ModelAndView的生成与解析

妖狐艹你老母 2023-01-02 01:28 188阅读 0赞

在调用完我们的业务逻辑之后，springmvc会生成一个modelAndView对象，然后将他处理解析成view视图返回给前端。所以我们再来分析一下视图的生成以及解析规则。

接着我们上一节在handlerAdapter的初始化时说的调用handlerAdapter的handle方法，看看他到底是怎么生成view的

**业务处理**

mv = ha.handle(processedRequest, response, mappedHandler.getHandler());

**视图生成**

AbstractHandlerMethodAdapter  39  line
    
    public final ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception { 
            return this.handleInternal(request, response, (HandlerMethod)handler);
        }
    
    RequestMappinjgHandlerAdapter  464  line
    
    protected ModelAndView handleInternal(HttpServletRequest request, HttpServletResponse response, HandlerMethod handlerMethod) throws Exception { 
    		//检查请求是否合法 （请求方式以及session的检查）
            this.checkRequest(request);
            ModelAndView mav;
            //使用session加锁 这一块是false 所以看esle分支
            if (this.synchronizeOnSession) { 
                HttpSession session = request.getSession(false);
                if (session != null) { 
                    Object mutex = WebUtils.getSessionMutex(session);
                    synchronized(mutex) { 
                        mav = this.invokeHandlerMethod(request, response, handlerMethod);
                    }
                } else { 
                    mav = this.invokeHandlerMethod(request, response, handlerMethod);
                }
            } else { 
            	//执行业务 往下看
                mav = this.invokeHandlerMethod(request, response, handlerMethod);
            }
    		//缓存的处理
            if (!response.containsHeader("Cache-Control")) { 
                if (this.getSessionAttributesHandler(handlerMethod).hasSessionAttributes()) { 
                    this.applyCacheSeconds(response, this.cacheSecondsForSessionAttributeHandlers);
                } else { 
                    this.prepareResponse(response);
                }
            }
    
            return mav;
        }

**业务逻辑的处理**

RequestMappingHandlerAdapter   503  line
    
    protected ModelAndView invokeHandlerMethod(HttpServletRequest request, HttpServletResponse response, HandlerMethod handlerMethod) throws Exception { 
    		//包装一个ServletWebRequest
            ServletWebRequest webRequest = new ServletWebRequest(request, response);
    
            ModelAndView var15;
            try { 
            	一些准备工作  创建ModelFactory、ModelAndViewContainer、WebAsyncManager并设置一些属性值
                ......
                
    			//执行业务
                invocableMethod.invokeAndHandle(webRequest, mavContainer, new Object[0]);
                if (asyncManager.isConcurrentHandlingStarted()) { 
                    result = null;
                    return (ModelAndView)result;
                }
    			
    			//获取视图
                var15 = this.getModelAndView(mavContainer, modelFactory, webRequest);
            } finally { 
                webRequest.requestCompleted();
            }
    
            return var15;
        }

**执行业务**

ServletInvocableHandlerMethod  50  line
    
    public void invokeAndHandle(ServletWebRequest webRequest, ModelAndViewContainer mavContainer, Object... providedArgs) throws Exception { 
    		//解析请求的参数，并且执行我们的controller的方法，拿到返回值
            Object returnValue = this.invokeForRequest(webRequest, mavContainer, providedArgs);
            //设置相应状态
            this.setResponseStatus(webRequest);
            if (returnValue == null) { 
                if (this.isRequestNotModified(webRequest) || this.getResponseStatus() != null || mavContainer.isRequestHandled()) { 
                    this.disableContentCachingIfNecessary(webRequest);
                    mavContainer.setRequestHandled(true);
                    return;
                }
            } else if (StringUtils.hasText(this.getResponseStatusReason())) { 
                mavContainer.setRequestHandled(true);
                return;
            }
    		//标识请求结果还没处理 
            mavContainer.setRequestHandled(false);
            Assert.state(this.returnValueHandlers != null, "No return value handlers");
    
            try { 
            	//处理请求结果 使用converter将结果写出去 outputstream流
                this.returnValueHandlers.handleReturnValue(returnValue, this.getReturnValueType(returnValue), mavContainer, webRequest);
            } catch (Exception var6) { 
                if (this.logger.isTraceEnabled()) { 
                    this.logger.trace(this.formatErrorForReturnValue(returnValue), var6);
                }
    
                throw var6;
            }
        }

**处理请求结果 这一块会决定返回试图还是返回json数据**

HandlerMethodReturnValueHandlerComposite  49 line
    
    public void handleReturnValue(@Nullable Object returnValue, MethodParameter returnType, ModelAndViewContainer mavContainer, NativeWebRequest webRequest) throws Exception { 
    		//根据返回值与返回值类型去获取返回值处理的handler
            HandlerMethodReturnValueHandler handler = this.selectHandler(returnValue, returnType);
            if (handler == null) { 
                throw new IllegalArgumentException("Unknown return value type: " + returnType.getParameterType().getName());
            } else { 
            	//使用handler来处理返回结果
            	//如果是json数据，则使用RequestResponseBodyMethodProcessor
            	//如果是ModelAndView，则使用ModelAndViewMethodRetuenValueHandler来处理
                handler.handleReturnValue(returnValue, returnType, mavContainer, webRequest);
            }
        }

