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• Check if table exists

  - by Dmitry

  I have a desktop application with a database embedded in it. When I execute my program I need to check that specific table exists, or create it if not. Given a Connection object named conn for my database, how could I check this?

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• Pass Alot of Parameters on a Form to Action Struts2

  - by Neeraj

  I have been working on migrating a web application from Struts1 to Struts2. I have a simple Form with around 45 Fields (basically a grid with data). I have to capture all those in Struts2 Action.I noticed that in struts2 we have OGNL through which we just write getters setters in action itself by declaring fields locally to get those variables flowing in the request. I cannot write 45 getters/setters in my action, there must be a way to pass whole object(a POJO) from jsp to Action layer. In Struts 1, we normally get a ActionForm Object and/or get request parameters in a map and then populate. Any help or suggestions will be appreciated.

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• Reflection: take values from an unknown running alpplication

  - by Dr.Lesh

  I'm writing an application that searchs for Semaphore types in the fields of unknown classes in unknown application (passed by user). I made it using Reflection and it worked. Now I want to fill up these semaphores with values, taking them from a running instance of this unknown application. So i took the class with "main" method of this unknown application, made a newInstance, and passed it when invoking the main method to start the application: Class mainClass = getItSomeWhere(); Object instance = mainClass.newInstance(); Method mainMethod = mainClass.getDeclaredMethod("main", new Class[]{String[].class}); mainMethod.invoke(instance, new Object[]{args}); and it worked fine. Now, how can I get the semaphore values, taking them from the classes of this running application, when I only have an instance of the main class? Many thanks for the answers.

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• Creating custom Android project templates in Eclipse?

  - by Rich

  Every app I make starts out with a number of common base classes, interfaces, utility classes and a basic package structure that has been working for me. Is there a way for me to set up a project template in Eclipse that will give me all of the basic Android project stuff PLUS a bunch of custom packages, classes and interfaces? I guess I could just put all of this stuff into one or more libraries as opposed to creating a whole project template, so if you have a preferred approach or information/links/etc on how to do any of the above, please share (I'm relatively inexperienced with Eclipse, so the more detail the better). Thanks.

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• download file exception handling

  - by klaus-vlad

  Hi, In my application I download several critical files from a server, and I want to write some code that handles the case where the a file download didn't complete for a reason or other ,to retry downloading it at next startup. The function that downloads a file at a time however throws only MalformedURLException and IOException , but if these exceptions are thrown that means that the download didn't even begin. How should I arrange things so I can treat the case where a download failed , even if it began ? download(String file) throws MalformedURLException ,IOException { }

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• longest common subsequence

  - by davit-datuashvili

  i have following code public class LCS1 { public static String lcs(String a,String b) { String x; String y; int alen=a.length(); int blen=b.length(); if (alen==0 || blen==0) { return ""; } else if (a.charAt(alen-1)==b.charAt(blen-1)) { return lcs(a.substring(0,alen-1),b.substring(0,blen-1)); } else { x=lcs(a,b.substring(0,blen-1)); y=lcs(a.substring(0,alen-1),b); } return (x.length()>y.length()) ? x : y; } public static void main(String[]args){ String a="computer"; String b="houseboat"; System.out.println(lcs(a,b)); } } it should return "out" but returns nothing what is problem?

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• What is null an instanceof?

  - by kunjaan

  Is null an instance of anything? What set does 'null' belong to? What is null? How is it represented in the memory?

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• calendar.getInstance() or calendar.clone()

  - by Pangea

  I need to make a copy of a given date 100s of times (I cannot pass-by-reference). I am wondering which of the below two are better options newTime=Calendar.getInstance().setTime(originalDate); OR newTime=originalDate.clone(); Performance is of main conern here. thx.

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• can't explain NullPointerException

  - by John Pope

  In the following code, i have a method to get a Vector of persons with the same zodiac sign. persoane is a Vector. I keep getting a NullPointerException at the if condition (persoane is definetly not null). I am unable to see why. Any help would be greatly appreciated public Vector<Persoana> cautaDupaZodie(String zodie) { Vector<Persoana> rezultat= new Vector<Persoana>(); for(int i=0; i<persoane.size(); i++) { if(persoane.get(i).getData().getZodie().equals(zodie)) //the exception occurs here { rezultat.add(persoane.get(i)); } } return rezultat; }

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• Binary search in rotated sorted list

  - by Algorist

  I am having a sorted list which is rotated and I would like to do a binary search on that list to find the minimum element. Lets suppose initial list is {1,2,3,4,5,6,7,8} rotated list can be like {5,6,7,8,1,2,3,4} Normal binary search doesn't work in this case. Any idea how to do this.

