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  • Cache JSP based on URL parameter

    - by Satheesh
    I have a jsp file pageshow.jsp and the parameter id, Is there any way to cache the jsp file in server-side based on the url parameter Requesting page pageshow.jsp?id=100 get from cache instead of building from server Requesting page pageshow.jsp?id=200 get from cache instead of building from server Above two pages should have different cache content since their parameter are different This may avoid the rebuilding the jsp file in server side and also decrease the server load

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  • How often should we write unit tests?

    - by Midnight Blue
    Hi, I am recently introduced to the test-driven approach to development by my mentor at work, and he encourages me to write an unit-test whenenver "it makes sense." I understand some benefits of having a throughout unit-test suite for both regression testing and refractoring, but I do wonder how often and how throughout we should write unit-test. My mentor/development lead asks me to write a new unit test-case for a newly written control flow in a method that is already being tested by the exsisting test class, and I think it is an overkill. How often do you write your unit tests, and how detailed do you think your unit tests should be? Thanks!

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  • Generate URL for File

    - by Don
    The default output of File.toURL() is file:/c:/foo/bar These don't appear to work on windows, and need to be changed to file:///c:/foo/bar Does the format file:/c:/foo/bar work correctly on Unix (I don't have a Unix machine to test on)? Is there a library that can take care of generating a URL from a File that is in the correct format for the current environment?

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  • Getting specific values with regex

    - by David
    I need to knowingly isolate each row of the vCard and get its value. For instance, I want to get "5555" from X-CUSTOMFIELD. So far, my thoughts are: "X-CUSTOMFIELD;\d+" I have been looking at some tutorials and I am a little confused with what function to use? What would my regex above return? Would it give me the whole line or just the numerical part (5555)? I was thinking I i get the whole row, I can use substring to get the digits? BEGIN:VCARD VERSION:2.1 N:Last;First; FN:First Last TEL;HOME;VOICE:111111 TEL;MOBILE;VOICE:222222 X-CUSTOMFIELD;5555 END:VCARD

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  • Is there any point in using a volatile long?

    - by Adamski
    I occasionally use a volatile instance variable in cases where I have two threads reading from / writing to it and don't want the overhead (or potential deadlock risk) of taking out a lock; for example a timer thread periodically updating an int ID that is exposed as a getter on some class: public class MyClass { private volatile int id; public MyClass() { ScheduledExecutorService execService = Executors.newScheduledThreadPool(1); execService.scheduleAtFixedRate(new Runnable() { public void run() { ++id; } }, 0L, 30L, TimeUnit.SECONDS); } public int getId() { return id; } } My question: Given that the JLS only guarantees that 32-bit reads will be atomic is there any point in ever using a volatile long? (i.e. 64-bit). Caveat: Please do not reply saying that using volatile over synchronized is a case of pre-optimisation; I am well aware of how / when to use synchronized but there are cases where volatile is preferable. For example, when defining a Spring bean for use in a single-threaded application I tend to favour volatile instance variables, as there is no guarantee that the Spring context will initialise each bean's properties in the main thread.

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  • Error when running a basic Hadoop code

    - by Abhishek Shivkumar
    I am running a hadoop code that has a partitioner class inside the job. But, when I run the command hadoop jar Sort.jar SecondarySort inputdir outputdir I am getting a runtime error that says class KeyPartitioner not org.apache.hadoop.mapred.Partitioner. I have ensured that the KeyPartitioner class has extended the Partitioner class, but why am I getting this error? Here is the driver code: JobConf conf = new JobConf(getConf(), SecondarySort.class); conf.setJobName(SecondarySort.class.getName()); conf.setJarByClass(SecondarySort.class); conf.setInputFormat(TextInputFormat.class); conf.setOutputFormat(TextOutputFormat.class); conf.setMapOutputKeyClass(StockKey.class); conf.setMapOutputValueClass(Text.class); conf.setPartitionerClass((Class<? extends Partitioner<StockKey, DoubleWritable>>) KeyPartitioner.class); conf.setMapperClass((Class<? extends Mapper<LongWritable, Text, StockKey, DoubleWritable>>) StockMapper.class); conf.setReducerClass((Class<? extends Reducer<StockKey, DoubleWritable, Text, Text>>) StockReducer.class); and here is the code of the partitioner class: public class KeyPartitioner extends Partitioner<StockKey, Text> { @Override public int getPartition(StockKey arg0, Text arg1, int arg2) { int partition = arg0.name.hashCode() % arg2; return partition; } }

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  • what can cause large discrepancy between minor GC time and total pause time?

