本文实例为大家分享了Java实现文件上传的具体代码，具体内容如下

1、java代码：

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; }}

2、java代码：

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;}

3、html代码：

<!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>

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。