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  • Using the JPA Criteria API, can you do a fetch join that results in only one join?

    - by Shaun
    Using JPA 2.0. It seems that by default (no explicit fetch), @OneToOne(fetch = FetchType.EAGER) fields are fetched in 1 + N queries, where N is the number of results containing an Entity that defines the relationship to a distinct related entity. Using the Criteria API, I might try to avoid that as follows: CriteriaBuilder builder = entityManager.getCriteriaBuilder(); CriteriaQuery<MyEntity> query = builder.createQuery(MyEntity.class); Root<MyEntity> root = query.from(MyEntity.class); Join<MyEntity, RelatedEntity> join = root.join("relatedEntity"); root.fetch("relatedEntity"); query.select(root).where(builder.equals(join.get("id"), 3)); The above should ideally be equivalent to the following: SELECT m FROM MyEntity m JOIN FETCH myEntity.relatedEntity r WHERE r.id = 3 However, the criteria query results in the root table needlessly being joined to the related entity table twice; once for the fetch, and once for the where predicate. The resulting SQL looks something like this: SELECT myentity.id, myentity.attribute, relatedentity2.id, relatedentity2.attribute FROM my_entity myentity INNER JOIN related_entity relatedentity1 ON myentity.related_id = relatedentity1.id INNER JOIN related_entity relatedentity2 ON myentity.related_id = relatedentity2.id WHERE relatedentity1.id = 3 Alas, if I only do the fetch, then I don't have an expression to use in the where clause. Am I missing something, or is this a limitation of the Criteria API? If it's the latter, is this being remedied in JPA 2.1 or are there any vendor-specific enhancements? Otherwise, it seems better to just give up compile-time type checking (I realize my example doesn't use the metamodel) and use dynamic JPQL TypedQueries.

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  • select multiple double side

    - by Mercer
    hello, i want to do a select multiple double side like this : http://www.senamion.com/blog/jmultiselect2side.html (Demo2) but i don't know how i can retrieve my data when i click submit button..?

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  • Drools rule to filter element with a numeric property below a percentage of the total

    - by Mario
    Hello, I have just started using Drools on a small project and now I need to write a rule a bit complex and I don't really know what's the best way to do it. I am applying this rule to a list of objects of the same type (this class have a property called numberOfExecutions). I need to check for each element of the list if the numberOfExecutions of that element is bigger than 5% of the total numberOfExecutions (the sum of numberOfExecutions of all the elements in the list). I could not think of a nice way to implement this in drools so far, do you have a suggestion?

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  • JPA atomic query/save for multithreaded app

    - by TofuBeer
    I am in the midst of changing my JPA code around to make use of threads. I have a separate entity manager and transaction for each thread. What I used to have (for the single threaded environment) was code like: // get object from the entity manager X x = getObjectX(jpaQuery); if(x == null) { x = new X(); x.setVariable(foo); entityManager.persist(x); } With that code in the multi threaded environment I am getting duplicate keys since, I assume, getObjectX returns null for a thread, then that thread is swapped out, the next thread calls getObjextX, also getting null, and then both threads will create and persist a new X(). Short of adding in synchronization, is there an atomic way to get/save-if-doesn't-exist a value with JPA or should I rethink my approach EDIT: I am using the latest Eclipselink and MySql 5.1

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  • What happens if an exception is thrown in finalize()

    - by Psykocyber
    What would happen if an exception is thrown during the execution of finalize()? Is the stack unwind like normally? Does it continue finalize() and ignore the exception? Does it stop finalize() and continue GC the object? Or something else? I'm not looking for guidelines of using finalize() there are plently of pages explaining that.

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  • Partition loop understanding

    - by user1795732
    Why the loop body of the partition method never throws an ArrayIndexOutOfBounds Exception? public static int partition( int[] a, low, high ) { int k = low, m = low; /* loop invariant: * low <= k <= m <= high and * all elements in a[low..k-1] are RED (i.e., < pivot) and * all elements in a[k..m-1] are BLUE (i.e., >= pivot) */ while (m != high) { if (a[m] >= pivot) // a[m] is BLUE { } else { // a[m] is RED swap(a,k,m); k = k+1; } m = m+1; } return k; }

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  • Does importing of packages change visibility of classes?

    - by Roman
    I jsut learned that A class may be declared with the modifier public, in which case that class is visible to all classes everywhere. If a class has no modifier (the default, also known as package-private), it is visible only within its own package. This is a clear statement. But this information interfere with my understanding of importing of packages (which easily can be wrong). I thought that importing a package I make classes from the imported package visible to the importing class. So, how does it work? Are public classes visible to all classes everywhere under condition that the package containing the public class is imported? Or there is not such a condition? What about the package-private classes? They are invisible no mater if the containing package was imported or not? ADDED: It seems to me that I got 2 answers which are marked as good (up-voted) and which contradict eachother.

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  • Can you use regular expressions in struts-config.xml?

    - by rquinn
    I'm trying to route these two url's to different Actions. We are using Struts 1.2: /abc-def/products /abc-def I tried putting this action first: <action path="/abc*/products" type="com.business.exampleAction"> <forward name="success" path="/go"/> </action> and then this one after: <action path="/abc*" type="com.business.differentExampleAction"> <forward name="success" path="/goElsewhere"/> </action> but it always goes to the second action (differentExampleAction in this case). I've tried various iterations for the , like . or (.*), but haven't found anything that actually works yet. From what I've read, it seems like the only regular-expression-like characters allowed in struts-config are the wildcard symbols (* and **), but I hope I am wrong.

