JavaEE拾遗01--异步上传文件

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今天学习了JavaEE的Servlet的异步调用和文件上传，合着做了一个异步上传文件练习，注意到Servlet是多线程的，所以实际操作中不需要异步操作（我是这么觉得的），闲话少说，看代码

<%@ page language="java" contentType="text/html; charset=UTF-8"    pageEncoding="UTF-8"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>文件上传</title></head><body><form method="post" action="../upload" enctype="multipart/form-data">  文件名：<input type="text" id="name" name="name" /><br />选择上传文件：<input type="file" id="file" name="file" /><input type="submit" value="上传" /></form></body></html>

上面写了一个jsp页面，这个页面的<input type="file" /> 和<form method="post" action="../upload" enctype="multipart/form-data">是可以实现文件上传的秘密

接下来是处理文件上传的servlet

package liujie.jee.uploadfile;import java.io.IOException;import java.io.PrintWriter;import javax.servlet.AsyncContext;import javax.servlet.AsyncEvent;import javax.servlet.AsyncListener;import javax.servlet.ServletException;import javax.servlet.annotation.MultipartConfig;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import liujie.jee.bean.UploadFileExecutor;//使用注解表示这个servlet支持异步操作，@WebServlet(urlPatterns = { "/upload" }, name = "upload", asyncSupported = true)// 处理文件上传的servlet需要使用MultipartConfig标识@MultipartConfigpublic class UploadFileServlet extends HttpServlet {    private static final long serialVersionUID = 1L;    @Override    public void doPost(HttpServletRequest request, HttpServletResponse response)            throws IOException, ServletException {        response.setContentType("text/html;charset=utf-8");        PrintWriter out = response.getWriter();        // 得到文件名        String fileName = request.getParameter("name");        out.println("开始上传文件：" + fileName + ".</br>");        // 示例化异步调用        AsyncContext asct = request.startAsync();        // 设置任务超时时间为10分钟        asct.setTimeout(10 * 60 * 1000);        // 设置异步调用的监听器，当调用完成时提示        asct.addListener(new AsyncListener() {            // 出错时调用            @Override            public void onError(AsyncEvent event) {            }            // 完成时调用            @Override            public void onComplete(AsyncEvent event) {                out.println("文件：" + fileName + "上传完毕");            }            // 开始时调用            @Override            public void onStartAsync(AsyncEvent event) {            }            // 超时时调用            @Override            public void onTimeout(AsyncEvent event) {            }        });        asct.start(new UploadFileExecutor(asct));        /*         * out.println("文件大小为：" + fileSize + "</br>"); out.println("上传文件的类型是：" +         * part.getContentType() + ".</br>"); out.println("文件名为：" + filename +         * "</br>");         */    }}

注释比较详细，就不仔细介绍了

里面的异步任务实际上是启动了一个runnable对象，接下来是这个类的内容

package liujie.jee.bean;import java.io.IOException;import javax.servlet.AsyncContext;import javax.servlet.ServletException;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.Part;public class UploadFileExecutor implements Runnable {    private AsyncContext asct;    private Part part;    private final static String UPLODA_DIR = "z_uploadfiles";    public UploadFileExecutor(AsyncContext asct) {        this.asct = asct;    }    @Override    public void run() {        HttpServletRequest request = (HttpServletRequest) asct.getRequest();        String fileName = request.getParameter("name");        try {            // 获取上传的对象            Part part = request.getPart("file");            // 获取保存的路径并将文件吸入改路径            part.write(request.getServletContext().getRealPath(UPLODA_DIR)                    + "\\" + fileName);            // 完成调用            asct.complete();        } catch (IllegalStateException e) {            // TODO Auto-generated catch block            e.printStackTrace();        } catch (IOException e) {            // TODO Auto-generated catch block            e.printStackTrace();        } catch (ServletException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }    }}

注意要在应用根目录下面建立一个z_uploadfiles的目录放文件

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