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  • How do I check that an entity is unreferenced in JPA?

    - by Martin
    I have the following model @Entity class Element { @Id int id; @Version int version; @ManyToOne Type type; } @Entity class Type { @Id int id; @Version int version; @OneToMany(mappedBy="type") Collection<Element> elements; @Basic(optional=false) boolean disabled; } and would like to allow Type.disabled = true only if Type.elements is empty. Is there a way to do it atomically? I would like to prevent an insertion of an Element in a transaction while the corresponding Type is being disabled by an other transaction.

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  • What is the common way to program action listeners?

    - by Roman
    I just started to learn how to use action listeners. To my understanding it works in the following way: There are some classes which contains "addActionListener" method by default (for example classes for buttons). Using this method we add an action listener to an object. For example: listenedObject.addActionListener(listeningObject). When an action with the "listenedObject" is performed, the "actionPerformed" method of the "listeningObject" will be called. So, it means that when we program a class for the listeningObject, we need to put there "actionPerformed" method. What is not clear to me, should we create a new class for every object that we want to listen. It does not seem to me as an elegant solution. On the other hand, if we have one action listener class for all (or at least many) object, than we have a problem since a instance of this class will not know which object is calling the "actionPerformed" method (and we need to know that since actions performed by the actionPerformed differs depending on who is called for this method). In my opinion, for every listened object we need to create are "personal" action listener and we can do it by setting a specific value to the corresponding field of the action listener. But I am not sure that it is a standard way to go? How do usually people do it?

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  • Is it possible to create a timer in jscript that you can manually change without it being affected by timezones?

    - by Lixorp
    is it possible to create a timer where I can manually set the hours each day to a set number of hours but still remains accurate? For example; if I set the countdown for 5 hours at 2pm I want the timer to stop as soon as it hits 7pm. Also, when I set the timer for 5 hours I would like everyone in the world to see it countdown from 5 hours, no matter what the time is in their country. In the format: days hours minutes seconds. The reason I want to do this is for a streamer's website. He needs a flexible timer which can be manually changed and is the same worldwide for his viewers to know when he starts streaming. The current timer we're using at the moment; setInterval(function(){ var currentTime = new Date(); if(currentTime.getHours() > 19){ var countdownHours = (24 - currentTime.getHours()) + 19; }else if(currentTime.getHours() < 19){ var countdownHours = 19 - currentTime.getHours(); }else{ var countdownHours = 0; } var countdownMins = 59 - currentTime.getMinutes(); var countdownSecs = 60 - currentTime.getSeconds(); $('#countdown-days h1').text('0'); $('#countdown-hours h1').text(countdownHours); $('#countdown-minutes h1').text(countdownMins); $('#countdown-seconds h1').text(countdownSecs); }, 1000); As you can tell it isn't ideal for what we need it for since it counts down to 7pm in the timezone you're in. Any help/examples would be greatly appreciated, Thank you in advance, Lixorp.

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  • Velocity Templates - New Line.

    - by LdSe
    Hello all, I've been working with Apache's Velocity engine and a custom template. The thing is, that I haven't been able to generate a String with the corresponding line breaks. I tried almost everything that I found, such as using $esc.n and $esc.newline (I'm already using escape tools on my project) but it seems that the version I'm currently using doesn't support it (1.4), checked if putting '\n', '\\n' and even '\\\n' would work, but same thing. Does anyone have any solution to this? Thanks a lot in advance! Regards.

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  • ServiceLoader double iterator issues

    - by buge
    Is this a known issue? I had trouble finding any search results. When iterating over a ServiceLoader while an iteration already is in progress, the first iteration will be aborted. For example, assuming there are at least two implementations of Foo, the following code will fail with an AssertionError: ServiceLoader<Foo> loader = ServiceLoader.load(Foo.class); Iterator<Foo> iter1 = loader.iterator(); iter1.next(); Iterator<Foo> iter2 = loader.iterator(); while (iter2.hasNext()) { iter2.next(); } assert iter1.hasNext(); This only seems to occur, if the second iterator really terminates. The code will succeed in this variation for example: ServiceLoader<Foo> loader = ServiceLoader.load(Foo.class); Iterator<Foo> iter1 = loader.iterator(); iter1.next(); Iterator<Foo> iter2 = loader.iterator(); iter2.next(); assert iter1.hasNext(); Is this a bug or a feature? :p Is there a ticket for this already anywhere?

