mybatis嵌套查询和嵌套结果 SSM 框架的集成

mybatis 的运用

1.mybatis的了解

1.1 mybatis是ORM持久层框架,MyBatis是针对数据库交互的一个辅助框架，也是对jdbc做了的简单封装，以xml配置代替Java代码来管理数据库的交互细节.

1.2 MyBatis可以使用简单的XML或注解用于配置和原始映射，将接口和Java的POJO（Plain Old Java Objects，普通的Java对象）映射成数据库中的记录.

2.mybatis的映射器

2.1 SpringAOP 面向切面编程 --底层代理模式(额外产出一些子类)

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.

IDeptDao---->DeptMapper.java—DeptMapper.xml(namespace直接写DeptMapper.java的全限定名)

2.2高级查询

2.2.1 like(模糊查询) 使用concat

<if test="name!=null">
    and name like concat('%',#{name},'%')
</if>

2.2.2 注意转义符的运用

方案1:转义符号
<if test="maxSalePrice != null">
    <!--and saleprice &lt;= #{maxSalePrice}
</if>

方案2:cdata 的区域编译的时候便不会读取
xml 
<![CDATA[
 and saleprice <= #{maxSalePrice}
]]>

3.mybatis的嵌套结果 嵌套查询

3.1 多对一的 嵌套结果 嵌套查询

嵌套查询和嵌套结果
<mapper namespace="cn.itsource._06_manytoone1.EmployeeMapper">

嵌套结果
    <!--<resultMap id="employeeMap" type="employee">
        <id property="id" column="id"></id>
        <result property="name" column="name"></result>
        <result property="age" column="age"></result>
        <association property="department" javaType="Department">
            <id property="id" column="did"></id>
            <result property="name" column="dname"></result>
        </association>
    </resultMap>
    <select id="findAll" resultMap="employeeMap">
        SELECT
        e.id,
        e. NAME,
        e.age,
        d.id did,
        d. NAME dname
    FROM
        t_employee e
    JOIN t_department d ON e.did = d.id
    </select>-->
    嵌套查询 
    <resultMap id="employeeMap" type="employee">
        <id property="id" column="id"></id>
        <result property="name" column="name"></result>
        <result property="age" column="age"></result>
        <association property="department" javaType="Department" column="did" select="findDeptById">
        </association>
    </resultMap>
    <select id="findAll" resultMap="employeeMap">
        SELECT
        e.id,
        e. NAME,
        e.age,
        e.did
        FROM
        t_employee e
    </select>
    <select id="findDeptById" parameterType="long" resultType="department">
        select *  from t_department where id=#{id}
    </select>
</mapper>

3.2 一对多的嵌套结果 嵌套查询 (limit 分页用于嵌套查询,不能用于嵌套结果)

嵌套结果
<!--<resultMap id="deptMap" type="department">
        <id property="id" column="id"></id>
        <result property="name" column="name"></result>
        <collection property="employees" javaType="arraylist" ofType="Employee" >
            <id property="id" column="eid"></id>
            <result property="name" column="ename"></result>
            <result property="age" column="eage"></result>
        </collection>
    </resultMap>
    <select id="loadAll" resultMap="deptMap">
        SELECT
        d.id,
        d. NAME,
        e.id eid,
        e. NAME ename,
        e.age eage
        FROM
        t_department d
        JOIN t_employee e ON d.id = e.did
    </select>-->
嵌套查询
    <resultMap id="deptMap" type="department">
        <id property="id" column="id"></id>
        <result property="name" column="name"></result>
        <collection property="employees" column="id" javaType="arraylist" ofType="Employee" select="findEmptById"></collection>
    </resultMap>
    <select id="loadAll" resultMap="deptMap">
        select t.id,t.name from t_department t
        limit 0,1
    </select>
    <select id="findEmptById" parameterType="long" resultType="employee">
        select * from t_employee  where did =#{id}
    </select>

4.SSM 框架的搭建

4.1普通的web项目

4.1.1 结构图

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4.1.2 applicationContext.xml 的配置

 <beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:tx="http://www.springframework.org/schema/tx"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
	http://www.springframework.org/schema/beans/spring-beans.xsd
	http://www.springframework.org/schema/context
	http://www.springframework.org/schema/context/spring-context.xsd
	http://www.springframework.org/schema/tx
	http://www.springframework.org/schema/tx/spring-tx.xsd"> 
<!-- 配置整合mybatis过程 -->
    <!-- 1.配置数据库相关参数properties的属性：${url} -->
    <context:property-placeholder location="classpath:jdbc.properties" />
    <context:component-scan base-package="cn.itsource.ssm.service"/>

    <!-- 2.数据库连接池 -->
    <bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource">
        <!-- 配置连接池属性 -->
        <property name="driverClassName" value="${jdbc.driverClassName}" />
        <property name="url" value="${jdbc.url}" />
        <property name="username" value="${jdbc.username}" />
        <property name="password" value="${jdbc.password}" />
    </bean>

    <!-- 3.配置SqlSessionFactory对象 -->
    <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
        <!-- 注入数据库连接池 -->
        <property name="dataSource" ref="dataSource" />
        <!-- 配置MyBaties全局配置文件:mybatis-config.xml -->
        <property name="mapperLocations" value="classpath:cn/itsource/ssm/mapper/*Mapper.xml" />
        <!-- 配置mybatis 类型别名 -->
        <property name="typeAliasesPackage">
            <value>
                cn.itsource.ssm.domain
                cn.itsource.ssm.query
            </value>
        </property>
    </bean>

    <!-- 4.配置扫描mapper接口包，动态实现mapper接口，注入到spring容器中 扫描 MapperScannerConfigurer-->
    <!--一劳永逸-->
    <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
    <property name="basePackage" value="cn.itsource.ssm.mapper"></property>
    </bean>
    <!--事务-->
    <bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
        <property name="dataSource" ref="dataSource"></property>
    </bean>

    <!-- 配置基于注解的声明式事务 @Transactional-->
    <tx:annotation-driven transaction-manager="transactionManager" />

4.1.3 applicationContext-mvc.xml 的配置

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:mvc="http://www.springframework.org/schema/mvc"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.springframework.org/schema/context
       http://www.springframework.org/schema/context/spring-context.xsd
       http://www.springframework.org/schema/mvc
       http://www.springframework.org/schema/mvc/spring-mvc.xsd">

    <!--扫描controller-->
    <context:component-scan base-package="cn.itsource.ssm.controller" />
    <!--静态资源处理-->
    <mvc:default-servlet-handler />
    <!--识别@requestMapper等注解支持-->
    <mvc:annotation-driven />
    <!--配置视图解析器-->
    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/" />
        <property name="suffix" value=".jsp" />
    </bean>

</beans>

4.1.4web.xml的配置

<?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">
    <!--配置spring-mvc 的核心控制器-->
    <!--方案1:独立容器方案,spring和springmvc都有自己context-->
    <!--1.1 spring容器初始化-->
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>
    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>classpath:applicationContext.xml</param-value>
    </context-param>

    <!--1.2 配置springmvc-->
    <servlet>
        <servlet-name>springmvc</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>springmvc</servlet-name>
        <!--/*会拦截所有包括jsp-->
        <!--/会拦截所有但是不包含jsp-->
        <url-pattern>/</url-pattern>
    </servlet-mapping>
    <!--
        post请求乱码解决
       get请求实在tomcat猫中配置
    -->
    <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>

最后

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