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Javaweb - upload and download files

高洛峰

Oct 10, 2016 am 09:11 AM

一、前言

在Javaweb中，上傳下載是經(jīng)常用到的功能，對于文件上傳，瀏覽器在上傳的過程中是以流的過程將文件傳給服務(wù)器，一般都是使用commons-fileupload這個(gè)包實(shí)現(xiàn)上傳功能，因?yàn)閏ommons-fileupload依賴于commons-io這個(gè)包，所以需要下載這兩個(gè)包c(diǎn)ommons-fileupload-1.2.1.jar和commons-io-1.3.2.jar，筆者已經(jīng)打包好(點(diǎn)擊下載)

1、搭建環(huán)境

創(chuàng)建Web項(xiàng)目，將包導(dǎo)入到項(xiàng)目lib下

Javaweb - upload and download files

2、實(shí)現(xiàn)文件上傳

(第一種上傳的方法)

新建upload.jsp頁面

<%@ 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>upload file</title>
</head>
<body>
    <!--這里的<%=request.getContextPath()%>是表示項(xiàng)目的絕對路徑，也就是說不管你以后將項(xiàng)目拷貝到哪個(gè)位置，它都會(huì)找到準(zhǔn)確的路徑  -->
    <form action="<%=request.getContextPath()%>/uploadServlet" enctype="multipart/form-data" method="post">
        <span>選擇文件：</span><input type="file" name="file1">
        <input type="submit" value="上傳">
    </form>
</body>
</html>

新建處理文件上傳的Servlet

package com.load;

import java.io.File;
import java.io.IOException;
import java.util.List;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
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;
@WebServlet("/uploadServlet")
public class uploadServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    public uploadServlet() {
        super();
    }
    /* fileupload 包中， HTTP 請求中的復(fù)雜表單元素都被看做一個(gè) FileItem 對象；
     * FileItem 對象必須由 ServletFileUpload 類中的 parseRequest() 方法解析 HTTP 請求
     * （即被包裝之后的 HttpServletRequest 對象）出來，即分離出具體的文本表單和上傳文件
     * */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //通過isMultipartContent()方法：分析請求里面是不是有文件上的請求，
        boolean isMultipart = ServletFileUpload.isMultipartContent(request);
        if(isMultipart){
            //創(chuàng)建可設(shè)置的磁盤節(jié)點(diǎn)工廠
            DiskFileItemFactory factory = new DiskFileItemFactory();
            //獲取請求的上下文信息
            ServletContext servletContext = request.getServletContext();
            //緩存目錄，每個(gè)服務(wù)器特定的目錄
            File repository = (File) servletContext.getAttribute("javax.servlet.context.tempdir");
            //設(shè)置服務(wù)器的緩存目錄
            factory.setRepository(repository);
            //ServletFileUpload 對象的創(chuàng)建需要依賴于 FileItemFactory 
            //工廠將獲得的上傳文件 FileItem 對象保存至服務(wù)器硬盤，即 DiskFileItem 對象。
            ServletFileUpload upload = new ServletFileUpload(factory);
            try {
                //解析即被包裝之后的 HttpServletRequest對象，既是分離文本表單和上傳文件（http請求會(huì)被包裝為HttpServletRequest）
                List<FileItem> items = upload.parseRequest(request);
                for(FileItem item:items){
                    String fieldName = item.getFieldName();    
                    String fileName = item.getName();
                    String contentType = item.getContentType();
                    boolean isInMemory = item.isInMemory();
                    long sizeInBytes = item.getSize();
                    //實(shí)例化一個(gè)文件
                    //request.getRealPath(獲取真實(shí)路徑)
                    File file = new File(request.getRealPath("/")+"/loads"+fileName.substring(fileName.lastIndexOf("\\")+1,fileName.length()));
                    item.write(file);
                }
            } catch (FileUploadException e) {
                e.printStackTrace();
            } catch (Exception e) {
                
                e.printStackTrace();
            }
        }
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}

(第二種上傳的方法)

新建Jsp頁面(同上，只是路徑改變下)

<%@ 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>upload file</title>
</head>
<body>
    <!--這里的<%=request.getContextPath()%>是表示項(xiàng)目的絕對路徑，也就是說不管你以后將項(xiàng)目拷貝到哪個(gè)位置，它都會(huì)找到準(zhǔn)確的路徑  -->
    <form action="<%=request.getContextPath()%>/uploadservlet1" enctype="multipart/form-data" method="post">
        <span>選擇文件：</span><input type="file" name="file1">
        <input type="submit" value="上傳">
    </form>
</body>
</html>

JSP頁面

建立Servlet處理上傳

package com.load;

import java.io.File;
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;
@WebServlet("/uploadservlet1")
@MultipartConfig(location="")
public class uploadservlet1 extends HttpServlet {
    private static final long serialVersionUID = 1L;
    public uploadservlet1() {
        super();
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        request.setCharacterEncoding("utf-8");
        
