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java基于servlet编写上传下载功能 类似文件服务器

作者：yunsyz

这篇文章主要为大家详细介绍了java基于servlet编写上传下载功能，类似文件服务器，文中示例代码介绍的非常详细，具有一定的参考价值，感兴趣的小伙伴们可以参考一下

本人闲来无事，写了个servlet，实现上传下载功能。启动服务后，可以在一个局域网内当一个小小的文件服务器。

一、准备工作

下载两个jar包： 

commons-fileupload-1.3.1.jar
commons-io-2.2.jar 

二、创建一个web工程

我的工程名叫：z-upload 

三、配置web.xml

 <?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xmlns="http://java.sun.com/xml/ns/javaee"
 xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
 id="WebApp_ID" version="3.0">
 <display-name>z-upload</display-name>
 <servlet>
 <servlet-name>UploadService</servlet-name>
 <servlet-class>com.syz.servlet.UploadService</servlet-class>
 </servlet>
 <servlet-mapping>
 <servlet-name>UploadService</servlet-name>
 <url-pattern>/*</url-pattern>
 </servlet-mapping>
</web-app>

 从以上配置可以看出，我的servlet类是UploadService，匹配的url是/*，意思是匹配所有访问url。 

四、写servlet类

 package com.syz.servlet;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Iterator;
import java.util.List;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.ProgressListener;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;


public class UploadService extends HttpServlet {

 public static final String LIST = "/list";

 public static final String FORM = "/form";

 public static final String HANDLE = "/handle";

 public static final String DOWNLOAD = "/download";

 public static final String DELETE = "/delete";

 public static final String UPLOAD_DIR = "/upload";

 private static final long serialVersionUID = 2170797039752860765L;

