1.servlet上传文件
servlet上传文件就是将客户端的文件上传到服务器端。
向服务器发送数据时，客户端发送的http请求正文采用“multipart/form-data”数据类型，他表示复杂的多个子部分的复合表单。
为了简化“multipart/form-data”数据的处理过程。可以使用Apache组织提供是的两个开源包来来实现上传。
fileupload软件包（commons-fileupload-1.2.1.jar）,负责文件上传的软件包。
io软件包（commons-io-1.4.jar）负责输入输出的软件包。
2.servlet上传文件相关类
2.1fileupload软件包把请求正文包含的复合表单的每个子部分看做FileItem对象。FileItem对象分为两种类型。
（1）formFiled:普通表单域类型，如表单中的文本和按钮等。
（2）非formFiled：上传文件类型，表单中的文件域就是这种类型。
2.2FileItemFactory接口和FileItem接口
FileItemFactory 是创建FileItem 对象的工厂。
DiskFileItemFactory 实现了FileItemFactory接口，DiskFileItemFactory用于创建DiskFileItem对象。
DiskFileItem对象用于把客户端上传的文件保存在客户端。
2.3ServletFileUpload 类
ServletFileUpload为文件上传处理器。和DiskFileItemFactory对象关联。
3.上传文件案例
上传文件页面（upload.html）
<!DOCTYPE html><html lang="en"><head> ???<meta charset="UTF-8"> ???<title>Title</title></head><body><form action="upload" enctype="multipart/form-data" method="POST"> ???<input name="username" size="30"> ???<input type="file" name="file1" size="30"> ???<input type="file" name="file2" size="30"> ???<input type="submit" name="submit" value="upload"></form></body></html>
上传文件的servlet类
package com.learn;import org.apache.commons.fileupload.FileItem;import org.apache.commons.fileupload.FileUploadException;import org.apache.commons.fileupload.disk.DiskFileItemFactory;import org.apache.commons.fileupload.servlet.ServletFileUpload;import org.apache.poi.common.usermodel.LineStyle;import javax.servlet.ServletConfig;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import java.io.File;import java.io.IOException;import java.io.PrintWriter;import java.util.Iterator;import java.util.List;public class ServletUpload extends HttpServlet { ???private String ?filePath; ???private String ?tempFilePath; ???@Override ???public void init(ServletConfig config) throws ServletException { ???????super.init(config); ???????//获取类文件路径初始化值 ???????filePath = config.getInitParameter("filePath"); ???????tempFilePath = config.getInitParameter("tempFilePath"); ???????System.out.println("init filepath:"+filePath); ???????System.out.println("tempFilePath:"+tempFilePath); ???????//获取文件路径真实值 ???????filePath = config.getServletContext().getRealPath(filePath); ???????tempFilePath = config.getServletContext().getRealPath(tempFilePath); ???????System.out.println("realPath:"+filePath); ???????System.out.println("tempFilePath"+tempFilePath); ???} ???@Override ???protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { ???????super.doPost(req, resp); ???????//设置返回内容为纯文字内容 ???????resp.setContentType("text/plain"); ???????resp.setCharacterEncoding("UTF-8"); ???????//获取输出对象 ???????PrintWriter out = ?resp.getWriter(); ???????//创建一个基于硬盘的FileItem工厂 ???????DiskFileItemFactory diskFileItemFactory = new DiskFileItemFactory(); ???????//设置向硬盘写数据的缓冲区大小，这里为4k ???????diskFileItemFactory.setSizeThreshold(4*1024); ???????//设置临时目录 ???????diskFileItemFactory.setRepository(new File(tempFilePath)); ???????//创建一个文件上传处理器 ???????ServletFileUpload servletFileUpload = new ServletFileUpload(diskFileItemFactory); ???????//设置文件上传的大小 ???????servletFileUpload.setSizeMax(4*1024*1024); ???????//获取参数 ???????try { ???????????//获取表单参数 ??????????List list = ?servletFileUpload.parseRequest(req); ??????????//获取迭代器 ??????????Iterator iterator = list.iterator(); ??????????//迭代列表 ???????????while(iterator.hasNext()){ ???????????????//将参数转型为FileItem类型 ???????????????FileItem fileItem = (FileItem) iterator.next(); ???????????????if(fileItem.isFormField()){ ???????????????????System.out.println("处理表单非文件类型数据"); ???????????????????processFormFiled(fileItem,out); ???????????????} else { ???????????????????System.out.println("处理吧表单文件类型数据"); ???????????????????processUploadFile( fileItem,out); ???????????????} ???????????} ???????????System.out.println("关闭输出流"); ???????????out.close(); ???????} catch (FileUploadException e) { ???????????e.printStackTrace(); ???????} catch (Exception e) { ???????????e.printStackTrace(); ???????} ???} ???private ?void processFormFiled(FileItem fileItem,PrintWriter printWriter){ ???????//获取表单域的名称 ???????String name = fileItem.getName(); ???????//获取表单域的值 ???????String value = fileItem.getString(); ???????printWriter.print("name:"+name+"value:"+value); ???} ???private ?void processUploadFile(FileItem fileItem,PrintWriter printWriter) throws Exception { ??????//获取文件名称 ???????String fileName = fileItem.getName(); ???????int i = fileName.lastIndexOf("\\"); ???????fileName = fileName.substring(i+1,fileName.length()); ???????//获取文件大小 ???????long fileSize = fileItem.getSize(); ???????System.out.println("fileName:"+fileName+"| fileSize:"+fileSize); ???????if("".equals(fileName) && fileSize == 0) ???????????return; ???????//将文件写入指定位置 ???????File upload = new File(filePath+File.separator+fileName); ???????fileItem.write(upload); ???????//输出结果 ???????printWriter.print(fileName+"is saved"); ???????System.out.println("处理完毕"); ???????printWriter.print("the size of "+fileName+" is "+fileSize); ???}}3.web.xml配置
???<servlet> ???????<servlet-name>upload</servlet-name> ???????<servlet-class>com.learn.ServletUpload</servlet-class> ???????<init-param> ???????????<param-name>filePath</param-name> ???????????<param-value>file</param-value> ???????</init-param> ???????<init-param> ???????????<param-name>tempFilePath</param-name> ???????????<param-value>temp</param-value> ???????</init-param> ???</servlet> ???<servlet-mapping> ???????<servlet-name>upload</servlet-name> ???????<url-pattern>/upload</url-pattern> ???</servlet-mapping>
servlet上传文件（四）
原文地址：http://www.cnblogs.com/wwyx-xi/p/7587741.html