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  • How to make a daemon which will accept arbitrary commands

    - by Jono
    Right now the program can be launched in a linux terminal. Once running you can type various commands and the program will do stuff on the machine until the user quits. I would like to make the program into a service that the user runs and it goes to the background. Then the user should be able to make commands to it. Like start and stop, and write something to a log and whatever else my program does. Note that I need to send it arbitrary commands that my program will handle, not just start and stop. Maybe this means it is no longer a daemon - I dont know. How do I do this? Also, if this is not too hard, I would like to be able to run multiple instances of this service. But it is not essential.

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  • Architecture of a secure application that encrypts data in the database.

    - by Przemyslaw Rózycki
    I need to design an application that protects some data in a database against root attack. It means, that even if the aggressor takes control over the machine where data is stored or machine with the application server, he can't read some business critical data from the database. This is a customer's requirement. I'm going to encrypt data with some assymetric algorithm and I need some good ideas, where to store private keys, so that data is secure as well as the application usability was quite comfortable? We can assume, for simplicity, that only one key pair is used.

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  • How to merge JOptionPane and Frame into one

    - by mike_hornbeck
    Hello. Currently I have a very basic file viewer working as follows : - in JOptionPane I browse for files, and set some variables to display (colors, line connecting etc) - previous windows loads a frame with drawn points Code : http://paste.pocoo.org/show/220066/ Now I'd like to throw it into one window, with JMenu for selecting files and changing display parameters. How to get started ? Should I rewrite everything to JDialog ?

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  • how to query an embedded entity by using a query builder

    - by user577719
    I've searched quite a time for an answer to this question. Following Codesmell: @Entity public class Person { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) protected Integer id; @Column(nullable = true, length = 50) @Size(max = 50) private String name; @Embedded @Valid protected Adress adress; public void setId(Integer id) { this.id = id; } public Integer getId() { return this.id; } public void setName(String name) { this.name = name; } public void getName() { return this.name; } public void setAdress(Adress adress) { this.adress = adress; } public void getAdress() { return this.adress; } } @Embeddable public class Adress { @Column(nullable = false, length = 50) @Size(max = 50) @NotNull private String place; public void setPlace(String place) { this.place = place; } public void getPlace() { return this.place; } } public class PersonDaoJpa { public List<Ort> findByPerson(final Person person) { CriteriaBuilder builder = this.entityManager.getCriteriaBuilder(); CriteriaQuery<Person> query = builder.createQuery(Person.class); Root<Person> rootPerson = query.from(Person.class); List<Predicate> wherePredicates = new ArrayList<Predicate>(); if (person.getName() != null) { wherePredicates.add( builder.like(builder.lower(rootPerson.<String>get("name")), ort.getName().toLowerCase()) ); } Adresse adresse = ort.getAdresse(); if (adresse != null) { if(adresse.getPlace() != null) { // this won't work wherePredicates.add( builder.like(builder.lower(rootPerson.<String>get("person.adress.place")), adresse.getPlace().toLowerCase()) ); } } Predicate whereClause = builder.and(wherePredicates.toArray(new Predicate[0])); query.where(whereClause); return this.entityManager.createQuery(query).getResultList(); } } How can I access the Adress.place through rootPerson? rootPerson.get("place"), or rootPerson.get("adress.place") won't work...

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  • Is this a correct way to stop Execution Task

    - by Yan Cheng CHEOK
    I came across code to stop execution's task. private final ExecutorService executor = Executors.newSingleThreadExecutor(); public void stop() { executor.shutdownNow(); try { executor.awaitTermination(100, TimeUnit.DAYS); } catch (InterruptedException ex) { log.error(null, ex); } } public Runnable getRunnable() { return new Runnable() { public void run() { while (!Thread.currentThread().isInterrupted()) { // What if inside fun(), someone try to clear the interrupt flag? // Say, through Thread.interrupted(). We will stuck in this loop // forever. fun(); } } }; } I realize that, it is possible for Runnable to be in forever loop, as Unknown fun may Thread.sleep, clear the interrupt flag and ignore the InterruptedException Unknown fun may Thread.interrupted, clear the interrupt flag. I was wondering, is the following way correct way to fix the code? private final ExecutorService executor = Executors.newSingleThreadExecutor(); private volatile boolean flag = true; public void stop() { flag = false; executor.shutdownNow(); try { executor.awaitTermination(100, TimeUnit.DAYS); } catch (InterruptedException ex) { log.error(null, ex); } } public Runnable getRunnable() { return new Runnable() { public void run() { while (flag && !Thread.currentThread().isInterrupted()) { // What if inside fun(), someone try to clear the interrupt flag? // Say, through Thread.interrupted(). We will stuck in this loop // forever. fun(); } } }; }