 public void execute(HttpServletRequest req, HttpServletResponse resp)
   throws ServletException, IOException {
  System.out.println("execute...");
  System.out.println("------------begin---------------");
  req.setCharacterEncoding("UTF-8");
  String host = req.getRemoteHost();
  System.out.println("host:" + host);
  String uri = req.getRequestURI();
  System.out.println("uri:" + uri);
  ServletContext servletContext = this.getServletConfig()
    .getServletContext();
  // 上传文件的基本路径
  String basePath = servletContext.getRealPath(UPLOAD_DIR);
  // 上下文路径
  String contextPath = servletContext.getContextPath();
  System.out.println("contextPath:" + contextPath);
  // 截取上下文之后的路径
  String action = uri.substring(contextPath.length());
  System.out.println("action:" + action);
  // 依据action不同进行不同的处理
  if (action.equals(FORM)) {
   form(contextPath, resp);
  }
  else if (action.equals(HANDLE)) {
   boolean isMultipart = ServletFileUpload.isMultipartContent(req);
   System.out.println("isMultipart:" + isMultipart);
   if (!isMultipart) {
    return;
   }
   DiskFileItemFactory factory = new DiskFileItemFactory();
   File repository = (File) servletContext
     .getAttribute(ServletContext.TEMPDIR);
   System.out.println("repository:" + repository.getAbsolutePath());
   System.out.println("basePath:" + basePath);
   factory.setSizeThreshold(1024 * 100);
   factory.setRepository(repository);
   ServletFileUpload upload = new ServletFileUpload(factory);
   // 创建监听
   ProgressListener progressListener = new ProgressListener() {
    public void update(long pBytesRead, long pContentLength,
      int pItems) {
     System.out.println("当前文件大小:" + pContentLength + "\t已经处理:"
       + pBytesRead);
    }
   };
   upload.setProgressListener(progressListener);
   List<FileItem> items = null;
   try {
    items = upload.parseRequest(req);
    System.out.println("items size:" + items.size());
    Iterator<FileItem> ite = items.iterator();
    while(ite.hasNext()){
     FileItem item = ite.next();
     if(item.isFormField()){
      // handle FormField
     }else{
      // handle file
      String fieldName = item.getFieldName();
      String fileName = item.getName();
      fileName = fileName.substring(
        fileName.lastIndexOf(File.separator) + 1);
      String contentType = item.getContentType();
      boolean isInMemory = item.isInMemory();
      long sizeInBytes = item.getSize();
      System.out.println(fieldName + "\t" + fileName + "\t"
        + contentType + "\t" + isInMemory + "\t"
        + sizeInBytes);
      File file = new File(
        basePath + "/" + fileName + "_" + getSuffix());
      // item.write(file);
      InputStream in = item.getInputStream();
      OutputStream out = new FileOutputStream(file);
      byte[] b = new byte[1024];
      int n = 0;
      while ((n = in.read(b)) != -1) {
       out.write(b, 0, n);
      }
      out.flush();
      in.close();
      out.close();
     }
    }
    // 处理完后重定向到文件列表页面
    String href1 = contextPath + LIST;
    resp.sendRedirect(href1);
   }
   catch (FileUploadException e) {
    e.printStackTrace();
   }
   catch (Exception e) {
    e.printStackTrace();
   }
  }
  else if (action.equals(LIST)) {
   list(contextPath, basePath, resp);
  }
  else if (action.equals(DOWNLOAD)) {
   String id = req.getParameter("id");
   System.out.println("id:" + id);
   if (id == null) {
    return;
   }
   File file = new File(basePath);
   File[] list = file.listFiles();
   int len = list.length;
   boolean flag = false;
   for (int i = 0; i < len; i++) {
    File f = list[i];
    String fn = f.getName();
    if (f.isFile() && fn.lastIndexOf("_") > -1) {
     String fid = fn.substring(fn.lastIndexOf("_"));
     if (id.equals(fid)) {
      download(f, resp);
      flag = true;
      break;
     }
    }
   }
   if (!flag) {
    notfound(contextPath, resp);
   }
  }
  else if (action.equals(DELETE)) {
   String id = req.getParameter("id");
   System.out.println("id:" + id);
   if (id == null) {
    return;
   }
   File file = new File(basePath);
   File[] list = file.listFiles();
   int len = list.length;
   boolean flag = false;
   for (int i = 0; i < len; i++) {
    File f = list[i];
    String fn = f.getName();
    if (f.isFile() && fn.lastIndexOf("_") > -1) {
     String fid = fn.substring(fn.lastIndexOf("_"));
     if (id.equals(fid)) {
      f.delete();
      flag = true;
      break;
     }
    }
   }
   if (flag) {
    // 处理完后重定向到文件列表页面
    String href1 = contextPath + LIST;
    resp.sendRedirect(href1);
   }
   else {
    notfound(contextPath, resp);
   }
  }
  else {
   show404(contextPath, resp);
  }
  System.out.println("------------end---------------");
 }

 private void show404(String contextPath, HttpServletResponse resp)
   throws IOException {
  resp.setContentType("text/html;charset=utf-8");
  PrintWriter out = resp.getWriter();
  String href1 = contextPath + LIST;
  out.write("<html>");
  out.write("<head><title>404</title></thead>");
  out.write("<body>");
  out.write("<b>您所访问的页面不存在！<a href='" + href1 + "'>点击</a>返回文件列表</b>");
  out.write("</body>");
  out.write("</html>");
  out.close();
 }

 private void form(String contextPath, HttpServletResponse resp)
   throws IOException {
  resp.setContentType("text/html;charset=utf-8");
  PrintWriter out = resp.getWriter();
  String href1 = contextPath + LIST;
  out.write("<html>");
  out.write("<head><title>form</title></thead>");
  out.write("<body>");
  out.write("<b><a href='" + href1 + "'>点击</a>返回文件列表</b>");
  out.write(
    "<form action='handle' method='post' enctype='multipart/form-data' style='margin-top:20px;'>");
  out.write("<input name='file' type='file'/><br>");
  out.write("<input type='submit' value='上传'/><br>");
  out.write("</form>");
  out.write("</body>");
  out.write("</html>");
  out.close();
 }

 private void notfound(String contextPath, HttpServletResponse resp)
   throws IOException {
  resp.setContentType("text/html;charset=utf-8");
  PrintWriter out = resp.getWriter();
  String href1 = contextPath + LIST;
  out.write("<html><body><b>操作失败！文件不存在或文件已经被删除！<a href='" + href1
    + "'>点击</a>返回文件列表</b></body></html>");
  out.close();
 }

