java基于servlet编写上传下载功能类似文件服务器

前端技术 2023/09/06 Java

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

http://download.csdn.net/detail/yunsyz/9569680，特别提醒，下载要1分哦。

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phpstudy。

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