericTypeParameters(methodBuilder, genericArguments);       ParameterHelper.SetUpParameterConstraints(parameterTypes, genericTypeParameters);       SetUpReturnType(method, methodBuilder, genericTypeParameters);       if (method.IsGenericMethod)     {         methodBuilder.MakeGenericMethod(genericArguments);     }       ParameterHelper.SetUpParameters(parameterTypes, parameters, methodBuilder);       return methodBuilder; }   private static GenericTypeParameterBuilder[] GetGenericTypeParameters     (         MethodBuilder methodBuilder,         Type[] genericArguments     ) {     return methodBuilder.DefineGenericParameters(GenericsHelper.GetArgumentNames(genericArguments)); }   private static void SetUpReturnType(MethodInfo method, MethodBuilder methodBuilder, GenericTypeParameterBuilder[] genericTypeParameters) {     if (method.IsGenericMethodDefinition)     {         SetUpGenericDefinitionReturnType(method, methodBuilder, genericTypeParameters);     }     else     {         methodBuilder.SetReturnType(method.ReturnType);     } }   private static void SetUpGenericDefinitionReturnType(MethodInfo method, MethodBuilder methodBuilder, GenericTypeParameterBuilder[] genericTypeParameters) {     if (method.ReturnType == null)     {         methodBuilder.SetReturnType(typeof(void));     }     else if (method.ReturnType.IsGenericType)     {         methodBuilder.SetReturnType(genericTypeParameters.Where             (x => x.Name == method.ReturnType.Name).First());     }     else     {         methodBuilder.SetReturnType(method.ReturnType);     }             } Ok, there are a few helper methods missing, basically there is way to much code to put in this post, take a look at the code at http://rapidioc.codeplex.com/ to follow it through completely. Basically though, when dealing with generics there is extra work to do in terms of getting the generic argument types setting up any generic parameter constraints setting up the return type setting up the method as a generic All of the information is easy to get via reflection from the MethodInfo.   Emitting the new private method Emitting the new private method is relatively simple as it’s only function is calling the base method and returning a result if the return type is not void. ILGenerator il = privateMethodBuilder.GetILGenerator();   EmitCallBaseMethod(method, callBaseMethod, il);   private static void EmitCallBaseMethod(MethodInfo method, MethodInfo callBaseMethod, ILGenerator il) {     int privateParameterCount = method.GetParameters().Length;       il.Emit(OpCodes.Ldarg_0);       if (privateParameterCount > 0)     {         for (int arg = 0; arg < privateParameterCount; arg++)         {             il.Emit(OpCodes.Ldarg_S, arg + 1);         }     }       il.Emit(OpCodes.Call, callBaseMethod);       il.Emit(OpCodes.Ret); } So in the main method building method, an ILGenerator is created from the method builder. The ILGenerator performs the following actions: Load the class (this) onto the stack using the hidden argument Ldarg_0. Create an argument on the stack for each of the method parameters (starting at 1 because 0 is the hidden argument) Call the base method using the Opcodes.Call code and the MethodInfo we created earlier. Call return on the method   Conclusion Now we have the private methods prepared for calling the base method, we have reached the last of the relatively easy part of the proxy building. Hopefully, it hasn’t been too hard to follow so far, there is a lot of code so I haven’t been able to post it all so please check it out at http://rapidioc.codeplex.com/. The next section should be up fairly soon, it’s going to cover creating the delegates for calling the private methods created in this post.   Kind Regards, Sean.

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  • Understanding LINQ to SQL (11) Performance

