java基于servlet实现文件上传功能解析

最近项目需要做一个文件上传功能，做完了分享下，顺带当做笔记。
上传功能用后台用java实现，前端主要是js的ajax实现。后台还加入定时删除临时文件。
效果如图

首先是上传功能的主要类，下面是代码

package util.upload;
import java.io.File;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Iterator;
import java.util.List;
import java.util.UUID;

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

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

public class UploadServlet extends HttpServlet {

 private static final long serialVersionUID = -3100028422371321159L;
 private boolean isAllowed;
 private String upFileName;
  //定义合法后缀名的数组
 private String[] allowedExtName=new String[]
      {"zip","rar",//压缩文件
     "txt","doc","wps","docx","java",//文本
     "xls","xlsx",//表格
     "ppt","pptx",//幻灯片
     "pdf",//pdf
     "jpg","jpeg","bmp","gif","png"//图片
     };
 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 doPost(request, response);

 }

 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 //设置编码格式为utf-8
 request.setCharacterEncoding("utf-8");
 response.setCharacterEncoding("utf-8");
 //获取session，保存进度和上传结果，上传开始为nok,当为Ok表示上传完成
 HttpSession session=request.getSession();
 session.setAttribute("result", "nok");
 session.setAttribute("error", "");
 String error="";
 upFileName="";
 isAllowed=false;
 //给上传的文件设一个最大值，这里是不得超过100MB
 int maxSize=100*1024*1024;
 //创建工厂对象和文件上传对象
 DiskFileItemFactory factory=new DiskFileItemFactory();
 ServletFileUpload upload=new ServletFileUpload(factory);
 //创建上传监听器和设置监听器
 UploadListener listener=new UploadListener();
 session.setAttribute("LISTENER", listener);
 upload.setProgressListener(listener);
 //上传路径
 String path = request.getSession().getServletContext().getRealPath("/upload");
 String requestPath = request.getSession().getServletContext().getContextPath()+"/upload";
 File dirFile =new File(path);   //System.out.println(request.getSession().getServletContext().getContextPath());
 //如果文件夹不存在则创建
 if (!dirFile .exists() && !dirFile .isDirectory())
 {
  dirFile .mkdir();
 }
 //根据日期创建文件夹,保存到对应日期的文件夹下
 Date date=new Date();
 SimpleDateFormat sdf=new SimpleDateFormat("yyyyMMdd");
 String subDirName=sdf.format(date);
 File subDirFile=new File(path+"/"+subDirName);
 if (!subDirFile .exists() && !subDirFile .isDirectory())
 {
   subDirFile .mkdir();
 }
 try {
  //解析上传请求
  List<FileItem> items=upload.parseRequest(request);
  Iterator<FileItem> itr=items.iterator();
  while(itr.hasNext()){
  FileItem item=(FileItem)itr.next();
  //判断是否为文件域
  if(!item.isFormField()){   if(item.getName()!=null&&!item.getName().equals("")){
   //获取上传文件大小和文件名称
   long upFileSize=item.getSize();
   String fileName=item.getName();

   //获取文件后缀名
   String[] splitName=fileName.split("\\.");
   String extName=splitName[splitName.length-1];
   //检查文件后缀名
   for(String allowed:allowedExtName)
   {
    if(allowed.equalsIgnoreCase(extName))
    {
      isAllowed=true;
    }
   }
   if(!isAllowed){
     error="上传文件格式不合法！";
     break;
   }
   if(upFileSize>maxSize){
    error="您上传的文件太大了，请选择不超过100MB的文件!";
    break;
   }
   //此时文件暂存在服务器的内存中，构造临时对象
   File tempFile=new File(makeFileName(fileName));