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  • calculate business days including holidays

    - by ran
    i need to calculate the business days between two dates. ex : we have holiday(in USA) on july4th. so if my dates are date1 = 07/03/2012 date2 = 07/06/2012 no of business days b/w these dates should be 1 since july4th is holiday. i have a below method to calclulate the business days which will only counts week ends but not holidays. is there any way to calculate holidays also....please help me on this. public static int getWorkingDaysBetweenTwoDates(Date startDate, Date endDate) { Calendar startCal; Calendar endCal; startCal = Calendar.getInstance(); startCal.setTime(startDate); endCal = Calendar.getInstance(); endCal.setTime(endDate); int workDays = 0; //Return 0 if start and end are the same if (startCal.getTimeInMillis() == endCal.getTimeInMillis()) { return 0; } if (startCal.getTimeInMillis() > endCal.getTimeInMillis()) { startCal.setTime(endDate); endCal.setTime(startDate); } do { startCal.add(Calendar.DAY_OF_MONTH, 1); if (startCal.get(Calendar.DAY_OF_WEEK) != Calendar.SATURDAY && startCal.get(Calendar.DAY_OF_WEEK) != Calendar.SUNDAY) { ++workDays; } } while (startCal.getTimeInMillis() < endCal.getTimeInMillis()); return workDays; }

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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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  • When to use @Singleton in a Jersey resource

    - by dexter
    I have a Jersey resource that access the database. Basically it opens a database connection in the initialization of the resource. Performs queries on the resource's methods. I have observed that when I do not use @Singleton, the database is being open at each request. And we know opening a connection is really expensive right? So my question is, should I specify that the resource be singleton or is it really better to keep it at per request especially when the resource is connecting to the database? My resource code looks like this: //Use @Singleton here or not? @Path(/myservice/) public class MyResource { private ResponseGenerator responser; private Log logger = LogFactory.getLog(MyResource.class); public MyResource() { responser = new ResponseGenerator(); } @GET @Path("/clients") public String getClients() { logger.info("GETTING LIST OF CLIENTS"); return responser.returnClients(); } ... // some more methods ... } And I connect to the database using a code similar to this: public class ResponseGenerator { private Connection conn; private PreparedStatement prepStmt; private ResultSet rs; public ResponseGenerator(){ Class.forName("org.h2.Driver"); conn = DriverManager.getConnection("jdbc:h2:testdb"); } public String returnClients(){ String result; try{ prepStmt = conn.prepareStatement("SELECT * FROM hosts"); rs = prepStmt.executeQuery(); ... //do some processing here ... } catch (SQLException se){ logger.warn("Some message"); } finally { rs.close(); prepStmt.close(); // should I also close the connection here (in every method) if I stick to per request // and add getting of connection at the start of every method // conn.close(); } return result } ... // some more methods ... } Some comments on best practices for the code will also be helpful.

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  • converting result set to list

    - by akshay
    how can i conver result set to list? i am using following code but its not working properly private List<User> convertToList(ResultSet rs) { List<User> userList = new ArrayList(); User user = new User(); try { while (rs.next()) { user.setId(rs.getInt("id")); user.setUsername(rs.getString("username")); user.setFname(rs.getString("fname")); user.setLname(rs.getString("lname")); user.setUsertype(rs.getInt("usertype")); user.setPasswd(rs.getString("passwd")); user.setEmail(rs.getString("email")); userList.add(user); } } catch (SQLException ex) { Logger.getLogger(UserDAO.class.getName()).log(Level.SEVERE, null, ex); } finally { closeConnection(); } return userList; }

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  • Is this a correct iText design?

    - by Lucas
    I´m making some pdf reports to be used on a web app. I wonder if the way I´m taking to make the designs is appropriated. This would be a screenshot of the way I´m doing the things. As you can see, I´m using tables to position everything in the document. I think this is a pretty much similar design to HTML. But I want to know is there is a better way to get the same result I got. This is the document without cell borders: I could post the code if necessary. By the way, why should I spend long hours programming these kind of stuff with iText tool when I could do things faster and maybe better looking with iReport? I like iText, it´s just a question. Sorry for my english and thanks!