    - by cxcg
    We have a latency-sensitive application, and are experiencing some GC-related pauses we don't fully understand. We occasionally have a minor GC that results in application pause times that are much longer than the reported GC time itself. Here is an example log snippet: 485377.257: [GC 485378.857: [ParNew: 105845K-621K(118016K), 0.0028070 secs] 136492K-31374K(1035520K), 0.0028720 secs] [Times: user=0.01 sys=0.00, real=1.61 secs] Total time for which application threads were stopped: 1.6032830 seconds The total pause time here is orders of magnitude longer than the reported GC time. These are isolated and occasional events: the immediately preceding and succeeding minor GC events do not show this large discrepancy. The process is running on a dedicated machine, with lots of free memory, 8 cores, running Red Hat Enterprise Linux ES Release 4 Update 8 with kernel 2.6.9-89.0.1EL-smp. We have observed this with (32 bit) JVM versions 1.6.0_13 and 1.6.0_18. We are running with these flags: -server -ea -Xms512m -Xmx512m -XX:+UseConcMarkSweepGC -XX:NewSize=128m -XX:MaxNewSize=128m -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+PrintGCApplicationStoppedTime -XX:-TraceClassUnloading Can anybody offer some explanation as to what might be going on here, and/or some avenues for further investigation?

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  • What do the external JSF libraries/frameworks add?

    - by kgrad
    I have seen mention of a bunch of external JSF Libraries such as ICEfaces, Richfaces, etc. However, I am unsure as to what these libraries actually add over just using JSF 2.0. Are they just additional components that are pre-built? I know that PrettyFaces adds URL rewriting, and I Believe that ICEFaces/Richfaces add Ajax enabled components? What are some other major component libraries, what are their benefits / why should people use them? Additionally, what does a framework like SEAM add over using straight JSF2 with EJB? Is MYFaces simply a different implementation of JSF?

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  • Hibernate: fetching multiple bags efficiently

    - by Jens Jansson
    Hi! I'm developing a multilingual application. For this reason many objects have in their name and description fields collections of something I call LocalizedStrings instead of plain strings. Every LocalizedString is basically a pair of a locale and a string localized to that locale. Let's take an example an entity, let's say a book -object. public class Book{ @OneToMany private List<LocalizedString> names; @OneToMany private List<LocalizedString> description; //and so on... } When a user asks for a list of books, it does a query to get all the books, fetches the name and description of every book in the locale the user has selected to run the app in, and displays it back to the user. This works but it is a major performance issue. For the moment hibernate makes one query to fetch all the books, and after that it goes through every single object and asks hibernate for the localized strings for that specific object, resulting in a "n+1 select problem". Fetching a list of 50 entities produces about 6000 rows of sql commands in my server log. I tried making the collections eager but that lead me to the "cannot simultaneously fetch multiple bags"-issue. Then I tried setting the fetch strategy on the collections to subselect, hoping that it would do one query for all books, and after that do one query that fetches all LocalizedStrings for all the books. Subselects didn't work in this case how i would have hoped and it basically just did exactly the same as my first case. I'm starting to run out of ideas on how to optimize this. So in short, what fetching strategy alternatives are there when you are fetching a collection and every element in that collection has one or multiple collections in itself, which has to be fetch simultaneously.

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  • No operations allowed after statement closed issue

    - by Washu
    I have the next methods in my singleton to execute the JDBC connections public void openDB() throws ClassNotFoundException, IllegalAccessException, InstantiationException, SQLException { Class.forName("com.mysql.jdbc.Driver").newInstance(); String url = "jdbc:mysql://localhost/mbpe_peru";//mydb conn = DriverManager.getConnection(url, "root", "admin"); st = conn.createStatement(); } public void sendQuery(String query) throws SQLException { st.executeUpdate(query); } public void closeDB() throws SQLException { st.close(); conn.close(); } And I'm having a problem in a void where i have to call this twice. private void jButton1ActionPerformed(ActionEvent evt) { Main.getInstance().openDB(); Main.getInstance().sendQuery("call insertEntry('"+EntryID()+"','"+SupplierID()+"');"); Main.getInstance().closeDB(); Main.getInstance().openDB(); for(int i=0;i<dataBox.length;i++){ Main.getInstance().sendQuery("call insertCount('"+EntryID()+"','"+SupplierID()+"','"+BoxID()+"'); Main.getInstance().closeDB(); } } I have already tried to keep the connection open and send the 2 querys and after that closed and it didnt work... The only way it worked was to not use the methods, declare the commands for the connection and use different variables for the connection and the statement. I thought that if i close the Connecion and the Statement I could use the variable once again since is a method but I'm not able to. Is there any way to solve this using my methods for the JDBC connection?

