Servlet的非阻塞式IO实战

迈不过友情╰ 2021-07-24 21:13 345阅读 0赞

**一 编写Servlet**

package lee;
    
    import javax.servlet.*;
    import javax.servlet.http.*;
    import javax.servlet.annotation.*;
    
    import java.io.*;
    
    
    @WebServlet(urlPatterns="/async",asyncSupported=true)
    public class AsyncServlet extends HttpServlet
    {
        public void service(HttpServletRequest request ,
            HttpServletResponse response)
            throws IOException , ServletException
        {
            response.setContentType("text/html;charset=GBK");
            PrintWriter out = response.getWriter();
            out.println("<title>非阻塞IO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 context = request.startAsync();
            // 设置异步调用的超时时长
            context.setTimeout(60 * 1000);
            ServletInputStream input = request.getInputStream();
            // 为输入流注册监听器
            input.setReadListener(new MyReadListener(input, context));
            out.println("结束Servlet的时间："
                + new java.util.Date() + ".<br/>");
            out.flush();
        }
    }

**二 编写监听器**

package lee;
    
    import javax.servlet.*;
    import java.io.*;
    
    
    public class MyReadListener implements ReadListener
    {
        private ServletInputStream input;
        private AsyncContext context;
        public MyReadListener(ServletInputStream input , AsyncContext context)
        {
            this.input = input;
            this.context = context;
        }
    
        @Override
        public void onDataAvailable()
        {
            System.out.println("数据可用！！");
            try
            {
                // 暂停5秒，模拟读取数据是一个耗时操作。
                Thread.sleep(5000);
                StringBuilder sb = new StringBuilder();
                int len = -1;
                byte[] buff = new byte[1024];
                // 采用原始IO方式读取浏览器向Servlet提交的数据
                while (input.isReady() && (len = input.read(buff)) > 0)
                {
                    String data = new String(buff , 0 , len);
                    sb.append(data);
                }
                System.out.println(sb);
                // 将数据设置为request范围的属性
                context.getRequest().setAttribute("info" , sb.toString());
                // 转发到视图页面
                context.dispatch("/async.jsp");
            }
            catch (Exception ex)
            {
                ex.printStackTrace();
            }
        }
        @Override
        public void onAllDataRead()
        {
            System.out.println("数据读取完成");
        }
        @Override
        public void onError(Throwable t)
        {
            t.printStackTrace();
        }
    }

**三 视图**

form.html

<!DOCTYPE html>
    <html>
    <head>
        <meta name="author" content="Yeeku.H.Lee(CrazyIt.org)" />
        <meta http-equiv="Content-Type" content="text/html; charset=gbk" />
        <title>  </title>
    </head>
    <body>
    <form action="async" method="post">
        用户名：<input type="text" name="name"/><br/>
        密码：<input type="text" name="pass"/><br/>
        <input type="submit" value="提交">
        <input type="reset" value="重设">
    </form>
    </body>
    </html>

async.jsp

<%@ page contentType="text/html; charset=GBK" language="java"
        session="false"%>
    <div style="background-color:#ffffdd;height:80px;">
    浏览器提交数据为：${info}<br/>
    <%=new java.util.Date()%>
    </div>

**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 1][]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5ncWl1bWluZw_size_16_color_FFFFFF_t_70]: /images/20210724/71b3d3f01d2f40ae99ba221c0972a066.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5ncWl1bWluZw_size_16_color_FFFFFF_t_70 1]: /images/20210724/5e6eb7563a1c45fab00ec4572bde7897.png