springmvc 3.2開始就支持servlet3.0的異步請求。日常咱們請求一個controller通常都是同步的,若是在代碼執行中,遇到耗時的業務操做,那servlet容器線程就會被鎖死,當有其餘請求進來的時候就會受堵了。java
springmvc3.2以後支持異步請求,可以在controller中返回一個Callable或者DeferredResult。當返回Callable的時候,大概的執行過程以下:web
- 當controller返回值是Callable的時候,springmvc就會啓動一個線程將Callable交給TaskExecutor去處理
- 而後DispatcherServlet還有全部的spring攔截器都退出主線程,而後把response保持打開的狀態
- 當Callable執行結束以後,springmvc就會從新啓動分配一個request請求,而後DispatcherServlet就從新調用和處理Callable異步執行的返回結果,而後返回視圖
DeferredResult的執行過程和Callable差很少,惟一不一樣的時候,DeferredResult是由應用程序其餘線程執行返回結果,而Callable是由TaskExecutor執行返回結果。spring
springmvc配置異步請求json
1.須要在web.xml加上servlet3.0的scheme庫mvc
2.在web.xml的servlet還有filter添加<asyncsupported>true</async-supported>子節點
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<!-- springMVC的Servlet配置 --> < servlet > < servlet-name >dispatcher</ servlet-name > < servlet-class >org.springframework.web.servlet.DispatcherServlet</ servlet-class > < init-param > < param-name >contextConfigLocation</ param-name > < param-value >classpath*:META-INF/dispatcher-context.xml</ param-value > </ init-param > < load-on-startup >1</ load-on-startup > < async-supported >true</ async-supported > </ servlet > <!-- 編碼攔截 --> < filter > < filter-name >CharacterEncodingFilter</ filter-name > < filter-class >org.springframework.web.filter.CharacterEncodingFilter</ filter-class > < async-supported >true</ async-supported > < init-param > < param-name >encoding</ param-name > < param-value >UTF-8</ param-value > </ init-param > < init-param > < param-name >forceEncoding</ param-name > < param-value >true</ param-value > </ init-param > </ filter > |
3.而後就能夠在controller中執行異步請求了
利用Callable執行異步請求,並返回視圖
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@RequestMapping ( "/mvc25" ) public Callable<String> mvc25() { return new Callable<String>() { @Override public String call() throws Exception { Thread.sleep( 2000 ); return "task/task" ; } }; } |
利用Callable執行異步請求,並把請求結果經過@response由httpmessageconverter進行轉化返回客戶端
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@RequestMapping ( "/mvc26" ) @ResponseBody public Callable<String> mvc26() { return new Callable<String>() { @Override public String call() throws Exception { Thread.sleep( 2000 ); return "hello task" ; } }; } |
能夠自定義客戶端超時間
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@RequestMapping ( "/mvc27" ) @ResponseBody public WebAsyncTask<String> mvc27() { Callable<String> callable = new Callable<String>() { @Override public String call() throws Exception { Thread.sleep( 10000 ); return "hello task" ; } }; return new WebAsyncTask<String>( 10000 , callable); } |
若是在線程的執行過程當中,遇到異常,處理過程和普通請求的同樣,你能夠用@ExceptionHandler來處理或者定義全局的HandlerExceptionResolver來處理
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@RequestMapping ( "/mvc28" ) @ResponseBody public Callable<String> mvc28() { Callable<String> callable = new Callable<String>() { @Override public String call() throws Exception { Thread.sleep( 2000 ); throw new RuntimeException(); } }; return callable; } @ExceptionHandler (RuntimeException. class ) @ResponseBody public JSONObject handlerException(){ JSONObject jsonObject = new JSONObject(); jsonObject.put( "aaa" , 123 ); return jsonObject ; } |
還能夠經過返回DeferredResult返回,DeferredResult的做用是返回一個實例給其餘線程來處理這個異步請求。
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@RequestMapping ( "/mvc29" ) @ResponseBody public DeferredResult<String> mvc29() { DeferredResult<String> deferredResult = new DeferredResult<String>(); dealInOtherThread(deferredResult); return deferredResult; } private void dealInOtherThread(DeferredResult<String> deferredResult) { try { Thread.sleep( 2000 ); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } deferredResult.setResult( "hello task" ); } |
dealInOtherThread處理完成,setResult的時候就會觸發springmvc分配一個request到DispatcherServlet,而後DispatcherServlet處理DeferredResult的返回結果,並返回視圖。
DeferredResult還提供了其餘返回來處理線程請求,例如onTimeout(Runnable) 還有onCompletion(Runnable),onTimeout能夠註冊一個線程回調,當請求延時的時候的回調函數,onCompletion能夠註冊一個請求完成的回調函數。