二、Mybatis增、删、改、查基于XML和注解

2020-12-22网站开发发消息

文件结构

2.1基于XML的增、删、改、查

2.1.1定义sql映射文件

?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="com.config.userMapper"
    !-- 根据id得到一个user对象 --
    !-- 参数类型：parameterType  resultType:结果集类型(全类名)--
    select id="getUser" parameterType="int"
        resultType="com.entity.User"
        select * from user where id=#{id}
    /select

    !-- 插入操作 --
    insert id="addUser" parameterType="com.entity.User"
       insert into user(name,age) values(#{name},#{age})
    /insert

    !-- 删除操作 --
    delete id="deleteUser" parameterType="int"
       delete from user where id=#{id}
    /delete

    !-- 更新操作 --
    update id="updateUser" parameterType="com.entity.User"
       update user set name=#{name},age=#{age} where id=#{id}
    /update

    !-- 查询所有 --
    select id="getAllUsers" resultType="com.entity.User"
        select * from user 
    /select
/mapper

2.1.2在config.xml文件中注册这个映射文件

mappers
       mapper resource="com/config/userMapper.xml"/
/mappers

2.1.3定义一个MybatisUtil类，主要用于获取SqlSession

package com.util;

import java.io.IOException;
import java.io.Reader;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

public class MybatisUtil {
    public static SqlSession getSession() throws IOException
    {
        String resource = "config.xml";
        //加载 mybatis 的配置文件（它也加载关联的映射文件）
        Reader reader = Resources.getResourceAsReader(resource);
        //构建 sqlSession 的工厂
        SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(reader);
        //openSession的参数设置为true表示自动提交
        SqlSession session=sessionFactory.openSession(true);
        return session;
    }

}

2.1.4定义相应的测试方法

package com.test;

import java.io.IOException;
import java.io.Reader;
import java.util.List;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;

import com.entity.User;
import com.util.MybatisUtil;



public class Test1 {

    @Test
    public void getUser() throws IOException
    {
        String resource = "config.xml";
        //加载 mybatis 的配置文件（它也加载关联的映射文件）
        Reader reader = Resources.getResourceAsReader(resource);
        //构建 sqlSession 的工厂
        SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(reader);
        //创建能执行映射文件中 sql 的 sqlSession
        SqlSession session = sessionFactory.openSession();
        //映射 sql 的标识字符串
        String statement = "com.config.userMapper.getUser";
        //执行查询返回一个唯一 user 对象的 sql
        User user = session.selectOne(statement, 15);
        session.close();
        System.out.println(user);
    }

    //测试插入
    @Test
    public void addUser() throws IOException
    {
        SqlSession session=MybatisUtil.getSession();
        String statement="com.config.userMapper.addUser";
        //insert表示有几天记录发生了变化
        int insert=session.insert(statement, new User(-1,"王五",29));
        session.close();
        System.out.println(insert);
    }

    //测试删除
    @Test
    public void deleteUser() throws IOException
    {
        SqlSession session=MybatisUtil.getSession();
        String statement="com.config.userMapper.deleteUser";
        int delete=session.delete(statement, 15);
        session.close();
        System.out.println(delete);
    }

    //测试更新
    @Test
    public void updateUser() throws IOException
    {
        SqlSession session=MybatisUtil.getSession();
        String statement="com.config.userMapper.updateUser";
        int update=session.update(statement, new User(16,"马六",34));
        session.close();
        System.out.println(update);
    }

    //测试获得整个表
    @Test
    public void getAllUsers() throws IOException
    {
        SqlSession session=MybatisUtil.getSession();
        String statement="com.config.userMapper.getAllUsers";
        ListUser list=session.selectList(statement);
        for(User user:list)
        {
            System.out.println(user);
        }
        session.close();
    }
}

2.2基于注解的增、删、改、查

2.2.1定义sql映射接口

package com.inter;

import java.util.List;

import org.apache.ibatis.annotations.Delete;
import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.annotations.Update;

import com.entity.User;



public interface UserMapper {

    @Insert("insert into user(name,age) values(#{name},#{age})")
    public int add(User user);

    @Delete("delete from user where id=#{id}")
    public int deleteById(int id);

    @Update("update user set name=#{name},age=#{age} where id=#{id}")
    public int update(User user);

    @Select("select * from user where id=#{id}")
    public User getById(int id);

    @Select("select * from user")
    public ListUser getAll();

}

2.2.2在config.xml中注册这个映射接口

mappers
      mapper class="com.inter.UserMapper"/ 
/mappers

2.2.3编写测试方法

package com.test;

import java.io.IOException;
import java.util.List;

import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.junit.Test;

import com.entity.User;
import com.inter.UserMapper;
import com.util.MybatisUtil;



public class Test2 {

    //测试添加
    @Test
    public void testAdd() throws IOException
    {
        SqlSession session=MybatisUtil.getSession();

        UserMapper mapper=session.getMapper(UserMapper.class);
        int add=mapper.add(new User(-1,"王五",12));
        session.close();
        System.out.println(add);
    }

    //测试删除
    @Test
    public void testDelete() throws IOException
    {
        SqlSession session=MybatisUtil.getSession();
        UserMapper mapper=session.getMapper(UserMapper.class);
        int delete=mapper.deleteById(17);
        session.close();
        System.out.println(delete);
    }

    //测试更新
    @Test
    public void testUpdate() throws IOException
    {
        SqlSession session=MybatisUtil.getSession();
        UserMapper mapper=session.getMapper(UserMapper.class);
        int update=mapper.update(new User(16,"王五",17));
        session.close();
        System.out.println(update);
    }

    //测试查询
    @Test
    public void testGetUsers() throws IOException
    {
        SqlSession session=MybatisUtil.getSession();
        UserMapper mapper=session.getMapper(UserMapper.class);
        ListUser list=mapper.getAll();
        for(User user:list)
        {
            System.out.println(user);
        }
        session.close();
    }

}