HttpClientFactory

package net.kittyandbear;
//2012-11-13 johnpfeiffer requires maven: org.apache.httpcomponents - httpclient and httpmime  4.2.2 , commons-logging-1.1.1
/*
 * performance note: "While HttpClient instances are thread safe and can be shared between multiple threads of execution, it is highly recommended that each thread maintains its own dedicated instance of HttpContext."
 *  http://hc.apache.org/httpcomponents-client-ga/tutorial/html/connmgmt.html#d5e639
 *
 *  Example Usage:
 *
 *      HttpClientFactory myHttpClientFactory = HttpClientFactory.getInstance();
 *      myHttpClientFactory.setMaxConnectionsOverall(200);
 *      myHttpClientFactory.setMaxConnectionsPerRoute(100);
 *      httpclient = HttpClientFactory.getStaticHttpClient();
 */
//TODO: research whether an enum singleton pattern would be better


import org.apache.http.client.HttpClient;
import org.apache.http.conn.scheme.PlainSocketFactory;
import org.apache.http.conn.scheme.Scheme;
import org.apache.http.conn.scheme.SchemeRegistry;
import org.apache.http.conn.ssl.SSLSocketFactory;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.impl.conn.PoolingClientConnectionManager;

public class HttpClientFactory
{
    private PoolingClientConnectionManager cm;
    private Scheme http;
    private Scheme https;
    private int maxConnectionsPerRoute = 100;
    private int maxConnectionsOverall = 100;
    private static HttpClient httpclient = null;

    // Eager initialization to improve response time when httpclient is first used
    private static final HttpClientFactory INSTANCE = new HttpClientFactory();

    private HttpClientFactory()
    {
        // Prepare the connection configurations (http and https capabilities, pool manager, maxconnections, etc.)
        SchemeRegistry schemeRegistry = new SchemeRegistry();
        https = new Scheme("https", 443, SSLSocketFactory.getSocketFactory());
        schemeRegistry.register(https);
        http = new Scheme("http", 80, PlainSocketFactory.getSocketFactory());
        schemeRegistry.register(http);
        cm = new PoolingClientConnectionManager(schemeRegistry);
        cm.setDefaultMaxPerRoute(maxConnectionsPerRoute);  // Override PoolingClientConnectionManager default of 2 concurrent connections per Route
        cm.setMaxTotal(maxConnectionsOverall); // Override PoolingClientConnectionManager default of 20 connections total
        httpclient = new DefaultHttpClient(cm);
    }

    // Allows dependency injection, especially for EasyMock
    void setPoolingClientConnectionManager( PoolingClientConnectionManager cm )
    {
        this.cm = cm;
    }

    public static HttpClientFactory getInstance()
    {
        return INSTANCE;
    }

    public static HttpClient getStaticHttpClient()
    {
        return httpclient;
    }

    public int getMaxConnectionsPerRoute()
    {
        return cm.getDefaultMaxPerRoute();
    }

    public int getMaxConnectionsOverall()
    {
        return cm.getMaxTotal();
    }

    // Ensure modifications to the factory's connection pool configuration are thread safe
    public synchronized void setMaxConnectionsPerRoute(int maxConnectionsPerRoute) throws IllegalArgumentException
    {
        if (maxConnectionsPerRoute < 1)
        {
            throw new IllegalArgumentException("ERROR: maxConnectionsPerRoute must be larger than 0");
        }
        this.maxConnectionsPerRoute = maxConnectionsPerRoute;
        cm.setDefaultMaxPerRoute(maxConnectionsPerRoute);
        httpclient = new DefaultHttpClient(cm);
    }

    // Ensure modifications to the factory's connection pool configuration are thread safe
    public synchronized void setMaxConnectionsOverall(int maxConnectionsOverall) throws IllegalArgumentException
    {
        if (maxConnectionsOverall < 1)
        {
            throw new IllegalArgumentException("ERROR: maxConnectionsOverall must be larger than 0");
        }
        this.maxConnectionsOverall = maxConnectionsOverall;
        cm.setMaxTotal(maxConnectionsOverall);
        httpclient = new DefaultHttpClient(cm);
    }

} // end class