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  • servlet connection to DB

    - by underW
    Initially, after reading books on the subject, I firmly believed that the algorithm for working with a database from a servlet is as follows: create a connection - connect to the database - form a request - send the request to the database - get the query results - process them - close connection - OK. Now, with a better understanding of the practical side, I realized that nobody does it that way, and everything happens through a connection pool according to the following algorithm: initialize the servlet - create a connection pool - a request comes from a user - take a free connection from the pool - form a request - send the request to the database - get the query results - process them - return the connection back to the pool - ok. Now I have this problem: We have 100 users, they are divided into 10 groups, each group has it's own username and password to connect to the database. Moreover, each group may have different rights to the database. How am I supposed to use a connection pool in this situation? If I understand correctly, a pool is nothing more than just a group of similar connections with a single login and password. And here I have 10 pairs of username / password. It looks like I cannot use the pool in this situation. What should I do?

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  • @Resource annotation is null at run-time.

    - by Andrew
    I'm using GlassFish v3. The following field is declared in a class: @Resource private javax.sql.DataSource _data_source; The following is declare in web.xml: <data-source <namejava:app/env/data</name <class-namecom.mysql.jdbc.Driver</class-name <server-namelocalhost</server-name <port-number3306</port-number <usermyUser</user <passwordmyPass</password </data-source At run-time _data_source is empty. What am I doing wrong?

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  • Expose jar resources over web

    - by Heavy Bytes
    I have a web-service (with Spring-WS). I have a jar with several schemas (schema1.xsd, schema2.xsd and schema3.xsd) which I include in my web service. Is there a way to expose the schemas from the jar through a servlet somehow in my web-service wep app? My Spring MessageDispatcherServlet is mapped to /ws/ I would like my schemas to be exposed to /schemas/schema1.xsd /schemas/schema2.xsd and so on. I have an idea how to do it with a servlet, but it's too verbose and there has to be a nicer way. The way I am thinking is have a servlet filter and everything that hits /schemas/ check if it is in my list of allowed resources and display it. This has to be a server agnostic solution. (For instance http://tuckey.org/urlrewrite/ will not work). Thanks.

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  • combobox in j2me

    - by learn
    how can i keep the combobox on the form in j2me with out using frameworks? i have tried this but it is not showing any drop down for selection. ChoiceGroup CoursePOP = new ChoiceGroup ("Pop Up choice", Choice.EXCLUSIVE, new String[] {"Python", "J2ME","Symbian"}, null);

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  • "Overriding" instance variables in subtype: Possible risks?

    - by sebastiangeiger
    Say I had a class SuperClass and two subclasses SubClassA and SubClassB that inherit from SuperClass. abstract class SuperClass{ ... List someList; ... } class SubClassA extends SuperClass{ ... List<String> someList; ... } class SubClassB extends SuperClass{ ... List<Integer> someList; ... } That way it is convenient because I can get someList.size() in Superclass and have Typesafety in the Subclasses. The problem is that it does not "feel" right, can you think of potential hazards this apporach has that I am not aware of?

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  • need to clean malformed tags using regular expression

    - by Brian
    Looking to find the appropriate regular expression for the following conditions: I need to clean certain tags within free flowing text. For example, within the text I have two important tags: <2004:04:12 and . Unfortunately some of tags have missing "<" or "" delimiter. For example, some are as follows: 1) <2004:04:12 , I need this to be <2004:04:12> 2) 2004:04:12>, I need this to be <2004:04:12> 3) <John Doe , I need this to be <John Doe> I attempted to use the following for situation 1: String regex = "<\\d{4}-\\d{2}-\\d{2}\\w*{2}[^>]"; String output = content.replaceAll(regex,"$0>"); This did find all instances of "<2004:04:12" and the result was "<2004:04:12 ". However, I need to eliminate the space prior to the ending tag. Not sure this is the best way. Any suggestions. Thanks

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  • doubt in Exceptions

    - by Ajay Singh
    class MyException extends Exception { MyException() {} MyException(String msg) { super(msg);} } public class NewException { static void f() throws MyException { System.out.println("throwing exception from f()"); throw new ClassCastException(); } static void g() throws MyException { System.out.println("throwing exception from g()"); throw new MyException("parametrized "); } public static void main(String ...strings ) { try { f(); } catch(MyException e) { e.printStackTrace(System.out); } try { g(); } catch(MyException e) { e.printStackTrace(System.out); } } } In the function f() iam specifying that "MyException " exception will be thrown and actually iam throwing some other exception which has no relation with MyException but still the compiler does not report any complain.Why is it so??