   //指定文件上传服务器的目录及文件名称
   File file=new File(path+"/"+subDirName+"/",tempFile.getName());

   item.write(file);//第一种写文件方法
   upFileName=requestPath+"/"+subDirName+"/"+tempFile.getName();
 if(upFileName.equals("")){
   error="没选择上传文件！";
 }
 System.out.println(upFileName);
   /*//构造输入流读文件 第二种写文件方法
   InputStream is=item.getInputStream();
   int length=0;
   byte[] by=new byte[1024];

   FileOutputStream fos=new FileOutputStream(file);

   while((length=is.read(by))!=-1){
    fos.write(by, 0, length);
    //Thread.sleep(10);
   }
   fos.close();
   //Thread.sleep(1000);*/
   }else{
   error="没选择上传文件！";
   }
  }
  }
 } catch (Exception e) {
  e.printStackTrace();
  error="上传文件出现错误:"+e.getMessage();
 }
 if(!error.equals("")){
   System.out.println(error);
  session.setAttribute("error", error);
 }else{ 

  session.setAttribute("result", "OK");
  session.setAttribute("filename",upFileName);
 }
 }
 /**
 * 为防止文件覆盖的现象发生，要为上传文件产生一个唯一的文件名
 * @param filename 原文件名
 * @return 生成的唯一文件名
 */
 private String makeFileName(String filename){

   return UUID.randomUUID().toString() + "_" + filename;
  }
}

其中需要引入commons-fileupload-1.3.1.jar,commons-io-2.4.jar
上传过程中，我们需要实时获取上传进度等信息，引入的库里为我们添加了一个ProgressListener接口，我们再写一个类实现这个接口，上面类中添加该接口

//创建工厂对象和文件上传对象
 DiskFileItemFactory factory=new DiskFileItemFactory();
 ServletFileUpload upload=new ServletFileUpload(factory);
 //创建上传监听器和设置监听器
 UploadListener listener=new UploadListener();
 session.setAttribute("LISTENER", listener);
 upload.setProgressListener(listener);

下面是这个监听类的具体实现代码

package util.upload;

import org.apache.commons.fileupload.ProgressListener;

public class UploadListener implements ProgressListener{

  private volatile long
  bytesRead = 0L,//上传的字节数
  contentLength = 0L,//总字节数
  item = 0L;
   public UploadListener()
    {
      super();
    }

   @Override
   public void update(long aBytesRead, long aContentLength, int anItem) {

    bytesRead = aBytesRead;
     contentLength = aContentLength;
     item = anItem;
   }
   public long getBytesRead()
   {
     return bytesRead;
   }
   public long getContentLength()
   {
     return contentLength;
   }

   public long getItem()
   {
     return item;
   }
}

现在能获取上传进度等信息了，但还需要一个servlet返回给前端，下面实现

package util.upload;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.HashMap;
import java.util.Map;

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

import org.apache.commons.fileupload.ProgressListener;

import com.google.gson.Gson;
/**
 获取上传进度,上传路径,错误,上传结果等信息
 */

public class GetProgressServlet extends HttpServlet{

 private static final long serialVersionUID = -3596466520775012991L;

 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 doPost(request, response);
 }

 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
   request.setCharacterEncoding("utf-8");
   response.setCharacterEncoding("utf-8");
   UploadListener listener= null;
   HttpSession session = request.getSession();
   String error=(String) session.getAttribute("error");
   String result= (String) session.getAttribute("result");
   String fileName=(String) session.getAttribute("filename");
   PrintWriter out = response.getWriter();
   long bytesRead = 0,contentLength = 0;
   if (session != null)
    {
      listener = (UploadListener)session.getAttribute("LISTENER");

      if (listener == null)
      {
        return;
      }
      else
      {
        bytesRead = listener.getBytesRead();//上传的字节数
        contentLength = listener.getContentLength();//总字节数

      }
      //自己定义的返回格式
      String rp=bytesRead+","
          +contentLength+","
          +error+","
          +result+","
          +fileName;