    - by Dixin
    [LINQ via C# series] LINQ to SQL has a lot of great features like strong typing query compilation deferred execution declarative paradigm etc., which are very productive. Of course, these cannot be free, and one price is the performance. O/R mapping overhead Because LINQ to SQL is based on O/R mapping, one obvious overhead is, data changing usually requires data retrieving:private static void UpdateProductUnitPrice(int id, decimal unitPrice) { using (NorthwindDataContext database = new NorthwindDataContext()) { Product product = database.Products.Single(item => item.ProductID == id); // SELECT... product.UnitPrice = unitPrice; // UPDATE... database.SubmitChanges(); } } Before updating an entity, that entity has to be retrieved by an extra SELECT query. This is slower than direct data update via ADO.NET:private static void UpdateProductUnitPrice(int id, decimal unitPrice) { using (SqlConnection connection = new SqlConnection( "Data Source=localhost;Initial Catalog=Northwind;Integrated Security=True")) using (SqlCommand command = new SqlCommand( @"UPDATE [dbo].[Products] SET [UnitPrice] = @UnitPrice WHERE [ProductID] = @ProductID", connection)) { command.Parameters.Add("@ProductID", SqlDbType.Int).Value = id; command.Parameters.Add("@UnitPrice", SqlDbType.Money).Value = unitPrice; connection.Open(); command.Transaction = connection.BeginTransaction(); command.ExecuteNonQuery(); // UPDATE... command.Transaction.Commit(); } } The above imperative code specifies the “how to do” details with better performance. For the same reason, some articles from Internet insist that, when updating data via LINQ to SQL, the above declarative code should be replaced by:private static void UpdateProductUnitPrice(int id, decimal unitPrice) { using (NorthwindDataContext database = new NorthwindDataContext()) { database.ExecuteCommand( "UPDATE [dbo].[Products] SET [UnitPrice] = {0} WHERE [ProductID] = {1}", id, unitPrice); } } Or just create a stored procedure:CREATE PROCEDURE [dbo].[UpdateProductUnitPrice] ( @ProductID INT, @UnitPrice MONEY ) AS BEGIN BEGIN TRANSACTION UPDATE [dbo].[Products] SET [UnitPrice] = @UnitPrice WHERE [ProductID] = @ProductID COMMIT TRANSACTION END and map it as a method of NorthwindDataContext (explained in this post):private static void UpdateProductUnitPrice(int id, decimal unitPrice) { using (NorthwindDataContext database = new NorthwindDataContext()) { database.UpdateProductUnitPrice(id, unitPrice); } } As a normal trade off for O/R mapping, a decision has to be made between performance overhead and programming productivity according to the case. In a developer’s perspective, if O/R mapping is chosen, I consistently choose the declarative LINQ code, unless this kind of overhead is unacceptable. Data retrieving overhead After talking about the O/R mapping specific issue. Now look into the LINQ to SQL specific issues, for example, performance in the data retrieving process. The previous post has explained that the SQL translating and executing is complex. Actually, the LINQ to SQL pipeline is similar to the compiler pipeline. It consists of about 15 steps to translate an C# expression tree to SQL statement, which can be categorized as: Convert: Invoke SqlProvider.BuildQuery() to convert the tree of Expression nodes into a tree of SqlNode nodes; Bind: Used visitor pattern to figure out the meanings of names according to the mapping info, like a property for a column, etc.; Flatten: Figure out the hierarchy of the query; Rewrite: for SQL Server 2000, if needed Reduce: Remove the unnecessary information from the tree. Parameterize Format: Generate the SQL statement string; Parameterize: Figure out the parameters, for example, a reference to a local variable should be a parameter in SQL; Materialize: Executes the reader and convert the result back into typed objects. So for each data retrieving, even for data retrieving which looks simple: private static Product[] RetrieveProducts(int productId) { using (NorthwindDataContext database = new NorthwindDataContext()) { return database.Products.Where(product => product.ProductID == productId) .ToArray(); } } LINQ to SQL goes through above steps to translate and execute the query. Fortunately, there is a built-in way to cache the translated query. Compiled query When such a LINQ to SQL query is executed repeatedly, The CompiledQuery can be used to translate query for one time, and execute for multiple times:internal static class CompiledQueries { private static readonly Func<NorthwindDataContext, int, Product[]> _retrieveProducts = CompiledQuery.Compile((NorthwindDataContext database, int productId) => database.Products.Where(product => product.ProductID == productId).ToArray()); internal static Product[] RetrieveProducts( this NorthwindDataContext database, int productId) { return _retrieveProducts(database, productId); } } The new version of RetrieveProducts() gets better performance, because only when _retrieveProducts is first time invoked, it internally invokes SqlProvider.Compile() to translate the query expression. And it also uses lock to make sure translating once in multi-threading scenarios. Static SQL / stored procedures without translating Another way to avoid the translating overhead is to use static SQL or stored procedures, just as the above examples. Because this is a functional programming series, this article not dive into. For the details, Scott Guthrie already has some excellent articles: LINQ to SQL (Part 6: Retrieving Data Using Stored Procedures) LINQ to SQL (Part 7: Updating our Database using Stored Procedures) LINQ to SQL (Part 8: Executing Custom SQL Expressions) Data changing overhead By looking into the data