Question

我的Java Web App从数据库中读取数据但是当我尝试编写某些东西时，JPA说好了，但数据库没有改变。我调用“merge”方法，数据不会保存在数据库中，只保存在内存中。我可以直接在数据库中进行SELECT并查看旧数据。但是，如上所示，Java控制台不会抛出任何异常。

Java控制台：

INFO: [EL Finest]: 2011-10-14 15:02:41.847--UnitOfWork(13027895)--Thread(Thread[http-thread-pool-8080-(6),10,Grizzly])--Merge clone with references user1

更改密码的被调用方法：

public static User changePassword(String username, String oldPassword, String newPassword){
        User user = userFacade.find(username);
        if(user != null && user.getPassword().equals(oldPassword)){
            user.setPassword(newPassword);
            userFacade.edit(user); // supposed to save the new password on database, but it's not
            // at this point, the user has a new password on memory, but on database the password is still the old one
            return user;
        }
        return null;
    }

的persistence.xml：

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0" 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">
    <persistence-unit name="APP1PU" transaction-type="RESOURCE_LOCAL">
        <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
        <class>com.company.User</class>
        <properties>
            <property name="javax.persistence.jdbc.url" value="jdbc:mysql://127.0.0.1:3306/app1"/>
            <property name="javax.persistence.jdbc.password" value="12345"/>
            <property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver"/>
            <property name="javax.persistence.jdbc.user" value="root"/>
            <property name="eclipselink.logging.level" value="FINEST"/>
        </properties>
    </persistence-unit>
</persistence>

User.java：

@Entity
@Table(name = "user")
@Cache (
     type=CacheType.NONE
     )
public class User implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @Basic(optional = false)
    private String username;

    @Basic(optional = false)
    private String password;

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }
}

UserFacade.java

public class UserFacade {
    private EntityManagerFactory emf = Persistence.createEntityManagerFactory("APP1PU");

    private EntityManager em;

    protected EntityManager getEntityManager() {
        if( em == null ){
            em = emf.createEntityManager();
        }
        return em;
    }

    public void create(User entity) {
        getEntityManager().persist(entity);
    }

    public void edit(User entity) {
        getEntityManager().merge(entity);
    }

    public void remove(User entity) {
        getEntityManager().remove(getEntityManager().merge(entity));
    }

    public User find(Object id) {
        return getEntityManager().find(entityClass, id);
    }

}

任何人都可以理解这种行为的原因？或者有一些我可以做的测试的建议吗？

提前致谢！

Answer 1

写入操作后尝试entityManager.flush()。或者在写操作之前启动事务（entityManager.getTransaction().begin()），然后在结束时关闭它（entityManager.getTransaction().commit()）

JPA读取但不会持续存在

1 个答案: