厲害了，Servlet3的異步處理機制

Servlet3釋出好幾年了，又有多少人知道它的新特性呢？下面簡單介紹下。

主要增加了以下特性：

1、異步處理支援

2、可插性支援

3、注解支援，零配置，可不用配置web.xml

...

異步處理是什麼鬼？ 直接操起鍵盤幹。 @WebServlet(name = "index", urlPatterns = { "/" }, asyncSupported = true)

public classIndexServletextends HttpServlet {

@Override

protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

resp.setContentType("text/html");

try {

PrintWriter out = resp.getWriter();

out.println("servlet started.

");

out.flush();

AsyncContext asyncContext = req.startAsync();

asyncContext.addListener(getListener());

asyncContext.start(new IndexThread(asyncContext));

out.println("servlet end.

} catch (Exception e) {

e.printStackTrace();

}

/**

* 異步線程結果監聽

* @author javastack

* @return

*/

private AsyncListener getListener() {

return new AsyncListener() {

public voidonComplete(AsyncEvent asyncEvent) throws IOException {

asyncEvent.getSuppliedResponse().getWriter().close();

System.out.println("thread completed.");

public voidonError(AsyncEvent asyncEvent) throws IOException {

System.out.println("thread error.");

public voidonStartAsync(AsyncEvent asyncEvent) throws IOException {

System.out.println("thread started.");

public voidonTimeout(AsyncEvent asyncEvent) throws IOException {

System.out.println("thread timeout.");

};

public classIndexThreadimplements Runnable {

private AsyncContext asyncContext;

public IndexThread(AsyncContext asyncContext) {

this.asyncContext = asyncContext;

public void run() {

Thread.sleep(5000);

PrintWriter out = asyncContext.getResponse().getWriter();

out.println("hello servlet3.

asyncContext.complete();

通路localhost:8080/test

頁面首先輸出

servlet started.

servlet end.

過了5秒後再輸出

hello servlet3.

可以看出servlet立馬傳回了，但沒有關閉響應流，隻是把response響應傳給了線程，線程再繼續輸出，我們可以将比較費資源消耗時間的程式放到異步去做，這樣很大程式上節省了servlet資源。

Springmvc3.2開始也加入了servlet3異步處理這個特性，有興趣的同學可以去研究下。

從上面的servlet注解也可以看出來，servlet3完全解放了web.xml配置，通過注解可以完全代替web.xml配置。