Mybatis 需要注意的问题

最新推荐文章于 2022-08-08 15:47:17 发布

Lawrence_shpeng

最新推荐文章于 2022-08-08 15:47:17 发布

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分类专栏： JAVA 文章标签： mybatis java 增删改查

本文链接：https://blog.youkuaiyun.com/ouhuanyixie8627/article/details/57983837

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本文介绍MyBatis框架下如何实现基本的增删改查操作，并通过具体示例详细展示了配置文件与接口映射的方法，以及解决常见的InvalidBoundStatement错误。

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mybatis：Invalid bound statement (not found)

当出现mybatis 出现这个错误时需要注意

使用了接口编程方式

实体类User

配置文件UserMapper.xml

接口文件UserMapper.java

public interface UserMapper {
public User selectUserById(int id);
}

注意在配置文件中

<mapper namespace="db.UserMapper">

    <select id="selectUserById" parameterType="int" resultType="entity.User">
        select * from user where id = #{id}
    </select>

</mapper>

namespace 要与接口文件UserMapper.java保持一致

select元素中的id要与 UserMapper.java中的方法名保持一致

mybatis 增删改查

UserMapper.xml文件

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
    "http://mybatis.org/dtd/mybatis-3-mapper.dtd">



<mapper namespace="db.UserMapper">

    <resultMap type="entity.User"   id="resultListUser">
    <id column="id" property="id"/>
    <result column="userName" property="userName"/>
    <result column="userAge"   property="userAge"/>
    <result column="userAddress" property="userAddress"/>
    </resultMap>

      <select id="selectUserById" parameterType="int" resultType="entity.User">
        select id,userName,userAge,userAddress from user where id=#{id}
    </select>
    <select id="selectUsers" parameterType="string" resultMap="resultListUser">
        select * from user where userName like #{userName}
    </select>

     

    <insert id="addUser" parameterType="entity.User"   useGeneratedKeys="true" keyProperty="id">
       insert into user(userName,userAge,userAddress) values(#{userName},#{userAge},#{userAddress})
    </insert>

    <update id="updateUser" parameterType="entity.User">
    update user set userName=#{userName},userAge=#{userAge},userAddress=#{userAddress} where id=#{id}
    </update>

    <delete id="deleteUser" parameterType="int">
         delete from user where id=#{id}
    </delete>
</mapper>

UserMapper.java

package db;

import java.util.List;

import entity.User;

public interface UserMapper {

   public User selectUserById(int id);
   public List<User> selectUsers(String userName);
   public void addUser(User user);
   public void updateUser(User user);
   public void deleteUser(int id);

}

增删改查类
public class TestAddupdatedelete{

public void findlist(){
       SqlSession session= SqlSessionHelper.getSessionFactory().openSession();

       try{

           UserMapper userMapper = session.getMapper(UserMapper.class);
           List<User> users = userMapper.selectUsers("%");

           for(User user:users){
               System.out.println(user.getUserAddress()+" "+user.getUserName());
           }

       }finally{
           session.clearCache();
           session.close();
       }
   }

public void addUser(User user){
   if(user ==null){
       user = new User();
       user.setUserAddress("武林广场");
       user.setUserAge("80");
       user.setUserName("青鸟");
   }


   SqlSession session = SqlSessionHelper.getSessionFactory().openSession();
   UserMapper userMapper = session.getMapper(UserMapper.class);
   userMapper.addUser(user);
   session.commit();
   System.out.println("当前增加的用户id为"+user.getId());

   try{

   }finally{
       if(session != null)
           session.close();
   }

}

public void update(){
   SqlSession session = SqlSessionHelper.getSessionFactory().openSession();
   UserMapper userMapper = session.getMapper(UserMapper.class);

   try{
       User user = userMapper.selectUserById(4);
       user.setUserAddress("上海市青浦区");
       userMapper.updateUser(user);
       session.commit();
   }finally{
       session.close();
   }

}

public void delete(){
   SqlSession session = SqlSessionHelper.getSessionFactory().openSession();
   UserMapper userMapper = session.getMapper(UserMapper.class);

   try{
       userMapper.deleteUser(4);
       session.commit();
   }finally{
       session.close();
   }

}

}