[英]Servlet for download files from a specific folder?
我是JAVA技術的新手,特別是Servlets。我需要創建一個Web應用程序項目,它有一個上傳和下載文件到服務器(tomcat)。我已經有一個上傳servlet,工作正常。
我還有一個在互聯網上找到的下載servlet。但問題是這個servlet只允許下載一個特定的文件,並且在servlet中給出了這個特定文件的路徑。 我需要讓客戶端查看我的上傳文件夾的全部內容,並從該文件夾中選擇要下載的文件。
下載servlet的代碼是這樣的:
import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class DownloadServlet extends javax.servlet.http.HttpServlet implements
javax.servlet.Servlet {
static final long serialVersionUID = 1L;
private static final int BUFSIZE = 4096;
private String filePath;`
public void init() {
// the file data.xls is under web application folder
filePath = getServletContext().getRealPath("") + File.separator;// + "data.xls";
}
protected void doGet(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
File file = new File(filePath);
int length = 0;
ServletOutputStream outStream = response.getOutputStream();
ServletContext context = getServletConfig().getServletContext();
String mimetype = context.getMimeType(filePath);
// sets response content type
if (mimetype == null) {
mimetype = "application/octet-stream";
}
response.setContentType(mimetype);
response.setContentLength((int)file.length());
String fileName = (new File(filePath)).getName();
// sets HTTP header
response.setHeader("Content-Disposition", "attachment; filename=\"" + fileName + "\"");
byte[] byteBuffer = new byte[BUFSIZE];
DataInputStream in = new DataInputStream(new FileInputStream(file));
// reads the file's bytes and writes them to the response stream
while ((in != null) && ((length = in.read(byteBuffer)) != -1))
{
outStream.write(byteBuffer,0,length);
}
in.close();
outStream.close();
}
}
JSP頁面是這樣的:
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
<!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=ISO-8859-1">
<title>Download Servlet Test</title>
</head>
<body>
Click on the link to download: <a href="DownloadServlet">Download Link</a>
</body>
</html>
我搜索了很多servlet,但所有這些都是這樣的......他們只允許下載一個特定的文件。 誰能幫我? 非常感謝你!
由於您正在處理doGet
方法上的數據,因此可以將參數傳遞給servlet,您可以在其中指明要下載的文件的名稱。 為此,您應該假定文件名存在於基本路徑中。 代碼可能是這樣的:
HTML
<body>
Click on the link to download:
<a href="DownloadServlet?fileName=data.xls">Download Link</a>
</body>
Java Servlet代碼:
protected void doGet(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
//retrieving the parameter by its name
String fileName = request.getParameter("fileName"); //this will return `data.xls`
//using the File(parent, child) constructor for File class
File file = new File(filePath, fileName);
//verify if the file exists
if (file.exists()) {
//move the code to download your file inside here...
} else {
//handle a response to do nothing
}
}
請注意,由於代碼現在使用File(String parent, String child)
構造函數,因此filePath
不應再包含分隔符(這將由Java處理):
public void init() {
// the file data.xls is under web application folder
filePath = getServletContext().getRealPath("");
}
你可以這樣做
public void doGet(HttpServletRequest req, HttpServletResponse res){
res.setContentType("text/html);
PrintWriter out=response.getWriter();
String fileName="home.txt";
String filePath="d:\\";
response.setContentType("APPLICATION/OCTET-STREAM");
response.setHeader("Content-Disposition","attachment;fileName=\""+fileName+"\"");
int i;
FileInputStream file=new FileInputStream(filePath +fileName);
while((i=file.read()) !=-1){
out.write(i);
}
file.close();
out.close();
}
// get MIME type of the file
String mimeType = context.getMimeType(fullPath);
if (mimeType == null) {
// set to binary type if MIME mapping not found
mimeType = "application/octet-stream";
}
System.out.println("MIME type: " + mimeType);
// set content attributes for the response
response.setContentType(mimeType);
response.setContentLength((int) downloadFile.length());
這個更詳細的問題以及如何改進的問題: https : //stackoverflow.com/questions/41914092/how-change-servlet-which-download-single-file-but-can-folderfew-files-in-fold
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