org.attribyte.api.pubsub.impl.server.PingServlet.java Source code

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Here is the source code for org.attribyte.api.pubsub.impl.server.PingServlet.java

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/*
 * Copyright 2014 Attribyte, LLC
 *
 * Licensed 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 org.attribyte.api.pubsub.impl.server;

import com.google.common.base.Joiner;
import com.google.common.collect.Sets;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
import java.net.InetAddress;
import java.net.InterfaceAddress;
import java.net.NetworkInterface;
import java.net.SocketException;
import java.util.Enumeration;
import java.util.Set;

@SuppressWarnings("serial")
public class PingServlet extends HttpServlet {

    /**
     * Creates the servlet.
     * @param instanceName The instance name.
     * @param enumerateInterfaces Should network interface names be enumerated?
     */
    public PingServlet(final String instanceName, final boolean enumerateInterfaces) {
        this.instanceName = instanceName;
        this.enumerateInterfaces = enumerateInterfaces;
    }

    private static final String CONTENT_TYPE = "text/plain";
    private static final String CACHE_CONTROL_HEADER = "Cache-Control";
    private static final String NO_CACHE_VALUE = "must-revalidate,no-cache,no-store";
    private static final Joiner nameJoiner = Joiner.on(',').skipNulls();
    private final String instanceName;
    private final boolean enumerateInterfaces;

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setStatus(200);
        response.setHeader(CACHE_CONTROL_HEADER, NO_CACHE_VALUE);
        response.setContentType(CONTENT_TYPE);
        try (PrintWriter writer = response.getWriter()) {
            writer.println(nameJoiner.join(getPublicNames()));
        }
    }

    /**
     * Gets all public names (IP, hostname).
     * Always starts with "pong" and contains the instance name, if specified.
     * @return The list of names.
     */
    private Set<String> getPublicNames() {

        Set<String> names = Sets.newHashSetWithExpectedSize(8);
        names.add("pong");
        if (instanceName != null && instanceName.length() > 0) {
            names.add(instanceName);
        }

        if (enumerateInterfaces) {
            try {
                Enumeration<NetworkInterface> interfaces = NetworkInterface.getNetworkInterfaces();
                while (interfaces.hasMoreElements()) {
                    NetworkInterface iface = interfaces.nextElement();
                    if (!iface.isLoopback() && !iface.isPointToPoint() && !iface.isVirtual() && iface.isUp()) {
                        for (final InterfaceAddress interfaceAddress : iface.getInterfaceAddresses()) {
                            InetAddress addy = interfaceAddress.getAddress();
                            if (!addy.isLoopbackAddress() && !addy.isMulticastAddress()
                                    && !addy.isLinkLocalAddress() && !addy.isSiteLocalAddress()
                                    && !addy.isAnyLocalAddress()) {
                                String hostAddress = addy.getHostAddress();
                                if (!hostAddress.contains("%")) {
                                    names.add(hostAddress);
                                    String hostname = addy.getHostName();
                                    if (hostname != null) {
                                        names.add(hostname);
                                    }
                                }
                            }
                        }
                    }
                }
            } catch (SocketException se) {
                //Ignore
            }
        }
        return names;
    }

}