springMVC核心流程分析與視圖解析
DispatcherServlet依賴關(guān)系圖

DispatcherServlet.png

示例代碼

package com.mvc;
public class MyWebApplicationInitializer implements WebApplicationInitializer {
    @Override
    public void onStartup(ServletContext servletContext)  {
        //初始化spring 容器  以注解的方式
        AnnotationConfigWebApplicationContext ac = new AnnotationConfigWebApplicationContext();
        ac.register( AppConfig.class);
        DispatcherServlet servlet = new DispatcherServlet(ac);
        ServletRegistration.Dynamic registration = servletContext.addServlet("app", servlet);
        registration.setLoadOnStartup(1);
//        registration.setInitParameter("contextConfigLocation","spring mvc.xml 的地址");
        registration.addMapping("*.do");
    }
}

package com.mvc;
@Controller
public class TestController {
    @RequestMapping("/test.do")
    @ResponseBody                                                   //user 對象  Map
    public Object test(String name, HttpServletRequest request, HttpServletResponse response ){
        request.getParameter("name");
        Map hashMap = new HashMap();
        hashMap.put("key","value");
        return  hashMap;
    }

    @RequestMapping("/model.do")
    //@ResponseBody 加注釋訪問靜態(tài)資源 /app/index.html
    public String model(HttpServletRequest request,HttpServletResponse response){
        // /app/index.html
        return "index";
    }
}

package com.mvc;
@Component("/test1.do")
public class HandleController implements HttpRequestHandler {
    @Override
    public void handleRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("111");
    }
}

package com.mvc;
import org.springframework.web.servlet.mvc.Controller;
@Component("/user.do")
public class BeanNameController implements Controller{
    @Override
    public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) throws Exception {
        System.out.println("beanName");
        return null;
    }
}

package com;
@Configuration
@ComponentScan("com.mvc")
@EnableWebMvc
public class AppConfig implements WebMvcConfigurer{
    
    @Override
    public void configureViewResolvers(ViewResolverRegistry registry) {
        registry.jsp( "/app/",".html" );
    }
    @Override
    public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
        converters.add( new FastJsonHttpMessageConverter() );
    }
}

核心調(diào)用流程

FrameworkServlet#doGet

doGet.png

FrameworkServlet#processRequest

processRequest.png

doService.png

DispatcherServlet#doDispatch
在doDispatch方法中主要有三個重要邏輯
getHandler() 獲取處理映射器mappedHandler
getHandlerAdapter() 獲取處理適配器HandlerAdapter
ha.handle() 處理適配器調(diào)用處理映射器的handler(類)得到ModelAndView視圖

獲取HandlerExecutionChain

從handlerMappers集合遍歷
RequestMappingHandlerMapping
BeanNameUrlHandlerMapping
WebMvcConfigurationSupport/$EmptyHandlerMapping

debug分析請求是test.do

添加了注解@RequestMapping("/test.do")
DispatcherServlet#getHandler
對handlerMappings進行遍歷處理查詢

getHandler.png

RMHgetHandler.png

getHandlerInternal.png

lookupPath.png

lookupHandlerMethod.png

handlerMethod.png

createWithResolvedBean.png

HandlerMethod1.png

executionChain.png

getHandlerExecutionChain.png

returnhandler.png

debug分析請求是user.do的獲取handler

注解Component("/user.do") BeanNameController類實現(xiàn)了Controller

getHandler-user.png

對handlerMappings集合進行遍歷。首先對RequestMapperHandlerMapper調(diào)用處理聊训。對lookupHandlerMethod方法調(diào)用從mappingRegistry查找窒篱，此時這里查找不到

handNoMatch-user.png

handlerMaplookupHandler.png

會從handlerMap集合獲取到/user.do的bean
AbstractUrlHandlerMapping#buildPathExposingHandler
構(gòu)建HandlerExecutionChain并返回

buildPathExposingHandler.png

BeanNameUHMgethandler.png

debug分析請求是test1.do的獲取handler

@Component("/test1.do") HandleController實現(xiàn)了HttpRequestHandler
AbstractUrlHandlerMapping#lookupHandler

loolupHandler-test1.png

gethandlerchain-test1.png

獲取HandlerAdapter

從handlerAdapters集合遍歷
RequestMappingHandlerAdapter
HttpRequestHandlerAdapter
SimpleControllerHandlerAdapter

test.do調(diào)用

@RequestMapping("/test.do") @Controller注解

getHandlerAdapter.png

getHandlerAdapter-test.png

supports.png

supportsInternal.png

getHandlerAdapter_test.png

調(diào)用user.do

@Component("/user.do") BeanNameController實現(xiàn)了Controller
Controller類全路徑org.springframework.web.servlet.mvc.Controller

SimpleControllerHAsupports.png

調(diào)用test1.do

@Component("/test1.do") HandleController實現(xiàn)了HttpRequestHandler

getHandler-test1.png

HttpRequestHandlerAdaptersupports.png

總結(jié)：

本章主要分析得到的HandlerExecutionChain(包括handler和過濾器)和處理適配器HandlerAdapter
HandlerExecutionChain有兩種情況
1、加了@RequestMapping注解的
RequestMappingHandlerMapping處理映射器處理亚兄，handler返回HandlerMethod(方法)
2混稽、實現(xiàn)了Controller或HttpRequestHandler接口的
BeanNameUrlHandlerMapping處理映射器處理，handler返回實現(xiàn)類的類名
HandlerAdapter有三種情況
1审胚、@RequestMapping匈勋，返回類型RequestMappingHandlerAdapter
2、實現(xiàn)了Controller膳叨，返回類型SimpleControllerHandlerAdapter
3洽洁、實現(xiàn)了HttpRequestHandler，返回類型HttpRequestHandlerAdapter