      //System.out.println(rp);
      out.print(rp);
      /*   //返回json格式数据
      Map<String,Object> map=new HashMap<String,Object>();
      map.put("bytesRead", bytesRead);
      map.put("contentLength", contentLength);
      map.put("error", error);
      map.put("result", result);
      map.put("fileName", fileName);
      Gson gson=new Gson();
      String json=gson.toJson(map);
      out.print(json);*/
      out.flush();
      out.close();
    }
 }
}

后台上传的功能代码写完了，下面实现上传的前端，首先是html

<!DOCTYPE html>
  <html>
  <head>
    <meta charset="utf-8" />
    <script type="text/javascript" src="js/upfile.js" charset="utf-8"></script>
    <link rel="stylesheet" type="text/css" href="css/upfile.css">
  </head>
  <body >
    <a href="javascript:addOne()">添加</a>
    <div id="target">
      <input type="file" id="file" name="file" onchange="addfile(event)" multiple/>
    </div>
    <span id="test">0</span>
  </body>
</html>

界面比较简单，就一个添加的a标签，负责上传的input隐藏起来
css文件主要渲染的上传进度的显示

      #file {
        display: none;
      }
      .pro{
        width:500px;
      }
      .pborder {

        position: relative;
        width: 500px; /* 宽度 */
        border: 1px solid #B1D632;
        padding: 1px;
      }

      .drawpro {
        width: 0px;
        display: block;
        position: relative;
        background: #B1D632;
        color: #333333;
        height: 20px; /* 高度 */
        line-height: 20px; /* 必须和高度一致，文本才能垂直居中 */
      }

      .pspan {
        position: absolute;
        width: 500px;
        text-align: center;
        font-weight: bold;
      }

接着是前端的重点，js文件

//显示上传信息的html
var upfile_html = '<div class="pborder"><div class="drawpro">'
    + '<span class="pspan">0%</span></div></div><span name="path"></span><img src="common/upload/images/del.png" style="float:right" width="20" height="20" name="del" onclick=abortUpload(this)>';

var targetDIV_id = "target";//显示上传文件的目标div的ID
var httpXML = null;//发送上传请求的XMLHttpRequest对象
var httpProgress = null;//发送请求进度信息的XMLHttpRequest对象
var oldFileList = new Array();//修改时保存已有附件信息的列表
var uplist = new Array();//保存上传文件的列表
var f_input;//上传文件的input对象
var flag = true;//是否可以上传下一个文件标志
var uurl = "Upload";//上传文件的请求url
var gurl = "getProgress";//获取上传进度信息的url
var cancelFlag = 0;//取消标志
var timer, waittimer;//定时器
var nowID = 0;//正在上传文件的id
var ID = 0;//队列中最后一个文件的id

/**
 * 文件对象
 */
function UploadFile(id, file) {
  this.id = id;
  this.file = file;
  this.state = 0;
  this.path = "";
}
/**
 * 初始化的方法
 */
window.onload = function init() {
  f_input = document.getElementById("file");
  var tdiv = document.getElementById(targetDIV_id);

  var oldspan = tdiv.getElementsByTagName("SPAN");

  for ( var i = 0; i < oldspan.length; i++) {
    oldFileList.push(oldspan[i].getAttribute("name"));
  }
}

/**
 * 选择一个文件上传
 */
function addOne() {
  f_input.value = null;
  f_input.click();
}

