Android example source code file (IdleCache.java)

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

Java - Android tags/keywords

android, check_interval, connection, empty_check_max, entry, httphost, idle_cache_max, idlecache, idlereaper, interruptedexception, os, thread, timeout

The IdleCache.java Android example source code

/*
 * Copyright (C) 2008 The Android Open Source Project
 *
 * 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.
 */

/**
 * Hangs onto idle live connections for a little while
 */

package android.net.http;

import org.apache.http.HttpHost;

import android.os.SystemClock;

/**
 * {@hide}
 */
class IdleCache {

    class Entry {
        HttpHost mHost;
        Connection mConnection;
        long mTimeout;
    };

    private final static int IDLE_CACHE_MAX = 8;

    /* Allow five consecutive empty queue checks before shutdown */
    private final static int EMPTY_CHECK_MAX = 5;

    /* six second timeout for connections */
    private final static int TIMEOUT = 6 * 1000;
    private final static int CHECK_INTERVAL = 2 * 1000;
    private Entry[] mEntries = new Entry[IDLE_CACHE_MAX];

    private int mCount = 0;

    private IdleReaper mThread = null;

    /* stats */
    private int mCached = 0;
    private int mReused = 0;

    IdleCache() {
        for (int i = 0; i < IDLE_CACHE_MAX; i++) {
            mEntries[i] = new Entry();
        }
    }

    /**
     * Caches connection, if there is room.
     * @return true if connection cached
     */
    synchronized boolean cacheConnection(
            HttpHost host, Connection connection) {

        boolean ret = false;

        if (HttpLog.LOGV) {
            HttpLog.v("IdleCache size " + mCount + " host "  + host);
        }

        if (mCount < IDLE_CACHE_MAX) {
            long time = SystemClock.uptimeMillis();
            for (int i = 0; i < IDLE_CACHE_MAX; i++) {
                Entry entry = mEntries[i];
                if (entry.mHost == null) {
                    entry.mHost = host;
                    entry.mConnection = connection;
                    entry.mTimeout = time + TIMEOUT;
                    mCount++;
                    if (HttpLog.LOGV) mCached++;
                    ret = true;
                    if (mThread == null) {
                        mThread = new IdleReaper();
                        mThread.start();
                    }
                    break;
                }
            }
        }
        return ret;
    }

    synchronized Connection getConnection(HttpHost host) {
        Connection ret = null;

        if (mCount > 0) {
            for (int i = 0; i < IDLE_CACHE_MAX; i++) {
                Entry entry = mEntries[i];
                HttpHost eHost = entry.mHost;
                if (eHost != null && eHost.equals(host)) {
                    ret = entry.mConnection;
                    entry.mHost = null;
                    entry.mConnection = null;
                    mCount--;
                    if (HttpLog.LOGV) mReused++;
                    break;
                }
            }
        }
        return ret;
    }

    synchronized void clear() {
        for (int i = 0; mCount > 0 && i < IDLE_CACHE_MAX; i++) {
            Entry entry = mEntries[i];
            if (entry.mHost != null) {
                entry.mHost = null;
                entry.mConnection.closeConnection();
                entry.mConnection = null;
                mCount--;
            }
        }
    }

    private synchronized void clearIdle() {
        if (mCount > 0) {
            long time = SystemClock.uptimeMillis();
            for (int i = 0; i < IDLE_CACHE_MAX; i++) {
                Entry entry = mEntries[i];
                if (entry.mHost != null && time > entry.mTimeout) {
                    entry.mHost = null;
                    entry.mConnection.closeConnection();
                    entry.mConnection = null;
                    mCount--;
                }
            }
        }
    }

    private class IdleReaper extends Thread {

        public void run() {
            int check = 0;

            setName("IdleReaper");
            android.os.Process.setThreadPriority(
                    android.os.Process.THREAD_PRIORITY_BACKGROUND);
            synchronized (IdleCache.this) {
                while (check < EMPTY_CHECK_MAX) {
                    try {
                        IdleCache.this.wait(CHECK_INTERVAL);
                    } catch (InterruptedException ex) {
                    }
                    if (mCount == 0) {
                        check++;
                    } else {
                        check = 0;
                        clearIdle();
                    }
                }
                mThread = null;
            }
            if (HttpLog.LOGV) {
                HttpLog.v("IdleCache IdleReaper shutdown: cached " + mCached +
                          " reused " + mReused);
                mCached = 0;
                mReused = 0;
            }
        }
    }
}