我正在使用 Spring、JPA 和 Hibernate。这是我用来调试更大的 JPA 相关问题的玩具示例。然而，这个试图持久化一个非常基本的实体的简单示例HelloBean，似乎创建了分离的对象。据我所知，调用对象应该将实体设置为由持久性上下文管理persist。EntityManager但是，它没有，merge也不适用于此。输出如下：
Starting...
Service found in context as: net.solasistim.hello.HelloService@3b7a687b
Hibernate: insert into HelloBean (message) values (?)
Is bean attached? = false
Hibernate: select hellobean0_.id as id1_0_0_, hellobean0_.message as message2_0_0_ from HelloBean hellobean0_ where hellobean0_.id=?
Is bean attached? = false
为简洁起见省略了导入。
Hello.java::
public class Hello {
public static void main(String[] args) throws Exception {
ApplicationContext context =
new ClassPathXmlApplicationContext("beans.xml");
System.out.println("Starting...");
HelloService svc = (HelloService) context.getBean("helloService");
System.out.println("Service found in context as: " + svc);
HelloBean bean1 = new HelloBean();
bean1.setMessage("This is bean 1.");
HelloBean bean2 = new HelloBean();
bean2.setMessage("This is bean 2.");
svc.persist(bean2);
System.out.println("Is bean attached? = " + svc.isAttached(bean2));
HelloBean newBean = svc.merge(bean2);
System.out.println("Is bean attached? = " + svc.isAttached(newBean));
}
}
HelloService.java::
@Service
@Transactional
public class HelloService {
@PersistenceContext private EntityManager em;
public void persist(HelloBean entity) {
em.persist(entity);
}
public HelloBean merge(HelloBean entity) {
return em.merge(entity);
}
public void delete(HelloBean entity) {
em.remove(entity);
}
public boolean isAttached(HelloBean entity) {
return em.contains(entity);
}
}
HelloBean.java::
@Entity
public class HelloBean {
@Id
@GeneratedValue
private long id;
private String message;
public void setMessage(String message) {
this.message = message;
}
public String getMessage() {
return this.message;
}
}
pom.xml::
<project>
<modelVersion>4.0.0</modelVersion>
<groupId>net.solasistim.hello</groupId>
<artifactId>hello</artifactId>
<version>1</version>
<packaging>jar</packaging>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.11</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>3.2.2.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-orm</artifactId>
<version>3.2.2.RELEASE</version>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-core</artifactId>
<version>4.2.0.Final</version>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-entitymanager</artifactId>
<version>4.2.0.Final</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.24</version>
</dependency>
</dependencies>
</project>
beans.xml::
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:tx="http://www.springframework.org/schema/tx"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd
http://www.springframework.org/schema/tx
http://www.springframework.org/schema/tx/spring-tx-3.1.xsd">
<context:component-scan base-package="net.solasistim.hello"/>
<context:annotation-config />
<bean id="entityManagerFactory"
class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
<property name="persistenceUnitName" value="my-persistence-unit"/>
</bean>
<!-- These two are needed for @Transactional annotations to be processed.
Nothing will be committed without them. -->
<tx:annotation-driven/>
<bean id="transactionManager"
class="org.springframework.orm.jpa.JpaTransactionManager">
<property name="entityManagerFactory" ref="entityManagerFactory" />
</bean>
</beans>
persistence.xml::
<?xml version="1.0"?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd"
version="2.0">
<persistence-unit name="my-persistence-unit">
<provider>org.hibernate.ejb.HibernatePersistence</provider>
<properties>
<property name="hibernate.dialect"
value="org.hibernate.dialect.MySQLDialect" />
<property name="hibernate.connection.driver_class"
value="com.mysql.jdbc.Driver" />
<property name="hibernate.connection.url"
value="jdbc:mysql://localhost:3306/jpa_test" />
<property name="hibernate.connection.username"
value="root" />
<property name="hibernate.connection.password"
value="" />
<property name="hibernate.show_sql" value="true" />
<property name="hibernate.hbm2ddl.auto" value="create" />
</properties>
</persistence-unit>
</persistence>