 private void download(File f, HttpServletResponse resp)
   throws IOException {
  String fn = f.getName();
  String fileName = fn.substring(0, fn.lastIndexOf("_"));
  System.out.println("fileName:" + fileName);
  resp.reset();
  resp.setContentType("application/octet-stream");
  String encodingFilename = new String(fileName.getBytes("GBK"),
    "ISO8859-1");
  System.out.println("encodingFilename:" + encodingFilename);
  resp.setHeader("content-disposition",
    "attachment;filename=" + encodingFilename);
  InputStream in = new FileInputStream(f);
  OutputStream out = resp.getOutputStream();
  byte[] b = new byte[1024];
  int n = 0;
  while ((n = in.read(b)) != -1) {
   out.write(b, 0, n);
  }
  out.flush();
  in.close();
  out.close();
 }

 private void list(String contextPath, String basePath,
   HttpServletResponse resp)
   throws IOException {
  String href_u = contextPath + FORM;
  resp.setContentType("text/html;charset=utf-8");
  PrintWriter out = resp.getWriter();
  out.write("<html>");
  out.write("<head><title>list</title></thead>");
  out.write("<body>");
  out.write("<b>我要<a href='" + href_u + "'>上传</a></b><br>");
  out.write(
    "<table border='1' style='border-collapse:collapse;width:100%;margin-top:20px;'>");
  out.write("<thead>");
  out.write("<tr>");
  out.write("<th>序号</th><th>文件名</th><th>操作</th>");
  out.write("</tr>");
  out.write("</thead>");
  out.write("<tbody>");
  File file = new File(basePath);
  File[] list = file.listFiles();
  System.out
    .println("basePath:" + basePath + "\tlist.size:" + list.length);
  int len = list.length;
  int no = 1;
  for (int i = 0; i < len; i++) {
   File f = list[i];
   System.out.println(i + "\t" + f.getName());
   String fn = f.getName();
   if (f.isFile() && fn.lastIndexOf("_") > -1) {
    String filename = fn.substring(0, fn.lastIndexOf("_"));
    String id = fn.substring(fn.lastIndexOf("_"));
    String href1 = contextPath + DOWNLOAD + "?id=" + id;
    String href2 = contextPath + DELETE + "?id=" + id;
    StringBuilder sb = new StringBuilder();
    sb.append("<tr>");
    sb.append("<td>");
    sb.append(no++);
    sb.append("</td>");
    sb.append("<td>");
    sb.append(filename);
    sb.append("</td>");
    sb.append("<td>");
    sb.append("<a href='");
    sb.append(href1);
    sb.append("'>下载</a> <a href='");
    sb.append(href2);
    sb.append("' onclick='return confirm(\"您确定要删除吗？\");'>删除</a>");
    sb.append("</td>");
    sb.append("</tr>");
    out.write(sb.toString());
   }
  }
  out.write("</tbody>");
  out.write("</table>");
  out.write("</body>");
  out.write("</html>");
  out.close();
 }

 public void doGet(HttpServletRequest req, HttpServletResponse resp)
   throws ServletException, IOException {
  System.out.println("doGet...");
  execute(req, resp);
 }

 public void doPost(HttpServletRequest req, HttpServletResponse resp)
   throws ServletException, IOException {
  System.out.println("doPost...");
  execute(req, resp);
 }

 private String getSuffix() {
  Date date = new Date();
  SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMddHHmmssSSS");
  String suffix = sdf.format(date);
  return suffix;
 }
}

其实UploadService类可以直接实现service方法，而不用实现doGet、doPost方法。

以上servlet我也不想多解释什么，自己看代码吧。

五、效果图

1.项目结构图

2.404页面

/*会匹配所有包括空字符，所以图片中的路径会匹配，在UploadService中的if判断中出现在else中，因为此时的action是空字符。

3.文件列表页面

4.上传表单页面

5.下载

6.删除

7.文件找不到，如果你点删除时，文件在服务器上已经不存在，那么会进入此页面

8.打包的源码工程和war包

其中z-upload是eclipse源码工程，z-upload.war是打好的war包

全工程就两个jar包，一个web.xml和一个servlet类，可以自己从文章中拷贝过去测试一下，如果是懒人，可以下载。

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持脚本之家。

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