        //取得上傳文件，讀取文件
        Part part =  request.getPart("file1");
        //定義一個(gè)變量去接收文件名
        String filename = null;
        //Content-Disposition: 就是當(dāng)用戶想把請求所得的內(nèi)容存為一個(gè)文件的時(shí)候提供一個(gè)默認(rèn)的文件名
        //Content-Disposition：告訴瀏覽器以下載的方式打開文件
        for (String content : part.getHeader("content-disposition").split(";")) {
            System.out.println(content);
            //取得文件名
            if (content.trim().startsWith("filename")) {
                //截取文件名
                filename = content.substring(
                        content.indexOf(&#39;=&#39;) + 1).trim().replace("\"", "");
            }
        }
        //輸出流
         OutputStream out = null;
         //輸入流
         InputStream filecontent = null;
         //File.separator  取得系統(tǒng)的分割線等數(shù)據(jù)
         out = new FileOutputStream(new File("e:/loads" + File.separator + filename));
         int read;
        //獲得一個(gè)輸入流
        filecontent = part.getInputStream();
        final byte[] bytes = new byte[1024];
        
        while ((read = filecontent.read(bytes)) != -1) {
            out.write(bytes, 0, read);
        }
       System.out.println("New file " + filename + " created at " + "/loads");
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }
}

(第三種上傳的方法)

這里使用的是jspSmartUpload包上傳下載，筆者認(rèn)為這種上傳下載較為簡單，但是好像不是很多人用，不懂，下載地址在這里(點(diǎn)我下載)

創(chuàng)建HTML頁面

<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>上傳文件</title>
</head>
<body>
    <p> </p>
    <p align="center">上傳文件選擇</p>
    <form method="post" Action="../DouploadServlet" enctype="multipart/form-data">
        <table width="75%" border="1" align="center">
            <tr><td><div align="center">
                1.<input type="file" name="file1" >
            </div></td></tr>
                <tr><td><div align="center">
                2.<input type="file" name="file2" >
            </div></td></tr>
                <tr><td><div align="center">
                3.<input type="file" name="file3" >
            </div></td></tr>
                <tr><td><div align="center">
                <input type="submit" name="Submit" value="上傳他">
            </div></td></tr>
        </table>
    </form>
</body>
</html>

創(chuàng)建Servlet處理上傳文件

package com.load;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.jsp.JspFactory;
import javax.servlet.jsp.PageContext;

import com.jspsmart.upload.File;
import com.jspsmart.upload.SmartUpload;
import com.jspsmart.upload.SmartUploadException;
@WebServlet("/DouploadServlet")
public class DouploadServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
       
    public DouploadServlet() {
        super();
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        //新建一個(gè)智能上傳對象
        SmartUpload su = new SmartUpload();
        /*
         *  PageContext pageContext;
            HttpSession session;
            ServletContext application;
            ServletConfig config;
            JspWriter out;
            Object page = this;
            HttpServletRequest request, 
            HttpServletResponse response
            其中page對象，request和response已經(jīng)完成了實(shí)例化，而其它5個(gè)沒有實(shí)例化的對象通過下面的方式實(shí)例化
            pageContext = jspxFactory.getPageContext(this, request, response,null, true, 8192, true);
         */
        //通過Jsp工廠類獲取上下文環(huán)境
        PageContext pagecontext = JspFactory.getDefaultFactory().getPageContext(this, request, response, null, true, 8192, true);
        //上傳初始化
        su.initialize(pagecontext);

        //上傳文件
        try {
            su.upload();
            //將上傳文件保存到指定目錄
            int count = su.save("/share");
            out.println(count+"個(gè)文件上傳成功!<br>"+su.toString());
        } catch (SmartUploadException e) {
            e.printStackTrace();
        }
        
        //逐個(gè)提取上傳文件信息
        for(int i=0;i<su.getFiles().getCount();i++){
            File file = su.getFiles().getFile(i);
            //如果文件不存在
            if(file.isMissing()) continue;
            
            //顯示當(dāng)前文件信息
            out.println("<table border=1>");
            out.println("<tr><td>表單項(xiàng)名(FieldName)</td></td>"+file.getFieldName()+"</td></tr>");
            out.println("<tr><td>文件長度</td><td>"+file.getSize()+"</td></tr>");
            out.println("<tr><td>文件名</td><td>"+file.getFileName()+"</td></tr>");
            out.println("<tr><td>文件擴(kuò)展名</td><td>"+file.getFileExt()+"</td></tr>");
            out.println("<tr><td>文件全名</td><td>"+file.getFilePathName()+"</td></tr>");
            out.println("</table><br>");
        }
    }

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

}

3、實(shí)現(xiàn)文件下載

(第一種文件下載)

注意：該代碼是直接訪問Servlet類的

package com.load;