updating process, it also needs a lot of work: Begins transaction Processes the changes (ChangeProcessor) Walks through the objects to identify the changes Determines the order of the changes Executes the changings LINQ queries may be needed to execute the changings, like the first example in this article, an object needs to be retrieved before changed, then the above whole process of data retrieving will be went through If there is user customization, it will be executed, for example, a table’s INSERT / UPDATE / DELETE can be customized in the O/R designer It is important to keep these overhead in mind. Bulk deleting / updating Another thing to be aware is the bulk deleting:private static void DeleteProducts(int categoryId) { using (NorthwindDataContext database = new NorthwindDataContext()) { database.Products.DeleteAllOnSubmit( database.Products.Where(product => product.CategoryID == categoryId)); database.SubmitChanges(); } } The expected SQL should be like:BEGIN TRANSACTION exec sp_executesql N'DELETE FROM [dbo].[Products] AS [t0] WHERE [t0].[CategoryID] = @p0',N'@p0 int',@p0=9 COMMIT TRANSACTION Hoverer, as fore mentioned, the actual SQL is to retrieving the entities, and then delete them one by one:-- Retrieves the entities to be deleted: exec sp_executesql N'SELECT [t0].[ProductID], [t0].[ProductName], [t0].[SupplierID], [t0].[CategoryID], [t0].[QuantityPerUnit], [t0].[UnitPrice], [t0].[UnitsInStock], [t0].[UnitsOnOrder], [t0].[ReorderLevel], [t0].[Discontinued] FROM [dbo].[Products] AS [t0] WHERE [t0].[CategoryID] = @p0',N'@p0 int',@p0=9 -- Deletes the retrieved entities one by one: BEGIN TRANSACTION exec sp_executesql N'DELETE FROM [dbo].[Products] WHERE ([ProductID] = @p0) AND ([ProductName] = @p1) AND ([SupplierID] IS NULL) AND ([CategoryID] = @p2) AND ([QuantityPerUnit] IS NULL) AND ([UnitPrice] = @p3) AND ([UnitsInStock] = @p4) AND ([UnitsOnOrder] = @p5) AND ([ReorderLevel] = @p6) AND (NOT ([Discontinued] = 1))',N'@p0 int,@p1 nvarchar(4000),@p2 int,@p3 money,@p4 smallint,@p5 smallint,@p6 smallint',@p0=78,@p1=N'Optimus Prime',@p2=9,@p3=$0.0000,@p4=0,@p5=0,@p6=0 exec sp_executesql N'DELETE FROM [dbo].[Products] WHERE ([ProductID] = @p0) AND ([ProductName] = @p1) AND ([SupplierID] IS NULL) AND ([CategoryID] = @p2) AND ([QuantityPerUnit] IS NULL) AND ([UnitPrice] = @p3) AND ([UnitsInStock] = @p4) AND ([UnitsOnOrder] = @p5) AND ([ReorderLevel] = @p6) AND (NOT ([Discontinued] = 1))',N'@p0 int,@p1 nvarchar(4000),@p2 int,@p3 money,@p4 smallint,@p5 smallint,@p6 smallint',@p0=79,@p1=N'Bumble Bee',@p2=9,@p3=$0.0000,@p4=0,@p5=0,@p6=0 -- ... COMMIT TRANSACTION And the same to the bulk updating. This is really not effective and need to be aware. Here is already some solutions from the Internet, like this one. The idea is wrap the above SELECT statement into a INNER JOIN:exec sp_executesql N'DELETE [dbo].[Products] FROM [dbo].[Products] AS [j0] INNER JOIN ( SELECT [t0].[ProductID], [t0].[ProductName], [t0].[SupplierID], [t0].[CategoryID], [t0].[QuantityPerUnit], [t0].[UnitPrice], [t0].[UnitsInStock], [t0].[UnitsOnOrder], [t0].[ReorderLevel], [t0].[Discontinued] FROM [dbo].[Products] AS [t0] WHERE [t0].[CategoryID] = @p0) AS [j1] ON ([j0].[ProductID] = [j1].[[Products])', -- The Primary Key N'@p0 int',@p0=9 Query plan overhead The last thing is about the SQL Server query plan. Before .NET 4.0, LINQ to SQL has an issue (not sure if it is a bug). LINQ to SQL internally uses ADO.NET, but it does not set the SqlParameter.Size for a variable-length argument, like argument of NVARCHAR type, etc. So for two queries with the same SQL but different argument length:using (NorthwindDataContext database = new NorthwindDataContext()) { database.Products.Where(product => product.ProductName == "A") .Select(product => product.ProductID).ToArray(); // The same SQL and argument type, different argument length. database.Products.Where(product => product.ProductName == "AA") .Select(product => product.ProductID).ToArray(); } Pay attention to the argument length in the translated SQL:exec sp_executesql N'SELECT [t0].[ProductID] FROM [dbo].[Products] AS [t0] WHERE [t0].[ProductName] = @p0',N'@p0 nvarchar(1)',@p0=N'A' exec sp_executesql N'SELECT [t0].[ProductID] FROM [dbo].[Products] AS [t0] WHERE [t0].[ProductName] = @p0',N'@p0 nvarchar(2)',@p0=N'AA' Here is the overhead: The first query’s query plan cache is not reused by the second one:SELECT sys.syscacheobjects.cacheobjtype, sys.dm_exec_cached_plans.usecounts, sys.syscacheobjects.[sql] FROM sys.syscacheobjects INNER JOIN sys.dm_exec_cached_plans ON sys.syscacheobjects.bucketid = sys.dm_exec_cached_plans.bucketid; They actually use different query plans. Again, pay attention to the argument length in the [sql] column (@p0 nvarchar(2) / @p0 nvarchar(1)). Fortunately, in .NET 4.0 this is fixed:internal static class SqlTypeSystem { private abstract class ProviderBase : TypeSystemProvider { protected int? GetLargestDeclarableSize(SqlType declaredType) { SqlDbType sqlDbType = declaredType.SqlDbType; if (sqlDbType <= SqlDbType.Image) { switch (sqlDbType) { case SqlDbType.Binary: case SqlDbType.Image: return 8000; } return null; } if (sqlDbType == SqlDbType.NVarChar) { return 4000; // Max length for NVARCHAR. } if (sqlDbType != SqlDbType.VarChar) { return null; } return 8000; } } } In this above example, the translated SQL becomes:exec sp_executesql N'SELECT [t0].[ProductID] FROM [dbo].[Products] AS [t0] WHERE [t0].[ProductName] = @p0',N'@p0 nvarchar(4000)',@p0=N'A' exec sp_executesql N'SELECT [t0].[ProductID] FROM [dbo].[Products] AS [t0] WHERE [t0].[ProductName] = @p0',N'@p0 nvarchar(4000)',@p0=N'AA' So that they reuses the same query plan cache: Now the [usecounts] column is 2.

