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htmlvar upfile_html = '<div><div>' + '<span>0%</span></div></div><span name="path"></span><img src="common/upload/images/del.png" style="float:right" name="del" onclick=abortUpload(this)>';var targetDIV_id = "target";//显示上传文件的目标div的IDvar 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urlvar gurl = "getProgress";//获取上传进度信息的urlvar cancelFlag = 0;//取消标志var timer, waittimer;//定时器var nowID = 0;//正在上传文件的idvar 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。