java基于servlet编写上传下载功能 类似文件服务器

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我们。