/**
 * 选中文件后将文件对象添加到队列，开始上传
 *
 */
function addfile(evt) {
  var f = f_input.files[0];
  if (f != undefined) {
    var uf = new UploadFile(ID, f);
    uplist.push(uf);
    var div = document.createElement("DIV");
    div.setAttribute("id", "pro" + (ID));
    div.setAttribute("class", "pro");
    div.innerHTML = upfile_html;
    var targetDiv = document.getElementById(targetDIV_id);
    targetDiv.appendChild(div);
    div.getElementsByTagName("SPAN")[1].innerHTML = "文件名:"
        + uplist[ID].file.name;
    waittimer = setInterval("upload()", 1000);
    ID++;
  }
}
/**
 * 将队列中的文件上传
 */
function upload() {

  if (flag == true) {

    if (uplist.length > 0) {

      var uf;
      for ( var i = 0; i < uplist.length; i++) {
        if (uplist[i].state == 0) {
          uf = uplist[i];
          uplist[i].state = 1;
          break;
        }
      }

      if (uf != undefined & uf != null) {
        flag = false;
        if (window.XMLHttpRequest) {
          httpUP = new XMLHttpRequest();
        } else if (window.ActiveXObject) {
          httpUP = new ActiveXObject("Microsoft.XMLHTTP");
        }
        var formData = new FormData();
        formData.append("file", uf.file);
        httpUP.open("POST", uurl, true);
       httpUP.upload.addEventListener('progress', uploadProgress, false);
        httpUP.send(formData);
        nowID = uf.id;
        timer = setInterval("getP()", 50);
      }
    }
  }
}

/**
 * 获取上传进度等信息
 */
function getP() {
  if (window.XMLHttpRequest) {
    httpProgress = new XMLHttpRequest();
  } else if (window.ActiveXObject) {
    httpProgress = new ActiveXObject("Microsoft.XMLHTTP");
  }
  httpProgress.onreadystatechange = onProgress;
  httpProgress.open("post", gurl, true);
  httpProgress.setRequestHeader("Content-type",
      "application/x-www-form-urlencoded");
  httpProgress.send("&timeStamp=" + (new Date()).getTime());
}

/**
 * 处理返回的上传信息，显示到界面
 */
function onProgress() {
  if (httpProgress.readyState == 4 && httpProgress.status == 200) {
    result = httpProgress.responseText;
    var result = result.replace(/(^\s*)|(\s*$)/g, "");
    var res = result.split(",");
    var now = parseInt(res[0]);
    var all = parseInt(res[1]);
    var err = res[2];
    var state = res[3];
    var path = res[4];
    var per = (now / all * 100).toFixed(2);
    var prodiv = document.getElementById("pro" + nowID);

    if (prodiv != null & prodiv != undefined) {
      if (err != "" & err != null & err.length > 0) {
        window.clearInterval(timer);
        if (cancelFlag == 1) {
          err = "上传终止";
          cancelFlag = 0;
        }
        prodiv.getElementsByTagName("DIV")[0].style.display = "none";
        prodiv.getElementsByTagName("SPAN")[1].innerHTML = err;
        httpUP.abort();
        flag = true;
        uplist[nowID].state = 3;
        return;
      }
      if (state == "OK") {
        prodiv.getElementsByTagName("DIV")[0].style.display = "none";
        var tmpf = uplist[nowID].file;
        prodiv.getElementsByTagName("SPAN")[1].innerHTML = "文件名:"
            + tmpf.name;
        window.clearInterval(timer);
        flag = true;
        uplist[nowID].state = 2;
        uplist[nowID].path = path;
        return;
      }
      prodiv.getElementsByTagName("DIV")[1].style.width = per * 5 + "px";
      prodiv.getElementsByTagName("SPAN")[0].innerHTML = per + "%";

    }
  }
}

/**
 * 取消上传的方法
 */
function abortUpload(obj) {
  var idStr = obj.parentNode.id;
  var id = idStr.slice(3);
  if (uplist[id].state == 1) {
    httpUP.abort();
    flag = true;
    cancelFlag = 1;
  } else {
    uplist[id].state = 3;
  }
  document.getElementById(idStr).remove();

}
/**
 * 获取上传文件的路径
 * @returns 格式化后字符串
 */
function getFileListStr() {

  var str = "";
  if (oldFileList.length > 0) {
    for ( var i = 0; i < oldFileList.length; i++) {
      if (oldFileList[i] != null & oldFileList[i] != ""
          & oldFileList[i] != undefined) {
        str = str + oldFileList[i] + ",";
      }

