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  • How does Hibernate detect dirty state of an entity object?

    - by ???'Lenik
    Is it using some kind of byte codes modification to the original classes? Or, maybe Hibernate get the dirty state by compare the given object with previously persisted version? I'm having a problem with hashCode() and equals() methods for complicated objects. I feel it would be very slow to compute hash code if the object has collection members, and cyclic references are also a problem. If Hibernate won't use hashCode()/equals() to check the dirty state, I guess I should not use equals()/hashCode() for the entity object (not value object), but I'm also afraid if the same operator (==) is not enough. So, the questions are: How does Hibernate know if a property of an object is changed? Do you suggest to override the hashCode()/equals() methods for complicated objects? What if they contains cyclic references? And, also, Would hashCode()/equals() with only the id field be enough?

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  • Can I assign a maven dependency to a specific repo?

    - by mds
    So I have several large projects that use up to 8 different external repos, all specified in settings.xml rather than in poms. A lot of our internal dependencies are snapshots, so this obviously causes a lot of checking for updates across several external repos, when they are all in our internal repo. So my question is, is there a way to setup a profile/filter or anything similar where I can ensure that an update will only be checked for in a specific repo(s)? This is all in the spirit of better/quicker builds. Thanks!

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  • Injecting EntityManager Vs. EntityManagerFactory

    - by SB
    A long question, please bear with me. We are using Spring+JPA for a web application. My team is debating over injecting EntityManagerFactory in the GenericDAO(a DAO based on Generics something on the lines provided by APPFUSE, we do not use JpaDaosupport for some reason) over injecting an EntityManager. We are using "application managed persistence". The arguments against injecting a EntityManagerFactory is that its too heavy and so is not required, the EntityManager does what we need. Also, as Spring would create a new instance of a DAO for every web request(I doubt this) there are not going to be any concurrency issues as in the same EntityManager instance is shared by two threads. The argument for injecting EFM is that its a good practice over all its always good to have a handle to a factory. I am not sure which is the best approach, can someone please enlighten me? SB

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  • Where should I initialize variables for an OO Recursive Descent Parse Tree?

    - by Vasto
    I'd like to preface this by stating that this is for a class, so please don't solve this for me. One of my labs for my cse class is creating an interpreter for a BNF that was provided. I understand most of the concepts, but I'm trying to build up my tree and I'm unsure where to initialize values. I've tried in both the constructor, and in the methods but Eclipse's debugger still only shows the left branch, even though it runs through completely. Here is my main procedure so you can get an idea of how I'm calling the methods. public class Parser { public static void main(String[] args) throws IOException { FileTokenizer instance = FileTokenizer.Instance(); FileTokenizer.main(args); Prog prog = new Prog(); prog.ParseProg(); prog.PrintProg(); prog.ExecProg(); } Now here is My Prog class: public class Prog { private DeclSeq ds; private StmtSeq ss; Prog() { ds = new DeclSeq(); ss = new StmtSeq(); } public void ParseProg() { FileTokenizer instance = FileTokenizer.Instance(); instance.skipToken(); //Skips program (1) // ds = new DeclSeq(); ds.ParseDS(); instance.skipToken(); //Skips begin (2) // ss = new StmtSeq(); ss.ParseSS(); instance.skipToken(); } I've tried having Prog() { ds = null; ss = null; } public void ParseProg() { FileTokenizer instance = FileTokenizer.Instance(); instance.skipToken(); //Skips program (1) ds = new DeclSeq(); ds.ParseDS(); ... But it gave me the same error. I need the parse tree built up so I can do a pretty print and an execute command, but like I said, I only get the left branch. Any help would be appreciated. Explanations why are even more so appreciated. Thank you, Vasto

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  • Problem at JUnit test with generics

    - by Tom Brito
    In my utility method: public static <T> T getField(Object obj, Class c, String fieldName) { try { Field field = c.getDeclaredField(fieldName); field.setAccessible(true); return (T) field.get(obj); } catch (Exception e) { e.printStackTrace(); fail(); return null; } } The line return (T) field.get(obj); gives the warning "Type safety: Unchecked cast from Object to T"; but I cannot perform instanceof check against type parameter T, so what am I suppose to do here?

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  • leiningen - how to add dependencies for local jars?