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  • W2k8, Sybase Driver, Permissions

    - by Clustermagnet
    Trying to get a .net (32bit) app running on a Windows 2008 server. My experience in the Windows world is quite limited. Is this related to the Full/Medium trust settings? Have been Googling for quite some time. Appreciate your feedback! Seeing the following error: Required permissions cannot be acquired. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.Security.Policy.PolicyException: Required permissions cannot be acquired. Source Error: An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below. Stack Trace: [PolicyException: Required permissions cannot be acquired.] System.Security.SecurityManager.ResolvePolicy(Evidence evidence, PermissionSet reqdPset, PermissionSet optPset, PermissionSet denyPset, PermissionSet& denied, Boolean checkExecutionPermission) +7606467 System.Security.SecurityManager.ResolvePolicy(Evidence evidence, PermissionSet reqdPset, PermissionSet optPset, PermissionSet denyPset, PermissionSet& denied, Int32& securitySpecialFlags, Boolean checkExecutionPermission) +57 [FileLoadException: Could not load file or assembly 'Sybase.Data.AseClient, Version=1.155.1000.0, Culture=neutral, PublicKeyToken=26e0f1529304f4a7' or one of its dependencies. Failed to grant minimum permission requests. (Exception from HRESULT: 0x80131417)] System.Reflection.Assembly._nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, Assembly locationHint, StackCrawlMark& stackMark, Boolean throwOnFileNotFound, Boolean forIntrospection) +0 System.Reflection.Assembly.nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, Assembly locationHint, StackCrawlMark& stackMark, Boolean throwOnFileNotFound, Boolean forIntrospection) +43 System.Reflection.Assembly.InternalLoad(AssemblyName assemblyRef, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection) +127 System.Reflection.Assembly.InternalLoad(String assemblyString, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection) +142 System.Reflection.Assembly.Load(String assemblyString) +28 System.Web.Configuration.CompilationSection.LoadAssemblyHelper(String assemblyName, Boolean starDirective) +46 [ConfigurationErrorsException: Could not load file or assembly 'Sybase.Data.AseClient, Version=1.155.1000.0, Culture=neutral, PublicKeyToken=26e0f1529304f4a7' or one of its dependencies. Failed to grant minimum permission requests. (Exception from HRESULT: 0x80131417)] System.Web.Configuration.CompilationSection.LoadAssemblyHelper(String assemblyName, Boolean starDirective) +613 System.Web.Configuration.CompilationSection.LoadAllAssembliesFromAppDomainBinDirectory() +203 System.Web.Configuration.CompilationSection.LoadAssembly(AssemblyInfo ai) +105 System.Web.Compilation.BuildManager.GetReferencedAssemblies(CompilationSection compConfig) +178 System.Web.Compilation.WebDirectoryBatchCompiler..ctor(VirtualDirectory vdir) +163 System.Web.Compilation.BuildManager.BatchCompileWebDirectoryInternal(VirtualDirectory vdir, Boolean ignoreErrors) +53 System.Web.Compilation.BuildManager.BatchCompileWebDirectory(VirtualDirectory vdir, VirtualPath virtualDir, Boolean ignoreErrors) +175 System.Web.Compilation.BuildManager.CompileWebFile(VirtualPath virtualPath) +86 System.Web.Compilation.BuildManager.GetVPathBuildResultInternal(VirtualPath virtualPath, Boolean noBuild, Boolean allowCrossApp, Boolean allowBuildInPrecompile) +261 System.Web.Compilation.BuildManager.GetVPathBuildResultWithNoAssert(HttpContext context, VirtualPath virtualPath, Boolean noBuild, Boolean allowCrossApp, Boolean allowBuildInPrecompile) +101 System.Web.Compilation.BuildManager.GetVirtualPathObjectFactory(VirtualPath virtualPath, HttpContext context, Boolean allowCrossApp, Boolean noAssert) +126 System.Web.Compilation.BuildManager.CreateInstanceFromVirtualPath(VirtualPath virtualPath, Type requiredBaseType, HttpContext context, Boolean allowCrossApp, Boolean noAssert) +62 System.Web.UI.PageHandlerFactory.GetHandlerHelper(HttpContext context, String requestType, VirtualPath virtualPath, String physicalPath) +33 System.Web.UI.PageHandlerFactory.GetHandler(HttpContext context, String requestType, String virtualPath, String path) +37 System.Web.MaterializeHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +307 System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +155 Version Information: Microsoft .NET Framework Version:2.0.50727.4959; ASP.NET Version:2.0.50727.4955

