做Jpa& Hibernate加载数据在数据库中异步变化？

问题描述

 创建或替换视图my_view为
选择cc.CCID ccid 
 sm.SMCODE smcode，
 NVL（sm.smname，cc.ccname）sname 
从CC cc 
内部加入SM sm 
在cc。 id = sm.id; 
  

我使用 jpa 2.1 和 hibernate 4.3.7 将我的视图映射到我的实体。
我的实体类看起来像这样：

  public class CCRequest implements Serializable {
 
 private static final long serialVersionUID = 1L; 
 
私人字符串ccId; 
 
私人字符串smCode; 
 
 private String sName; 
} 
  

我的映射xml看起来像这样：

 <？xml version =1.0encoding =UTF-8？> 
< entity-mappings xmlns =http://xmlns.jcp.org/xml/ns/persistence/orm
 version =2.1> 
< entity class =CCRequestname =CCRequest001> 
< table name =my_view/> 
<属性> 
< id name =ccId> 
< column name =ccid/> 
< / id> 
< basic name =smCode> 
< column name =smcode/> 
< / basic> 
< basic name =sName> 
< column name =sname/> 
< / basic> 
< / attributes> 
< / entity> 
< / entity-mappings> 
  

所以我用jpa正确地查询我的实体并返回所有记录。
这是问题所在，当我异步更改数据库中的数据时，令人震惊的是，我的jpa查询返回以前的记录。
我做错了什么？

解决方案

我遇到的问题是，在4月的春天之前， JpaTemplate 用于处理jpa实体，我将 EntityManager 传递给 JpaTemplate 以编程方式从 EntityManagerFactory 的一个实例中执行，没有问题。

JpaTemplate 本身可以做任何事情来清除 EntityManager 并清除缓存。
当我迁移到Spring 4时，我遇到了 JpaTemplate 已被删除，因此我必须使用 EntityManager 直。


我通过 EntityManagerFactory 的实例以编程方式获得 EntityManager 的实例。


我有一个 EntityManagerProvider 类，它创建一个 EntityManager 的实例。 EntityManagerFactory 。

  public class EntityManagerProvider {
 
 public static EntityManager createEntityManager（EntityManagerFactory entityManagerFactory）{
 return entityManagerFactory.createEntityManager（）; 
 
 
 $ / code> 

我得到这样的entityManager实例：

 < bean id =entityManagerclass =com.tosan.novin.sipa.bo.da.jpa.EntityManagerFactoryProviderfactory-method = createEntityManager > 
< constructor-arg index =0ref =entityManagerFactory/> 
< / bean> 
  

但是我明白如果我想要 EntityManager 管理事务和刷新的唯一方法是使用 @PersistenceContext 在我的bean中注入 EntityManager 。





  @PersistenceContext 
受保护的EntityManager em; 
  

我对这种方式有点困惑，但是我的问题通过这种方法解决了。

I have an oracle view in which I query my db.

create or replace view my_view as
Select cc.CCID ccid
       sm.SMCODE smcode,
       NVL(sm.smname, cc.ccname) sname
  From CC cc
 Inner Join SM sm
    On cc.id = sm.id;

I use jpa 2.1 and hibernate 4.3.7 to map my view to my entity.My entity class looks like this:

public class CCRequest implements Serializable {

    private static final long serialVersionUID = 1L;

    private String ccId;

    private String smCode;

    private String sName;
}

And my mapping xml looks like this:

<?xml version="1.0" encoding="UTF-8"?>
<entity-mappings xmlns="http://xmlns.jcp.org/xml/ns/persistence/orm"
                 version="2.1">
    <entity class="CCRequest" name="CCRequest001">
        <table name="my_view"/>
        <attributes>
            <id name="ccId">
                <column name="ccid"/>
            </id>
            <basic name="smCode">
                <column name="smcode"/>
            </basic>
            <basic name="sName">
                <column name="sname"/>
            </basic>
        </attributes>
    </entity>
</entity-mappings> 

So I query my entity with jpa properly and it returns all my records.Here is the problem, when I change my data in DB asynchronously, Shockingly my jpa query returns previous records.Have I done something wrong?

解决方案

The problem I was facing was that in spring before 4, which we had JpaTemplate for working with jpa entities, I passed EntityManager to the instances of JpaTemplate programmatically from an instance of EntityManagerFactory with no problem.

JpaTemplate itself would do any thing for flushing EntityManager and clearing cache.When I migrate to spring 4 I faced that JpaTemplate has been dropped so I have to work with EntityManager directly.

I get instance of EntityManager programmatically from an instance of EntityManagerFactory.

I have a EntityManagerProvider class which create an instance of EntityManager from an instance of EntityManagerFactory.

public class EntityManagerProvider {

    public static EntityManager createEntityManager(EntityManagerFactory entityManagerFactory) {
        return entityManagerFactory.createEntityManager();
    }
}

I get entityManager instance like this:

<bean id="entityManager" class="com.tosan.novin.sipa.bo.da.jpa.EntityManagerFactoryProvider" factory-method="createEntityManager">
        <constructor-arg index="0" ref="entityManagerFactory"/>
</bean>

But I understand that if I want EntityManager to manage transactions and flushing the only way is use of @PersistenceContext for injecting EntityManager into my beans.

@PersistenceContext
protected EntityManager em;

I am a little confused yet with this manner but my problem solved with this approach.

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