Spring之MVC模塊

Spring MVC的Controller用于處理用戶的請求。Controller相當于Struts 1里的Action，他們的實現機制、運行原理都類似

Controller是個接口，一般直接繼承AbstrcatController，并實現handleRequestInternal方法。handleRequestInternal方法相當于Struts 1的execute方法

import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.mvc.AbstractController;

public class CatController extends AbstractController{
      private ICatService catService;
      //setter、getter略

      protected ModelAndView handleRequestInternal(HttpServletRequestrequest,HttpServletResponse response) throws Exception{
             String action =request.getParameter(＂action＂);
             if(＂list＂.equals(action)){
                    return this.list(request,response);
             }
      }

      protected ModelAndView list(HttpServletRequestrequest,HttpServletResponse response) throws Exception{
             List<Cat> catList = catService.listCat();
             request.setAttribute(＂catList＂, catList);
             returnnew ModelAndView(＂cat/listCat＂);
      }

}

Spring MVC沒有內置數據的封裝，開發者可以自己封裝數據轉換代碼

Spring MVC獨特的地方在于view層的處理上。handleRequestInternal返回ModelAndView對象，可以看做是對JSP對象的封裝。ModelAndIView直接接受JSP頁面的路徑。例如參數＂cat/listCat＂，只是JSP路徑的一部分，實際完整的路徑是＂WEB-INF/jsp/cat/catList.jsp＂，路徑前后的部分是配置在配置文件中的

除了制定JSP路徑，ModelAndView還可以直接傳遞Model對象到View層，而不用事先放到request中，例如new ModelAndView(＂cat/listCat＂,＂cat＂,cat)，如果傳遞多個參數，可以使用Map，如

Map map = newHashMap();
map.put(＂cat＂,cat);
map.put(＂catList＂,catList);
return new ModelAndView(＂cat/listCat＂,map);

一般使用一個獨立的xml文件如spring-action.xml專門配置web相關的組件

<?xml version= ＂1.0＂ encoding=＂UTF-8＂?>
<!DCTYPE beansPUBLIC ＂-//SPRING//DTD BEAN//EN＂
  ＂http://www.springframework.org/dtd/spring-beans.dtd＂>
<beans>
      <bean id=＂viewResolver＂ class=＂org.springframework.web.servlet.view.InternalResourceViewResolver＂>
             <property name=＂prefix＂>
                    <value>/WEB-INF/jsp/</value><!--  JSP前綴-->
             </property>
             <property name=＂suffix＂>
                    <value>.jsp</value>                 <!--  JSP后綴-->
             </property>

      <!-- 配置URL Mapping-->
      <bean id=＂urlHandlerMapping＂ class=＂org.springframework.web.servlet.handler.SimpleUrlHandleMapping＂>
             <property name=＂mappings＂>
                    <props><!—Controller的URL會被配置成＂cat.mvc＂-->
                           <prop key=＂cat.mvc＂>catController</prop>
                    <props>
             </property>
      </bean>
      <bean id=＂catController＂ class=＂com.clf.spring.CatController＂>
             <property name=＂catService＂ ref=＂catService＂></property>
      </bean>
</beans>

web.xml配置

<context-param><!--  Spring配置文件的位置-->
      <param-name>contextConfigLocation</param-name>
      <param-value>
             /WEB-INF/classes/applicationContext.xml,
             /WEB-INF/classes/spring-action.xml   
      </param-value>
</context-param>

<listener><!--  使用Listener加載Spring配置文件-->
      <listener-class>
             org.springframework.web.context.ContextLoaderListener
      </listener-class>
</listener>

<servlet><!--  spring分發器-->
      <servlet-name>spring</servlet-name>
      <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
      <init-param>
             <param-name>contextConfigLocation</param-name>
             <param-value>/WEB-INF/classes/spring-action.xml</param-value>
      </init-param>
      <load-on-startup>1</load-on-startup><!--  啟動時加載-->
</servlet>

<servlet-mapping>
      <servlet-name> spring </servlet-name>
      <url>*.mvc</url>
</servlet-mapping>

如果一個Controller要處理多個業務邏輯，可以使用MultiActionController，相當于Struts 1中的DispatchAction，能根據某個參數將不同的請求分發到不同的方法上

import org.springframework.web.servlet.mvc.multiaction.MultiActionController;

public class CatController extends AbstractController{
      private ICatService catService;
      //setter、getter略

      protected ModelAndView add(HttpServletRequestrequest,HttpServletResponse response) throws Exception{
             ……
             return new ModelAndView(＂cat/addCat＂);
      }

      protected ModelAndView list(HttpServletRequestrequest,HttpServletResponse response) throws Exception{
             List<Cat> catList = catService.listCat();
             request.setAttribute(＂catList＂, catList);
             return new ModelAndView(＂cat/listCat＂);
      }

}

配置到spring-action.xml

<bean id=＂paraMethodResolver＂ class=＂org.springframework.web.servlet.mvc.multiaction.ParameterMethodNameResolver＂>
      <property name=＂paramName＂>
             <value>action</value><!--  配置分發參數-->
      </property>
      <property name=＂defaultMethodName＂>
             <value>list</value><!--  配置默認的執行方法-->
      </property>
</bean>

<bean id=＂urlHandlerMapping＂ class=＂org.springframework.web.servlet.handler.SimpleUrlHandleMapping＂>
             <property name=＂mappings＂>
                    <props>
                           <prop key=＂cat.mvc＂>catController</prop><!--  訪問＂cat.mvc＂則交給catController處理-->
                           <prop key=＂catMulti.mvc＂>catMultiController</prop><!--  訪問＂catMulti.mvc＂則交給catMultiController處理-->
                    <props>
             </property>
      </bean>

      <bean id=＂catController＂ class=＂com.clf.spring.CatMultiController＂>
             <property name=＂catService＂ ref=＂catService＂></property>
      </bean>

      <bean id=＂catMultiController＂ class=＂com.clf.spring.CatController＂>
             <property name=＂catService＂ ref=＂catService＂></property>
      </bean>