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  • Drop down list population fails after validation fails

    - by sarah
    Hi All, I am polpulating data in drop down reading from request scope,i am doing validaiton of fe w field after submission i wont get data in drop down i am using struts and the corresponding form bean defn is like <action path="/userProcess" name="userForm" type="com.actions.UserManagementAction" parameter="method" input="/views/AddUsers.jsp" scope="request" > <forward name="success" path="/views/User_Management.jsp" /> </action> and the drop down listing is <select name="roleName"> <c:forEach items="${roleNames}" var="role"> <option value="${role}">${role}</option> </c:forEach> </select> how should i handle this ?

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  • Php security question

    - by Camran
    I have a linux server, and I am about to upload a classifieds website to it. The website is php based. That means php code adds/removes classifieds, with the help of the users offcourse. The php-code then adds/removes a classified to a database index called Solr (like MySql). Problem is that anybody can currently access the database, but I only want the website to access the database (solr). Solr is on port 8983 as standard btw. My Q is, if I add a rule in my firewall (iptables), to only allow connections coming from the servers IP to the Solr port nr, would this solve my issue? Thanks

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  • Any way to anticipate session timeout ?

    - by Tom
    Hi, Is there a way to "catch" the session timeout event, so as to retrieve data from HttpSession before its invalidated ? We're implementing the Filter Interface, and in the doFilter method, the user we stored in the session object at login is null when session times out. Thanks in advance.

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  • best way to avoid sql injection

    - by aauser
    I got similar domain model 1) User. Every user got many cities. @OneToMany(targetEntity=adv.domain.City.class...) 2) City. Every city got many districts @OneToMany(targetEntity=adv.domain.Distinct.class) 3) Distintc My goal is to delete distinct when user press delete button in browser. After that controller get id of distinct and pass it to bussiness layer. Where method DistinctService.deleteDistinct(Long distinctId) should delegate deliting to DAO layer. So my question is where to put security restrictions and what is the best way to accomplish it. I want to be sure that i delete distinct of the real user, that is the real owner of city, and city is the real owner of distinct. So nobody exept the owner can't delete ditinct using simple url like localhost/deleteDistinct/5. I can get user from httpSession in my controller and pass it to bussiness layer. After that i can get all cities of this user and itrate over them to be sure, that of the citie.id == distinct.city_id and then delete distinct. But it's rather ridiculous in my opinion. Also i can write sql query like this ... delete from t_distinct where t_distinct.city_id in (select t_city.id from t_city left join t_user on t_user.id = t_city.owner_id where t_user.id = ?) and t_distinct.id = ? So what is the best practice to add restrictions like this. I'm using Hibernate, Spring, Spring MVC by the way.. Thank you

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  • How to reduce the Number of threads running at instance in jetty server ?

    - by Thirst for Excellence
    i would like to reduce the live threads on server to reduce the bandwidth consumption for data(data pull while application launching time) transfer from my application to clients in my application. i did setting like is this setting enough to reduce the bandwidth consumption on jetty server ? Please help me any one 1) in Jetty.xml: <Set name="ThreadPool"> <New class="org.eclipse.jetty.util.thread.QueuedThreadPool"> <name="minThreads"> 1 > <Set name="maxThreads" value=50> 2: services-config.xml channel-definition id="my-longpolling-amf" class="mx.messaging.channels.AMFChannel" endpoint url="http://MyIp:8400/blazeds/messagebroker/amflongpolling" class="flex.messaging.endpoints.AMFEndpoint" properties <polling-enabled>true</polling-enabled> <polling-interval-seconds>1</polling-interval-seconds> <wait-interval-millis>60000</wait-interval-millis> <client-wait-interval-millis>1</client-wait-interval-millis> <max-waiting-poll-requests>50</max-waiting-poll-requests> </properties> </channel-definition>

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  • Scrolling down an awt.List

    - by nico
    As from subject, I have an awt.List object. When I add something to the list I would like to scroll it down to show the last inserted object. For instance: myList.add("sometext"); myList.select(myList.getItemCount()-1); myList.showSelectedItem(); // Or something like that The documentation does not seem to list any method that does something like that, can anybody help please?

