传统的连接池比如proxool，会使用List存放所有的连接，通过读写锁来修改连接的状态，标示该连接是否是可用，而BoneCP采用了分区的方式提高了获取数据库连接的并发性，类似ConcurrentHashMap解决并发问题的思想。
下面看下主要的几个类：
- BoneCPDataSource：实现了DataSource接口，接收数据库的配置并对外提供获取数据库连接的功能，第一次获取连接时会初始化连接池BoneCP对象。
public Connection getConnection() throws SQLException {
FinalWrapper<BoneCP> wrapper = this.pool;
if (wrapper == null) {
synchronized (this) {
if (this.pool == null) {
try{
if (this.getDriverClass() != null){
loadClass(this.getDriverClass());
}
logger.debug(this.toString());
this.pool = new FinalWrapper<BoneCP>(new BoneCP(this));
} catch (ClassNotFoundException e) {
throw new SQLException(PoolUtil.stringifyException(e));
}
}
wrapper = this.pool;
}
}
return wrapper.value.getConnection();
}
- BoneCp：负责连接池的初始化、获取数据库连接的功能，初始化流程：
- 根据配置文件中分区的个数创建ConnectionPartition对象，并根据配置文件中的最小连接数为每个分区创建连接
- 为每个ConnectionPartition创建三个线程，PoolWatchThread用于数据库新连接的建立，ConnectionMaxAgeThread用于连接最大存活时间的检查，ConnectionTesterThread最大空闲时间的检查
public BoneCP(BoneCPConfig config) throws SQLException { Class<?> clazz; try { jvmMajorVersion = 5; clazz = Class.forName(connectionClass , true, config.getClassLoader()); clazz.getMethod("createClob"); // since 1.6 jvmMajorVersion = 6; clazz.getMethod("getNetworkTimeout"); // since 1.7 jvmMajorVersion = 7; } catch (Exception e) { // do nothing } try { this.config = Preconditions.checkNotNull(config).clone(); // immutable } catch (CloneNotSupportedException e1) { throw new SQLException("Cloning of the config failed"); } this.config.sanitize(); this.statisticsEnabled = config.isStatisticsEnabled(); this.closeConnectionWatchTimeoutInMs = config.getCloseConnectionWatchTimeoutInMs(); this.poolAvailabilityThreshold = config.getPoolAvailabilityThreshold(); this.connectionTimeoutInMs = config.getConnectionTimeoutInMs(); if (this.connectionTimeoutInMs == 0){ this.connectionTimeoutInMs = Long.MAX_VALUE; } this.nullOnConnectionTimeout = config.isNullOnConnectionTimeout(); this.resetConnectionOnClose = config.isResetConnectionOnClose(); this.clientInfo = jvmMajorVersion > 5 ? config.getClientInfo() : null; AcquireFailConfig acquireConfig = new AcquireFailConfig(); acquireConfig.setAcquireRetryAttempts(new AtomicInteger(0)); acquireConfig.setAcquireRetryDelayInMs(0); acquireConfig.setLogMessage("Failed to obtain initial connection"); if (!config.isLazyInit()){ try{ Connection sanityConnection = obtainRawInternalConnection(); sanityConnection.close(); } catch (Exception e){ if (config.getConnectionHook() != null){ config.getConnectionHook().onAcquireFail(e, acquireConfig); } throw PoolUtil.generateSQLException(String.format(ERROR_TEST_CONNECTION, config.getJdbcUrl(), config.getUsername(), PoolUtil.stringifyException(e)), e); } } if (!config.isDisableConnectionTracking()){ this.finalizableRefQueue = new FinalizableReferenceQueue(); } this.asyncExecutor = MoreExecutors.listeningDecorator(Executors.newCachedThreadPool()); this.config = config; this.partitions = new ConnectionPartition[config.getPartitionCount()]; String suffix = ""; if (config.getPoolName()!