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  • How to provide i18n service for developer and end user

    - by user247245
    Many android applications have quite poor i18n-support, and for an understandable reason, as it adds much work for the developer. From a both intuitive and cultural point of view it would be a good thing if end-users could translate the apps themself, and OTA share the translation, without reinstalling the app itself. In concept; as wikipedia, some add content easily, others only use what's there. It's of course important that the service is as easy as possible to use, both for app-developers, and people willing to transcribe. To keep it simple, this is the solution I'm concidering; Developer perspective: Developer uses a customized setContentView when open activities/layouts that will seach for thanslations of xml-entries. (below) The customized version is provided as a free downloadable library/class..., turning the i18n feature to more or less a one liner. User perspective: User downloads app without any translation As app launches, it checks locale running at phone, and will look for a translated xml-file at shared space in SD. If no or old transcribed xml (above), try to download new from internet-service (ansync). This is all done by library above, no need for intents. Translator perspective: Separate app to provide translations for any app using the i18n service above. (Could be just a webapp), with some form of QA on translators/input. QUESTION: Now, for this to work efficiently, it has to be AeasyAP for the developer to even bother, and the most fluent solution would be a customized version of setContentView, that simply loads the translated values from external xml, instead of the ones in the apk. Is this possible at all, and if not, what's your suggested solutions? (And of course, Happy New Year, feliz ano novo, blwyddyn newydd dda, Gott Nytt År, kontan ane nouvo, szczesliwego nowego roku ...) Regards, /T

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  • How to test unescaped &nbsps; as a whitespace

    - by gleery
    I use apache common lang to unescape a block of html text which contains &nbsp;, I want to filter out blocks that contains only whitespaces. But I can't test the   as a whitespace. It's not in the normal whitespace list(http://en.wikipedia.org/wiki/Whitespace_character), and I try to print its Hex form by calling Character.getNumericValue which return -1. &nbsp should be a whitespace,isn't? But How can I test it?

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  • Oval collision detection not working properly

    - by William
    So I'm trying to implement a test where a oval can connect with a circle, but it's not working. edist = (float) Math.sqrt(Math.pow((px + ((pwidth/2) )) - (bx + (bsize/2)), 2) + Math.pow(-((py + ((pwidth/2)) ) - (bx + (bsize/2))), 2)); and here is the full code (requires Slick2D): import org.newdawn.slick.AppGameContainer; import org.newdawn.slick.BasicGame; import org.newdawn.slick.Color; import org.newdawn.slick.GameContainer; import org.newdawn.slick.Graphics; import org.newdawn.slick.Input; import org.newdawn.slick.SlickException; public class ColTest extends BasicGame{ float px = 50; float py = 50; float pheight = 50; float pwidth = 50; float bx = 200; float by = 200; float bsize = 200; float edist; float pspeed = 3; Input input; public ColTest() { super("ColTest"); } @Override public void init(GameContainer gc) throws SlickException { } @Override public void update(GameContainer gc, int delta) throws SlickException { input = gc.getInput(); try{ if(input.isKeyDown(Input.KEY_UP)) py-=pspeed; if(input.isKeyDown(Input.KEY_DOWN)) py+=pspeed; if(input.isKeyDown(Input.KEY_LEFT)) px-=pspeed; if(input.isKeyDown(Input.KEY_RIGHT)) px+=pspeed; } catch(Exception e){} } public void render(GameContainer gc, Graphics g) throws SlickException { g.setColor(new Color(255,255,255)); g.drawString("col: " + col(), 10, 10); g.drawString("edist: " + edist + " dist: " + dist, 10, 100); g.fillRect(px, py, pwidth, pheight); g.setColor(new Color(255,0,255)); g.fillOval(px, py, pwidth, pheight); g.setColor(new Color(255,255,255)); g.fillOval(200, 200, 200, 200); } public boolean col(){ edist = (float) Math.sqrt(Math.pow((px + ((pwidth/2) )) - (bx + (bsize/2)), 2) + Math.pow(-((py + ((pwidth/2)) ) - (bx + (bsize/2))), 2)); if(edist <= (bsize/2) + (px + (pwidth/2))) return true; else return false; } public float rotate(float x, float y, float ox, float oy, float a, boolean b) { float dst = (float) Math.sqrt(Math.pow(x-ox,2.0)+ Math.pow(y-oy,2.0)); float oa = (float) Math.atan2(y-oy,x-ox); if(b) return (float) Math.cos(oa + Math.toRadians(a))*dst+ox; else return (float) Math.sin(oa + Math.toRadians(a))*dst+oy; } public static void main(String[] args) throws SlickException { AppGameContainer app = new AppGameContainer( new ColTest() ); app.setShowFPS(false); app.setAlwaysRender(true); app.setTargetFrameRate(60); app.setDisplayMode(800, 600, false); app.start(); } }

