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MyBatis进阶讲解+ssm集成

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标签:data   xsd   dash   framework   注解   loader   for   bean   形式   

1.sql映射器Mapper

MyBatis基于动态代理机制,让我们无需再编写Dao的实现。

传统Dao接口,现在名称统一以Mapper结尾,还有我们映射器配置文件要和映射器在同一个包。

1.1使用映射器步骤:

(1)根据需求,创建模型相关的Mapper接口

(2)编写映射文件

  a)*Mapper.xml的命名空间,必须和接口的“全限定名”一致

  b)定义sql标签的id,需要和“接口的方法”一致

 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="cn.itsource._01_mapper.TeacherMapper">
 5     <!-- 查询 findAll()
 6         resultType 返回类型
 7     -->
 8     <select id="findAll" resultType="Teacher">
 9         select * from t_teacher
10     </select>
11 </mapper>

 

(3)测试

1 @Test
2 public void findAll() {
3     SqlSession sqlSession = MyBatisUtils.INSTANCE.getSqlSession();
4     //MyBatis动态代理
5     TeacherMapper mapper = sqlSession.getMapper(TeacherMapper.class);
6     mapper.findAll().forEach(t -> System.out.println(t));
7 }

2.高级查询

 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="cn.itsource._02_query.TeacherMapper">
 5     <!-- 查询 findAll()
 6         resultType 返回类型
 7     -->
 8     <select id="findAll" resultType="Teacher">
 9         select * from t_teacher
10     </select>
11     <select id="queryAll" parameterType="teacherQuery" resultType="Teacher">
12         select * from t_teacher
13         <where>
14             <if test="name!=null">
15                 and name like concat("%",#{name},"%")
16             </if>
17             <if test="minAge!=null">
18                 and age &gt; #{minAge}
19             </if>
20             <if test="maxAge!=null">
21                 and age &lt; #{maxAge}
22             </if>
23             <!-- 放入CDATA区域里面被xml忽略解析
24             <if test="maxAge != null">
25                 <![CDATA[
26                   and age < #{maxAge}
27                 ]]>
28             </if>-->
29         </where>
30     </select>
31 </mapper>

注意:

1.where:里面所有的条件如果都在前面加上and,并且最后会把第一个and替换为where

2.if 判断条件是否满足,如果是并且用and

3.模糊查询
  方案1:不能用#
         and ( name like %#{keywords}% or password like %#{keywords}% )
  方案2:用$  sql注入
         and ( name like ‘%${keywords}%‘ or password like ‘%${keywords}%‘ )
  方案3:用mysql中字符串拼接函数concat
         and ( name like concat(‘%‘,#{keywords},‘%‘) or password like ‘%${keywords}%‘ )

4.如果有特殊符号:

  方案1:转义符号,如“<”可以写成"&lt;",">"写成"&gt;"等等

  方案2:CDATA(上面的例子已经使用过)

3.ResultMap结果集映射

3.1为什么要使用结果映射

解决表字段名和对象属性名不一样的情况

关联对象查询,在mybatis不会默认查询出来,需要自己查询结果并且通过resultMap来配置

3.2关联映射分类

表与表之间的关系有:

一对一,一对多,多对一,多对多…

3.3关联映射处理方式

MyBatis提供两种方式处理我们关联对象,嵌套查询嵌套结果

嵌套结果:发送一条sql,查询所有的信息(本身+关联对象)

嵌套查询:发送1+n条sql

3.3.1多对一(一对一)——嵌套结果

 1 <!--嵌套结果(多对一),发送一条sql查询数据-->
 2 <resultMap id="studentMap" type="student">
 3     <id property="id" column="id"/>
 4     <result property="name" column="name"/>
 5     <result property="age" column="age"/>
 6     <association property="teacher" javaType="teacher">
 7         <id property="id" column="tid"/>
 8         <result property="name" column="tname"/>
 9         <result property="age" column="tage"/>
10     </association>
11 </resultMap>
12 <select id="findAll" resultMap="studentMap">
13     select s.id,s.name,s.age,t.id tid,t.name tname,t.age tage
14     from t_student s join t_teacher t on s.teacher_id=t.id
15 </select>

3.3.2多对一(一对一)——嵌套查询

 1 <!--嵌套查询,发送1+n条sql查询数据-->
 2 <resultMap id="studentMap" type="student">
 3     <id property="id" column="id"/>
 4     <result property="name" column="name"/>
 5     <result property="age" column="age"/>
 6     <association property="teacher" javaType="teacher" column="teacher_id" select="queryByTeacherId"/>
 7 </resultMap>
 8 <select id="findAll" resultMap="studentMap">
 9     select * from t_student
10 </select>
11 <select id="queryByTeacherId" parameterType="long" resultType="teacher">
12     select * from t_teacher where id=#{id}
13 </select>

3.3.3一对多(多对多)——嵌套结果

 1 <!--嵌套结果(一对多),发送一条sql查询数据-->
 2 <resultMap id="teacherMap" type="teacher">
 3     <id property="id" column="id"/>
 4     <result property="name" column="name"/>
 5     <result property="age" column="age"/>
 6     <collection property="students" javaType="arrayList" ofType="student">
 7         <id property="id" column="sid"/>
 8         <result property="name" column="sname"/>
 9         <result property="age" column="sage"/>
10     </collection>
11 </resultMap>
12 <select id="findAll" resultMap="teacherMap">
13     select t.id,t.name,t.age,s.id sid,s.name sname,s.age sage
14     from t_teacher t join t_student s on t.id=s.teacher_id
15 </select>