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  • How to create GUI as inner class with WindowBuilder

    - by Tim Kemp
    I would like to use WindowBuilder in Eclipse to construct Swing GUIs. The JPanels I need to build will be inner classes in a non-GUI wrapper, like so: public class MyWrapper extends MyBaseClass { ... class MyPanel extends JPanel { ... } } So my question is this: can I construct MyPanel using WindowBuilder? If so, how should I set it up? If anyone is interested, the wrapper is an abstract base class which the plug-ins I am developing for my app must extend; deployment concerns mean that it's not really practical to put the GUIs in a separate JAR either so I pretty much have to do it this way. My current workflow, which is awful, is to build the GUI in NetBeans and paste the entire generated class into Eclipse where I connect it up to the methods in my wrapper. I am very hopeful that WindowBuilder will let me work more reliably and efficiently if I can trick it into generating code in MyPanel, not MyWrapper. Thanks

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  • Compilation Error related

    - by aparna
    Given: 11. public static void test(String str) { 12. int check = 4; 13. if (check = str.length()) { 14. System.out.print(str.charAt(check -= 1) +", "); 15. } else { 16. System.out.print(str.charAt(0) + ", "); 17. } 18. } and the invocation: 21. test("four"); 22. test("tee"); 23. test("to"); What is the result? A. r, t, t, B. r, e, o, C. Compilation fails. D. An exception is thrown at runtime. Answer: C Can you explain why the compilation fails please?

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  • Partition loop understanding

    - by user1795732
    Why the loop body of the partition method never throws an ArrayIndexOutOfBounds Exception? public static int partition( int[] a, low, high ) { int k = low, m = low; /* loop invariant: * low <= k <= m <= high and * all elements in a[low..k-1] are RED (i.e., < pivot) and * all elements in a[k..m-1] are BLUE (i.e., >= pivot) */ while (m != high) { if (a[m] >= pivot) // a[m] is BLUE { } else { // a[m] is RED swap(a,k,m); k = k+1; } m = m+1; } return k; }

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  • Strange performance behaviour

    - by plastilino
    I'm puzzled with this. In my machine Direct calculation: 375 ms Method calculation: 3594 ms, about TEN times SLOWER If I place the method calulation BEFORE the direct calculation, both times are SIMILAR. Woud you check it in your machine? class Test { static long COUNT = 50000 * 10000; private static long BEFORE; /*--------METHOD---------*/ public static final double hypotenuse(double a, double b) { return Math.sqrt(a * a + b * b); } /*--------TIMER---------*/ public static void getTime(String text) { if (BEFORE == 0) { BEFORE = System.currentTimeMillis(); return; } long now = System.currentTimeMillis(); long elapsed = (now - BEFORE); BEFORE = System.currentTimeMillis(); if (text.equals("")) { return; } String message = "\r\n" + text + "\r\n" + "Elapsed time: " + elapsed + " ms"; System.out.println(message); } public static void main(String[] args) { double a = 0.2223221101; double b = 122333.167; getTime(""); /*--------DIRECT CALCULATION---------*/ for (int i = 1; i < COUNT; i++) { Math.sqrt(a * a + b * b); } getTime("Direct: "); /*--------METHOD---------*/ for (int k = 1; k < COUNT; k++) { hypotenuse(a, b); } getTime("Method: "); } }

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  • Quickest way to clone a GregorianCalendar?

    - by wds
    I'm trying to make a deep copy of an object, including a GregorianCalendar instance. I'm always wary of using clone() and it doesn't seem to have been overridden here, so I'm just doing the copy field by field. Ideally, there'd be a copy constructor, which I could use like so: GregorianCalendar newCalendar = new GregorianCalendar(oldCalendar); Unfortunately I can't find any such functionality in the API and am stuck trying to figure out which fields I need to get an exact copy. So, to make a copy of one of these calendars, how would you do it? Am I missing some simple shortcut here?

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  • Can you use Ant to Build/Modify XML files?

