关于GenericJDBCException的问题

在spring和hibernate整合的初步阶段，还没有编辑hibernate.cfg.xml这个文件，只有一个beans.xml文件。此时遇到了一个bug。

Exception in thread "main" org.hibernate.exception.GenericJDBCException: could not insert: [com.test.model.User]
at org.hibernate.exception.SQLStateConverter.handledNonSpecificException(SQLStateConverter.java:126)
at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:114)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66)
at org.hibernate.id.insert.AbstractReturningDelegate.performInsert(AbstractReturningDelegate.java:64)
at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2176)
at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2656)
at org.hibernate.action.EntityIdentityInsertAction.execute(EntityIdentityInsertAction.java:71)
at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:279)
at org.hibernate.event.def.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:321)
at org.hibernate.event.def.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:204)
at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:130)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:210)
at org.hibernate.event.def.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:56)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:195)
at org.hibernate.event.def.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:50)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:93)
at org.hibernate.impl.SessionImpl.fireSave(SessionImpl.java:563)
at org.hibernate.impl.SessionImpl.save(SessionImpl.java:551)
at org.hibernate.impl.SessionImpl.save(SessionImpl.java:547)
at com.test.dao.impl.UserDAOImpl.save(UserDAOImpl.java:33)
at com.test.service.UserService.add(UserService.java:30)
at com.test.action.UserAction.main(UserAction.java:23)
Caused by: java.sql.SQLException: Field 'id' doesn't have a default value
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1055)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:956)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3515)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3447)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1951)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2101)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2554)
at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1761)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2046)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:1964)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:1949)
at org.apache.commons.dbcp.DelegatingPreparedStatement.executeUpdate(DelegatingPreparedStatement.java:102)
at org.hibernate.id.IdentityGenerator$GetGeneratedKeysDelegate.executeAndExtract(IdentityGenerator.java:94)
at org.hibernate.id.insert.AbstractReturningDelegate.performInsert(AbstractReturningDelegate.java:57)
... 18 more

主要看第一行，是一个GenericJDBCException类型错误，把错误在网上找了一下，大多数回答都是基于有了hibernate.cfg.xml这个文件的情况下回答的，如：

原因：当使用bookid当主键的时候使用hibernate 并且将其实体映射 <generator class="native" /> 设为自动增长时会报此异常，因为uuid为字符型的无法使用数字型的自动增长。

解决方法：只需要将<generator class="native" /> 在实体中删除掉问题即可解决。

分析了一下，是主键递增方式的问题。我的User.java中有这么一个注解@GeneratedValue（具体这个注解什么意思，可以在网上查查，推荐个链接http://blog.csdn.net/u012493207/article/details/50846616）

User.java代码如下（这里是改之前的，多了一个@GeneratedValue）

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;

@Entity
public class User {
    private int id;
    private String name;
    
    @Id
    @GeneratedValue
    public int getid() {
        return id;
    }
    public void setid(int id) {
        this.id = id;
    }
    public String getname() {
        return name;
    }
    public void setname(String name) {
        this.name = name;
    }
    
}

只需要把@GeneratedValue去掉就行了。