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  • How to create a very simple external FastCGI configuration in apache?

    - by Thiado de Arruda
    I have an externally started FastCGI application that listens on socket '/tmp/foo.sock' and a directory of static files in '/srv/static'. Apache has all needed permissions on the socket and the directories. What I need : All requests starting with '/static' should be handled by apache using the contents of '/srv/static'. All other requests should be handled by the FastCGI application. Here is my current virtual host configuration: <VirtualHost *:80> ServerAdmin [email protected] ServerName www.foo.com ServerAlias foo.com Alias /static /srv/static FastCgiExternalServer /* -socket /tmp/foo.sock ErrorLog /var/log/apache2/error.log # Possible values include: debug, info, notice, warn, error, crit, # alert, emerg. LogLevel warn CustomLog /var/log/apache2/access.log combined </VirtualHost> Even though this seems simple, its giving me quite the headache. According to http://www.fastcgi.com/mod_fastcgi/docs/mod_fastcgi.html#FastCgiExternalServer the first parameter to 'FastCgiExternalServer' should be a 'filename' that when matched will cause apache to delegate the request to the external FastCGI app. What am I missing here?

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  • How to make a file load in my program when a user double clicks an associated file.

    - by Edward Boyle
    I assume in this article that file extension association has been setup by the installer. I may address file extension association at a later date, but for the purpose of this article, I address what sometimes eludes new C# programmers. This is sometimes confusing because you just don’t think about it — you have to access a file that you rarely access when making Windows forms applications, “Program.cs” static class Program { /// /// The main entry point for the application. /// [STAThread] static void Main() { Application.EnableVisualStyles(); Application.SetCompatibleTextRenderingDefault(false); Application.Run(new Form1()); } } There are so many ways to skin this cat, so you get to see how I skinned my last cat. static class Program { /// /// The main entry point for the application. /// [STAThread] static void Main(string[] args) { Application.EnableVisualStyles(); Application.SetCompatibleTextRenderingDefault(false); Form1 mainf = new Form1(); if (args.Length > 0) { try { if (System.IO.File.Exists(args[0])) { mainf.LoadFile= args[0]; } } catch { MessageBox.Show("Could not open file.", "Could not open file.", MessageBoxButtons.OK, MessageBoxIcon.Information); } } Application.Run(mainf); } } It may be easy to miss, but don’t forget to add the string array for the command line arguments: static void Main(string[] args) this is not a part of the default program.cs You will notice the mainf.LoadFile property. In the main form of my program I have a property for public string LoadFile ... and the field private string loadFile = String.Empty; in the forms load event I check the value of this field. private void Form1_Load(object sender, EventArgs e) { if(loadFile != String.Empty){ // The only way this field is NOT String.empty is if we set it in // static void Main() of program.cs // LOAD it however it is needed OpenFile, SetDatabase, whatever you use. } }

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  • Render an image with separate layers for shadows/reflections in 3D Studio Max?

