java servlet上传文件并把文件内容显示在网页中

servlet3.0(JDK1.6)自带的API即可实现本地文件的上传，Servlet3.0新增了Part接口，HttpServletRequest的getPart()方法取得Part实现对象。下面我实现了文件的上传以及将上传的文件显示在网页上（主要目的是实现本地文件在网页上的显示，我采取了先上传文件，在读取上传的文件，将读取的内容显示在网页上）。

Java代码实现：

 package FileUpload.servlet;

 import java.io.BufferedReader;
 import java.io.File;
 import java.io.FileReader;
 import java.io.IOException;
 import java.io.PrintWriter;

 import javax.servlet.ServletException;
 import javax.servlet.annotation.*;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 import javax.servlet.http.Part;

 /**
  * Servlet implementation class FileUploadServlet
  */
 //上传文件被保存的路径
 @MultipartConfig(
         location="E:\\eclipse\\workspace\\TestAceEditor\\FileUpload"
         )
 @WebServlet(urlPatterns={"/fileUpload"})

 public class FileUploadServlet extends HttpServlet {
     private static final long serialVersionUID = 1L;
     //private static final Log log = LogFactory.getLog(UploadFileAction.class);
     //private String fileNameExtractorRegex = "filename=\".+\"";

     /**
      * @see HttpServlet#HttpServlet()
      */
     public FileUploadServlet() {
         super();
         // TODO Auto-generated constructor stub
     }

     //获得指定文件的内容
     private String getFileContent(String fileName){
         File file = new File(fileName);
         BufferedReader reader = null;
         String ans = "";
         try{
             reader = new BufferedReader(new FileReader(file));
             String tmpString = null;
             //一行一行的读取文件里面的内容
             while((tmpString = reader.readLine()) != null){
                 ans += tmpString + "\n";//保存在ans里面
             }
         }catch(IOException e){
             e.printStackTrace();
         }finally{
             if(reader != null)
             {
                 try{
                     reader.close();
                 }catch(IOException e1){
                     e1.printStackTrace();
                 }
             }
         }
         //返回获得的文件内容
         return ans;
     }
     //获得上传文件的文件名
     private String getFilename(Part part){

         if(part == null){
             return null;
         }
         //获得文件名的方法是根据一本书上的代码来的，忘记书名了，以后补上
         String contentDispositionHeader = part.getHeader("content-disposition");

         String fileName = null;
         String[] elements = contentDispositionHeader.split(";");
         for(String element:elements){
             if(element.trim().startsWith("filename")){
                 fileName = element.substring(element.indexOf('=') + 1).trim().replace("\"", "");
                 break;
             }
         }
         fileName = fileName.substring(fileName.lastIndexOf('\\') + 1);
 //        Pattern pattern = Pattern.compile(fileNameExtractorRegex);
 //        Matcher matcher = pattern.matcher(contentDispositionHeader);
 //        String fileName = null;
 //        if(matcher.find()){
 //            fileName = matcher.group();
 //            fileName = fileName.substring(10, fileName.length()-1);
 //        }  

         return fileName;
     }

     /**
      * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
      */
     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
         // TODO Auto-generated method stub
         request.getRequestDispatcher("fileUpload.jsp").forward(request, response);
     }

     /**
      * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
      */
     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
         // TODO Auto-generated method stub
         //set the encoding
         request.setCharacterEncoding("UTF-8");

         //请求（form中为file类型的输入框的名字为filename）发送过来时，使用getPart()方法取得Part实现对象
         Part part = request.getPart("filename");
         String fileName = getFilename(part);

         if(fileName != null && !fileName.isEmpty()){
             part.write(fileName);
         }

         //从指定文件路径获得文件内容
         String filePath = "E:\\eclipse\\workspace\\TestAceEditor\\FileUpload" + "\\" + fileName;
         String fileContent = getFileContent(filePath);

         //write to browser
 //        response.setContentType("text/html");
 //        PrintWriter writer = response.getWriter();
 //        writer.print("<br/>Uploaded file name: "+ fileName);
 //        writer.print("<br/>Size: "+part.getSize());
 //
 //        String author = request.getParameter("author");
 //        writer.print("<br/>Author: "+author);
         //设置属性，在jsp文件中可以使用EL获得fileContent对象里的内容
         request.setAttribute("fileContent", fileContent);
         request.getRequestDispatcher("fileUpload.jsp").forward(request, response);

     }

 }

jsp代码如下：

 <%@ page language="java" contentType="text/html; charset=UTF-8"
     pageEncoding="UTF-8"%>
 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 <html>
 <head>
 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 <title>fileupload</title>

 <style type="text/css" media="screen">
     body {
         overflow: hidden;
     }

     #editor {
         margin: 0;
         position: absolute;
         top: 130px;
         bottom: 0;
         left: 0;
         right: 0;
     }
  </style>

 </head>

 <body>

 <div style="margin:left">
 <h1>editor my code</h1>
 </div>

 <div style="background:#BFEFFF">
 <form action="fileUpload" enctype="multipart/form-data" method="post">
 Select file to show <input type="file" name="filename"/>
 <input type="submit" value="Show"/>
 </form>
 </div>

 <div id="editor">
 <!-- show the content in the uploading file -->
 ${fileContent}
 </div>

 </body>
 </html>

上传效果如下：

不用管里面说的图2（其实就是Java代码中说的MultipartConfig中的location），我把之前写文档的截图直接拿过来~

注意编码，统一utf-8吧，包括上传的文件的编码。