Mybatis

举个小栗子

mybatis配置文件（XML配置文件）

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd">
<!--通过这个配置文件，完成mybatis与数据库的连接  -->
<configuration>
<!--mybatis 在实例化的时候，会自动扫描这个包下的所有类，用于后续 sql 语句的 resultType-->
    <typeAliases>
        <package name="com.iweb.entity"/>
    </typeAliases>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="url" value="jdbc:mysql://localhost:3306/iweb?characterEncoding=utf-8"/>
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="mapper/user.xml"/>
    </mappers>
</configuration>

user.xml（实现增删改查的sql语句）

<?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.iweb.entity">
    <select id="listUser" resultType="User">select * from user</select>
<!--    parameterType:表示传入的参数类型，可以是基本数据类型，也可以是引用类型
        基本类型中需要注意：如果传入的参数为整型，参数“_int” 表示 int 类型，参数“int” 表示 Integer 类型-->
    <insert id="addUser" parameterType="User">insert into user values (#{userId},#{username},#{password})</insert>
    <delete id="deleteUser" parameterType="String">delete from user where userId = #{userId}</delete>
    <update id="updateUser" parameterType="User">update user set username = #{username},password = #{password} where userId = #{userId}</update>
    <select id="getUser" parameterType="String" resultType="User">select * from user where userId = #{userId}</select>
<!--    模糊查询-->
    <select id="listUserByNameLike" parameterType="String" resultType="User">select * from user where username like concat('%',#{0},'%')</select>
<!--    复杂查询-->
    <select id="listUserByIdAndNameLike" parameterType="map" resultType="User">select * from user where userId > #{userId} and username like concat('%',#{username},'%')</select>
</mapper>

使用做sql查询（Test）

public void test1() throws IOException {
    private SqlSession sqlSession;
    @Before
    public void init() throws IOException {
        // 输入流读取配置文件信息
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        // 基于配置文件获取 mybatis 的一级缓存对象
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        // 基于这个一级缓存，创建一个二级缓存
        sqlSession = sql