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  • issue of JSTL forEach iterate from arrayList

    - by Mickey
    In my code, I have used ArrayList which stores the number format like '$0.00 to $1,000,000.00' in each index of array list. while iterate in JSP through tag, its values are printing like $0.00 to $1 as a first string, 000 as a second string and 000.00 as a thrid string. but it has to print like '$0.00 to $1,000,000.00'. what will be the problem is? Thanks in advance

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  • How do I prevent use of beta classes from google guava library?

    - by mjlee
    We have been using Google collections in the production for several months. We would like to start using guava for additional functions. However, I'm afraid to bring guava into our product stack b/c some developers may start to use 'beta' classes. We have various unit-tests in our code but at this point, I prefer not to include 'beta' class b/c it is subject to change in the future. Is there any easy way to do detect if the project includes any 'beta' guava classes?

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  • android - How to draw only the sprite from an image on the canvas

    - by user1320494
    this is the first time for me here, so I hope I'm doing this right :) My question is the following: how do I draw the sprite from an image on the canvas, so that I don't get the entire (squared) image to show, but only the parts of the image I want (= the sprite). For example, I have an image of a robot on a white background and I only want to see the robot, and not the white background. I hope someone here can help me with this problem, because it's giving me headaches of not knowing how to do it :P

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  • Why I cannot see an image if I do not use the full name of an image?

    - by Roman
    I try to add an image to JPanel. It works if I specify the full name of the image (including name of all folders). But I want my software to be machine independent (another machine does not have the same folder structure as my machine has). So, I put my image to the same place where the source is and in my code I use just name of the image (no folders' names). It does not work. I put my image into the folder where my executables are. It does not work again. So, why it does not work and what can I do with that?

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  • listView.setAdapter doesn't work

    - by Bowiz2
    I have a listview called quotesList, and I am trying to use an adapter to put information in it. Here is my code: ListView listView = (ListView) findViewById(R.id.quotesList); String[]values={"Android","iOS","Windows Phone","Other Stuff"}; ArrayAdapter<String> adapter=new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1, android.R.id.text1,values); listView.setAdapter(adapter); The only error that Eclipse shows is in the listView.setAdapter(adapter) line. The bold represents where the red squiggly is. Syntax error on token "adapter", VariableDeclaratorId expected after this token The period after listView gives an error as well, but I'm pretty sure its just related to the other error, as its a syntax error. Syntax error on token(s), misplaced construct(s) Thanks in advance!

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  • How to dynamically import javascript and css files

    - by marcos
    i Want to import a given css or javascript file depending os some conditions, in my Servlet i have: protected void doPost(...) { if(condition) { //import some javascript or css file here } } I need this behavior since i have too many files to import and the files name may vary according to the condition Is it possible?

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  • Benefits of arrays

    - by Vitalii Fedorenko
    As I see it, the advantages of List over array are pretty obvious: Generics provide more precise typing: List<Integer>, List<? extends Number>, List<? super Integer>. List interface has a bunch useful methods: addAll, remove etc. While for arrays all standard operations except get/set must be performed in a procedure manner by passing it to a static method. Collections offer different implementations like ArrayList, LinkedList, unmodifieable and synchronized lists, which can be hidden under common List interface. OOB length control. As disadvantages I can only mention absence of syntactic sugar and runtime type check. At the same time supporting of both structures requires frequent using of asList and toArray methods, which makes code less readable. So I am curious if there are any important benefits of using arrays that I miss.

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