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  • Aggregation, Association and Composition (examples of code given)

    - by Bukocen
    I have such a simple example: public class Order { private ArrayList<Product> orders = new ArrayList<Product>(); public void add(Product p) { orders.add(p); } } Is it aggregation or composition? I guess it's composition, because orders will be delated after delete of Order, right? Unfortunately it was a task and answer was different;/ Do you know why? second problem: public class Client extends Person { String adress = ""; Orders orders = new Orders(); public Client(String n, String sn) { name = n; surName = sn; } public String getAddress() { return adress; } public Orders getOrders() { return this.orders; } } Is it Association between Client and Orders? My teacher told me that this is association, but I was wondering why it's not a aggregation/composition - he told me that aggregation or composition occur only when one class contains few instances of different class - is that right? I guess not, because e.g. car contains ONE wheel and it's aggregation I guess? What type of relation is that and why? Greetings

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  • Null Pointer Exception

    - by user1507835
    I am getting a null pointer exception, but I dont know why. I checked to see if the cell was null before I read it to a string. So, why is that string null? private void fillArray() private void fillArray() { try { readBook = new HSSFWorkbook(readFile); } catch (IOException e) { System.out .println("If we know what we're doing, no one should ever see this line."); } if (readBook != null) {HSSFSheet infoSheet = readBook.getSheetAt(0); HSSFRow headingsRow = infoSheet.getRow(0); int i = 0; HSSFCell cell = headingsRow.getCell(i); String columnHeading = cell.toString(); while (cell != null && !(cell.toString().equals(""))) { cell = headingsRow.getCell(i); columnHeading = cell.toString(); columnHeadings.add(columnHeading); i++; } if(columnListIsSetup == false) { createList(); columnListIsSetup = true; } }

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  • Getting instance of a class in ArrayList

    - by user1499974
    I have a small problem with ArrayList. You see, I wish to get an instance of RenderNewHUD in my renderer class, which has a list of registered renderers. I did not want to create a variable for this due to limitations and awkwardness. Here is my code. RenderNewHUD hud = renderer.renderList.get(RenderNewHUD()); How exactly can I go along getting the instance of RenderNewHUD without creating a new instance? If you need any more of my code, just ask. Sorry if this is a very dumb question - I have looked EVERYWHERE for an answer.

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  • does anyone see any issues with this thread pattern?

    - by prmatta
    Here is a simple thread pattern that I use when writing a class that needs just one thread, and needs to a specific task. The usual requirements for such a class are that it should be startable, stopable and restartable. Does anyone see any issues with this pattern that I use? public class MyThread implements Runnable { private boolean _exit = false; private Thread _thread = null; public void start () { if (_thread == null) { _thread = new Thread(this, "MyThread"); _thread.start(); } } public void run () { while (_exit) { //do something } } public void stop () { _exit = true; if (_thread != null) { _thread.interrupt(); _thread = null; } } } I am looking for comments around if I am missing something, or if there is a better way to write this.

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  • Playing a .wav sound file in JPanel/JFrame using javax (Swing)

    - by JavaIceCream
    I need some code example on how I would use a filepath from a harddrive location to then play a .wav sound file when opened in swing GUI. I don't need it to show a play button, or pause or stop. I just want it to play when I select the 'Sound' option from my 'Files' in my window (I know how to do that already, no need to explain that). So basically, just how to play a .wav sound file from a filepath (i.e. c:/cake/thereisnone.wav) inside of a JFrame. And how can I easily apply methods to that sound file afterwards. Also, if anyone knows how to apply methods on a BufferedImage in a JFrame, that would be helpful too. Thank you very much everyone!

