Servlet异步处理实战

偏执的太偏执、 2021-07-24 22:55 417阅读 0赞

**一 编写异步处理的Servlet类**

package lee;
    
    import javax.servlet.*;
    import javax.servlet.http.*;
    import javax.servlet.annotation.*;
    
    import java.io.*;
    import java.util.*;
    
    
    @WebServlet(urlPatterns="/async",asyncSupported=true)
    public class AsyncServlet extends HttpServlet
    {
        @Override
        public void doGet(HttpServletRequest request
            , HttpServletResponse response)throws IOException,ServletException
        {
            response.setContentType("text/html;charset=GBK");
            PrintWriter out = response.getWriter();
            out.println("<title>异步调用示例</title>");
            out.println("进入Servlet的时间："
                + new java.util.Date() + ".<br/>");
            // 创建AsyncContext，开始异步调用
            AsyncContext actx = request.startAsync();
            // 设置异步调用的超时时长
            actx.setTimeout(60 * 1000);
            // 启动异步调用的线程，该线程以异步方式执行
            actx.start(new GetBooksTarget(actx));
            out.println("结束Servlet的时间："
                + new java.util.Date() + ".<br/>");
            out.flush();
        }
    }

**二 异步线程类**

package lee;
    
    import javax.servlet.*;
    import javax.servlet.http.*;
    import javax.servlet.annotation.*;
    
    import java.io.*;
    import java.util.*;
    
    
    public class GetBooksTarget implements Runnable
    {
        private AsyncContext actx = null;
        public GetBooksTarget(AsyncContext actx)
        {
            this.actx = actx;
        }
        public void run()
        {
            try
            {
                // 等待5秒钟，以模拟业务方法的执行
                Thread.sleep(5 * 1000);
                ServletRequest request = actx.getRequest();
                List<String> books = new ArrayList<String>();
                books.add("疯狂Java讲义");
                books.add("轻量级Java EE企业应用实战");
                books.add("疯狂Ajax讲义");
                request.setAttribute("books" , books);
                actx.dispatch("/async.jsp");
            }
            catch(Exception e)
            {
                e.printStackTrace();
            }
        }
    }

**三 视图**

<%@ page contentType="text/html; charset=GBK" language="java"
        session="false"%>
    <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
    <ul>
    <c:forEach items="${books}" var="book">
        <li>${book}</li>
    </c:forEach>
    </ul>
    <%out.println("业务调用结束的时间：" + new java.util.Date());
    if (request.isAsyncStarted()) {
        // 完成异步调用
        request.getAsyncContext().complete();
    }%>

**四 测试**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5ncWl1bWluZw_size_16_color_FFFFFF_t_70][]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5ncWl1bWluZw_size_16_color_FFFFFF_t_70]: /images/20210724/40c38ee4e8bf48c8be82909f0278f09d.png