    - by Bernd Plontsch
    I have a scene with a simple object standing on a ground in the center. Caused by lights and the ground material there is some shadow and reflection on the ground surrounding the object. How can I render an image containing 3 separate layers for the object the ground the reflection / shadow on the ground Which format to use for this (it should include all 3 layers + I should be able to enable/disable them in Photoshop)? How do I define or prepare those layers for being rendering as image layers?

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  • CISCO 2911 Router configuration

    - by bala
    Device cisco 2911 router configuration support is required please. I have exchange server 2010 configured and working without any errors the problem is in cisco router configuration when exchange server sends emails out the receives WAN IP not the public ip. I have configured RDNS lookups with our MX record IP addesses that match the FQDN but all our emails are rejected because it does not match with the public ip. Receiving mails problem is not an problem all mails are coming through. i am sure i am missing something on the router configuration that does not sends the public ip, can any one help me to solve this issue. Note; I've got 1 WAN IP & 8 Public IP from ISP . Find below the running configuration. Building configuration... Current configuration : 2734 bytes ! ! Last configuration change at 06:32:13 UTC Tue Apr 3 2012 ! NVRAM config last updated at 06:32:14 UTC Tue Apr 3 2012 ! NVRAM config last updated at 06:32:14 UTC Tue Apr 3 2012 version 15.1 service timestamps debug datetime msec service timestamps log datetime msec service password-encryption ! hostname BSBG-LL ! boot-start-marker boot-end-marker ! ! enable secret 5 $x$xHrxxxxx5ox0 enable password 7 xx23xx5FxxE1xx044 ! no aaa new-model ! no ipv6 cef ip source-route ip cef ! ! ! ! ! ip flow-cache timeout active 1 ip domain name yourdomain.com ip name-server 213.42.20.20 ip name-server 195.229.241.222 multilink bundle-name authenticated ! ! crypto pki token default removal timeout 0 ! ! license udi pid CISCO2911/K9 ! ! username bsbg ! ! ! ! ! ! interface Embedded-Service-Engine0/0 no ip address shutdown ! interface GigabitEthernet0/0 ip address 192.168.0.9 255.255.255.0 ip flow ingress ip nat inside ip virtual-reassembly in duplex auto speed 100 no cdp enable ! interface GigabitEthernet0/1 ip address 213.42.xx.x2 255.255.255.252 ip nat outside ip virtual-reassembly in duplex auto speed auto no cdp enable ! interface GigabitEthernet0/2 no ip address shutdown duplex auto speed auto ! ip forward-protocol nd ! no ip http server no ip http secure-server ! ip nat inside source list 120 interface GigabitEthernet0/1 overload ip nat inside source static tcp 192.168.0.4 25 94.56.89.100 25 extendable ip nat inside source static tcp 192.168.0.4 53 94.56.89.100 53 extendable ip nat inside source static udp 192.168.0.4 53 94.56.89.100 53 extendable ip nat inside source static tcp 192.168.0.4 110 94.56.89.100 110 extendable ip nat inside source static tcp 192.168.0.4 443 94.56.89.100 443 extendable ip nat inside source static tcp 192.168.0.4 587 94.56.89.100 587 extendable ip nat inside source static tcp 192.168.0.4 995 94.56.89.100 995 extendable ip nat inside source static tcp 192.168.0.4 3389 94.56.89.100 3389 extendable ip nat inside source static tcp 192.168.0.4 443 94.56.89.101 443 extendable ip nat inside source static tcp 192.168.0.12 80 94.56.89.102 80 extendable ip nat inside source static tcp 192.168.0.12 443 94.56.89.102 443 extendable ip nat inside source static tcp 192.168.0.12 3389 94.56.89.102 3389 extendable ip route 0.0.0.0 0.0.0.0 213.42.69.41 ! access-list 120 permit ip 192.168.0.0 0.0.0.255 any ! ! ! control-plane ! ! ! line con 0 exec-timeout 5 0 line aux 0 line 2 no activation-character no exec transport preferred none transport input all transport output pad telnet rlogin lapb-ta mop udptn v120 ssh stopbits 1 line vty 0 4 password 7 xx64xxD530D26086Dxx login transport input all ! scheduler allocate 20000 1000 end