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


//直接使用Http://localhost:8080/Test1/download進(jìn)行下載，但是這個(gè)有缺陷，如果下載文件名中有中文，就會(huì)變成亂碼現(xiàn)象！
@WebServlet("/download")
public class download extends HttpServlet {
    private static final long serialVersionUID = 1L;

    public download() {
        super();
    }
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
         response.setContentType("text/plain;charset=utf-8");
         response.setCharacterEncoding("utf-8");
         response.setHeader("Location","中文.txt");
         response.setHeader("Content-Disposition", "attachment; filename=" + "賬號.txt");
         OutputStream outputStream = response.getOutputStream();
         InputStream inputStream = new FileInputStream("E:/loads"+"/賬號.txt");
         byte[] buffer = new byte[1024];
         int i = -1;
         while ((i = inputStream.read(buffer)) != -1) {
          outputStream.write(buffer, 0, i);
         }
         outputStream.flush();
         outputStream.close();
    }
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

}

(第二種下載方法)

新建jsp頁面選擇下載

<%@ 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>下載</title>
</head>
<body>
    <a href="../DoDownloadServlet?filename=呵呵.txt">點(diǎn)擊下載</a>
</body>
</html>

Jsp頁面代碼

創(chuàng)建Servlet類進(jìn)行下載（注意：該下載如果文件名是中文的話，一樣會(huì)出現(xiàn)亂碼現(xiàn)象）

package com.load;

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URLEncoder;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.jsp.JspFactory;
import javax.servlet.jsp.PageContext;

import org.hsqldb.lib.StringUtil;

import com.jspsmart.upload.SmartUpload;
import com.jspsmart.upload.SmartUploadException;

@WebServlet("/DoDownloadServlet")
public class DoDownloadServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    public DoDownloadServlet() {
        super();
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //得到下載文件的名稱
        //String filename = request.getParameter("filename");
        //String filename = new String(FileName.getBytes("iso8859-1"),"UTF-8");
        //新建SmartUpload對象
        SmartUpload su = new SmartUpload();
        PageContext pagecontext = JspFactory.getDefaultFactory().getPageContext(this, request, response, null, true, 8192, true);
        //上傳初始化
        su.initialize(pagecontext);
        //設(shè)置禁止打開該文件
        su.setContentDisposition(null);
        //下載文件
        try {
            su.downloadFile("/listener/"+filename);
        } catch (SmartUploadException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}

(第三種下載的方法)

同上的jsp頁面代碼，這里就不再重復(fù)了。

新建Serlvet類，實(shí)現(xiàn)下載功能（注意：這里文件名就算是中文名，也不會(huì)出現(xiàn)亂碼問題了！）

package com.load;

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URLEncoder;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.jsp.JspFactory;
import javax.servlet.jsp.PageContext;

import org.hsqldb.lib.StringUtil;

import com.jspsmart.upload.SmartUpload;
import com.jspsmart.upload.SmartUploadException;

@WebServlet("/DoDownloadServlet")
public class DoDownloadServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    public DoDownloadServlet() {
        super();
    }


    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //獲得文件名稱
        String path1 = request.getParameter("filename");
        //獲得路徑名稱
        String path = request.getSession().getServletContext().getRealPath("/listener/"+path1);
         // path是根據(jù)日志路徑和文件名拼接出來的
         File file = new File(path);
         String filename = file.getName();
        try {
              //判斷是否是IE11
              Boolean flag= request.getHeader("User-Agent").indexOf("like Gecko")>0;
            //IE11 User-Agent字符串:Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; rv:11.0) like Gecko
            //IE6~IE10版本的User-Agent字符串:Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.0; Trident/6.0)
               if (request.getHeader("User-Agent").toLowerCase().indexOf("msie") >0||flag){
                   filename = URLEncoder.encode(filename, "UTF-8");//IE瀏覽器
               }else {
                //先去掉文件名稱中的空格,然后轉(zhuǎn)換編碼格式為utf-8,保證不出現(xiàn)亂碼,
                //這個(gè)文件名稱用于瀏覽器的下載框中自動(dòng)顯示的文件名
                filename = new String(filename.replaceAll(" ", "").getBytes("UTF-8"), "ISO8859-1");
                //firefox瀏覽器
                //firefox瀏覽器User-Agent字符串: 
                //Mozilla/5.0 (Windows NT 6.1; WOW64; rv:36.0) Gecko/20100101 Firefox/36.0
               }  InputStream fis = new BufferedInputStream(new FileInputStream(path));
               byte[] buffer;
               buffer = new byte[fis.available()];
                  fis.read(buffer);
                  fis.close();
                  response.reset();
                  response.addHeader("Content-Disposition", "attachment;filename=" +filename);
                  response.addHeader("Content-Length", "" + file.length());
                  OutputStream os = response.getOutputStream();
                  response.setContentType("application/octet-stream");
                  os.write(buffer);// 輸出文件
                  os.flush();
                  os.close();
              } catch (IOException e) {
               e.printStackTrace();
              }
                System.out.println(filename);
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}

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