mybatis-config.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">
<!-- 通过这个配置标签,完成mybatis与数据库的连接 -->
<configuration>
<!-- 引入jdbc.properties文件 -->
<properties resource="jdbc.properties"></properties>
<!-- 配置mybatis的log实现为LOG4J -->
<settings>
<setting name="logImpl" value="LOG4J"/>
<!-- 设置全局缓存 -->
<setting name="cacheEnabled" value="true"/>
</settings>
<!-- 引入与数据库表对应的javaBean的包 注意:别名为类名首字母大写 :User -->
<typeAliases>
<package name="com.pp.pojo"/>
</typeAliases>
<environments default="development">
<environment id="development">
<!-- 配置事务管理 采用jdbc -->
<transactionManager type="JDBC"></transactionManager>
<!-- POOLED是mybatis的数据源,jndi是基于tomcat的数据源 -->
<dataSource type="POOLED">
<property name="driver" value="${driver}"/>
<property name="url" value="${url}?useUnicode=true&characterEncoding=utf8"/>
<property name="username" value="${username}"/>
<property name="password" value="${password}"/>
</dataSource>
</environment>
</environments>
<!-- 引入mapper.xml文件 -->
<mappers>
<mapper resource="com/pp/dao/UserMapper.xml"/>
<mapper resource="com/pp/dao/RoleMapper.xml"/>
</mappers>
</configuration>
连接数据库的配置文件: jdbc.properties(这个文件要引入mybatis配置文件中)
driver=com.mysql.jdbc.Driver url=jdbc:mysql://127.0.0.1:3306/testdb username=root password=123
Mapper配置文件: UserMapper.xml(专门存储sql语句的配置文件)(这个文件要引入mybatis配置文件中)
<?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.pp.dao.UserMapper">
<!--1. -->
<!-- 因为返回一条数据 类型用int接收 -->
<select id="count" resultType="int">
select count(1) from user
</select>
<!-- 2. -->
<!-- Bean中的Object属性用association标签表示 association标签中的result为role对象的属性 -->
<!-- javaType为Role是因为别名 -->
<resultMap type="User" id="userMap">
<result property="id" column="id"/>
<result property="userName" column="userName"/>
<result property="userCode" column="userCode"/>
<result property="userPassword" column="userPassword"/>
<association property="role" javaType="Role">
<result property="roleName" column="roleName"/>
</association>
</resultMap> -->
<!--3. -->
<!-- type为User 这个返回结果是User对象 property是属性 addressList是集合 ofType是集合中的对象,即泛型 -->
<!-- 对象属性为集合 用collection标签表示 标签里面的是集合中对象(泛型对象)的属性 -->
<resultMap type="User" id="getAddressByUserMap">
<result property="id" column="userId"/>
<collection property="addressList" ofType="Address">
<id property="id" column="a_id"/>
<result property="postCode" column="postCode"/>
<result property="addressContent" column="addressContent"/>
</collection>
</resultMap>
<!-- resultMap对应标签,标签 -->
<!-- parameterType为调用方法时的参数类型 -->
<select id="getAddressByUser" resultMap="getAddressByUserMap" parameterType="User">
select *,a.id as a_id from user u,address a where u.id=a.userId and u.id=#{id}
</select>
</mapper>
test类(junit) 增删改需要sqlSession.commit();提交事务
private Logger logger=Logger.getLogger(this.getClass());
@Test
public void conTest(){
String resources="mybatis-config.xml";
int count = 0;
SqlSession sqlSession=null;
InputStream is=null;
try {
//1.读取配置文件输入流
is=Resources.getResourceAsStream(resources);
//2.创建sqlSessionFactory对象,完成对配置文件的读取
SqlSessionFactory sqlSessionFactory=new SqlSessionFactoryBuilder().build(is);
//3.创建sqlSessin对象
sqlSession=sqlSessionFactory.openSession();
//4.调用mapper.xml文件进行数据操作
count=sqlSession.selectOne("com.pp.dao.UserMapper.count");
//测试输出
logger.debug(count);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally{
sqlSession.close();
try {
is.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
Assert.assertEquals(5, count);
}
mybatis特性之一
动态sql
涉及标签:
if
choose when otherwise
trim where set
foreach
1.
<select id="getRoleList" resultType="Role" parameterType="Role">
select * from role
<where>
<choose>
<when test="roleCode!=null">
and roleCode like CONCAT('%',#{roleCode},'%')
</when>
<when test="roleName!=null">
and roleName like CONCAT('%',#{roleName},'%')
</when>
<otherwise></otherwise>
</choose>
</where>
</select>
//where 标签相同sql语句where 智能省略第一个判断的and,就不用加 1=1 这样的语句
//choose 标签相同switch
//when 标签相同case 当满足一个条件时,追加sql语句后,跳出choose
//otherwise 标签相同switch中的default 当所有条件都不满足时,执行此标签内的语句
2.
<where>
<if test="roleCode!=null">
and roleCode like CONCAT('%',#{roleCode},'%')
</if>
<if test="roleName!=null">
and roleName like CONCAT('%',#{roleName},'%')
</if>
</where>
//if标签 判断如满足条件则追加语句
3.
<trim prefix="where" prefixOverrides="and|or">
<when test="roleCode!=null">
and roleCode like CONCAT('%',#{roleCode},'%')
</when>
<when test="roleName!=null">
and roleName like CONCAT('%',(#roleName),'%')
</when>
</trim>
//trim标签 追加where关键字 间隔符是and 或者 or trim也会在满足第一个条件时,舍去其语句中and
4.
<update id="updateRole" parameterType="Role">
update role
<set>
<if test="roleCode!=null and roleCode!=''">
roleCode=#{roleCode},
</if>
<if test="roleName!=null">
roleName=#{roleName}
</if>
</set>
where id=#{id}
</update>
//update 也有set标签 添加set关键字 后面判断条件追加语句
5.
<update id="updateRole" parameterType="Role">
update role
<trim prefix="set" prefixOverrides=",">
<if test="roleCode!=null and roleCode!=''">
roleCode=#{roleCode},
</if>
<if test="roleName!=null">
roleName=#{roleName}
</if>
</trim>
where id=#{id}
</update>
//trim标签 前缀为set 意为追加set关键字 prefixOverrides值, 间隔符号为,
6.
<resultMap type="User" id="userMapBydepId">
<result property="id" column="id"/>
<result property="userCode" column="userCode"/>
<result property="userName" column="userName"/>
</resultMap>
<!-- 传入的参数如果是数组 key:array 集合 key:list-->
<select id="getUserBydepIds" resultMap="userMapBydepId" >
select * from user where depId in
<foreach collection="array" item="depIds" open="(" separator="," close=")">
#{depIds}
</foreach>
</select>
//select * from user where depId in(1,2) 查询表user字段depId为1和2的数据
//数组collection为array
//open,separator,close 定义in后面的格式 :(?,?)
//不需要写parameterType
<select id="getUserBydepIds" resultMap="userMapBydepId" >
select * from user where depId in
<foreach collection="list" item="depIds" open="(" separator="," close=")">
#{depIds}
</foreach>
</select>
//集合collection为list
关于缓存
一级缓存 session作用域
二级缓存 全局作用域
全局缓存
mybatis配置文件:
<settings>
<setting name="cacheEnabled" value="true"/>
</settings>
开一级缓存的话 一定要开全局缓存 不生效
在mapper.xml中设置缓存 默认不开启
<cache eviction="FIFO" flushInterVal="60000" size="512" readOnly="true"/>