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  • IBM PS/2 Keyboard with OS X 10.6 and PS2->USB Converter

    - by public static void
    Just got a new Mac Pro at work and as I can't stand the ZX Spectrum-esque 'dead flies' feel of the new Apple keyboards, I brought my trusty IBM SpaceSaver II to the office (with a USB/PS2 adapter) All seems generally to work ok - even the Trackpoint 'nipple' but periodically the modifier keys, notably the Ctrl and Windows keys seem to go into 'sticky' mode so that typing an 'S' brings up the save dialog, 'O' = open dialog etc. etc. Its generally fixed by switching windows and then returning back to the offending one, but this is really beginning to cheese me off. Can anyone suggest a fix?

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  • How can I use timer to stop another thread? [on hold]

    - by Haoda Fu
    How can we stop another thread based on a timer? I was trying to use timer to stop another thread. But I didn't got a success. To better illustrate my point and for your easy to understand the key issue. I made the following sample example. Your help is really appreciated using System; using System.Collections.Generic; using System.Text; using System.Threading; using System.Timers; namespace TestCodes { public static class Program { private static Thread nT = new Thread(PrintABC); private static System.Timers.Timer aTimer; public static void Main() { aTimer = new System.Timers.Timer(1000); aTimer.Elapsed += TimerCallback; aTimer.Interval = 1000; aTimer.Enabled = true; nT.Start(); Console.ReadLine(); } private static void TimerCallback(Object o, ElapsedEventArgs e) { nT.Join(); Console.WriteLine("Complete the PrintABC"); GC.Collect(); } private static void PrintABC() { for (int iter = 1; iter < 300; iter++) { Console.WriteLine(iter+"abc"); Console.ReadKey(); //Thread.Sleep(100); } } } }

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  • configuration issue with respect to .htaccess file on ubuntu

    - by Registered User
    I am building an application tshirtshop I have following configuration in /etc/apache2/sites-enabled/tshirtshop <VirtualHost *:80> ServerAdmin webmaster@localhost DocumentRoot /var/www/tshirtshop <Directory /var/www/tshirtshop> Options Indexes FollowSymLinks AllowOverride All Order allow,deny allow from all </Directory> ErrorLog ${APACHE_LOG_DIR}/error.log # Possible values include: debug, info, notice, warn, error, crit, # alert, emerg. LogLevel warn CustomLog ${APACHE_LOG_DIR}/access.log combined </VirtualHost> and following in .htaccess file in location /var/www/tshirtshop/.htaccess <IfModule mod_rewrite.c> # Enable mod_rewrite RewriteEngine On # Specify the folder in which the application resides. # Use / if the application is in the root. RewriteBase /tshirtshop #RewriteBase / # Rewrite to correct domain to avoid canonicalization problems # RewriteCond %{HTTP_HOST} !^www\.example\.com # RewriteRule ^(.*)$ http://www.example.com/$1 [R=301,L] # Rewrite URLs ending in /index.php or /index.html to / RewriteCond %{THE_REQUEST} ^GET\ .*/index\.(php|html?)\ HTTP RewriteRule ^(.*)index\.(php|html?)$ $1 [R=301,L] # Rewrite category pages RewriteRule ^.*-d([0-9]+)/.*-c([0-9]+)/page-([0-9]+)/?$ index.php?DepartmentId=$1&CategoryId=$2&Page=$3 [L] RewriteRule ^.*-d([0-9]+)/.*-c([0-9]+)/?$ index.php?DepartmentId=$1&CategoryId=$2 [L] # Rewrite department pages RewriteRule ^.*-d([0-9]+)/page-([0-9]+)/?$ index.php?DepartmentId=$1&Page=$2 [L] RewriteRule ^.*-d([0-9]+)/?$ index.php?DepartmentId=$1 [L] # Rewrite subpages of the home page RewriteRule ^page-([0-9]+)/?$ index.php?Page=$1 [L] # Rewrite product details pages RewriteRule ^.*-p([0-9]+)/?$ index.php?ProductId=$1 [L] </IfModule> the site is working on localhost and is working as if there is no .htaccess rule specified i.e. if I were to view a page as http://localhost/tshirtshop/nature-d2 then I get a 404 Error but if I view the same page as http://localhost/tshirtshop/index.php?DepartmentId=2 then I can view it. sudo apache2ctl -M Loaded Modules: core_module (static) log_config_module (static) logio_module (static) mpm_prefork_module (static) http_module (static) so_module (static) alias_module (shared) auth_basic_module (shared) authn_file_module (shared) authz_default_module (shared) authz_groupfile_module (shared) authz_host_module (shared) authz_user_module (shared) autoindex_module (shared) cgi_module (shared) deflate_module (shared) dir_module (shared) env_module (shared) mime_module (shared) negotiation_module (shared) php5_module (shared) reqtimeout_module (shared) rewrite_module (shared) setenvif_module (shared) status_module (shared) Syntax OK What is the mistake if any one can point out in above configuration, or else I need to check any thing else?

