HttpServer的使用

Programmers must implement the HttpHandler interface. This interface provides a callback which is invoked to handle incoming requests from clients. A HTTP request and its response is known as an exchange. HTTP exchanges are represented by the HttpExchange class. The HttpServer class is used to listen for incoming TCP connections and it dispatches requests on these connections to handlers which have been registered with the server.

A minimal Http server example is shown below:

   class MyHandler implements HttpHandler {
       public void handle(HttpExchange t) throws IOException {
           InputStream is = t.getRequestBody();
           read(is); // .. read the request body
           String response = "This is the response";
           t.sendResponseHeaders(200, response.length());
           OutputStream os = t.getResponseBody();
           os.write(response.getBytes());
           os.close();
       }
   }
   ...

   HttpServer server = HttpServer.create(new InetSocketAddress(8000));
   server.createContext("/applications/myapp", new MyHandler());
   server.setExecutor(null); // creates a default executor
   server.start();
   

The example above creates a simple HttpServer which uses the calling application thread to invoke the handle() method for incoming http requests directed to port 8000, and to the path /applications/myapp/.

The HttpExchange class encapsulates everything an application needs to process incoming requests and to generate appropriate responses.

Registering a handler with a HttpServer creates a HttpContext object and Filter objects can be added to the returned context. Filters are used to perform automatic pre- and post-processing of exchanges before they are passed to the exchange handler.

For sensitive information, a HttpsServer can be used to process "https" requests secured by the SSL or TLS protocols. A HttpsServer must be provided with a HttpsConfiguratorobject, which contains an initialized SSLContext. HttpsConfigurator can be used to configure the cipher suites and other SSL operating parameters. A simple example SSLContext could be created as follows:

   char[] passphrase = "passphrase".toCharArray();
   KeyStore ks = KeyStore.getInstance("JKS");
   ks.load(new FileInputStream("testkeys"), passphrase);

   KeyManagerFactory kmf = KeyManagerFactory.getInstance("SunX509");
   kmf.init(ks, passphrase);

   TrustManagerFactory tmf = TrustManagerFactory.getInstance("SunX509");
   tmf.init(ks);

   SSLContext ssl = SSLContext.getInstance("TLS");
   ssl.init(kmf.getKeyManagers(), tmf.getTrustManagers(), null);
   

In the example above, a keystore file called "testkeys", created with the keytool utility is used as a certificate store for client and server certificates. The following code shows how the SSLContext is then used in a HttpsConfigurator and how the SSLContext and HttpsConfigurator are linked to the HttpsServer.

    server.setHttpsConfigurator (new HttpsConfigurator(sslContext) {
        public void configure (HttpsParameters params) {

        // get the remote address if needed
        InetSocketAddress remote = params.getClientAddress();

        SSLContext c = getSSLContext();

        // get the default parameters
        SSLParameters sslparams = c.getDefaultSSLParameters();
        if (remote.equals (...) ) {
            // modify the default set for client x
        }

        params.setSSLParameters(sslparams);
        // statement above could throw IAE if any params invalid.
        // eg. if app has a UI and parameters supplied by a user.

        }
    });