在SELECT查询中使用Hibernate ConstraintViolationException [英] Hibernate ConstraintViolationException on SELECT query

问题描述

我有一个多字段唯一约束的持久类。但定义的唯一约束对于我来说是不够的，因为在这些字段中，不相等但相似的值也是唯一的。

我实现了一个 checkUniqueConstraint 方法。
在添加和更新DAO类的方法中，我在调用 checkUniqueConstraint 之前添加或更新持久化对象。

checkUniqueConstraint 方法只是运行一个SELECT查询来找到类似于输入的对象，并且抛出一个检查Exception在哪里找到一些。

  public class PersistClassDao {
 public void checkUniqueConstraint（PersistClass persistObject）throws DuplicateEntityException {
 / ** 
 *创建查询字符串，查找类似的持久对象输入参数。 
 ** / 
尝试{
 PersistClass result =（PersistClass）query.uniqueResult（）; 
 if（result！= null&&（persistObject.getId（）== null || persistObject.getId（）！= result.getId（）））{
 throw new DuplicateEntityException（exceptionMessage， ）; 
} 
} catch（NonUniqueResultException e）{
 throw new DuplicateEntityException（exceptionMessage）; 
 
 
 $ b public long add（/ *新的persistObject * /的字段）抛出DuplicateEntityException {
 //创建persistObject的transisent实例
 PersistClass newObject = getPersistClass（/ * new persistObject * /的字段）; 
 checkUniqueConstraint（newObject）; 
尝试{
 getCurrentSession（）。save（newObject）; 
 getCurrentSession（）。flush（）; 
返回newObject.getId（）; 
} catch（ConstraintViolationException e）{
 throw new DuplicateEntityException（）; 
 
 
 
 
 
 
 $我有一个transactionl服务mehod添加和另一个更新。
 
 
当我运行我的测试时， 
 
 
 
 
首先添加2个persistObjects（通过服务方法）。
 
然后更新一个（通过服务方法）它们，以便类似于其他
 
 
我期望抛出DuplicatException 
 
 
 
 
 
但是真的是一个org.hibernate.exception。 ConstraintViolationException抛出checkUniqueConstraint !! 
 
 
为什么？ 
解决方案
问题必须出现在 FlushMode 中。 Hibernate默认在执行查询之前刷新实体，请参阅 http ：//docs.jboss.org/hibernate/core/3.5/javadocs/org/hibernate/FlushMode.html#AUTO 。
 
 
 
您必须有部分初始化新实体，将它们与会话绑定的实体相关联，然后尝试执行查询。 Hibernate会话在查询之前执行flush操作，并以ConstraintViolationException失败，这是正常的。
 
 
 
解决方案： 
 
 
 
 
在整个应用程序的cfg文件中将 FlushMode 更改为 COMMIT ，
 
只修改一个会话 session.setFlushMode（FlushMode.COMMIT）或
 
 
通过调用query.setFlushMode（FlushMode），可以将更改的影响缩小到单个查询。 COMMIT）。
 
 
 
I have a Persistent Class with multi-field unique constraint on it. But defined unique constraint is not sufficient for me because on one those field non-equal but similar values are unique too.


I implement a checkUniqueConstraint method.
In add and update  methods of DAO class, I call checkUniqueConstraint before adding or updating persist object.

checkUniqueConstraint method just run a SELECT query to find object similar to input and throw a check Exception where find some ones.
public class PersistClassDao {    
public void checkUniqueConstraint(PersistClass persistObject) throws DuplicateEntityException {
    /**
    * creating a query string that find persist objects similar to input parameter.
    **/
    try {
        PersistClass result = (PersistClass) query.uniqueResult();
        if(result != null && (persistObject.getId() == null  || persistObject.getId() != result.getId())){
            throw new DuplicateEntityException(exceptionMessage, "");
        } 
    } catch (NonUniqueResultException e) {
        throw new DuplicateEntityException(exceptionMessage);
    }
}

public long add(/* field of new persistObject*/) throws DuplicateEntityException {
    //creates a transisent instance of persistObject
    PersistClass newObject = getPersistClass(/* field of new persistObject*/);
    checkUniqueConstraint(newObject);
    try {
        getCurrentSession().save(newObject);
        getCurrentSession().flush();
        return newObject.getId();
    } catch (ConstraintViolationException e) {
        throw new DuplicateEntityException();
    }
}
I have a transactionl service mehod for add and another for update.

When I run my test that


First add 2 persistObjects (through service method).
Then update one (through service method) them so that be similar to the other
I expect that DuplicatException be thrown


But really a org.hibernate.exception. ConstraintViolationException  thrown through checkUniqueConstraint!!

Why? 
解决方案
The problem must be in FlushMode. Hibernate by default flushes entities before executing queries, see http://docs.jboss.org/hibernate/core/3.5/javadocs/org/hibernate/FlushMode.html#AUTO.

You must have partially initialized new entities, associated them with the session-bounded ones and now try to do the query. Hibernate session executes flush just before the query and fails with ConstraintViolationException, which is OK.

Solution:

change FlushMode to COMMIT in cfg file for the entire application, 
modify just a single session by session.setFlushMode(FlushMode.COMMIT) or 
you can narrow the impact of the change down to the single Query by calling query.setFlushMode(FlushMode.COMMIT).


                        
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