    }
  }
  for ( var i = 0; i < uplist.length; i++) {
    var f = uplist[i];
    if (f.state == 2) {
      str = str + f.path + ",";
    }
  }
  return str;
}
/**
 * 移除修改时已有的旧附件
 *
 */
function removeOld(btn) {
  var num = btn.getAttribute("name");
  oldFileList[num - 1] = null;
  btn.parentNode.remove();
}
  function uploadProgress(e) {
        if (e.lengthComputable) {
          var iBytesUploaded = e.loaded;
          var iBytesTotal = e.total;
          document.getElementById("test").innerHTML=iBytesUploaded+"/"+iBytesTotal;
        }
      }

使用ajax发送上传文件，获取上传进度，结果等信息。
使用的html5的file API，所以必须ie9以上的才可以兼容，火狐还有个问题，ajax请求不立即返回，直到所有ajax请求都发送完了，才都返回同一个结果，这就导致上传进度不显示。不过上传进度信息也可以使用html5的file api获取，其中加了一点代码，页面下面test的div里的数值就是在前端获取到的进度。

上传的都实现完了，接着是处理上传后的临时文件，因为使用的uuid命名文件，所以文件会生成很多，没用的需要定时处理。使用ServletContextListener：
在 Servlet API 中有一个 ServletContextListener 接口，它能够监听 ServletContext 对象的生命周期，实际上就是监听 Web 应用的生命周期。

当Servlet 容器启动或终止Web 应用时，会触发ServletContextEvent 事件，该事件由ServletContextListener 来处理。在 ServletContextListener 接口中定义了处理ServletContextEvent 事件的两个方法。
利用其特性，实现定时删除临时文件的功能，代码如下：

package util.upload;

import java.io.IOException;
import java.io.InputStream;
import java.util.Date;
import java.util.Properties;
import java.util.Timer;
import java.util.TimerTask;

import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

/**
 * 时间监听器
 *
 *
 */
public class TempFileListener implements ServletContextListener {
  private Timer timer;
  private SystemTaskTest systemTask;
  private static String every_time_run;
  static {
    Properties prop = new Properties();
    InputStream inStrem = TempFileManager.class.getClassLoader()
        .getResourceAsStream("tempfile.properties");
    try {
      prop.load(inStrem);
      System.out.println(inStrem);
      every_time_run = prop.getProperty("every_time_run"); 

    } catch (IOException e) {
      e.printStackTrace();
    } finally {
      try {
        inStrem.close();
      } catch (IOException e) {
        e.printStackTrace();
      }
    }
  } 

  // 监听器初始方法
  public void contextInitialized(ServletContextEvent sce) { 

    timer = new Timer();
    systemTask = new SystemTaskTest(sce.getServletContext()
        .getRealPath("/"), sce.getServletContext());
    try {
      System.out.println("定时器已启动");
      // 监听器获取网站的根目录
      String path = sce.getServletContext().getRealPath("/");
      Long time = Long.parseLong(every_time_run) * 1000;// 循环执行的时间
      System.out.println("time" + time);
      // 第一个参数是要运行的代码，第二个参数是从什么时候开始运行，第三个参数是每隔多久在运行一次。重复执行
      timer.schedule(systemTask, 10000, time);
      System.out.println("已经添加任务调度表");
    } catch (Exception e) {
      e.printStackTrace();
    }
  } 

  public void contextDestroyed(ServletContextEvent sce) {
    try {
      timer.cancel();
    } catch (Exception e) {
    }
  }
} 

/**
 * 时间任务器
 *
 */
class SystemTaskTest extends TimerTask {
  private ServletContext context;
  private String path;
  public SystemTaskTest(String path, ServletContext context) {
    this.path = path;
    this.context = context;
  } 

