Java Web 使用Servlet 实现上传图片功能！

话不多说。先创建一个JSP页面：index.jsp 和一个images 文件夹

<form action="<%=request.getContextPath()%>/upload" method="post" enctype="multipart/form-data"><input type="file" name="file" /><input type="submit" /></form><img src="<%=request.getContextPath() %>/images/1223.jpg" />

后面的img 是在网页显示出你上传的文件，方便验证你的图片是否上传成功！其中的1223.jpg 是你选择的上传的文件名称。

接下来创建一个Servlet类（UploadServlet.java） 把注释路径改为 “ /upload ” ，

再添加一行注释：@MultipartConfig(fileSizeThreshold=1024*1024,maxFileSize=1024*1024*5, maxRequestSize=1024*1024*5*5) 设置上传文件的属性（大小）

代码如下：

@WebServlet("/upload")@MultipartConfig(fileSizeThreshold=1024*1024,maxFileSize=1024*1024*5, maxRe qestSize=1024*1024*5*5)  

下面贴出整个类的完整代码：

package com.sve.web.servlet;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;import javax.servlet.ServletException;import javax.servlet.annotation.MultipartConfig;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.servlet.http.Part;/** * Servlet implementation class UploadServlet */@WebServlet("/upload")@MultipartConfig(fileSizeThreshold=1024*1024,maxFileSize=1024*1024*5, maxRequestSize=1024*1024*5*5)public class UploadServlet extends HttpServlet {private static final long serialVersionUID = 1L;           /**     * @see HttpServlet#HttpServlet()     */    public UploadServlet() {        System.out.println("upload");        // TODO Auto-generated constructor stub    }/** * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) */protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// TODO Auto-generated method stubresponse.getWriter().append("Served at: ").append(request.getContextPath());}/** * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) */protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// TODO Auto-generated method stub final Part filePart = request.getPart("file");     String fileName=getFileName(filePart);     OutputStream out =new FileOutputStream(request.getRealPath(".")+"/images/"+fileName.substring(fileName.lastIndexOf("\\")+1, fileName.length()));     InputStream filecontent=filePart.getInputStream();      int read;     final byte[] bytes = new byte[1024];     while ((read = filecontent.read(bytes)) != -1) {         out.write(bytes, 0, read);     }     response.getOutputStream().write("upload".getBytes());}private String getFileName(final Part part) {     final String partHeader = part.getHeader("content-disposition");           for (String content : part.getHeader("content-disposition").split(";")) {        if (content.trim().startsWith("filename")) {            return content.substring(            content.indexOf('=') + 1).trim().replace("\"", "");        }     }     return null;}}


运行选择图片文件，注意修改img标签中images后面的文件名，改为你选择的文件名称就好了。
下面为执行过后再次访问的的效果图：
第一次打开idnex页面是没有图片的，所以不回家在出图片。执行过一遍后再访问 发现已经加载出来你上传的图片！所以一个简单的上传文件功能就实现啦！