    - by signalseeker
    Hi, I want to use leiningen to build and develop my clojure project. Is there a way to modify project.clj to tell it to pick some jars from local directories? I have some proprietary jars that cannot be uploaded to public repos. Also, can leiningen be used to maintain a "lib" directory for clojure projects? If a bunch of my clojure projects share the same jars, I don't want to maintain a separate copy for each of them. Thanks

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  • JSP template inheritance

    - by Ryan
    Coming from a background in Django, I often use "template inheritance", where multiple templates inherit from a common base. Is there an easy way to do this in JSP? If not, is there an alternative to JSP that does this (besides Django on Jython that is :) base template <html> <body> {% block content %} {% endblock %} </body> <html> basic content {% extends "base template" %} {% block content %} <h1>{{ content.title }} <-- Fills in a variable</h1> {{ content.body }} <-- Fills in another variable {% endblock %} Will render as follows (assuming that conten.title is "Insert Title Here", and content.body is "Insert Body Here") <html> <body> <h1>Insert title Here <-- Fills in a variable</h1> Insert Body Here <-- Fills in another variable </body> <html>

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  • Using HSQLDB in production environments

    - by lewap
    I want to use HSQLDB in a production environment for stroring some data in memory and for data export using files. Does anybody have experience with using hsqldb in production environments? Is hsqldb treating server resources gracefully and does it cleanup unused resources properly?

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  • How to set default values to all wrong or null parameters of method?

    - by Roman
    At the moment I have this code (and I don't like it): private RenderedImage private RenderedImage getChartImage (GanttChartModel model, String title, Integer width, Integer height, String xAxisLabel, String yAxisLabel, Boolean showLegend) { if (title == null) { title = ""; } if (xAxisLabel == null) { xAxisLabel = ""; } if (yAxisLabel == null) { yAxisLabel = ""; } if (showLegend == null) { showLegend = true; } if (width == null) { width = DEFAULT_WIDTH; } if (height == null) { height = DEFAULT_HEIGHT; } ... } How can I improve it? I have some thoughts about introducing an object which will contain all these parameters as fields and then, maybe, it'll be possible to apply builder pattern. But still don't have clear vision how to implement that and I'm not sure that it's worth to be done. Any other ideas?

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  • auto resize content of label

    - by user161004
    i have got a label in my program which displays a image. The problem id if an image is selected which is greater than the size of the label,only some part of the image is displayed while others are not displayed. What should i do so that the enire image is displayed???

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  • How can you tell if an activities state is stored?

    - by Joren
    I have an activity which pulls some JSON from my server, and then uses it to draw a list. That list launches further activities. My problem is that I can't figure out a way to tell if the activity is still alive when you go back to it, so I end up re-querying my JSON from the server and redrawing the list every time the user goes back to the activity. How can I tell if my activity is still alive so I can skip the redraw?

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  • Representing element as boolean with JAXB?

    - by Marcus
    We have this XML: <Summary> <ValueA>xxx</ValueA> <ValueB/> </Summary> <ValueB/> will never have any attributes or inner elements. It's a boolean type element - it exists (true) or it doesn't (false). JAXB generated a Summary class with a String valueA member, which is good. But for ValueB, JAXB generated a ValueB inner class and a corresponding member: @XmlElement(name = "ValueB") protected Summary.ValueB valueB; But what I'd like is a boolean member and no inner class: @XmlElement(name = "ValueB") protected boolean valueB; How can you do this? I'm not looking to regenerate the classes, I'd like to just make the code change manually. Update: In line with the accepted answer, we created a new method returning the boolean value conditional on whether valueB == null. As we are using Hibernate, we annotated valueB with @Transient and annotated the boolean getter with Hibernate's @Column annotation.

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  • Change size of ImageIcon in a JRadioButton

    - by Frederik Wordenskjold
    I simply want to change the size (diameter) of the actual (default) ImageIcon of my JRadioButton. I've changed the size of the font displayed in the widget, so it really looks silly with such a large radiobutton. JRadioButton button = new JRadioButton("Button"); button.setFont(new Font("Lucida Grande",Font.PLAIN, 11)); gives me this giant button: Do I really have to create my own ImageIcon? Or can I somehow scale the default one, without too much of a hassle?

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  • Transactions in hibernate

    - by kumar1425
    Hi I new to hibernate In my project, i need to handle transactions. How to handle declarative transactions with in two classes Examples: //class 1 class A{ createA() { insert(A); } } //class 2 class B { createB() { insert(B); } } //class 3 @Transaction(Exception.class) class C { test() { create(A); create(B); } } As per the above code is there any possibility to handle transactions, in such a way that if the insert in classA success and the insert in the classB fails then the transaction should rollback and remove the record inserted in the table A corresponding to the Class A please help me with this using declarative transactions.... Thanks in adavace....

