09.JavaWeb-MyBatis

3.MyBatis        

        MyBatis 是一款优秀的持久层框架，它支持自定义 SQL、存储过程以及高级映射。MyBatis 免除了几乎所有的 JDBC 代码以及设置参数和获取结果集的工作。

3.1 配置MyBatis

3.1.1 导入依赖

    <dependency>
      <groupId>mysqlgroupId>
      <artifactId>mysql-connector-javaartifactId>
      <version>8.0.33version>
    dependency>
    <dependency>
      <groupId>org.mybatisgroupId>
      <artifactId>mybatisartifactId>
      <version>3.5.6version>
    dependency>

3.1.2 配置MyBatis的xml文件

"1.0" encoding="UTF-8" ?>
configuration
  PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
  "https://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
  <environments default="development">
    <environment id="development">
      <transactionManager type="JDBC"/>
      <dataSource type="POOLED">
        <property name="driver" value="${driver}"/>
        <property name="url" value="${url}"/>
        <property name="username" value="${username}"/>
        <property name="password" value="${password}"/>
      dataSource>
    environment>
  environments>
  <mappers>
    <mapper resource="org/mybatis/example/BlogMapper.xml"/>
  mappers>
configuration>

3.1.3 配置mapper相应的xml文件

"1.0" encoding="UTF-8" ?>
mapper
  PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
  "https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="org.mybatis.example.BlogMapper">
  <select id="selectBlog" resultType="Blog">
    select * from Blog where id = #{id}
  select>
mapper>

3.2使用MyBatis

        在要使用mybatis的类中操作

3.2.1 加载mybatis主配置文件

String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);

3.2.2 创建工厂对象

 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

3.2.3 创建SqlSession对象

                用来调用sql语句操作数据库

SqlSession sqlSession = sqlSessionFactory.openSession();

3.2.4 创建Mapper相应的接口

        注意：
        * 1.方法的名字与对象sql的id保持一致
        * 2.对应xml的namespace值必须是对应接口的类型全名

3.2.5 接口中创建需要的方法（crud）

    List findAll();
    Employee findById(int id);
    Employee findByIdAndName(Map map);
    Employee findByIdAndName(Employee employee);
 
    //@Param()其实就是将参数封装为map对象，注解的内容作为key，参数的值作为值
    Employee findByIdAndName(@Param("id")int id,@Param("name") String name);
 
    //增
    boolean add(Employee employee);
    //改
    void update(@Param("id") int id,@Param("name") String name);

3.2.6 mapper相应的xml文件创建相应的sql语句

<mapper namespace="com.woniuxy.mapper.EmployeeMapper">
    
    
    <select id="findByIdAndName" resultType="com.woniuxy.entity.Employee">
        select * from employee where id = #{id} and name = #{name}
    select>
 
    <insert id="add">
        insert into employee values(null,#{cellphone},#{password},#{avatar},#{name},'0');
    insert>
    <update id="update">
        update employee set name = #{name} where id = #{id}
    update>

3.2.7 通过sqlSession得到接口实现的对象

EmployeeMapper mapper = sqlSession.getMapper(EmployeeMapper.class);

 3.2.8 调用接口的方法实现相应的操作

        //5.单参
        Employee byId = mapper.findById(1);
        System.out.println(byId);
 
        //6.多参
        Map map = new HashMap<>();
        map.put("id",1);
        map.put("name","小李");
        Employee byIdAndName = mapper.findByIdAndName(map);
        System.out.println("map"+byIdAndName);
 
        Employee arg = new Employee();
        arg.setId(1);
        arg.setName("小李");
        Employee byIdAndName1 = mapper.findByIdAndName(arg);
        System.out.println("arg:"+byIdAndName1);

3.3 传参的三种方法

        mysql不支持多个参数单独传递，只能一个数据或者多个数据（map、entity、array、list）

    Employee findByIdAndName(Map map);
    Employee findByIdAndName(Employee employee);
 
    //@Param()其实就是将参数封装为map对象，注解的内容作为key，参数的值作为值
    Employee findByIdAndName(@Param("id")int id,@Param("name") String name);

        实例对象与注解的方法比较好用，map一般不用