**获取视图**

RequestMappingHandlerAdapter  654  line
    
    private ModelAndView getModelAndView(ModelAndViewContainer mavContainer, ModelFactory modelFactory, NativeWebRequest webRequest) throws Exception { 
    		//更新下默认的Model
            modelFactory.updateModel(webRequest, mavContainer);
            //如果需要返回视图，那么上面使用handler处理结果的时候会将这个置为false
            if (mavContainer.isRequestHandled()) { 
                return null;
            } else { 
                ModelMap model = mavContainer.getModel();
                ModelAndView mav = new ModelAndView(mavContainer.getViewName(), model, mavContainer.getStatus());
                if (!mavContainer.isViewReference()) { 
                	//设置视图的名字
                    mav.setView((View)mavContainer.getView());
                }
    
                if (model instanceof RedirectAttributes) { 
                    Map<String, ?> flashAttributes = ((RedirectAttributes)model).getFlashAttributes();
                    HttpServletRequest request = (HttpServletRequest)webRequest.getNativeRequest(HttpServletRequest.class);
                    if (request != null) { 
                        RequestContextUtils.getOutputFlashMap(request).putAll(flashAttributes);
                    }
                }
    
                return mav;
            }
        }

**设置视图的名字**

DispatcherServlet  504  line
    
    this.applyDefaultViewName(processedRequest, mv);
    
    536  line
    
    private void applyDefaultViewName(HttpServletRequest request, @Nullable ModelAndView mv) throws Exception { 
    		//如果需要返回试图，并且视图名字为null，也就是我们没设置视图名字，那么使用默认的接口名作为视图名字
            if (mv != null && !mv.hasView()) { 
                String defaultViewName = this.getDefaultViewName(request);
                if (defaultViewName != null) { 
                    mv.setViewName(defaultViewName);
                }
            }
        }

**视图渲染**

DispatcherServlet   546  line
    
    private void processDispatchResult(HttpServletRequest request, HttpServletResponse response, @Nullable HandlerExecutionChain mappedHandler, @Nullable ModelAndView mv, @Nullable Exception exception) throws Exception { 
            boolean errorView = false;
            异常处理
            ......
    
            if (mv != null && !mv.wasCleared()) { 
            	//视图渲染 往下看
                this.render(mv, request, response);
                if (errorView) { 
                    WebUtils.clearErrorRequestAttributes(request);
                }
            } 
            ......
        }
    
    DispatcherServlet   713  line
    
    protected void render(ModelAndView mv, HttpServletRequest request, HttpServletResponse response) throws Exception { 
            Locale locale = this.localeResolver != null ? this.localeResolver.resolveLocale(request) : request.getLocale();
            response.setLocale(locale);
            String viewName = mv.getViewName();
            View view;
            if (viewName != null) { 
            	//这一块使用我们配置的视图解析器去解析这个视图， 将视图名字拼上我们的请求转发的前后缀
                view = this.resolveViewName(viewName, mv.getModelInternal(), locale, request);
            }
            try { 
               	//视图渲染
                view.render(mv.getModelInternal(), request, response);
            } 
        }
    
    AbstractView   141  line
    
    public void render(@Nullable Map<String, ?> model, HttpServletRequest request, HttpServletResponse response) throws Exception { 
            
            Map<String, Object> mergedModel = this.createMergedOutputModel(model, request, response);
            this.prepareResponse(request, response);
            //处理视图
            this.renderMergedOutputModel(mergedModel, this.getRequestToExpose(request), response);
        }

**处理视图**

InternalResourceView   46   line
    
    protected void renderMergedOutputModel(Map<String, Object> model, HttpServletRequest request, HttpServletResponse response) throws Exception { 
            this.exposeModelAsRequestAttributes(model, request);
            this.exposeHelpers(request);
            //获取页面跳转路径 视图解析其实就是获取页面跳转的地址，然后去进行页面跳转
            String dispatcherPath = this.prepareForRendering(request, response);
            RequestDispatcher rd = this.getRequestDispatcher(request, dispatcherPath);
            if (rd == null) { 
            } else { 
                if (this.useInclude(request, response)) { 
                    response.setContentType(this.getContentType());
                    rd.include(request, response);
                } else { 
    				//请求转发 这里也就是setvlet的forward方法
                    rd.forward(request, response);
                }
            }
        }

这一块代码很繁杂，很乱，简单总结一下  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxMDAxOTQ1_size_16_color_FFFFFF_t_70]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxMDAxOTQ1_size_16_color_FFFFFF_t_70]: /images/20221120/d70d00602b204e27bba0e267eb9cedf0.png