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  • problem in deleting record

    - by akshay
    I have a entity manager em1 .em1 starts a transcation tx on db1 table1.Now inside tx i call a API getdata().This API creastes a new entitymanger em2 and return 1 record.Now if entity manger em1 tries to delete the record returned by em1 , it hangs.Code times out.Is the record locked by em1.How can ii solve this problem? create em1 //em1 start transcation tx1 tx1.start Object r = getData(); em1 tried to delete r //code hangs here tx1.commit Object getData(){ create em2 return data found using em2 }

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  • Is this technically thread safe despite being mutable?

    - by Finbarr
    Yes, the private member variable bar should be final right? But actually, in this instance, it is an atomic operation to simply read the value of an int. So is this technically thread safe? class foo { private int bar; public foo(int bar) { this.bar = bar; } public int getBar() { return bar; } } // assume infinite number of threads repeatedly calling getBar on the same instance of foo.

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  • Should member variables of global objects be made global as well?

    - by David Wong
    I'm developing plugins in Eclipse which mandates the use of singleton pattern for the Plugin class in order to access the runtime plugin. The class holds references to objects such as Configuration and Resources. In Eclipse 3.0 plug-in runtime objects are not globally managed and so are not generically accessible. Rather, each plug-in is free to declare API which exposes the plug-in runtime object (e.g., MyPlugin.getInstance() In order for the other components of my system to access these objects, I have to do the following: MyPlugin.getInstance().getConfig().getValue(MyPlugin.CONFIGKEY_SOMEPARAMETER); , which is overly verbose IMO. Since MyPlugin provides global access, wouldn't it be easier for me to just provide global access to the objects it manages as well? MyConfig.getValue(MyPlugin.CONFIGKEY_SOMEPARAMETER); Any thoughts? (I'm actually asking because I was reading about the whole "Global variable access and singletons are evil" debates)

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  • What is a good solution to link different tables in Hibernate based on some field value?

    - by serg555
    I have article table and several user tables a_user, b_user, ... with exactly the same structure (but different data). I can't change anything in *_user tables except their table name prefix but can change everything else (user tables contain only user information, there is nothing about article or user_type in them). I need to link article to a user (many-to-one), but user table name is defined by user_type field. For example Article table record: ... user_id="5" user_type="a" means that it is linked to a user with id=5 from a_user table (id 5 is not unique in users scope, each user table can have its id 5). Any suggestions how to handle this situation? How can I map this relation in Hibernate (xml mapping, no annotations) so it will automatically pick up correct user for an article during select/update? How should I map user tables (one or multiple classes?)? I would need to run some queries like this: from Article a where a.userType=:type and a.user.name=:name Thanks.

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  • Installer for web application

    - by Xinus
    We have developed a web application which is to be deployed by nontechnical person. Therefor I want to create an installer for it. Installer has functions of installing JVM, Apache Tomcat, and the web application war file depending on whether they are installed or not. Is there any installation suit which I can use to achieve this?

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  • executorservice to read data from database in chuncks and run process on them

    - by TazMan
    I'm trying to write a process that would read data from a database and upload it onto a cloud datastore. How can I decide the partition strategy of the data? I want to query the table in chunks and process each chunk in 10 threads. Each thread basically will send the data to an individual node on a 10 node cluster on the cloud.. Where in the below multi threading code will the dataquery to extract and send 10 concurrent requests for uploading data to cloud would be? public class Caller { public static void main(String[] args) { ExecutorService executor = Executors.newFixedThreadPool(10); for (int i = 0; i < 10; i++) { Runnable worker = new DomainCDCProcessor(i); executor.execute(worker); } executor.shutdown(); while (!executor.isTerminated()) { } System.out.println("Finished all threads"); } }

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  • sqlite database help

    - by mamila
    Hi all i have some questions regarding database in android. 1. in my project, I would like to create a database with single table. i would also like to insert data on this table from word or excel document. is it possible? if so please how can i do it? some code snippets would be of great help. 2. i have four different activities which i would like them to interact with this single table. the first is the main activity and its purpose is just to launch the other three activities according to user choice. so it has no interaction with the db. but the other three activities will read from the table whenever called. can you please tell me how to call the dbhelper on these activities. am kind of unable to do this.and am currently creating one db per each activity which is not the optimal way. any help is really appreciated and would be better if very soon tahnks

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  • Should we or should we not check in the classes folder in WEB-INF directory into SVN?

    - by Vatsala
    I use SVN, and am learning how to use it along with eclipse IDE. The first time I add classes to my package, there is no problem, the generated class files get into SVN smoothly. The moment I edit them, I get this message - "WEB-INF/classes" is obstructed. I try the "clean-up" command and the clean up command says "WEB-INF/classes" folder is locked. I use TortoiseSVN as my SVN client. I know why this is happening. It probably because the Eclipse overwrites all the files while generating classes and then causes this - Is it inappropriate to commit the class files into SVN? If not, what should I do to commit these class files smoothly?

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  • tiled images in swing

    - by sasquatch90
    I have task to prepare two windows with swing. One contains grid of squares, with random numbers in them. In second I need to load pieces of tiled image and then show them in the correct order, forming tiled image. Windows should look like this : http://img535.imageshack.us/img535/3129/lab8a.jpg Okay so how to bite this ? I've used swing only few times to draw some 2d polylines, so basically I just theoretically now what to do. Ok, so window number 1: I start with creating Jframe for the window. Then I do for loop and in it create 16 JLabels with random numbers in them ? How to set margins between each tile and the whole window ? Window number 2 : So I start the same, but instead of loading numbers I add images ? Now, how can I load image from file and then set it as background ?