  /**
   * 把要定时执行的任务就在run中
   */
  public void run() {
    TempFileManager etf;
    try { 

      System.out.println("开始执行任务!");
      // 需要执行的代码
      System.out.println(new Date().toLocaleString()); 

      etf = new TempFileManager(path);
      etf.run();    

      System.out.println("指定任务执行完成!");
    } catch (Exception e) {
      e.printStackTrace();
    }
  }
}

上面只是监听器，负责定时调用删除临时文件的方法，具体实现是下面的类

package util.upload;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.util.Date;
import java.util.Properties;

/**
 * 删除服务器上的文件
 *
 */ 

public class TempFileManager implements Runnable {
  private String path;//路径 

  private static String RETENTION_TIME = "1440";// 文件保存的时间 一天单位分
  static {
    Properties prop = new Properties();
    InputStream inStrem = TempFileManager.class.getClassLoader()
        .getResourceAsStream("execl.properties");
    try {
      prop.load(inStrem);
      RETENTION_TIME = prop.getProperty("file_retention_time"); 

    } catch (IOException e) {
      e.printStackTrace();
    } finally {
      try {
        inStrem.close();
      } catch (IOException e) {
        e.printStackTrace();
      }
    }
  }
  /**
   * 构造函数。初始化参数
   * @param path
   */
  public TempFileManager(String path) {
    this.path = path; 

  }
  /**
   * 把线程要执行的代码放在run()中
   */
  public void run() {
    System.out.println("文件管理开始=========");
    path = path + "upload";
    System.out.println("文件管理路径===" + path);
    File file = new File(path);
    deletefiles(file);
  } 

  /**
   * 批量删除文件
   *
   * @param folder
   */
  public void deletefiles(File folder) {
  if(folder.isDirectory()){

    File[] files = folder.listFiles();
    if(files.length<=0){
      if(!folder.getAbsolutePath().equalsIgnoreCase(path)){
      if(canDeleteFile(folder)){
        if (folder.delete()) {
          System.out.println("文件夹" + folder.getName() + "删除成功!");
        } else {
          System.out.println("文件夹" + folder.getName()
              + "删除失败!此文件夹内的文件可能正在被使用");
        }
      }
      }
    }
    for (int i = 0; i < files.length; i++) { 

      if(files[i].isDirectory())
      {
      deletefiles(files[i]);
      }else{
        deleteFile(files[i]);
      }

    }
  }
  } 

  /**
   * 删除文件
   *
   * @param file
   */
  private void deleteFile(File file) {
    try {
      if (file.isFile()) {
        // 删除符合条件的文件
        if (canDeleteFile(file)) {
          if (file.delete()) {
            System.out.println("文件" + file.getName() + "删除成功!");
          } else {
            System.out.println("文件" + file.getName()
                + "删除失败!此文件可能正在被使用");
          }
        } else { 

        }
      } else {
        System.out.println("没有可以删除的文件了");
      } 

    } catch (Exception e) {
      System.out.println("删除文件失败========");
      e.printStackTrace();
    }
  } 

  /**
   * 判断文件是否能够被删除
   */
  private boolean canDeleteFile(File file) {
    Date fileDate = getfileDate(file);
    Date date = new Date();
    long time = (date.getTime() - fileDate.getTime()) / 1000 / 60
        - Integer.parseInt(RETENTION_TIME);// 当前时间与文件间隔的分钟
//    System.out.println("time=="+time);
    if (time > 0) {
      return true;
    } else {
      return false;
    } 

  } 

  /**
   * 获取文件最后的修改时间
   *
   * @param file
   * @return
   */
  private Date getfileDate(File file) {
    long modifiedTime = file.lastModified();
    Date d = new Date(modifiedTime);
    return d;
  } 

}

判断文件是否超时，超时就自动删除，并且能自动删除文件夹。

以上就是本文的全部内容，希望对大家学习java程序设计有所帮助。