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  • Synchronize JTextFields Values by PropertyChangeListener

    - by gt_ebuddy
    I want to copy the value of a jTextField - TXTFLD1 to another jTextField -TXTFLD2 when the value at TXTFLD1 changes. I choose propertychangelistener because i cannot detect when the value at TXTFLD1 is changed, Because it is changed by some external code which i cannot modify now. The test code is as follows : public class TxtFldSync extends JFrame { private JButton BTN1 = null; private JTextField TXTFLD1 = null; private JTextField TXTFLD2 = null; public static void main(String[] args) { TxtFldSync thisClass = new TxtFldSync(); thisClass.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); thisClass.setVisible(true); } public TxtFldSync() { super(); this.setSize(300, 200); BTN1 = new JButton(); BTN1.setBounds(new Rectangle(178, 38, 67, 17)); TXTFLD1 = new JTextField(); TXTFLD1.setBounds(new Rectangle(32, 42, 83, 20)); TXTFLD2 = new JTextField(); TXTFLD2.setBounds(new Rectangle(30, 78, 83, 20)); //listeners TXTFLD1.addPropertyChangeListener("value", new PropertyChangeListener() { @Override public void propertyChange(PropertyChangeEvent arg0) { TXTFLD2.setText(TXTFLD1.getText()+"set by change listener"); //this doesnot work why ? } }); BTN1.addActionListener( new ActionListener() { @Override public void actionPerformed(ActionEvent arg0) { TXTFLD1.setText("Action Performed"); //i what to set same value to TXTFLD2 using property change listener } }); this.setContentPane(new Container()); this.getContentPane().add(BTN1); this.getContentPane().add(TXTFLD1); this.getContentPane().add(TXTFLD2); } } Why the property change listener is not working. What are the other alternatives solution for this problem?

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  • Maven + Tomcat acceleration

    - by Bar
    I am writing a web application with Maven in the Eclipse IDE, and use Tomcat servlet container. So, I run Maven like this: mvn clean compile. It is reasonable that after this oepration I must re-run Tomcat so it can reinitialize the context (Sysdeo Tomcat launcher helps a lot). The problem is Maven execution and subsequebt Tomcat re-running takes noticable amount of time (like 10+ seconds for Maven and 20+ sec. for Tomcat, because of logging, Hibernate mappings, etc.) every time I do it. Is there any automated and more faster solution for these two operatioins? As I see it, a way better solution can be moving re-compiled classes only to the target dir.

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  • Will this be garbage collected in JVM?

    - by stjowa
    I am running the following code every two minutes via a Timer: object = new Object(this); Potentially, this is a lot of objects being created and a lot of objects being overwritten. Do the overwritten objects get garbage collected, even with a reference to itself being used in the newly created object? I am using JDK 1.6.0_13. Thanks for the help.

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  • public (static) swap() method vs. redundant (non-static) private ones...

    - by Helper Method
    I'm revisiting data structures and algorithms to refresh my knowledge and from time to time I stumble across this problem: Often, several data structures do need to swap some elements on the underlying array. So I implement the swap() method in ADT1, ADT2 as a private non-static method. The good thing is, being a private method I don't need to check on the parameters, the bad thing is redundancy. But if I put the swap() method in a helper class as a public static method, I need to check the indices every time for validity, making the swap call very unefficient when many swaps are done. So what should I do? Neglect the performance degragation, or write small but redundant code?

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  • Exception handling pattern

    - by treefrog
    It is a common pattern I see where the error codes associated with an exception are stored as Static final ints. when the exception is created to be thrown, it is constructed with one of these codes along with an error message. This results in the method that is going to catch it having to look at the code and then decide on a course of action. The alternative seems to be- declare a class for EVERY exception error case Is there a middle ground ? what is the recommended method ?

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