创建的线程数超出了要求

Question

I am writing a multi threaded client program which listens for a connection which comes from the web browser.My problem is more threads are created than should be.For eg if i type in a url in the browser ,Just one thread should be created but in my case ,multiple threads are created.

public void running() {

    try {
        for(;;){
        Socket socket=server.accept();
        Thread t= new Thread( new ClientHandler(socket));
        t.start();
         // calls the start method to start a thread which also starts the run method
        System.out.println("Thread id is " +t.getId() );}
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

}
             public static void main(String[] args) {

    Server server= new Server();
    server.running();
}
 }

Answer 1

The code presented will create one thread for each incoming connection. No more.

If you are getting more threads than you are expecting, then the most obvious explanation is that the web browser is opening more connections to your server than you are expecting. For example, the browser may attempt to fetch a 'favico' for your "site" ... or send a HEAD before attempting a GET.

Another possibility is that those extra threads that you are seeing are daemon threads created by the JVM; eg the garbage collector thread, the finalizer thread and so on. Or maybe they never actually existed ... and you are misinterpreting something.

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The other thing to note is that it is a BAD IDEA to implement an HTTP service using plain TCP/IP sockets. It is a lot of work to implement HTTP properly, and the chances are that you will get it a bit ... or a lot ... wrong, resulting in service that doesn't interoperate well with different browsers. It is better to use an existing HTTP "stack"; eg an existing web application server / framework, or maybe the Apache HttpComponents stack.

Answer 2

.For eg if i type in a url in the browser ,Just one thread should be created but in my case ,multiple threads are created.

Only if you assume the browser will create one connection. You don't know that, and the evidence is against you. If the data returned by the URL contains relative URLs to images etc the browser will open additional connections to retrieve them concurrently.