使用JPA与Hibernate实现：entityManager.remove - 无法正常工作 [英] Using JPA with Hibernate implementation: entityManager.remove - not working

问题描述

我通过 Hibernate 4.1.4.Final 实现使用JPA。我的问题是，我不能得到 EntityManager＃remove（）工作。所有其他：更新，插入，选择操作工作正常，除了这一个。

我的 persistence.xml 文件：

 <持久性单位名称= myEntityManager > 
< provider> org.hibernate.ejb.HibernatePersistence< / provider> 
< class> core.entity.Answer< / class> 
< class> core.entity.BaseEntity< / class> 
< exclude-unlisted-classes> true< / exclude-unlisted-classes> 
< validation-mode> NONE< / validation-mode> 
<属性> 
< property name =hibernate.dialectvalue =org.hibernate.dialect.MySQLDialect/> 
< property name =hibernate.show_sqlvalue =true/> 
< property name =hibernate.hbm2ddl.autovalue =update/> 
< / properties> 
< / persistence-unit> 
  

我的 实体:( BaseEntity类只包含主键 - ID）



  @Entity 
 @Table（name =ANSWER）
 @Inheritance（strategy = InheritanceType.TABLE_PER_CLASS）
 public class Answer BaseEntity {
 
 @Column（name =ANSWER_VALUE ）
 private String answerValue; 
 
 @ManyToOne（fetch = FetchType.EAGER）
 @JoinColumn（name =QUESTION_ID，nullable = false）
 private问题问题; 
 
 // overrided equals，hascode，toString 
 //所有getter和setters 
} 
  

在调用时：

  public void remove（T entity）{
 this .entityManager.remove（this.entityManager.merge（实体））; 
} 
  

还试过：



  this.entityManager.remove（实体）; 
  

和：



  T ref = entityManager.getReference（entityClass，primaryKey）; 
 entityManager.remove（ref）; 
  

不运气:(它不会删除的记录答案数据库。



我使用Spring配置来配置实体管理器，如下所示：

 < bean id =persistenceUnitManagerclass =org.springframework.orm.jpa.persistenceunit.DefaultPersistenceUnitManager> 
< property name =persistenceXmlLocations> 
< list> 
< value> classpath *：META-INF / persistence.xml< /值> 
< / list> 
< / property> 
< property name =defaultDataSourceref =dataSource/> 
< / bean> 
 
< bean id =entityManagerFactoryclass =org.springframework.orm .jpa.LocalContainerEntityManagerFactoryBean> 
< property name =persistenceUnitManagerref =persistenceUnitManager/> 
< property name =persistenceUnitNamevalue =myEntityManager/> 
< / bean> 
 
< bean id =tra nsactionManagerclass =org.springframework.orm.jpa.JpaTransactionManager> 
< property name =entityManagerFactoryref =entityManagerFactory/> 
< / bean> 
 
< tx：annotation-driven proxy-target-class =truetransaction-manager =transactionManager/> 
  

remove 在方法注释为 @Transactional 注释。所以它不应该是交易问题。

我启用了Hibernate SQL日志记录，所有其他日志记录。我没有在任何地方看到 delete 查询会被执行或者任何错误。

的选择。请咨询。

编辑 可能这也有帮助：

>

我从其他实体获得答案列表。答案是这样定义的：

  @OneToMany（fetch = FetchType.LAZY，cascade = CascadeType.ALL，mappedBy =evaluationPart ）
私人列表<答案> answers = new LinkedList<>（）; 
  

调用如下所示：

 列表与LT;应答和GT; answers = evaluationPart.getAnswers（）; 
 if（answers！= null&& answers.size（）> 0）{
 for（Answer answer：answers）{
 answerFacade.remove（answer）; //这会调用enetityManager.remove 
 
 
 code $ <$ $ p 
 
解决方案
我可能没有这个主题，但这些可能是问题所在。 
 
 
 第一个原因  -  
没有在此条目中定义的cascadeType 
  @ManyToOne（fetch = FetchType.EAGER）
 @JoinColumn（name = QUESTION_ID，可为空= false）
私人问题问题; 
  