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• What is the difference between the Facade and Adapter Pattern?

  - by devoured elysium

  I've been reading both definitions and they seem quite the same. Could anyone point out what are their differences? Thanks

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• Jboss Seam Booking Example Extract Shared Libs From Ear

  - by michael lucas

  Example Booking Application, which JBoss Seam is shipped with, build into EAR file of about 7 MB. That's pretty much if you consider deploying this package to a remote Jboss server and possibly redeploying it package many times during your regular work. Lib files like richfaces and jsf-facelet make the lion's share of that EAR size. Why can't we just extract lib files into jboss-web.deployer directory on JBoss 4.2.0 GA server?

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• In ArrayBlockingQueue, why copy into ReentrantLock field into local final variable?

  - by mjlee

  In ArrayBlockingQueue, any method that requires lock will get set 'final' local variable before calling 'lock()'. public boolean offer(E e) { if (e == null) throw new NullPointerException(); final ReentrantLock lock = this.lock; lock.lock(); try { if (count == items.length) return false; else { insert(e); return true; } } finally { lock.unlock(); } } Is there any reason to set a local variable 'lock' from 'this.lock' when field 'this.lock' is final also. Additionally, it also set local variable of E[] before acting on. private E extract() { final E[] items = this.items; E x = items[takeIndex]; items[takeIndex] = null; takeIndex = inc(takeIndex); --count; notFull.signal(); return x; } Is there any reason for copying to local final variable?

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• How to discard time intervals with Time Series / XYPlots using JFreeChart?

  - by Alex Arnon

  Hi All, I am building a set of chart displays, one of which is for a month display of daily trading - that is, one point of data per day (closing). Since there is no trade during weekends and holidays, I need to discard these data points. Not only that, but data points should still appear adjacent to each other, regardless of any gaps in time. This can be seen in any such chart e.g. in the 3 month graph for Nasdaq on Yahoo Finance - see how weekends are skipped. My question is: how should one correctly implement this in JFreeChart? Thanks in advance!

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• How to read log4j output to a web page?

  - by Ran

  I have a web page, used for admin purposes, which runs a task (image fetching from a remote site). In order to be able to debug the task using the browser only, no ssh etc, I'd like to be able to read all log output from the executing thread and spit it out to the web page. The task boils down to: Changing log level for current thread at the beginning of the call and restore when the call is done. Reading all log output by current thread and storing it in a string. So in pseudocode my execute() method would look like this: (I'm using struts2) public String execute() throws Exception { turnLoggingLevelToDebugOnlyForThisThread() ... do stuff... restoreLoggingLevelForThisThread() String logs = readAllLogsByThisThread(); } Can this be done with log4j? I'm using tomcat, struts2, log4j and slf4j.

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• Spring Roo and aspect-oriented programming

  - by marcos

  Hello, i've been running some experiments of my own with Spring Roo and it seems to be pretty cool, but i noticed that this tool makes heavy use of AOP on the model layer. I'm thinking about creating a real project using Roo and what i would like to know is: Why AOP is everywhere? Is That ok? What are advantages and disadvantages of this approach? I'm quite new to aspect-oriented programming and some guidance would be greatly appreciated. Thanks in advance!

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• Encrypt string with public key only

  - by vlahovic

  i'm currently working on a android project where i need to encrypt a string using 128 bit AES, padding PKCS7 and CBC. I don't want to use any salt for this. I've tried loads of different variations including PBEKey but i can't come up with working code. This is what i currently have: String plainText = "24124124123"; String pwd = "BobsPublicPassword"; byte[] key = pwd.getBytes(); key = cutArray(key, 16); byte[] input = plainText.getBytes(); byte[] output = null; SecretKeySpec keySpec = null; keySpec = new SecretKeySpec(key, "AES"); Cipher cipher = Cipher.getInstance("AES/CBC/PKCS7Padding"); cipher.init(Cipher.ENCRYPT_MODE, keySpec); output = cipher.doFinal(input); private static byte[] cutArray(byte[] arr, int length){ byte[] resultArr = new byte[length]; for(int i = 0; i < length; i++ ){ resultArr[i] = arr[i]; } return resultArr; } Any help appreciated //Vlahovic

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• tomcat session replication without multicast

  - by Andreas Petersson

  i am planning to use 2 dedicated root servers rented at a hosting provider. those machines will run tomcat 6 in a cluster. if i will add additional machines later on - it is unlikely that they will be accessible with multicast, because they will be located in different subnets. is it possible to run tomcat without multicast? all tutorials for tomcat 6 clustering include multicast heartbeat. are there any alternatives to SimpleTcpCluster? or are other alternatives more appropriate in this situation?

