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服務(wù)器之家 - 編程語言 - JAVA教程 - Javaweb實現(xiàn)上傳下載文件的多種方法

Javaweb實現(xiàn)上傳下載文件的多種方法

2020-06-27 12:53升少 JAVA教程

本篇文章主要介紹了Javaweb實現(xiàn)上傳下載文件，有多種實現(xiàn)方式，需要的朋友可以參考下。

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這個包實現(xiàn)上傳功能，因為commons-fileupload依賴于commons-io這個包，所以需要下載這兩個包commons-fileupload-1.2.1.jar和commons-io-1.3.2.jar。

1、搭建環(huán)境

創(chuàng)建Web項目，將包導(dǎo)入到項目lib下

Javaweb實現(xiàn)上傳下載文件的多種方法

2、實現(xiàn)文件上傳

(第一種上傳的方法)

新建upload.jsp頁面

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<%@ 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()%>是表示項目的絕對路徑，也就是說不管你以后將項目拷貝到哪個位置，它都會找到準確的路徑 -->
  <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

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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 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();
          //實例化一個文件
          //request.getRealPath(獲取真實路徑)
          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)

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<%@ 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()%>是表示項目的絕對路徑，也就是說不管你以后將項目拷貝到哪個位置，它都會找到準確的路徑 -->
  <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>

建立Servlet處理上傳

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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");
    //定義一個變量去接收文件名
    String filename = null;
    //Content-Disposition: 就是當用戶想把請求所得的內(nèi)容存為一個文件的時候提供一個默認的文件名
    //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('=') + 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，筆者認為這種上傳下載較為簡單，但是好像不是很多人用，不懂。

創(chuàng)建HTML頁面

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<!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

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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)完成了實例化，而其它5個沒有實例化的對象通過下面的方式實例化
      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+"個文件上傳成功!<br>"+su.toString());
    } catch (SmartUploadException e) {
      e.printStackTrace();
    }
    
    //逐個提取上傳文件信息
    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;
      
      //顯示當前文件信息
      out.println("<table border=1>");
      out.println("<tr><td>表單項名(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);
  }
 
}

注意：代碼 int count = su.save("/share");表示你需要先建個文件夾，所以你可以先在Webcontent建立一個，然后將項目取消部署，再重新部署進去之后就會在運行那邊建立起一個文件夾了！

或者你可以直接找到運行的路徑，然后建立share文件夾。

Javaweb實現(xiàn)上傳下載文件的多種方法

3、實現(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

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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進行下載，但是這個有缺陷，如果下載文件名中有中文，就會變成亂碼現(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

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<%@ 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">點擊下載</a>
</body>
</html>

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

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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，實現(xiàn)下載功能（注意：這里文件名就算是中文名，也不會出現(xiàn)亂碼問題了！）

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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,
        //這個文件名稱用于瀏覽器的下載框中自動顯示的文件名
        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);
  }
}

以上就是本文的全部內(nèi)容，希望對大家的學(xué)習(xí)有所幫助，也希望大家多多支持服務(wù)器之家。

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