MyBatis

一、MyBatis核心配置文件mybatis-config.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
 3         "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration> 
              <environments default="mysql"> 
                     <environment id="mysql"> 
                           <transactionManager type="JDBC" /> 
                               <dataSource type="POOLED">
                      <property name="driver" value="com.mysql.jdbc.Driver" />
                                  <property name="url" value="jdbc:mysql://localhost:3306/mybatis" />              
                      <property name="username" value="root" />
                      <property name="password" value="root" />
                                </dataSource>
                           </environment>
                      </environments> 
             <mappers>
         <mapper resource="com/itheima/mapper/CustomerMapper.xml" />
             </mappers>
        </configuration>

 

二、映射文件×××Mapper.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
 3         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.wxy.mapper.CustomerMapper">
    <!--查-->
    <select id="findCustomerById" parameterType="Integer"
            resultType="com.wxy.pojo.Customer">
        select * from customer where id = #{id}
    </select>
    <select id="findCustomerByName" parameterType="String"
            resultType="com.wxy.pojo.Customer">
        select * from customer where username like concat('%',#{value},'%');
    </select>
    <select id="findCustomer" parameterType="com.wxy.pojo.Customer"
            resultType="com.wxy.pojo.Customer">
        select * from customer
    </select>
    <!--支持主键自增的数据库插入-->
    <insert id="addCustomer"  parameterType="com.wxy.pojo.Customer"
            keyProperty="id" useGeneratedKeys="true" >
        insert into customer(username,jobs,phone)
        values(#{username},#{jobs},#{phone})
    </insert>
    <!--不支持自增的数据库插入-->
    <insert id="addCustomer2"  parameterType="com.wxy.pojo.Customer">
        <selectKey keyProperty="id" order="AFTER" resultType="Integer">
            select last_insert_id()
        </selectKey>
        insert into customer(id,username,jobs,phone)
        values(#{id},#{username},#{jobs},#{phone})
    </insert>
    <!--改-->
    <update id="updateCustomer" parameterType="com.wxy.pojo.Customer">
        update customer set
        username=#{username},jobs=#{jobs},phone=#{phone}
        where id=#{id}
    </update>
    <!--删-->
    <delete id="deleteCustomer" parameterType="Integer">
        delete from customer where id=#{id}
    </delete>
</mapper>

三、MyBatis工作原理

//1.读取配置文件
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
//2.根据配置文件构建SqlSessionFactory
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
//3.通过SqlSessionFactory创建SqlSession
SqlSession sqlSession = sqlSessionFactory.openSession();
//4.SqlSession执行映射文件中定义的SQL语句，并返回映射结果
//即：调用映射文件中不同的子元素id,执行相应的操作
{
         Customer customer = sqlSession.selectOne("com.itheima.mapper"
                    + “.CustomerMapper.findCustomerById”, 1);          
}         
//5.关闭SqlSession
sqlSession.close();

log4j.properties日志文件：

log4j.rootLogger=ERROR, stdout
log4j.logger.com.wxy=DEBUG
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%5p [%t] - %m%n