Java code to implement file downloads
This is the implementation download class (servlet), with detailed idea codes such as the following:
You can also connect to a database
Package com.message;
Import javax.servlet.*;
Import javax.servlet.http.*;
Import java.io.*;
Import java.util.*;
public class Filedownservlet extends HttpServlet {
private static final String Content_Type = "text/html; CHARSET=GBK ";
Initialize Global Variables
public void Init () throws Servletexception {
}
Process the HTTP Get request
public void doget (HttpServletRequest request, httpservletresponse response) throws
Servletexception, IOException {
Response.setcontenttype (Content_Type);
Get the name of the downloaded file
String filename=request.getparameter ("filename");
Solve Chinese garbled problem
String Filename=new string (request.getparameter ("filename"). GetBytes ("Iso-8859-1"), "GBK");
Create a File object
File File=new file ("f://book//webroot//" +filename);
To set the encoding for response
Response.setcontenttype ("Application/x-msdownload");
Specify the size of the file to download
Response.setcontentlength ((int) file.length ());
Set additional file names
Response.setheader ("Content-disposition", "attachment;filename=" +filename);
Solve Chinese garbled characters
Response.setheader ("Content-disposition", "Attachment;filename=" +new String
(Filename.getbytes ("GBK"), "iso-8859-1"));
read out file to I/O stream
FileInputStream fis=new fileinputstream (file);
Bufferedinputstream buff=new bufferedinputstream (FIS);
byte [] b=new byte[1024];//equivalent to our cache
Long k=0;//This value is used to calculate how many bytes are currently actually downloaded
Get the output stream from the response object, ready to download
OutputStream Myout=response.getoutputstream ();
Start cycle Download
while (K<file.length ()) {
int J=buff.read (b,0,1024);
K+=j;
Writes the data in B to the client's memory
Myout.write (B,0,J);
}
Data that is written to the client's memory, flushed to disk
Myout.flush ();
}
Process the HTTP Post request
public void DoPost (HttpServletRequest request, httpservletresponse response) throws
Servletexception, IOException {
Doget (request, response);
}
Clean up resources
public void Destroy () {
}
}
This is the JavaBean, the main implementation and database connection, assuming that there is no database connection, you can directly do not this
Package com;
public class Messagebean {
Private String Message;
Public String GetMessage () {
return Message;
}
public void Setmessage (String message) {
message = message;
}
}
HTML page load write, or connect to database (case code also in)
<%@ page language= "java" import= "java.util.*,com.message.*" pageencoding= "GBK"%>
<jsp:directive.page import= "com. Messagebean; " />
<%
String path = Request.getcontextpath ();
String basepath = request.getscheme () + "://" +request.getservername () + ":" +request.getserverport () +path+ "/";
%>
<! DOCTYPE HTML PUBLIC "-//w3c//dtd HTML 4.01 transitional//en" >
<base href= "<%=basePath%>" >
<title>my JSP ' book.jsp ' starting page</title>
<meta http-equiv= "Pragma" content= "No-cache" >
<meta http-equiv= "Cache-control" content= "No-cache" >
<meta http-equiv= "Expires" content= "0" >
<meta http-equiv= "keywords" content= "keyword1,keyword2,keyword3" >
<meta http-equiv= "description" content= "This is my page" >
<!--
<link rel= "stylesheet" type= "Text/css" href= "Styles.css" >
-
<body>
<!--<a href= "Java.rar" >5.1 download book--java</a> <br>-->
<%
Vector vv= (vector) session.getattribute ("message");
for (int i=0;i<vv.size (); i++) {
Messagesbean mb= (Messagesbean) vv.get (i);
Out.println ("<tr>");
Out.println ("<td>" +mb.getsender () + "</td>");
Out.println ("<td>" +mb.getmess_time () + "</td>");
Out.println ("<td>" +mb.getgeter () + "</td>");
Out.println ("<td>" +mb.getmess_content () + "</td>");
String Filename=null;
Session.setattribute ("Java.rar", filename);
Get file name
Filename=getfilepath (). substring (Mb.getfilepath (). LastIndexOf ("/") +1);
Out.println ("<td><a href=filedownservlet?filename=java.rar>5.1 download book--java</a></td>");// Java.rar This can be changed into a variable
Out.println ("<td><a href=filedownservlet?filename=dos.rar>dos video tutorial </a></td>");
Out.println ("<td><a href=filedownservlet?filename= often use DOS commands to .rar> frequently using DOS command </a></td>");
Out.println ("</tr>");
// }
%>
</body>
//This is the Web. XML configuration file, which is very important, otherwise it is very difficult to implement OH
<?xml version= "1.0" encoding= "UTF-8"?
<web-app version= " 2.4 "
xmlns=" http://java.sun.com/xml/ns/j2ee "
xmlns:xsi=" http://www.w3.org/2001/ Xmlschema-instance "
xsi:schemalocation=" HTTP://JAVA.SUN.COM/XML/NS/J2EE
http://java.sun.com/ Xml/ns/j2ee/web-app_2_4.xsd
<servlet>
<description>this is the Description of my EE component</description>
<display-name>this is the display name of my EE component</display-name>
<servlet-name>filedownservlet</ Servlet-name>
<servlet-class>com.message.FileDownServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>FileDownServlet</servlet-name>
<url-pattern>/FileDownServlet</url-pattern>
</servlet-mapping>
</web-app>
Java code to implement file downloads
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