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  • Call an external web service from a servlet

    - by pAkY88
    Hi, I'm developing a servlet that gets a name of a web service and could be forward the request to an external web service, for example: "http://www.webservice.com/..." I have build a response wrapper that intercept response output but I can't forward request to an external web service, it works only if I redirect the request to a servlet that is on same server. Example: request.getRequestDispatcher("aMyServlet").forward(request, response) IT WORKS request.getRequestDispatcher("http://www.webservice.com/...").forward(request, response) IT DON'T WORKS because Tomcat search "http://www.webservice.com/..." on the server as a local resource. How can I do external request? Thanks

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  • Is there some way to assume @Nullable as default? (using FindBugs or any other free tool).

    - by alex2k8
    Consider such code public void m1(String text) { if(text == null) text = "<empty>"; System.out.println(text.toLowerCase()); } And this is a buggy version: public void m1(String text) { System.out.println(text.toLowerCase()); } If null value passed, the NullPointerException may be thrown. I would like the static-analysis tool (e.g. FindBugs) to report this issue. Unsuccessfully the FindBugs (at least by default) requires me to specify @Nullable annotation explicitly. public void m1(@Nullable String text) { System.out.println(text.toLowerCase()); // FindBugs: text must be nonnull but is marked as nullable } The problem is that if I forget to annotate it, the bug will be missed!!! How can I make the FindBugs (or any other free tool) to assume @Nullable by default?

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  • Calculating the angle between two points

    - by kingrichard2005
    I'm currently developing a simple 2D game for Android. I have a stationary object that's situated in the center of the screen and I'm trying to get that object to rotate and point to the area on the screen that the user touches. I have the constant coordinates that represent the center of the screen and I can get the coordinates of the point that the user taps on. I'm using the formula outlined in this forum: How to get angle between two points? -It says as follows "If you want the the angle between the line defined by these two points and the horizontal axis: double angle = atan2(y2 - y1, x2 - x1) * 180 / PI;". -I implemented this, but I think the fact the I'm working in screen coordinates is causing a miscalculation, since the Y-coordinate is reversed. I'm not sure if this is the right way to go about it, any other thoughts or suggestions are appreciated.

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  • SensorManager method crashes program

    - by Aidan
    Hi guys, When I run the following method my Android application crashes. I can't find the error because I get a "Source Not Found" error. Anyone have any idea's what I'm doing wrong? public void bearing(){ SensorManager sm = (SensorManager)getSystemService(Context.SENSOR_SERVICE); Sensor aSensor = sm.getDefaultSensor(Sensor.TYPE_ACCELEROMETER); Sensor mfSensor = sm.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD); sm.registerListener(myAccelerometerListener, aSensor, SensorManager.SENSOR_DELAY_UI); sm.registerListener(myMagneticFieldListener, mfSensor, SensorManager.SENSOR_DELAY_UI); float[] values = new float[3]; float[] R = new float[9]; SensorManager.getRotationMatrix(R, null, accelerometerValues, magneticFieldValues); SensorManager.getOrientation(R, values); //Convert from Radians to degrees values[0] = (float) Math.toDegrees(values[0]); values[1] = (float) Math.toDegrees(values[1]); values[2] = (float) Math.toDegrees(values[2]); }

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  • My method is too specific. How can I make it more generic?

    - by EricBoersma
    I have a class, the outline of which is basically listed below. import org.apache.commons.math.stat.Frequency; public class WebUsageLog { private Collection<LogLine> logLines; private Collection<Date> dates; WebUsageLog() { this.logLines = new ArrayList<LogLine>(); this.dates = new ArrayList<Date>(); } SortedMap<Double, String> getFrequencyOfVisitedSites() { SortedMap<Double, String> frequencyMap = new TreeMap<Double, String>(Collections.reverseOrder()); //we reverse order to sort from the highest percentage to the lowest. Collection<String> domains = new HashSet<String>(); Frequency freq = new Frequency(); for (LogLine line : this.logLines) { freq.addValue(line.getVisitedDomain()); domains.add(line.getVisitedDomain()); } for (String domain : domains) { frequencyMap.put(freq.getPct(domain), domain); } return frequencyMap; } } The intention of this application is to allow our Human Resources folks to be able to view Web Usage Logs we send to them. However, I'm sure that over time, I'd like to be able to offer the option to view not only the frequency of visited sites, but also other members of LogLine (things like the frequency of assigned categories, accessed types [text/html, img/jpeg, etc...] filter verdicts, and so on). Ideally, I'd like to avoid writing individual methods for compilation of data for each of those types, and they could each end up looking nearly identical to the getFrequencyOfVisitedSites() method. So, my question is twofold: first, can you see anywhere where this method should be improved, from a mechanical standpoint? And secondly, how would you make this method more generic, so that it might be able to handle an arbitrary set of data?

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  • Hibernate Query - Get latest versions by timestamp?

    - by Slim
    I have a database that is being used as a sort of version control system. That is, instead of ever updating any rows, I add a new row with the same information. Each row also contains a version column that is a date timestamp, so the only difference is the new row will have a more recent timestamp. What I'm having trouble with is writing an efficient hibernate query to return the latest version of these rows. For the sake of example, these are rows in a table called Product, the timestamped column is version. There are multiple versions of multiple products in the table. So there may be multiple versions (rows) of ProductA, multiple versions of ProductB, etc. And I would like to grab the latest version of each. Can I do this in just a single hibernate query? session.createQuery("select product from Product product where...?"); Or would this require some intermediate steps?

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