【HikariCP】【PoolEntry】源码学习

Hikari目前已经是springboot的默认数据库连接池，并且以高效和轻量著称，因为代码量比较少，所以可以阅读一下，学习一下，github地址：HikariCP

PoolEntry

实现了IConcurrentBagEntry接口，可以共享的连接，是连接池里的单个连接实体。

成员变量

• private static final AtomicIntegerFieldUpdater stateUpdater

• Connection connection
  数据库连接

• long lastAccessed
  上次访问毫秒数

• long lastBorrowed
  上次借用毫秒数

• private volatile int state = 0

• private volatile boolean evict
  是否已经移除出连接池

• private volatile ScheduledFuture endOfLife
  连接结束的最后回调

• private final FastList openStatements

• private final HikariPool hikariPool
  hikari连接池

• private final boolean isReadOnly
  是否只读

• private final boolean isAutoCommit
  是否自动提交

静态块

static
{
  stateUpdater = AtomicIntegerFieldUpdater.newUpdater(PoolEntry.class, "state");
}

静态块中就是对stateUpdater进行实例化，对state字段进行顺序更新

构造方法

PoolEntry(final Connection connection, final PoolBase pool, final boolean isReadOnly, final boolean isAutoCommit)
{
  this.connection = connection;
  this.hikariPool = (HikariPool) pool;
  this.isReadOnly = isReadOnly;
  this.isAutoCommit = isAutoCommit;
  this.lastAccessed = currentTime();
  this.openStatements = new FastList<>(Statement.class, 16);
}

构造方法传入的参数都是一一赋值，其中的openStatements是指定sql的Statement类型的16容量的FastList。

方法

• void recycle(final long lastAccessed)

void recycle(final long lastAccessed)
{
  if (connection != null) {
     this.lastAccessed = lastAccessed;
     hikariPool.recycle(this);
  }
}

如果连接存在，记录上次方法的时间戳，然后调用连接池的方法回收连接

• void setFutureEol(final ScheduledFuture endOfLife)

void setFutureEol(final ScheduledFuture endOfLife)
{
  this.endOfLife = endOfLife;
}

设置调度任务的回调

• Connection createProxyConnection(final ProxyLeakTask leakTask, final long now)

Connection createProxyConnection(final ProxyLeakTask leakTask, final long now)
{
  return ProxyFactory.getProxyConnection(this, connection, openStatements, leakTask, now, isReadOnly, isAutoCommit);
}

传入普通的连接创建一个代理连接

• void resetConnectionState(final ProxyConnection proxyConnection, final int dirtyBits)

void resetConnectionState(final ProxyConnection proxyConnection, final int dirtyBits) throws SQLException
{
  hikariPool.resetConnectionState(connection, proxyConnection, dirtyBits);
}

重置连接的状态，里面的方法涉及到位运算，为了提高运算效率。

• boolean isMarkedEvicted()

boolean isMarkedEvicted()
{
  return evict;
}

判断该连接是否已经被连接池移出

• void markEvicted()

void markEvicted()
{
  this.evict = true;
}

标记成已移除，将evict标成true

• void evict(final String closureReason)

void evict(final String closureReason)
{
  hikariPool.closeConnection(this, closureReason);
}

移除连接，调用的是连接池的closeConnection()方法，同时记录了关闭原因

• long getMillisSinceBorrowed()

long getMillisSinceBorrowed()
{
  return elapsedMillis(lastBorrowed);
}

计算上次使用该连接到现在共花费了多少毫秒

• Connection close()

Connection close()
{
  ScheduledFuture eol = endOfLife;
  if (eol != null && !eol.isDone() && !eol.cancel(false)) {
     LOGGER.warn("{} - maxLifeTime expiration task cancellation unexpectedly returned false for connection {}", getPoolName(), connection);
  }

  Connection con = connection;
  connection = null;
  endOfLife = null;
  return con;
}

关闭连接，检查连接的最后回调是否完成，如果没有完成那么输出日志，然后将连接和回调置空后返回连接的引用。