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  • Can I override spring beans instatiated with component scanning?

    - by Pablojim
    If I use component scanning in Spring 2.5 but then also define a controller in xml. Do I get two instances of this bean in my application context? If so which instance will be called for its related RequestMappings? <bean id="myController" class="domain.MyController"> <property name="filters"> <list> <ref local="filter1"/> <ref local="filter2"/> </list> </property> </bean>

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  • Twitter4J - Looking up profile details without logging in

    - by wvd
    Hello all, I've been using Twitter4J for a quite a while now, but I can't seem to find this particular feature. I want to be able to search on a name, and when the certain user is on twitter, I want to retrieve basic information such as tweets, followers (like you can access via http) - but how to do is in Twitter4J? Neither the code examples or the source could help me. Thanks, William van Doorn

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  • Instantiating spring beans in dynamically created classes.

    - by Xetius
    I am dynamically creating classes which contain spring beans, however the beans are not getting instantiated or initialised, leaving them as null. How do I make sure that a dynamically created class creates all of its spring beans properly? This is how I am dynamically creating the class: Class ctransform; try { ctransform = Class.forName(strClassName); Method handleRequestMethod = findHandleRequestMethod(ctransform); if (handleRequestMethod != null) { return (Message<?>) handleRequestMethod.invoke(ctransform.newInstance(), message); } } This leaves all spring bean objects within ctransform (of type strClassName) as null.

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  • Calling and consuming a JBoss Web Service from JavaScript (AJAX)

    - by Andreas Grech
    I am fiddling around with JBOSS's Web Services, and I have created the following: http://127.0.0.1:8080/IM/TestService?wsdl Now I need to access Web Methods from that Web Service from JavaScript. Say I have a web method named foo in TestService, how do I make an ajax call to it? I tried accessing the method via http://127.0.0.1:8080/IM/TestService/foo, but I'm getting an HTTP Status 404.

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  • What to do when ServerSocket throws IOException

    - by s5804
    Basically I want to create a rock solid server. while (keepRunning.get()) { try { Socket clientSocket = serverSocket.accept(); ... spawn a new thread to handle the client ... } catch (IOException e) { e.printStackTrace(); // NOW WHAT? } } In the IOException block, what to do? Is the Server socket at fault so it need to be recreated? For example wait a few seconds and then serverSocket = ServerSocketFactory.getDefault().createServerSocket(MY_PORT); However if the server socket is still OK, then it is a pity to close it and kill all previously accepted connections that are still communicating.

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  • checking boolean property in XML(Spring)

    - by Abhishek Bhandari
    I am using Spring Framework . While writing coustum SQL queries , i am unable check a parameter of boolean value. For example this is not working .. do some SQl cods The above checking is not working , it is evaluating as equal in both the cases when booleanVariable is true and false . i tried to replace compareValue ="tree" and "false". As that is a monkey work i do sometimes . is it possible to check the boolean property in XML like above .

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  • Connection Pooling in J2SE?

    - by Zombies
    It is hard to find a resource on this without finding J2EE, but here is what I am looking for: All I have is a standard J2SE app, it makes a lot of DB connections. I simply need to make use of a connection pool. Any suggestions?

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  • BufferedReader ready method in a while loop to determine EOF?

    - by BobTurbo
    I have a large file (wikipedia english arcticles only database as xml file) I am using to read one character at a time using BufferedReader. The psuedo code is: file = BufferedReader... while (file.ready()) character = file.read() is this actually valid? Or will ready just return false when it is waiting for the HDD to return data and not actually when the EOF has been reached? I tried to use if (file.read() == -1) but seemed to run into an infinite loop that I literally could not find. I am just wondering if it is reading the whole file as my statistics say 444 380 wikipedia pages have been read but I thought there were many more articles..

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  • Generics Type issue

    - by JohnJohnGa
    ArrayList<Integer> arrI = new ArrayList<Integer>(); ArrayList arrO = arrI; // Warning /* It is ok to add a String as it is an ArrayList of Objects but the JVM will know the real type, arrO is an arrayList of Integer... */ arrO.add("Hello"); /* How I can get a String in an ArrayList<Integer> ?? Even if the compiler told me that I will get an Integer! */ System.out.println(arrI.get(0)); Anybody can explain what's happening here?

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