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  • What is a good partitioning design/scheme for a multi-boot *nix system?

    - by static
    I'm planning to install Debian on my server. I would like to design the partitioning scheme in such a way, that I could install one or more other *nix distributives on that. So, reading many articles I think this scheme could be a good one for the initial idea of multi-boot: /grub /swap /LVM VG1 (for OS1) -> /boot (LV1) / (LV2) /tmp (LV3) /var ... /var/log /home /LVM VG2 (for OS2) -> /boot / /tmp /var /var/log /home ... (other distros) /LVM VG0 (for data) -> /data (LV1) But I'm confused a little bit now: what should be the labels for these partitions (unique or not) and what should be the mounting points looking as (/home (OS1) mounted to /home as well as /home (OS2)...)?

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  • Storing large array of tiles, but allowing easy access to data

    - by Cyral
    I've been thinking about this for a while. I have a 2D tile bases platformer in XNA with a large array of tile data, I've been running into memory problems with large maps. (I will add chunks soon!) Currently, Each tile contains an Item along with other properties like how its rotated, if it has forground / background, etc. An Item is static and has properties like the name, tooltip, type of item, how much light it emits, the collision it does to player, etc. Examples: public class Item { public static List<Item> Items; public Collision blockCollisionType; public string nameOfItem; public bool someOtherVariable,etc,etc public static Item Air public static Item Stone; public static Item Dirt; static Item() { Items = new List<Item>() { (Stone = new Item() { nameOfItem = "Stone", blockCollisionType = Collision.Solid, }), (Air = new Item() { nameOfItem = "Air", blockCollisionType = Collision.Passable, }), }; } } Would be an Item, The array of Tiles would contain a Tile for each point, public class Tile { public Item item; //What type it is public bool onBackground; public int someOtherVariables,etc,etc } Now, Most would probably use an enum, or a form of ID to identify blocks. Well my system is really nice just to find out about an item. I can simply do tiles[x,y].item.Name To get the name for example. I realized my Item property of the tile is over 1000 Bytes! Wow! What I'm looking for is a way to use an ID (Int or byte depending on how many items) instead of an Item but still have a method for retreiving data about the type of item a tile contains.

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  • Is it possible to restrict the connection duration per client on the router (say with OpenWRT)?

    - by static
    How to limit the connection duration per client per period (say, one MAC-address can connect only for 3 hours per week to the network). Where could be defined such a rule? In the firewall? So the rule should define not statically times (this is simple), when the client is allowed to access the network, but the duration of the connection per day/week/month, etc. How/where to implement such rules? Is it possible to do so with OpenWRT/DD-WRT?

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  • Fastest way to check if two square 2D arrays are rotationally and reflectively distinct

    - by kustrle
    The best idea I have so far is to rotate first array by {0, 90, 180, 270} degrees and reflect it horizontally or/and vertically. We basically get 16 variations [1] of first array and compare them with second array. if none of them matches the two arrays are rotationally and reflectively distinct. I am wondering if there is more optimal solution than this brute-force approach? [1] 0deg, no reflection 0deg, reflect over x 0deg, reflect over y 0deg, reflect over x and y 90deg, no reflection ...

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  • What is the `/etc/hostname` used/required for?

    - by static
    I found in the /etc/hostname my IP-address, than I deleted it and each time I use sudo - I get a message and a system email sudo: unable to resolve host (none) or if in the /etc/hostname is saved myhostname than sudo: unable to resolve host (myhostname). I know it is used to set the system's hostname via /etc/init.d/hostname.sh while booting process, but what is this setting required for (programs, services, daemons ...)? What if i set to localhost (so it doesn't happen any sudo: unable to resolve host (none) anymore, but is it still ok?)? UPD1: I found some information here: http://jblevins.org/log/hostname, but it is all about how to use it and not about - why it is required.

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