Servlet3发布好几年了，又有多少人知道它的新特性呢？下面简单介绍下。
主要增加了以下特性：
1、异步处理支持
2、可插性支持
3、注解支持，零配置，可不用配置web.xml
...
异步处理是什么鬼？
直接操起键盘干。
@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.
");
out.flush();
} catch (Exception e) {
e.printStackTrace();
}
}
/**
* 异步线程结果监听
* @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() {
try {
Thread.sleep(5000);
PrintWriter out = asyncContext.getResponse().getWriter();
out.println("hello servlet3.
");
out.flush();
asyncContext.complete();
} catch (Exception e) {
e.printStackTrace();
}
}
}
访问localhost:8080/test
页面首先输出
servlet started.
servlet end.
过了5秒后再输出
hello servlet3.
可以看出servlet立马返回了，但没有关闭响应流，只是把response响应传给了线程，线程再继续输出，我们可以将比较费资源消耗时间的程序放到异步去做，这样很大程序上节省了servlet资源。
Springmvc3.2开始也加入了servlet3异步处理这个特性，有兴趣的同学可以去研究下。
从上面的servlet注解也可以看出来，servlet3完全解放了web.xml配置，通过注解可以完全代替web.xml配置。
