This section describes how to view HTTP response header lines with a Web browser or with a Java program.
When the client program receives the HTTP response, it will look at the header lines
first. Based on information contained in header lines, the client program will
decide what to do with the actual response data in the entity body.
If you use a Web browser as a HTTP client program, it will process the data
in the entity body differently depending on mainly the "Content-Type" entity header line:
displaying the data as it is,
rendering the data as a HTML document and displaying the resulting information,
or passing the data to other registered programs to handle it.
Once the Web browser finishes processing the entity body, you can get some limited information
from the header lines. For example, you can click the right mouse button and select
the properties command on Internet Explorer, it will display some general properties
about this response in a pop up window. The properties displayed are not always
identical to the response header lines. The "Modified" property is probably identical
to the "Last-Modified" entity header line. The "Type" property is sometime related
to the "Content-Type" entity header line, and sometimes related to server side resource
that generated the response.
How to view all the header lines received in the HTTP response? I couldn't find
any existing tools to do this. So I wrote the following program to dump the entire
response including all header lines received from a Web server:
/**
* HttpRequestGet.java
* Copyright (c) 2002 by Dr. Herong Yang. All rights reserved.
*/
import java.io.*;
import java.net.*;
public class HttpRequestGet {
public static void main(String[] args) {
String path = "/index.html";
int port = 80;
String host = "localhost";
if (args.length > 0) path = args[0];
if (args.length > 1) port
= Integer.valueOf(args[1]).intValue();
if (args.length > 2) host = args[2];
String result = "";
try {
Socket c = new Socket(host,port);
BufferedWriter w = new BufferedWriter(new OutputStreamWriter(
c.getOutputStream()));
BufferedReader r = new BufferedReader(new InputStreamReader(
c.getInputStream()));
String m = "GET "+ path + " HTTP/1.0";
w.write(m,0,m.length());
w.newLine();
w.newLine();
w.flush();
while ((m=r.readLine())!= null) {
System.out.println(m);
}
w.close();
r.close();
c.close();
} catch (IOException e) {
System.err.println(e.toString());
}
}
}
