JavaWeb学习之路（七）——Mybatis常见操作

CURD

命名空间namespace

namespace的包名要和Dao/mapper接口的包名一致！

查询语句Select

选择，查询语句

• id：就是对应发namespace中的方法名

• resultType:Sql语句执行的返回值

• parameterType：参数类型

<select id="getUserById" resultType="top.huii.pojo.User" parameterType="int">
    select * from javaweb.user where id = #{id}
</select>

结果：User{id=1, name='张三', pwd='11111111'}

新增Insert

<insert id="addUser" parameterType="top.huii.pojo.User">
    insert into javaweb.user (id, name, pwd) values (#{id}, #{name}, #{pwd});
</insert>

修改Update

<update id="updateUser" parameterType="top.huii.pojo.User">
    update javaweb.user set name=#{name}, pwd=#{pwd} where id = #{id};
</update>

删除Delete

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

代码展示

• 工具类MybatisUtils

package top.huii.utils;

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 java.io.IOException;
import java.io.InputStream;

//sqlSessionFactory
public class MybatisUtils {
    private static SqlSessionFactory sqlSessionFactory;
    static {
        try {
//            获取sqlSessionFactory
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static SqlSession getSqlSession(){
        SqlSession sqlSession = sqlSessionFactory.openSession();
        return sqlSession;
    }
}

• 定义接口UserDao.java

package top.huii.dao;

import top.huii.pojo.User;

import java.util.List;

public interface UserDao {
    // 获取全部用户
    List<User> getUserList();

    // 根据id查询用户
    User getUserById(int id);

    // 插入一个用户
    int addUser(User user);

    // 修改用户
    int updateUser(User User);

    // 删除用户
    int deleteUser(int id);
}

• sql语句UserMapper.xml

<?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="top.huii.dao.UserDao">
    <select id="getUserList" resultType="top.huii.pojo.User">
        select * from javaweb.user;
    </select>
    <select id="getUserById" resultType="top.huii.pojo.User" parameterType="int">
        select * from javaweb.user where id = #{id};
    </select>
    <insert id="addUser" parameterType="top.huii.pojo.User">
        insert into javaweb.user (id, name, pwd) values (#{id}, #{name}, #{pwd});
    </insert>
    <update id="updateUser" parameterType="top.huii.pojo.User">
        update javaweb.user set name=#{name}, pwd=#{pwd} where id = #{id};
    </update>
    <delete id="deleteUser" parameterType="int">
        delete from javaweb.user where id=#{id};
    </delete>
</mapper>

• 测试UserDaoTest.java

package top.huii.dao;

import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
import top.huii.pojo.User;
import top.huii.utils.MybatisUtils;

import java.util.List;

public class UserDaoTest {
    @Test
    public void Test() {
//        获得sqlSession对象
        SqlSession sqlSession = MybatisUtils.getSqlSession();
//        方式1：getMapper 推荐
        UserDao mapper = sqlSession.getMapper(UserDao.class);
        List<User> userList = mapper.getUserList();

//        方式2 不推荐
//        List<User> userList = sqlSession.selectList("top.huii.dao.UserDao.getUserList");

        for (User user :
                userList) {
            System.out.println(user);
        }
        sqlSession.close();

    }

    @Test
    public void getUserById(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserDao mapper = sqlSession.getMapper(UserDao.class);

        User user = mapper.getUserById(1);
        System.out.println(user);

        sqlSession.close();
    }

    @Test
    public void addUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserDao mapper = sqlSession.getMapper(UserDao.class);

        int i = mapper.addUser(new User(4, "你好试试", "11122333"));
        if (i > 0){
            System.out.println("成功");
        }
        // 提交事务
        sqlSession.commit();
        sqlSession.close();
    }

    @Test
    public void updateUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserDao mapper = sqlSession.getMapper(UserDao.class);
        mapper.updateUser(new User(4, "1111", "12000"));

        sqlSession.commit();
        sqlSession.close();
    }

    @Test
    public void deleteUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserDao mapper = sqlSession.getMapper(UserDao.class);
        mapper.deleteUser(1);

        sqlSession.commit();
        sqlSession.close();
    }
}

万能Map

实体类中表太多，可以用map

配置解析

核心配置文件

MyBatis 的配置文件包含了会深深影响 MyBatis 行为的设置和属性信息。 配置文档的顶层结构如下：

• configuration（配置）
  • properties（属性）
  • settings（设置）
  • typeAliases（类型别名）
  • typeHandlers（类型处理器）
  • objectFactory（对象工厂）
  • plugins（插件）
  • environments（环境配置）
    • environment（环境变量）
      • transactionManager（事务管理器）
      • dataSource（数据源）
  • databaseIdProvider（数据库厂商标识）
  • mappers（映射器）