Java example source code file (HttpCorsServer.java)

This example Java source code file (HttpCorsServer.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

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Java - Java tags/keywords

exception, httpcorsserver, httpcorsserverinitializer, nioeventloopgroup, port, selfsignedcertificate, serverbootstrap, ssl, sslcontext

The HttpCorsServer.java Java example source code

/*
 * Copyright 2012 The Netty Project
 *
 * The Netty Project licenses this file to you under the Apache License,
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */
package io.netty.example.http.cors;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;
import io.netty.handler.ssl.SslContext;
import io.netty.handler.ssl.SslContextBuilder;
import io.netty.handler.ssl.util.SelfSignedCertificate;

/**
 * This example server aims to demonstrate
 * <a href="http://www.w3.org/TR/cors/">Cross Origin Resource Sharing (CORS) in Netty.
 * It does not have a client like most of the other examples, but instead has
 * a html page that is loaded to try out CORS support in a web brower.
 * <p>
 *
 * CORS is configured in {@link HttpCorsServerInitializer} and by updating the config you can
 * try out various combinations, like using a specific origin instead of a
 * wildcard origin ('*').
 * <p>
 *
 * The file {@code src/main/resources/cors/cors.html} contains a very basic example client
 * which can be used to try out different configurations. For example, you can add
 * custom headers to force a CORS preflight request to make the request fail. Then
 * to enable a successful request, configure the CorsHandler to allow that/those
 * request headers.
 *
 * <h2>Testing CORS
 * You can either load the file {@code src/main/resources/cors/cors.html} using a web server
 * or load it from the file system using a web browser.
 *
 * <h3>Using a web server
 * To test CORS support you can serve the file {@code src/main/resources/cors/cors.html}
 * using a web server. You can then add a new host name to your systems hosts file, for
 * example if you are on Linux you may update /etc/hosts to add an addtional name
 * for you local system:
 * <pre>
 * 127.0.0.1   localhost domain1.com
 * </pre>
 * Now, you should be able to access {@code http://domain1.com/cors.html} depending on how you
 * have configured you local web server the exact url may differ.
 *
 * <h3>Using a web browser
 * Open the file {@code src/main/resources/cors/cors.html} in a web browser. You should see
 * loaded page and in the text area the following message:
 * <pre>
 * 'CORS is not working'
 * </pre>
 *
 * If you inspect the headers being sent using your browser you'll see that the 'Origin'
 * request header is {@code 'null'}. This is expected and happens when you load a file from the
 * local file system. Netty can handle this by configuring the CorsHandler which is done
 * in the {@link HttpCorsServerInitializer}.
 *
 */
public final class HttpCorsServer {

    static final boolean SSL = System.getProperty("ssl") != null;
    static final int PORT = Integer.parseInt(System.getProperty("port", SSL? "8443" : "8080"));

    public static void main(String[] args) throws Exception {
        // Configure SSL.
        final SslContext sslCtx;
        if (SSL) {
            SelfSignedCertificate ssc = new SelfSignedCertificate();
            sslCtx = SslContextBuilder.forServer(ssc.certificate(), ssc.privateKey()).build();
        } else {
            sslCtx = null;
        }

        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup)
             .channel(NioServerSocketChannel.class)
             .handler(new LoggingHandler(LogLevel.INFO))
             .childHandler(new HttpCorsServerInitializer(sslCtx));

            b.bind(PORT).sync().channel().closeFuture().sync();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
}