Question

我是hibernate的新手，我正在使用带有MySQL的hibernate 3.0，我想使用数据库进行简单的数据库操作，如插入更新和删除。我获得了插入和删除的成功结果，但无法更新特殊领域。我有一个名为Employee的持久化类，其中包含Fname，Lname，Id和带有getter和setter的邮件。

这是我的主要方法： -

public static void main(String[] args) {
    Session session = null;
    Random r = new Random();
    try {
        /*
         * This step will read hibernate.cfg.xml
         * 
         * and prepare hibernate for use
         */
        SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory();
        session = sessionFactory.openSession();
        Transaction trx = session.beginTransaction();
        Contact contact = new Contact();
        contact = (Contact) session.get(Contact.class, new Long(1));
        // Create new instance of Contact and set
        // values in it by reading them from form object
        System.out.println("Inserting Record");
        contact.setId(r.nextLong() % 100);
        contact.setFirstName("123anand");
        contact.setLastName("nandurbarkar");
        contact.setEmail("anand_it1990@yahoo.com");
        trx.commit();
        session.update(contact);

这是我的conf文件： -

    <hibernate-configuration>
    <session-factory>
    <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
   <property name="hibernate.connection.url">jdbc:mysql://localhost/hibernatetutorial</property>
   <property name="hibernate.connection.username">root</property>
   <property name="hibernate.connection.password">root</property>
  <property name="hibernate.connection.pool_size">1</property>
 <property name="show_sql">true</property>
 <property name="dialect">org.hibernate.dialect.MySQLDialect</property>
 <property name="hibernate.hbm2ddl.auto">update</property>
    <!-- Mapping files -->
 <mapping resource="contact.hbm.xml"/>
 </session-factory>
</hibernate-configuration>

如果您知道如何解决此问题，请提供帮助。在此先感谢...

Answer 1

您无法更改实体的ID。如果您想了解其他属性的更新是如何工作的，请尝试以下方法：

public static void main(String[] args) {
    Session session = null;
    Random r = new Random();
    try {
        /*
         * This step will read hibernate.cfg.xml
         * 
         * and prepare hibernate for use
         */
        SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory();
        session = sessionFactory.openSession();
        Transaction trx = session.beginTransaction();
        Contact contact = new Contact();

        // Create new instance of Contact and set
        // values in it by reading them from form object
        System.out.println("Inserting Record");
        contact.setId(r.nextLong() % 100);
        contact.setFirstName("123anand");
        contact.setLastName("nandurbarkar");
        contact.setEmail("anand_it1990@yahoo.com");
        // this makes contact persistent. No SQL commands yet
        session.persist(contact);
        // sync the session. Here you get a SQL INSERT
        session.flush();

        // change some properties
        contact.setFirstName("ugo");

        // sync again.Here you get a SQL UPDATE
        session.flush()

        // Now, let's say you want to update an existing instance/record
        // with id = 123
        // retrieve the instance
        Contact c = session.get(Contact.class, new Long(123));
        c.setFirstName("new name");

        // sync the session with the db
        session.flush(); // <- here you get SQL UPDATE

        trx.commit();

Answer 2

我认为您需要在提交会话之前进行更新

所以交换你的最后两行应该可以使它工作： -

session.update(contact);  
trx.commit();

无法在hibernate中更新数据库

2 个答案: