First of all, my question is about HttpServer in Java to handle the POST request from a client, not about a Java client who can upload file to a web server.
OK. I am using a lightweight HttpServer in Java to handle “GET” || “POST” requests. The source code of the HttpServer is copied from http://www.prasannatech.net/2008/11/http-web-server-java-post-file-upload.html.
/*
* HTTPPOSTServer.java
* Author: S.Prasanna
* @version 1.00
*/
import java.io.*;
import java.net.*;
import java.util.*;
public class HTTPPOSTServer extends Thread {
static final String HTML_START =
"<html>" +
"<title>HTTP POST Server in java</title>" +
"<body>";
static final String HTML_END =
"</body>" +
"</html>";
Socket connectedClient = null;
BufferedReader inFromClient = null;
DataOutputStream outToClient = null;
public HTTPPOSTServer(Socket client) {
connectedClient = client;
}
public void run() {
String currentLine = null, postBoundary = null, contentength = null, filename = null, contentLength = null;
PrintWriter fout = null;
try {
System.out.println( "The Client "+
connectedClient.getInetAddress() + ":" + connectedClient.getPort() + " is connected");
inFromClient = new BufferedReader(new InputStreamReader (connectedClient.getInputStream()));
outToClient = new DataOutputStream(connectedClient.getOutputStream());
currentLine = inFromClient.readLine();
String headerLine = currentLine;
StringTokenizer tokenizer = new StringTokenizer(headerLine);
String httpMethod = tokenizer.nextToken();
String httpQueryString = tokenizer.nextToken();
System.out.println(currentLine);
if (httpMethod.equals("GET")) {
System.out.println("GET request");
if (httpQueryString.equals("/")) {
// The default home page
String responseString = HTTPPOSTServer.HTML_START +
"<form action=\"http://127.0.0.1:5000\" enctype=\"multipart/form-data\"" +
"method=\"post\">" +
"Enter the name of the File <input name=\"file\" type=\"file\"><br>" +
"<input value=\"Upload\" type=\"submit\"></form>" +
"Upload only text files." +
HTTPPOSTServer.HTML_END;
sendResponse(200, responseString , false);
} else {
sendResponse(404, "<b>The Requested resource not found ...." +
"Usage: http://127.0.0.1:5000</b>", false);
}
}
else { //POST request
System.out.println("POST request");
do {
currentLine = inFromClient.readLine();
if (currentLine.indexOf("Content-Type: multipart/form-data") != -1) {
String boundary = currentLine.split("boundary=")[1];
// The POST boundary
while (true) {
currentLine = inFromClient.readLine();
if (currentLine.indexOf("Content-Length:") != -1) {
contentLength = currentLine.split(" ")[1];
System.out.println("Content Length = " + contentLength);
break;
}
}
//Content length should be < 2MB
if (Long.valueOf(contentLength) > 2000000L) {
sendResponse(200, "File size should be < 2MB", false);
}
while (true) {
currentLine = inFromClient.readLine();
if (currentLine.indexOf("--" + boundary) != -1) {
filename = inFromClient.readLine().split("filename=")[1].replaceAll("\"", "");
String [] filelist = filename.split("\\" + System.getProperty("file.separator"));
filename = filelist[filelist.length - 1];
System.out.println("File to be uploaded = " + filename);
break;
}
}
String fileContentType = inFromClient.readLine().split(" ")[1];
System.out.println("File content type = " + fileContentType);
inFromClient.readLine(); //assert(inFromClient.readLine().equals("")) : "Expected line in POST request is "" ";
fout = new PrintWriter(filename);
String prevLine = inFromClient.readLine();
currentLine = inFromClient.readLine();
//Here we upload the actual file contents
while (true) {
if (currentLine.equals("--" + boundary + "--")) {
fout.print(prevLine);
break;
}
else {
fout.println(prevLine);
}
prevLine = currentLine;
currentLine = inFromClient.readLine();
}
sendResponse(200, "File " + filename + " Uploaded..", false);
fout.close();
} //if
}while (inFromClient.ready()); //End of do-while
}//else
} catch (Exception e) {
e.printStackTrace();
}
}
public void sendResponse (int statusCode, String responseString, boolean isFile) throws Exception {
String statusLine = null;
String serverdetails = "Server: Java HTTPServer";
String contentLengthLine = null;
String fileName = null;
String contentTypeLine = "Content-Type: text/html" + "\r\n";
FileInputStream fin = null;
if (statusCode == 200)
statusLine = "HTTP/1.1 200 OK" + "\r\n";
else
statusLine = "HTTP/1.1 404 Not Found" + "\r\n";
if (isFile) {
fileName = responseString;
fin = new FileInputStream(fileName);
contentLengthLine = "Content-Length: " + Integer.toString(fin.available()) + "\r\n";
if (!fileName.endsWith(".htm") && !fileName.endsWith(".html"))
contentTypeLine = "Content-Type: \r\n";
}
else {
responseString = HTTPPOSTServer.HTML_START + responseString + HTTPPOSTServer.HTML_END;
contentLengthLine = "Content-Length: " + responseString.length() + "\r\n";
}
outToClient.writeBytes(statusLine);
outToClient.writeBytes(serverdetails);
outToClient.writeBytes(contentTypeLine);
outToClient.writeBytes(contentLengthLine);
outToClient.writeBytes("Connection: close\r\n");
outToClient.writeBytes("\r\n");
if (isFile) sendFile(fin, outToClient);
else outToClient.writeBytes(responseString);
outToClient.close();
}
public void sendFile (FileInputStream fin, DataOutputStream out) throws Exception {
byte[] buffer = new byte[1024] ;
int bytesRead;
while ((bytesRead = fin.read(buffer)) != -1 ) {
out.write(buffer, 0, bytesRead);
}
fin.close();
}
public static void main (String args[]) throws Exception {
ServerSocket Server = new ServerSocket (5000);
System.out.println ("HTTP Server Waiting for client on port 5000");
while(true) {
Socket connected = Server.accept();
(new HTTPPOSTServer(connected)).start();
}
}
}
I read through the code, I think the code should be all right.
But when I try to upload a file, it will print out POST request, and then hang there and never receive any bytes.
If you are willing to, you can run the above source code directly. After launch it, you can type 127.0.0.1:5000 in a browser, and it will show a file upload, then if I try upload a file, it will hang there after printing PoST request.
If you are bored to read the code, may I ask the following simpler question?
So, what exactly Chrome or any other web browser do about form -> input type=’file’?
If I am using a ServerSocket to handle the HTTP request, I just get the InputStream of the request, and then all the content (including HTTP headers & the uploading file’s content) will go through that InputStream, right?
The above code can analyse the headers, but then it seems nothing is sent from the browser any more.
Can anyone pls help?
Thanks
It hangs because client (Chrome, in my case) does not provide
Content-Length.RFC 1867 is pretty vague about it. It kind of suggests it but does not force it and does not have an example. Apparently clients would not always send it. The code should safeguard against missing length. Instead it goes through the loop until it reaches the end of file. Then it hangs.
Using debugger is very helpful at times.