=null) { suffix="-"+config.getPoolName(); } this.keepAliveScheduler = Executors.newScheduledThreadPool(config.getPartitionCount(), new CustomThreadFactory("BoneCP-keep-alive-scheduler"+suffix, true)); this.maxAliveScheduler = Executors.newScheduledThreadPool(config.getPartitionCount(), new CustomThreadFactory("BoneCP-max-alive-scheduler"+suffix, true)); this.connectionsScheduler = Executors.newFixedThreadPool(config.getPartitionCount(), new CustomThreadFactory("BoneCP-pool-watch-thread"+suffix, true)); this.partitionCount = config.getPartitionCount(); this.closeConnectionWatch = config.isCloseConnectionWatch(); this.cachedPoolStrategy = config.getPoolStrategy() != null && config.getPoolStrategy().equalsIgnoreCase("CACHED"); if (this.cachedPoolStrategy){ this.connectionStrategy = new CachedConnectionStrategy(this, new DefaultConnectionStrategy(this)); } else { this.connectionStrategy = new DefaultConnectionStrategy(this); } boolean queueLIFO = config.getServiceOrder() != null && config.getServiceOrder().equalsIgnoreCase("LIFO"); if (this.closeConnectionWatch){ logger.warn(THREAD_CLOSE_CONNECTION_WARNING); this.closeConnectionExecutor = Executors.newCachedThreadPool(new CustomThreadFactory("BoneCP-connection-watch-thread"+suffix, true)); } for (int p=0; p < config.getPartitionCount(); p++){ ConnectionPartition connectionPartition = new ConnectionPartition(this); this.partitions[p]=connectionPartition; BlockingQueue<ConnectionHandle> connectionHandles = new LinkedBlockingQueue<ConnectionHandle>(this.config.getMaxConnectionsPerPartition()); this.partitions[p].setFreeConnections(connectionHandles); if (!config.isLazyInit()){ for (int i=0; i < config.getMinConnectionsPerPartition(); i++){ this.partitions[p].addFreeConnection(new ConnectionHandle(null, this.partitions[p], this, false)); } } if (config.getIdleConnectionTestPeriod(TimeUnit.SECONDS) > 0 || config.getIdleMaxAge(TimeUnit.SECONDS) > 0){ final Runnable connectionTester = new ConnectionTesterThread(connectionPartition, this.keepAliveScheduler, this, config.getIdleMaxAge(TimeUnit.MILLISECONDS), config.getIdleConnectionTestPeriod(TimeUnit.MILLISECONDS), queueLIFO); long delayInSeconds = config.getIdleConnectionTestPeriod(TimeUnit.SECONDS); if (delayInSeconds == 0L){ delayInSeconds = config.getIdleMaxAge(TimeUnit.SECONDS); } if (config.getIdleMaxAge(TimeUnit.SECONDS) < delayInSeconds && config.getIdleConnectionTestPeriod(TimeUnit.SECONDS) != 0 && config.getIdleMaxAge(TimeUnit.SECONDS) != 0){ delayInSeconds = config.getIdleMaxAge(TimeUnit.SECONDS); } this.keepAliveScheduler.schedule(connectionTester, delayInSeconds, TimeUnit.SECONDS); } if (config.getMaxConnectionAgeInSeconds() > 0){ final Runnable connectionMaxAgeTester = new ConnectionMaxAgeThread(connectionPartition, this.maxAliveScheduler, this, config.getMaxConnectionAge(TimeUnit.MILLISECONDS), queueLIFO); this.maxAliveScheduler.schedule(connectionMaxAgeTester, config.getMaxConnectionAgeInSeconds(), TimeUnit.SECONDS); } // watch this partition for low no of threads this.connectionsScheduler.execute(new PoolWatchThread(connectionPartition, this)); } if (!this.config.isDisableJMX()){ registerUnregisterJMX(true); } }当需要获取连接时采用策略模式从BoneCP定义的ConnectionPartition数组中随机选择一个获取连接，如果获取不到会尝试其它ConnectionPartition。创建连接的方式是直接使用java中的DriverManager来创建数据库连接，并放到对应ConnectionPartition的队列中。
-
ConnectionPartition：通过LinkedBlockingQueue维护数据库连接，获取连接时从队列中取出一个
-
ConnectionHandle：实现了Connection接口，对于close操作会将连接放回到指定ConnectionPartition的LinkedBlockingQueue队列中，这样就能复用连接，同时缓存创建的statement
-
ConnectionTesterThread和ConnectionMaxAgeThread会根据配置文件定时执行，在执行时会将ConnectionPartition中的LinkedBlockingQueue一次取出，判断连接的各种状态，符合条件后再放回LinkedBlockingQueue中，这期间会对连接池有比较大的性能影响