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  • Stuck at being unable to print a substring no more than 4679 characters

    - by Newcoder
    I have a program that does string manipulation on very large strings (around 100K). The first step in my program is to cleanup the input string so that it only contains certain characters. Here is my method for this cleanup: public static String analyzeString (String input) { String output = null; output = input.replaceAll("[-+.^:,]",""); output = output.replaceAll("(\\r|\\n)", ""); output = output.toUpperCase(); output = output.replaceAll("[^XYZ]", ""); return output; } When i print my 'input' string of length 97498, it prints successfully. My output string after cleanup is of length 94788. I can print the size using output.length() but when I try to print this in Eclipse, output is empty and i can see in eclipse output console header. Since this is not my final program, so I ignored this and proceeded to next method that does pattern matching on this 'cleaned-up' string. Here is code for pattern matching: public static List<Integer> getIntervals(String input, String regex) { List<Integer> output = new ArrayList<Integer> (); // Do pattern matching Pattern p1 = Pattern.compile(regex); Matcher m1 = p1.matcher(input); // If match found while (m1.find()) { output.add(m1.start()); output.add(m1.end()); } return output; } Based on this program, i identify the start and end intervals of my pattern match as 12351 and 87314. I tried to print this match as output.substring(12351, 87314) and only get blank output. Numerous hit and trial runs resulted in the conclusion that biggest substring that i can print is of length 4679. If i try 4680, i again get blank input. My confusion is that if i was able to print original string (97498) length, why i couldnt print the cleaned-up string (length 94788) or the substring (length 4679). Is it due to regular expression implementation which may be causing some memory issues and my system is not able to handle that? I have 4GB installed memory.

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  • javax.persistence.NoResultException: getSingleResult() did not retrieve any entities

    - by apple1988
    Hello, i have created a namedquery with ejb to check if the username is used. When the singleResult is null, then i get the following Exception : javax.persistence.NoResultException: getSingleResult() did not retrieve any entities But this exception is the result that i want when the username is free. ^^ Here is the code: public User getUserByUsername(String username) throws DAOException{ try{ Query q = em.createNamedQuery(User.getUserByUsername); q.setParameter("username", username); return (User) q.getSingleResult(); }catch(Exception e){ throwException(username, e); return null; } } Does anybody know what the problem is. :( I will return null andy don`t get an Exception. Thank you very much

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  • Reading ResultSet from multiple threads

    - by superdario
    Hello, In the database, I have a definition table that is read from the application once upon starting. This definition table rarely changes, so it makes sense to read it once and restart the application every time it changes. However, after the table is read (put into a ResultSet), it will be read by multiple handlers running in their own threads. How do you suggest to accomplish this? My idea was to populate a CachedRowSet, and then create a copy of this set (through the createCopy() method) for each handler every time a new request comes. Do you think this is wise? Does this offer a good performance? Thanks.

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  • How to export each open project in Eclipse as its own JAR?

    - by Freiheit
    I have several projects open in an Eclipse workspace. Like so: com.harbl.project.one com.harbl.project.two com.harbl.project.three I would like to export those as JARs in a batch such that I wind up with the following JAR files: ./com.harbl.project.one.jar ./com.harbl.project.two.jar ./com.harbl.project.three.jar Is this possible with one of the Eclipse wizards or working sets? Is my only option to export each one individually?

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  • Is it possible to include JButton in a JTable?

    - by Benjamin Confino
    I have a JTable that stores the results of a database query, so far so good. What I want is for the last column in each table to have a clickible JButton that will open the edit screen for the object represented in that row, and that means the button will need to know the details of the first column in the table from its own row (the ID from the database). Any advice? I already tried just adding JButtons but they turned into Text when I tried to run it.

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  • Spring MVC: should service layer be returning operation specific DTO's ?

    - by arrages
    In my Spring MVC application I am using DTO in the presentation layer in order to encapsulate the domain model in the service layer. The DTO's are being used as the spring form backing objects. hence my services look something like this: userService.storeUser(NewUserRequestDTO req); The service layer will translate DTO - Domain object and do the rest of the work. Now my problem is that when I want to retrieve a DTO from the service to perform say an Update or Display I can't seem to find a better way to do it then to have multiple methods for the lookup that return different DTO's like... EditUserRequestDTO userService.loadUserForEdit(int id); DisplayUserDTO userService.loadUserForDisplay(int id); but something does not feel right about this approach. The reason do have separate DTO's is that DisplayUserDTO is strongly typed to be read only and also there are many properties of user that are entities from a lookup table in the db (like city and state) so the DisplayUserDTO would have the string description of the properties while the EditUserRequestDTO will have the id's that will back the select drop down lists in the forms. What do you think? thanks

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