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。