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  • Performing regex on a stream

    - by takoi
    I have some large text files which im going to preform consecutive matching on (just capturing, not replacing). Im thinking its not such a good idea to keep the whole file in memory, but rather use a Reader. What i know about the input is that if there's a match, its not going to span more than 5 lines. So my idea was to have some sort of buffer which just keeps these 5 lines, or so, do the first search, and continue. But it has to "know" where the regex match ended for this to work. e.g if the match ends at line 2 it should start the next search from here. Is it possible to do something like this in an efficient way?

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  • Hibernate Unit tests - Reset schema

    - by Marco
    Hi, I'm testing the CRUD operations of my DAOs in JUnit tests. When i execute the single test, Hibernate always resets the schema and populates the DB in a known state. But when i execute multiple tests in a row, Hibernate resets the schema once, and then the data is accumulated during the execution of the tests. This is an unexpected behavior, so I'd like to add in the @Before method of the tests a function that explicitly resets the schema to avoid the pesistence of side data created by previous tests during the execution chain. Any tips? Thanks

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  • Private API and SMS content URI's on Android

    - by Shadow
    Without accessing private API's to get Content URI's, etc. for SMS, how are we expected to query this data? I am currently in the process of writing my own SMS app and I want to stay as compatible as possible. Without storing the information myself in my own database (such that I can store the text messages so that other programs can access the data when/if they delete my app) and without using private API's how the heck are we suppose to query SMS data?

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  • Space as grouping separator in printf

    - by blekione
    I know how to use comma in printf as grouping separator to print value in format like 1,000,000.00 to print it that way I'm using command System.out.printf ("%,.2f", value); but how to use space as grouping separator to format value like 1 000 000.00 I tried to find solution but solutions with using DecimalFormat look at now to complicate for me (beginner level). Is there as easy way as in example with comma to do it?

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  • how to selectively filter items in a collection

    - by Samuel
    I use the following snippet to filter the list of selected users, where isSelected is a boolean variable. Is there a simpler way (helper function) to populate the selectedUsers collection instead of writing the following lines of code. List<User> selectedUsers = new ArrayList<User>(0); for (User user : this.getUsers()) { if (user.isSelected()) { selectedUsers.add(user.getId()); } }

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  • Trimmed down JAXB for just unmarshalling?

    - by fiXedd
    I'm building an application where space is at a premium. I'd really like to use JAXB's unmarshalling capabilities, but including the whole library is out of the question. Has anyone paired it down so that only the bits needed for unmarshalling are included?

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  • Connecting to Sharepoint using HttpClient

    - by Aravindan R
    I am trying to connect to a Sharepoint 2007 using HttpClient 4. The Authentication scheme is NTLM and i wrote an implementation based on this (http://hc.apache.org/httpcomponents-client-ga/ntlm.html). When i try to connect supplying NTCredentials (username,password,host & domain), i get a 500 error saying "The requested function is not supported". I am trying to understand this error. Does anyone know what this error is? and Why is this occuring? Thanks

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  • Io exception: There is no process to read data written to a pipe.

    - by Srikanth
    I'm using Hibernate3.2+Websphere6.0+struts1.3.. After deploying ,application works fine. After some idle time ,i will get this type of error repeatedly,am not able to login at all. Im not using any connection pooling. i feel after idle time its not able to connect to the database again..if i restart the server everything works fine for some time...after that same story.. please help me out

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  • Set reference = null in finally block?

    - by deamon
    A colleague of mine sets reference to null in finally blocks. I think this is nonsense. public Something getSomething() { JDBCConnection jdbc=null; try { jdbc=JDBCManager.getConnection(JDBCTypes.MYSQL); } finally { JDBCManager.free(jdbc); jdbc=null; // <-- Useful or not? } } What do you think of it?

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  • Can Spring understand @Inject replacing Weld as a JSR-299 implementation?

    - by Thorbjørn Ravn Andersen
    I have noticed from several web pages that apparently Spring 3.0 supports @Inject from JSR-330. As we would really like to use JSR-299 syntax for dependency injection in our libraries for both web apps and stand-alone applications, and have alternatives to Weld, it would be nice if Spring could do this. Being a novice to Spring, I tried downloading the Spring Framework distribution and put all jars on the Eclipse build path. No Inject annotation so my existing test project using Weld did not compile. Can this be done with Spring? What do I need to do to get it running? (I am aware that Guice eventually will support this too. It is only in SVN for now, and if there is an official Spring release which can, that would be better.)

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  • Delete all previous records and insert new ones

    - by carlos
    When updating an employee with id = 1 for example, what is the best way to delete all previous records in the table certificate for this employee_id and insert the new ones?. create table EMPLOYEE ( id INT NOT NULL auto_increment, first_name VARCHAR(20) default NULL, last_name VARCHAR(20) default NULL, salary INT default NULL, PRIMARY KEY (id) ); create table CERTIFICATE ( id INT NOT NULL auto_increment, certificate_name VARCHAR(30) default NULL, employee_id INT default NULL, PRIMARY KEY (id) ); Hibernate mapping <?xml version="1.0" encoding="utf-8"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN" "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"> <hibernate-mapping> <class name="Employee" table="EMPLOYEE"> <id name="id" type="int" column="id"> <generator class="sequence"> <param name="sequence">employee_seq</param> </generator> </id> <set name="certificates" lazy="false" cascade="all"> <key column="employee_id" not-null="true"/> <one-to-many class="Certificate"/> </set> <property name="firstName" column="first_name"/> <property name="lastName" column="last_name"/> <property name="salary" column="salary"/> </class> <class name="Certificate" table="CERTIFICATE"> <id name="id" type="int" column="id"> <param name="sequence">certificate_seq</param> </id> <property name="employee_id" column="employee_id" insert="false" update="false"/> <property name="name" column="certificate_name"/> </class> </hibernate-mapping>

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