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• How to use locks/synchronization here

  - by MasterGberry

  I have this code block here and i need to make sure the rankedPlayersWaitingForMatch is synchronized between threads properly. I was going to use synchronize but that i don't think will work here because of the variable being used in the if statement. I read online about final Lock lock = new ReentrantLock(); but I am a bit confused on how to use it in this case properly with the try/finally block. Can I get a quick example? Thanks // start synchronization if (rankedPlayersWaitingForMatch.get(rankedType).size() >= 2) { Player player1 = rankedPlayersWaitingForMatch.get(rankedType).remove(); Player player2 = rankedPlayersWaitingForMatch.get(rankedType).remove(); // end synchronization // ... I don't want this all to be synchronized, just after the first 2 remove() } else { // end synchronization // ... }

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• SSL connection for testing purposes

  - by user308806

  Hello, I'm required to write a SSL connection, but It requires a signed certificate. There is a way to disable the checking so that I can only test my application. Regards,

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• What are the possible causes of JasperException

  - by CitadelCSCadet

  I have a JSP that takes an Arraylist from the session object and removes the items from it. It seemed to be working fine and then out of nowhere when I navigate to that page, the page is blank. I checked the Tomcat log files and in catalina.out I am receiving a JasperException an it is showing it as being on a line with the following for(int i; i < agentItems.size(); i++) agentItems is the name of the ArrayList I am using. I have been debugging it and can't seem to figure out what the problem might be. I have read that a JasperException is sometiems thrown as a JSP's NullPointerException. Is this true or am I just completely overlooking the problem? I have the web application running on a local machine and a intermediate server for development in which both of them have had no trouble. Why could it be that only on this server it is giving me problems?

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• What exception to throw when an important parameter/dependency is missing?

  - by Pentium10

  Take this method public List<String> getGroups() { if (this.getId().equals("")) return null; } I would like to throw exception instead returning null, what's the exception to throw when an important parameter/dependency has not been set?

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• Programatic cache creation

  - by Pablo Fernandez

  I switched from xml to programmatically cache creation and now I can't retrieve my cache by name. Here's a code snippet that shows what I'm doing maybe you can spot an obvious error? http://gist.github.com/405546 (I'm only showing the relevant lines here).

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• Best way to get a Web Service to return a database result as XML?

  - by John

  I am building a webservice using jax-rs and querying a DB2 z/OS database with SQLJ and getting the result set as an arraylist. I would like to return this list as XML, but not sure how to do it. Does anyone have an example of returning a result set as XML and is using an Arraylist the best way to do this? Should I use JAXB? if so how?

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• Read quicktime movie from servlet in a webpage?

  - by khue

  Hi, I have a servlet that construct response to a media file request by reading the file from server: File uploadFile = new File("C:\\TEMP\\movie.mov"); FileInputStream in = new FileInputStream(uploadFile); Then write that stream to the response stream. My question is how do I play the media file in the webpage using embed or object tag to read the media stream from the response? Here is my code in the servlet: public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { request.getParameter("location"); uploadFile(response); } private void uploadFile(HttpServletResponse response) { File transferFile = new File("C:/TEMP/captured.mov"); FileInputStream in = null; try { in = new FileInputStream(transferFile); } catch (FileNotFoundException e) { System.out.println("File not found"); } try { System.out.println("in byes i s" + in.available()); } catch (IOException e) { } DataOutputStream responseStream = null; try { responseStream = new DataOutputStream(response.getOutputStream()); } catch (IOException e) { System.out.println("Io exception"); } try { Util.copyStream(in, responseStream); } catch (CopyStreamException e) { System.out.println("copy Stream exception"); } try { responseStream.flush(); } catch (IOException e) { } try { responseStream.close(); } catch (IOException e) { } } And here is html page as Ryan suggested: <embed SRC="http://localhost:7101/movies/transferservlet" WIDTH=100 HEIGHT=196 AUTOPLAY=true CONTROLLER=true LOOP=false PLUGINSPAGE="http://www.apple.com/quicktime/"> Any ideas?

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