2016-08-05 45 views
0

我有一个用户等级:如何在Hibernate中从XML生成主键?

public class User{ 
    private Long userId; 
} 

而且我在XML中使用这样的:

<id name="userId" type="long" unsaved-value="null"> 
     <column name="USER_ID" not-null="true" /> 
     <generator class="native" /> 
</id> 

但是,当我试图保存用户对象不分配的用户id到我的对象得到以下错误:

Caused by: java.sql.SQLException: Field 'USER_ID' doesn't have a default value 
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:957) 
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3878) 
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3814) 
    at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2478) 
    at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2625) 
    at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2551) 
    at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1861) 
    at com.mysql.jdbc.PreparedStatement.executeUpdateInternal(PreparedStatement.java:2073) 
    at com.mysql.jdbc.PreparedStatement.executeUpdateInternal(PreparedStatement.java:2009) 
    at com.mysql.jdbc.PreparedStatement.executeLargeUpdate(PreparedStatement.java:5094) 
    at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:1994) 
    at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.executeUpdate(ResultSetReturnImpl.java:208) 
    ... 22 more 

我想让Hibernate为我生成id。我在这里错过了什么?

回答

2

您需要设置autoincrement为USER_ID列

ALTER TABLE users ADD USER_ID INT UNSIGNED NOT NULL AUTO_INCREMENT; 

native指令意味着你的数据库获取生成ID的责任。因为你没有设置在数据库端生成ID的策略,所以你得到了异常java.sql.SQLException: Field 'USER_ID' doesn't have a default value