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。