从零开始搭建ssm项目（三）配置spring

这是我的上一篇，没看过的可以在这里点击阅读 https://www.jianshu.com/p/00b5633b8477
上一篇是配置web.xml，最核心的配置就是DispatcherServlet。
里面的contextConfigLocation，读取的就是项目中spring包里的xml配置。

<init-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>classpath:spring/spring-*.xml</param-value>
</init-param>

有什么配置呢，我们来一探究竟。

从外到内，分别是spring-web.xml、spring-service.xml、spring-dao.xml

spring-web.xml

<?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-3.0.xsd">
    <!-- 配置SpringMVC -->
    <!-- 1.开启SpringMVC注解模式 -->
    <!-- 简化配置： 
        (1)自动注册DefaultAnootationHandlerMapping,AnotationMethodHandlerAdapter 
        (2)提供一些列：数据绑定，数字和日期的format @NumberFormat, @DateTimeFormat, xml,json默认读写支持 
    -->
    <mvc:annotation-driven />
    
    <!-- 2.静态资源默认servlet配置
        (1)加入对静态资源的处理：js,gif,png
        (2)允许使用"/"做整体映射
     -->
     <mvc:default-servlet-handler/>
     
     <!-- 3.配置jsp 显示ViewResolver -->
     <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="viewClass" value="org.springframework.web.servlet.view.JstlView" />
        <property name="prefix" value="/WEB-INF/jsp/" />
        <property name="suffix" value=".jsp" />
     </bean>
     
     <!-- 4.扫描web相关的bean -->
     <context:component-scan base-package="com.cyh.controller" />
</beans>

spring-web.xml里面的核心配置是InternalResourceViewResolver,目的是配置viewClass,prefix,suffix。
而配置了以后，又如何会使用到了，这就回到了DispatcherServlet了。
众所周知，DispatcherServlet.doService方法是核心方法，我们来一看究竟。

protected void doService(HttpServletRequest request, HttpServletResponse response) throws Exception {
        //记日志
        // Keep a snapshot of the request attributes in case of an include,
        // to be able to restore the original attributes after the include.
        //加载“org.springframework.web.servlet”里面的属性

        // Make framework objects available to handlers and view objects.
        //request.setAttribute
        
        try {
            doDispatch(request, response);//这里就是正题了
        }
    }

来看看doDispatch方法

protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
        
        try {
                // Process last-modified header, if supported by the handler.
                // Actually invoke the handler.
            processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
        }
    }

processDispatchResult方法里面的render方法

private void processDispatchResult(HttpServletRequest request, HttpServletResponse response,
            HandlerExecutionChain mappedHandler, ModelAndView mv, Exception exception) throws Exception {
        // Did the handler return a view to render?
        if (mv != null && !mv.wasCleared()) {
            render(mv, request, response);
            if (errorView) {
                WebUtils.clearErrorRequestAttributes(request);
            }
        }
    }

render方法里面的resolveViewName

protected void render(ModelAndView mv, HttpServletRequest request, HttpServletResponse response) throws Exception {
        
        View view;
        if (mv.isReference()) {
            // We need to resolve the view name.
            view = resolveViewName(mv.getViewName(), mv.getModelInternal(), locale, request);
            if (view == null) {
                throw new ServletException("Could not resolve view with name '" + mv.getViewName() +
                        "' in servlet with name '" + getServletName() + "'");
            }
        }
    }

然后，就跟到org.springframework.web.servlet.view.AbstractCachingViewResolver.resolveViewName(String, Locale)，里面的createView方法，然后跟到org.springframework.web.servlet.view.UrlBasedViewResolver.loadView(String, Locale),最终跟到org.springframework.web.servlet.view.InternalResourceViewResolver.buildView(String),buildView这个方法，会把viewClass、prefix、suffix等属性加载起来。

protected AbstractUrlBasedView buildView(String viewName) throws Exception {
        InternalResourceView view = (InternalResourceView) super.buildView(viewName);
        if (this.alwaysInclude != null) {
            view.setAlwaysInclude(this.alwaysInclude);
        }
        view.setPreventDispatchLoop(true);
        return view;
    }

spring-service.xml

<?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: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">
    <!-- 扫描service包下所有使用注解的类型 -->
    <context:component-scan base-package="com.cyh.service.impl" />

    <!-- 配置事务管理器 -->
    <bean id="transactionManager"
        class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
        <!-- 注入数据库连接池 -->
        <property name="dataSource" ref="dataSource" />
    </bean>

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

spring-dao.xml

<?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"
    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">
    <!-- 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" />

    <!-- 2.数据库连接池 -->
    <bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
        <!-- 配置连接池属性 -->
        <property name="driverClass" value="${jdbc.driver}" />
        <property name="jdbcUrl" value="${jdbc.url}" />
        <property name="user" value="${jdbc.username}" />
        <property name="password" value="${jdbc.password}" />

        <!-- c3p0连接池的私有属性 -->
        <property name="maxPoolSize" value="30" />
        <property name="minPoolSize" value="10" />
        <!-- 关闭连接后不自动commit -->
        <property name="autoCommitOnClose" value="false" />
        <!-- 获取连接超时时间 -->
        <property name="checkoutTimeout" value="10000" />
        <!-- 当获取连接失败重试次数 -->
        <property name="acquireRetryAttempts" value="2" />
    </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="configLocation" value="classpath:mybatis-config.xml" />
        <!-- 扫描entity包 使用别名 -->
        <property name="typeAliasesPackage" value="com.cyh.entity" />
        <!-- 扫描sql配置文件:mapper需要的xml文件 -->
        <property name="mapperLocations" value="classpath:mapper/*.xml" />
    </bean>

    <!-- 4.配置扫描Dao接口包，动态实现Dao接口，注入到spring容器中 -->
    <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
        <!-- 注入sqlSessionFactory -->
        <property name="sqlSessionFactoryBeanName" value="sqlSessionFactory" />
        <!-- 给出需要扫描Dao接口包 -->
        <property name="basePackage" value="com.cyh.dao.impl" />
    </bean>
</beans>