Mybatis的快速入门和两个配置文件的介绍。

一.Mybatis的快速入门 1.引入mybatis的坐标，mybatis下载地址：https://github.com/mybatis/mybatis-3


    
    
        mysql
        mysql-connector-java
        5.1.32
    
    
    
        org.mybatis
        mybatis
        3.4.6
    
    
    
        junit
        junit
        4.12
    
    
    
        log4j
        log4j
        1.2.17
    
    
    
        org.projectlombok
        lombok
        1.18.10

2.编写实体类（例子中用User），并且在数据库中建表

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
@Data
@AllArgsConstructor
@NoArgsConstructor
public class User {
    private String username;
    private int id;
    private String password;
}

3.编写MapConfig.xml配置文件

4.编写mapper.xml映射文件和mapper接口







    
        select * from user where id= #{id}

import domin.User;
public interface Usermapper {
    User findUserById(int id);
}

5.测试代码：

    @Test//简单查询
    public void test1() throws IOException {
        InputStream resourceAsStream = Resources.getResourceAsStream("mybatis_config.xml");
        SqlSessionFactory build = new SqlSessionFactoryBuilder().build(resourceAsStream);
        SqlSession sqlSession = build.openSession();
        Usermapper usermapper = sqlSession.getMapper(Usermapper.class);
        User user = usermapper.findUserById(4);
        System.out.println(user);
        sqlSession.commit();
    }

6.【拓展】：reasourses目录下添加log4j.xml的配置文件

7.【拓展】封装工具类

public class SqlSessionUtil {
    public static SqlSession getSqlSession(){
        InputStream resourceAsStream = null;
        SqlSession sqlSession=null;
        try {
            resourceAsStream = Resources.getResourceAsStream("mybatis_config.xml");
            SqlSessionFactory build = new SqlSessionFactoryBuilder().build(resourceAsStream);
            sqlSession = build.openSession(true);//自动提交事务
        } catch (IOException e) {
            e.printStackTrace();
        }
        return sqlSession;
    }
}

二.MapConfig.xml配置文件和mapper.xml映射文件详细解释： 1.MapConfig.xml配置文件

2.mapper.xml








    
    
        select * from user where username= #{username} 
    

    
    
        
        select * from user where username = #{username} and password = #{password}
    

    
    
        select * from user where username = #{username} and password = #{password}

@Test
    public void test3() throws IOException {
        SqlSession sqlSession = SqlSessionUtil.getSqlSession();
        Usermapper usermapper = sqlSession.getMapper(Usermapper.class);
        //第一种
        User user1 = usermapper.getUserByUsername("xueyimeng");
        System.out.println(user1);
        //第二种
        User user2 = usermapper.getUser("xueyimeng","123");
        System.out.println(user2);
        //第三种
        Map map=new HashMap<>();
        map.put("username","lisi");
        map.put("password","123");
        User user3 = usermapper.getUserByMap(map);
        System.out.println(user3);
        //第四种
        User user4 = usermapper.getUserByPojo(new User(4, "xueyimeng", "123"));
        System.out.println(user4);
        //第五种
        User user5 = usermapper.getUserByParam("xueyimeng", "123");
        System.out.println(user5);
    }

五种返回结果：

1.返回单个对象
2.返回多个对象（实体类的List集合）
3.返回单个数据
4.一条数据返回map集合
5.多条数据返回map集合（map集合的map集合）

    
    
        select * from user
    

    
    
        select * from user where id=#{id}
    

    
      
      
      
         select * from user

@Test//五种返回结果
    public void test4() throws IOException {
        SqlSession sqlSession = SqlSessionUtil.getSqlSession();
        Usermapper usermapper = sqlSession.getMapper(Usermapper.class);
        //第一种  返回一个对象
        User user1 = usermapper.getUserByUsername("xueyimeng");
        System.out.println(user1);
        //第二种  返回对象集合
        List users = usermapper.getUsers();
        System.out.println(users);
        //第三种  返回单个数据
        int count = usermapper.getCount();
        System.out.println(count);
        //第四种  查一条数据返回map集合
        Map map = usermapper.getUserToMap(4);
        System.out.println(map);
        //第五种  查多条数据返回map集合
          //5.1
        List> mapsOne = usermapper.getUsersToMapOne();
        System.out.println(mapsOne);
          //5.2
        Map mapsTwo = usermapper.getUsersToMapTwo();
        System.out.println(mapsTwo);
    }

特殊的SQL执行：

1.模糊查询
2.批量删除
3.动态获取表名
4.添加功能获取自增的主键

    
    
    
        select * from ${tableName}
    
    
    
    
        insert into user values (null,#{username},#{password})

    @Test//特殊Sql
    public void test5() throws IOException {
        SqlSession sqlSession = SqlSessionUtil.getSqlSession();
        Usermapper usermapper = sqlSession.getMapper(Usermapper.class);
        //第一种 模糊查询
        List users = usermapper.getUserByLike("梨");
        System.out.println(users);
        //第二种 批量删除
        int count = usermapper.deleteMore("1,2");
        System.out.println(count);
        //第三种 动态获取表名
        List users2 = usermapper.getUserByTable("user");
        System.out.println(users2);
        //第四种 添加功能获取自增的主键
        User user = new User("lisi", "123");
        usermapper.insertUser(user);
        System.out.println(user);
    }

resultMap的映射

1.普通的映射：

    
    
        
        
        
    
    
        SELECT *,goods.`id` goods_id FROM goods,USER WHERe goods.`user_id`=user.`id`
    


 
    
        
        
        
         
             
            
            
            
        
    
    
        select * from goods where id=#{id}

Mybatis的快速入门和两个配置文件的介绍。

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