从HttpServletRequest中读取文件内容

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这里介绍如何利用表单来将文件传输到服务器。

首先我们的前台jsp页面的源码如下

<%@ 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>上传文件</title></head><body>    <form action="file/fileUpload" enctype="multipart/form-data"        method="post">        <input type="file" name="fileUploader" multiple /><br />        <br /> <input type="submit" value="上传文件" />    </form></body></html>

web.xml中的配置如下

<?xml version="1.0" encoding="UTF-8"?><web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"    xmlns="http://java.sun.com/xml/ns/javaee" id="WebApp_ID" version="2.5">    <!--配置servlet -->    <servlet>        <servlet-name>FileUploadController</servlet-name>        <servlet-class>com.blog.upload.FileUploadController        </servlet-class>    </servlet>    <servlet-mapping>        <servlet-name>FileUploadController</servlet-name>        <url-pattern>/file/fileUpload</url-pattern>    </servlet-mapping></web-app>

接下来就是我们后台的代码了
在这里我将从HttpServletRequest中读取文件的方法封装成一个静态的方法，放在FilEUploadUtils.getFileContentFromRequest()。

则控制器的代码如下

package com.blog.upload;import java.io.IOException;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class FileUploadController extends HttpServlet {    private static final long serialVersionUID = 1L;    @Override    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {        String content=FilEUploadUtils.getFileContentFromRequest(request);  //获取文件的内容        System.out.println(content);                                        //输出文件的内容    }    @Override    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        super.doGet(req, resp);    }}

静态方法getFileContentFromRequest中的代码如下

package com.blog.upload;import java.io.BufferedInputStream;import java.io.BufferedReader;import java.io.IOException;import java.io.InputStream;import java.io.InputStreamReader;import javax.servlet.http.HttpServletRequest;import org.apache.tomcat.util.http.fileupload.FileItemIterator;import org.apache.tomcat.util.http.fileupload.FileItemStream;import org.apache.tomcat.util.http.fileupload.disk.DiskFileItemFactory;import org.apache.tomcat.util.http.fileupload.servlet.ServletFileUpload;public class FilEUploadUtils {    public static String getFileContentFromRequest(HttpServletRequest request){         try{            request.setCharacterEncoding("utf-8");            if(ServletFileUpload.isMultipartContent(request)) {                DiskFileItemFactory diskFileItemFactory=new DiskFileItemFactory();// 创建该对象                ServletFileUpload fileUpload=new ServletFileUpload(diskFileItemFactory);// 创建该对象                FileItemIterator itemIterator=fileUpload.getItemIterator(request);// 解析request 请求,并返回FileItemIterator集合                StringBuffer fileContent=new StringBuffer();                while(itemIterator.hasNext()) {                    FileItemStream itemStream=itemIterator.next();//从集合中获得一个文件流                    if(!itemStream.isFormField() && itemStream.getName().length() > 0) {    //过滤掉表单中非文件                        BufferedInputStream inputStream=new BufferedInputStream(itemStream.openStream());   //获得文件输入流                        inputStream.mark(itemStream.openStream().available()+1);                        //判断上传的文件的编码格式 支持 UTF-8 和 ANSI两种类型                        String charsetName=getFileCharsetName(inputStream);                        BufferedReader bufferedReader=new BufferedReader(new InputStreamReader(inputStream,charsetName));                        String lineTxt=null;                        while((lineTxt=bufferedReader.readLine()) != null) {                            fileContent.append(lineTxt+"\r");                        }                    }                }                return fileContent.toString();            }        } catch(Exception e) {            e.printStackTrace();        }        return null;    }    //判断上传的文件的编码格式 支持 UTF-8 和 ANSI两种类型    private static String getFileCharsetName(InputStream inputStream) throws IOException{        String charsetName="GBK";        byte[] typeByte = new byte[3];        inputStream.read(typeByte);        if (typeByte[0] == -17 && typeByte[1] == -69 && typeByte[2] == -65){            charsetName="UTF-8";        }        else{            charsetName="GBK";        }        inputStream.reset();        return charsetName;    }}

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