Java实现文件上传的方法

package com.github.reston.servlet; import java.io.File;import java.io.FileOutputStream;import java.io.IOException;import java.io.PrintWriter;import java.util.Iterator;import java.util.List; import javax.servlet.ServletConfig;import javax.servlet.ServletException;import javax.servlet.annotation.WebServlet;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.FileItemFactory;import org.apache.commons.fileupload.disk.DiskFileItemFactory;import org.apache.commons.fileupload.servlet.ServletFileUpload;import org.apache.commons.io.IOUtils; @WebServlet("/AjaxUpload")public class AjaxUpload extends HttpServlet{ @Override public void init(ServletConfig config) throws ServletException{  // TODO Auto-generated method stub  super.init(config); }  @Override protected void service(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException{  response.setContentType("text/html");  request.setCharacterEncoding("UTF-8");  boolean isMultipart=ServletFileUpload.isMultipartContent(request);   String basePath=getServletContext().getRealPath("/upload");  File baseDirectory=new File(basePath);  String filename="";  long start=0;  if(!baseDirectory.isDirectory()) baseDirectory.mkdirs();  if(isMultipart){   try{    FileItemFactory factory=new DiskFileItemFactory();    ServletFileUpload upload=new ServletFileUpload(factory);    @SuppressWarnings("unchecked") List<FileItem> fileItems=upload.parseRequest(request);    for(FileItem i:fileItems){     if(i.isFormField()){      String name=i.getFieldName();      String value=i.getString();      if(name.equals("start"))start=Long.parseLong(i.getString());     }    }    for(FileItem item:fileItems){     if(item.isFormField()) continue;     filename=item.getFieldName();     if(mkdir(basePath)){      File fileonserver=createFile(basePath,filename);      if(fileonserver.length()==0){       FileOutputStream fos=new FileOutputStream(fileonserver,true);       IOUtils.copy(item.getInputStream(),fos);      }      if(start>0){       FileOutputStream fos=new FileOutputStream(fileonserver,true);       IOUtils.copy(item.getInputStream(),fos);      }      PrintWriter pw=response.getWriter();      pw.write("{/"length/":/""+fileonserver.length()+"/"}");      pw.flush();     }    }   }catch(Exception e){   }  } }  private File createFile(String path,String name) throws IOException{     File tmp=new File(path,name);  if(!tmp.exists()){   tmp.createNewFile();  }  return tmp; }  private boolean mkdir(String path){  boolean result=true;  File tmp=new File(path);  if(!tmp.isDirectory()){   result=tmp.mkdirs();  }  return result; }}

var ajaxupload = function(e) { /**  * e url method data success error  */ var xmlhttprequest; if (window.XMLHttpRequest) {  xmlhttprequest = new XMLHttpRequest();  if (xmlhttprequest.overrideMimeType) {   xmlhttprequest.overrideMimeType("text/xml");  } } else if (window.ActiveXObject) {  var activeName = [ "MSXML2.XMLHTTP", "Microsoft.XMLHTTP" ];  for (var i = 0; i < activeName.length; i++) {   try {    xmlhttprequest = new ActiveXObject(activeName[i]);    break;   } catch (e) {    return;   }  } } if (xmlhttprequest == undefined || xmlhttprequest == null) {  alert("XMLHttpRequest对象创建失败！！");  return; } else {  this.xmlhttp = xmlhttprequest; }  var file = document.getElementById(e.id); if (this.xmlhttp != undefined && this.xmlhttp != null) {  e.method = e.method.toUpperCase();  if (e.method != "GET" && e.method != "POST") {   alert("HTTP的请求方法必须为GET或POST!!!");   return;  }  if (e.url == null || e.url == undefined) {   e.alert("HTTP的请求地址必须设置！");   return;  } }  this.xmlhttp.onreadystatechange = function() {  if (this.readyState == 4) {   if (this.status == 200) {    var responseText = this.responseText;    var responseXML = this.reponseXML;    if (e.success == undefined || e.success == null) {     alert("没有设置处理数据正确返回的方法");     alert("返回的数据：" + responseText);    } else {     e.success(responseText, responseXML);    }   } else {    if (e.error == undefined || e.error == null) {     alert("没有设置处理数据返回失败的处理方法！");     alert("HTTP的响应码：" + this.status + ",响应码的文本信息：" + this.statusText);    } else {     e.error(this.status, this.statusText);    }   }  } } // var formhtm="<form id='output' enctype='multipart/form-data' ></form>";   var filename = getFileName(e.id); this.xmlhttp.open(e.method, e.url, true); var data = new FormData(document.getElementById("output")); data.append("name", filename); data.append("start", e.data.start); data.append(filename, document.getElementById(e.id).files[0].slice(e.data.start, getFileSize(e.id))); this.xmlhttp.send(data);} function getFileName(id) { var path = document.getElementById(id).value var pos1 = path.lastIndexOf('/'); var pos2 = path.lastIndexOf('//'); var pos = Math.max(pos1, pos2); return path.substring(pos + 1);} function getFileSize(id) { return document.getElementById(id).files[0].size;}

<!DOCTYPE html><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><script type="text/javascript" src="test.js"></script> </head><body>   <input type="file" name="upload" id="upload" value="上传"/><span>请选择要上传的文件(小于1G)</span> <input type="button" value="上传" onclick="test();"/><form id="output" enctype="multipart/form-data" ></form> <script>  function test(){  ajaxupload({  id : "upload",  url : "/PCC/reston/AjaxUpload",  method : "POST",  data : {start:0},  success : function(e) {   var l=JSON.parse(e).length;   ajaxupload({    id : "upload",    url : "/PCC/reston/AjaxUpload",    method : "POST",    data : {start:l},    success : function(e) {    },    error : function(e) {     console.log(e);    }   });  },  error : function(e) {   console.log(e);  } });   }  </script></body> </html>