MyBatis

一、MyBatis核心配置文件mybatis-config.xml

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
 3         "http://mybatis.org/dtd/mybatis-3-config.dtd">
 4 <configuration> 
 5               <environments default="mysql"> 
 6                      <environment id="mysql"> 
 7                            <transactionManager type="JDBC" /> 
 8                                <dataSource type="POOLED">
 9                       <property name="driver" value="com.mysql.jdbc.Driver" />
10                                   <property name="url" value="jdbc:mysql://localhost:3306/mybatis" />              
11                       <property name="username" value="root" />
12                       <property name="password" value="root" />
13                                 </dataSource>
14                            </environment>
15                       </environments> 
16              <mappers>
17          <mapper resource="com/itheima/mapper/CustomerMapper.xml" />
18              </mappers>
19         </configuration>

二、映射文件×××Mapper.xml

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
 3         "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
 4 <mapper namespace="com.wxy.mapper.CustomerMapper">
 5     <!--查-->
 6     <select id="findCustomerById" parameterType="Integer"
 7             resultType="com.wxy.pojo.Customer">
 8         select * from customer where id = #{id}
 9     </select>
10     <select id="findCustomerByName" parameterType="String"
11             resultType="com.wxy.pojo.Customer">
12         select * from customer where username like concat('%',#{value},'%');
13     </select>
14     <select id="findCustomer" parameterType="com.wxy.pojo.Customer"
15             resultType="com.wxy.pojo.Customer">
16         select * from customer
17     </select>
18     <!--支持主键自增的数据库插入-->
19     <insert id="addCustomer"  parameterType="com.wxy.pojo.Customer"
20             keyProperty="id" useGeneratedKeys="true" >
21         insert into customer(username,jobs,phone)
22         values(#{username},#{jobs},#{phone})
23     </insert>
24     <!--不支持自增的数据库插入-->
25     <insert id="addCustomer2"  parameterType="com.wxy.pojo.Customer">
26         <selectKey keyProperty="id" order="AFTER" resultType="Integer">
27             select last_insert_id()
28         </selectKey>
29         insert into customer(id,username,jobs,phone)
30         values(#{id},#{username},#{jobs},#{phone})
31     </insert>
32     <!--改-->
33     <update id="updateCustomer" parameterType="com.wxy.pojo.Customer">
34         update customer set
35         username=#{username},jobs=#{jobs},phone=#{phone}
36         where id=#{id}
37     </update>
38     <!--删-->
39     <delete id="deleteCustomer" parameterType="Integer">
40         delete from customer where id=#{id}
41     </delete>
42 </mapper>

三、MyBatis工作原理

 1 //1.读取配置文件
 2 String resource = "mybatis-config.xml";
 3 InputStream inputStream = Resources.getResourceAsStream(resource);
 4 //2.根据配置文件构建SqlSessionFactory
 5 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
 6 //3.通过SqlSessionFactory创建SqlSession
 7 SqlSession sqlSession = sqlSessionFactory.openSession();
 8 //4.SqlSession执行映射文件中定义的SQL语句，并返回映射结果
 9 //即：调用映射文件中不同的子元素id,执行相应的操作
10 {
11          Customer customer = sqlSession.selectOne("com.itheima.mapper"
12                     + “.CustomerMapper.findCustomerById”, 1);          
13 }         
14 //5.关闭SqlSession
15 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