    - by user369701
    I am quite new to ant and have been looking at the tasks. I am trying to generate an xml file. Do I need to call an external process or does ant have some way to do this? It could be as simple as sending a string to a txt file and saving it as a .xml. Is it possible?

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  • Where is the error in my code?

    - by Lulu Larson
    /** Yields: a String that contains each capital Letter (in 'A'..'Z') whose representation is prime */ public static String primeChars() { String s = ""; // inv: s contains each capital in "A'..c-1 whose representation is prime for (char c = 'A'; c <= 'Z'; c=(char)(c+1)) { if (Loops.isPrime((int)c) == true) { s= s+1; } } // s contains each capital in 'A' ..'Z' whose rep is a prime return s; }

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  • Finding occurrences of element before and after the element in Array

    - by user3718040
    I am writing a algorithm, if an array contain 3 does not contain between two 1s. like this int array={5, 2, 10, 3, 15, 1, 2, 2} the above array contain 3, before 3 there is no 1 and after 3 is one 1 it should return True. int array={3,2,18,1,0,3,-11,1,3} in this array after first element of 3 there is two 1 it should return False. I have try following code public class Third { public static void main(String[] args){ int[] array = {1,2,4,3, 1}; for(int i=0;i<array.length;i++) { if(array[i]==3) { for(int j=0;j<array[i];j++) { if(array[j]==1) { System.out.println("I foud One before "+array[j]); }else { break; } System.out.println("yes i found the array:"+array[i]); } for(int z=0;z>array[i];z++) { if(array[z]==1) { System.out.println("I found after 3 is :"+array[z]); } break; } } } } } I am not getting exact result from my above code which i want.

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  • Threadpool with pasistant worker instances

    - by Matt Smokey-waters Holmes
    So basically what im trying to do is queue up tasks in a thread pool to be executed as soon as a worker becomes free, i have found various examples of this but in all cases the examples have been setup to use a new Worker instance for each job, i want persistent workers. Im trying to make a ftp backup tool, i have it working but because of the limitations of a single connection it is slow. What i ideally want to do is have a single connection for scanning directories and building up a file list then four workers to download said files. Here is an example of my worker /** * FTP Worker */ public class Worker implements Runnable { protected FTPClient _ftp; // Connection details protected String _host = ""; protected String _user = ""; protected String _pass = ""; // worker status protected boolean _working = false; public Worker(String host, String user, String pass) { this._host = host; this._user = user; this._pass = pass; } // Check if the worker is in use public boolean inUse() { return this._working; } @Override public void run() { this._ftp = new FTPClient(); this._connect(); } // Download a file from the ftp server public boolean download(String base, String path, String file) { this._working = true; boolean outcome = true; //create directory if not exists File pathDir = new File(base + path); if (!pathDir.exists()) { pathDir.mkdirs(); } //download file try { OutputStream output = new FileOutputStream(base + path + file); this._ftp.retrieveFile(file, output); output.close(); } catch (Exception e) { outcome = false; } finally { this._working = false; return outcome; } } // Connect to the server protected boolean _connect() { try { this._ftp.connect(this._host); this._ftp.login(this._user, this._pass); } catch (Exception e) { return false; } return this._ftp.isConnected(); } // Disconnect from the server protected void _disconnect() { try { this._ftp.disconnect(); } catch (Exception e) { /* do nothing */ } } } and basically i want to be able to call Worker.download(...) for each task in a queue whenever a worker becomes available without having to create a new connection to the ftp server for each download Any help would be appreciated as iv'e never used threads before and I'm going round in circles at the moment

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  • Can a plain servlet be configured as a seam component?

    - by stacker
    I created a plain servlet within a seam-gen (2.1.2) application, now I would like to use injection. Thus I annotated it with @Name and it's recognized as component: INFO [Component] Component: ConfigReport, scope: EVENT, type: JAVA_BEAN, class: com.mycompany.servlet.ConfigReport Unfortunatly the injection of the logger doesn't work NullPointerException in init() import org.jboss.seam.annotations.Logger; import org.jboss.seam.annotations.Name; import org.jboss.seam.log.Log; @Name("ConfigReport") public class ConfigReport extends HttpServlet { @Logger private Log log; public void init(ServletConfig config) throws ServletException { log.info( "BOOM" ); } } Is my approach abusive? What would be the alternatives (the client sending requests to the servlet is curl, not a browser)?

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