java实现返回新增主键ID的实例方法

<insert id="insertAndGetId" useGeneratedKeys="true" keyProperty="userId" parameterType="com.chenzhou.mybatis.User"> 
  insert into user(userName,password,comment) 
  values(#{userName},#{password},#{comment}) 
</insert>

public class User { 
  private int userId; 
  private String userName; 
  private String password; 
  private String comment; 

  //setter and getter 
}

public interface UserDao {  
  public int insertAndGetId(User user);  
}

User user = new User(); 
user.setUserName("chenzhou"); 
user.setPassword("xxxx"); 
user.setComment("测试插入数据返回主键功能"); 

System.out.println("插入前主键为："+user.getUserId()); 
userDao.insertAndGetId(user);//插入操作 
System.out.println("插入后主键为："+user.getUserId());