3.3.4一对多(多对多)——嵌套查询

 1 <!--嵌套查询,发送1+n条sql查询数据-->
 2 <resultMap id="teacherMap" type="teacher">
 3     <id property="id" column="id"/>
 4     <result property="name" column="name"/>
 5     <result property="age" column="age"/>
 6     <collection property="students" column="id" javaType="arrayList" ofType="student" select="queryStudent"/>
 7 </resultMap>
 8 <select id="findAll" resultMap="teacherMap">
 9     select * from t_teacher
10 </select>
11 <select id="queryStudent" parameterType="long" resultType="student">
12     select * from t_student where teacher_id=#{id}
13 </select>

4.缓存

4.1 jpa

一级缓存(自带)命中条件:同一个EntityManagerFactory,同一个EntityManager,同一个OID

二级缓存(需要配置实现):同一个EntityManagerFactory,不同的EntityManager,同一个OID

4.2 MyBatis

一级缓存:属于sqlSession级别,同一个SqlSessionFactory,同一个SqlSession,同一个id

二级缓存:属于sqlSessionFactory,同一个SqlSessionFactory,不同的SqlSession,同一个id

序列化:把对象转换成二进制形式,方便传输(特别需要保存到磁盘或者硬盘,需要进行序列化)

反序列化:把二进制的数据转换成对象

5.SSM集成

Spring+SpringMvc+MyBatis

框架集成核心:如果你的项目中,用到了Spring框架,那么其他框架主要就是和Spring集成。

那么和Spring集成的核心思路:

  1.把当前框架的核心类交给Spring管理

  2.如果框架有事务,那么事务也要统一交给Spring管理

步骤:

(1)导入jar包:今天以导入jar的方式,不是maven

 技术图片

(2)配置文件

applicationContext.xml:

  jdbc.properties--->Datasource ---->SqlSessionFactory----扫描Mapper--->事务管理器-开启注解事务

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <beans xmlns="http://www.springframework.org/schema/beans"
 3        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 4        xmlns:context="http://www.springframework.org/schema/context"
 5        xmlns:tx="http://www.springframework.org/schema/tx"
 6        xsi:schemaLocation="
 7        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
 8        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
 9        http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd
10 ">
11     <context:component-scan base-package="cn.itsource.ssm.service"/>
12     <!--读取jdbc.properties-->
13     <context:property-placeholder location="classpath:jdbc.properties"/>
14     <!--配置连接池-->
15     <bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
16         <property name="driverClassName" value="${jdbc.driverClassName}" />
17         <property name="url" value="${jdbc.url}" />
18         <property name="username" value="${jdbc.username}" />
19         <property name="password" value="${jdbc.password}" />
20     </bean>
21     <!--配置SqlSessionFactory-->
22     <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
23         <property name="dataSource" ref="dataSource"/>
24         <!--*Mapper.xml的位置-->
25         <property name="mapperLocations" value="classpath:cn/itsource/ssm/mapper/*Mapper.xml"/>
26         <!--别名配置-->
27         <property name="typeAliasesPackage">
28             <value>
29                 cn.itsource.ssm.domain
30                 cn.itsource.ssm.query
31             </value>
32         </property>
33     </bean>
34     <!-- 处理mapper接口 spring会扫描包产生很多子类 注入到service层-->
35     <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
36         <property name="basePackage" value="cn.itsource.ssm.mapper"/>
37     </bean>
38     <!--事务配置-->
39     <bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
40         <property name="dataSource" ref="dataSource"/>
41     </bean>
42     <tx:annotation-driven transaction-manager="transactionManager"/>
43 </beans>

applicationContext-mvc.xml:

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 3        xmlns:context="http://www.springframework.org/schema/context"
 4        xmlns:mvc="http://www.springframework.org/schema/mvc"
 5        xsi:schemaLocation="http://www.springframework.org/schema/beans
 6        http://www.springframework.org/schema/beans/spring-beans.xsd
 7        http://www.springframework.org/schema/context
 8        http://www.springframework.org/schema/context/spring-context.xsd
 9        http://www.springframework.org/schema/mvc
10        http://www.springframework.org/schema/mvc/spring-mvc.xsd">
11     <!--扫描controller层-->
12     <context:component-scan base-package="cn.itsource.ssm.controller"/>
13     <!--静态资源放行-->
14     <mvc:default-servlet-handler/>
15     <!--mvc特有注解支持-->
16     <mvc:annotation-driven/>
17     <!--配置视图解析器-->
18     <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
19         <property name="prefix" value="/WEB-INF/views/"/>
20         <property name="suffix" value=".jsp"/>
21     </bean>
22 </beans>

web.xml:

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
         version="3.1">
    <!--spring核心控制器-->
    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>classpath:applicationContext.xml</param-value>
    </context-param>
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>
    <!--springMvc核心控制器-->
    <servlet>
        <servlet-name>dispatcherServlet</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>classpath:applicationContext-mvc.xml</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>dispatcherServlet</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>
    <!--编码过滤器-->
    <filter>
        <filter-name>EncodingFilter</filter-name>
        <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
        <init-param>
            <param-name>encoding</param-name>
            <param-value>utf-8</param-value>
        </init-param>
    </filter>
    <filter-mapping>
        <filter-name>EncodingFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>
</web-app>

(3)包的层次结构:

技术图片

 

 

MyBatis进阶讲解+ssm集成

标签:data   xsd   dash   framework   注解   loader   for   bean   形式   

原文地址:https://www.cnblogs.com/wings-xh/p/11945044.html

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