 第二个原因（更多建议）
 
 
 
由于Answer的链表已映射到Question对象，因此不建议直接从列表中删除单个对象。更好地从链接列表中删除元素，然后更新/合并问题对象，该对象将在应答表上自动执行删除操作。
 
 
 
希望这有助于： p> 
I am using JPA over Hibernate 4.1.4.Final implementation. My problem is that I can't get EntityManager#remove() working. All other: update, insert, select operation are working just fine except this one.

My persistence.xml file:


<persistence-unit name="myEntityManager">
    <provider>org.hibernate.ejb.HibernatePersistence</provider>
    <class>core.entity.Answer</class>
    <class>core.entity.BaseEntity</class>
    <exclude-unlisted-classes>true</exclude-unlisted-classes>
    <validation-mode>NONE</validation-mode>
    <properties>
        <property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect"/>
        <property name="hibernate.show_sql" value="true"/>
        <property name="hibernate.hbm2ddl.auto" value="update"/>
    </properties>
</persistence-unit>


My Answer entity: (BaseEntity class just holds the primary key - ID)
@Entity
@Table(name = "ANSWER")
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
public class Answer extends BaseEntity {

    @Column(name = "ANSWER_VALUE")
    private String answerValue;

    @ManyToOne(fetch = FetchType.EAGER)
    @JoinColumn(name = "QUESTION_ID", nullable = false)
    private Question question;                

    //overrided equals, hascode, toString 
    // all getters and setters
}
When calling:
public void remove(T entity) {
    this.entityManager.remove(this.entityManager.merge(entity));
}
Also tried:
this.entityManager.remove(entity);
And:
T ref = entityManager.getReference(entityClass, primaryKey);
entityManager.remove(ref);
No luck :( it is not deleting the record of Answer from the database.

I am using Spring configuration to configure the entity manager like this:
<bean id="persistenceUnitManager" class="org.springframework.orm.jpa.persistenceunit.DefaultPersistenceUnitManager">
    <property name="persistenceXmlLocations">
        <list>
            <value>classpath*:META-INF/persistence.xml</value>
        </list>
    </property>
    <property name="defaultDataSource" ref="dataSource"/>
</bean>

<bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
    <property name="persistenceUnitManager" ref="persistenceUnitManager"/>
    <property name="persistenceUnitName" value="myEntityManager"/>
</bean>

<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
    <property name="entityManagerFactory" ref="entityManagerFactory"/>
</bean>

<tx:annotation-driven proxy-target-class="true" transaction-manager="transactionManager"/>
remove is called in the method which is annotated with @Transactional annotation. So it shouldn't be transactions issue.

I have enabled Hibernate SQL logging, all the other logging. I am not seeing anywhere that delete query would be executed or any error at all.

And I am really out of options here. Please advice.

EDIT

Maybe this will also help:

I am getting the list of answers from the other entity. The answers are defined like this:
@OneToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL, mappedBy = "evaluationPart")
private List<Answer> answers = new LinkedList<>();
Calling remove like this:
List<Answer> answers = evaluationPart.getAnswers();
if (answers != null && answers.size() > 0) {
    for (Answer answer : answers) {
        answerFacade.remove(answer); //This calls enetityManager.remove
    }
}

解决方案
I may be out of the topic but these can be the issues for the problem

First Reason - 
    No cascadeType defined in this entry
 @ManyToOne(fetch = FetchType.EAGER)
    @JoinColumn(name = "QUESTION_ID", nullable = false)
    private Question question;  
Second Reason (More of a suggestion)

As the linkedlist of Answer is mapped to the Question object, deleting a single object from the list directly is not recommended as a good practice. Better remove the element from the linked list and then update/merge the question object which will perform the remove operation automatically on the Answer table.

Hope this helps :)

                        
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