PoolEntry 参数讲解

 public abstract class PoolEntry<T, C> {

     private final String id;
     private final T route;　　//路由
     private final C conn;　　//http连接
     private final long created;　　//创建时间
     private final long validityDeadline;

     private long updated;

     private long expiry;

     private volatile Object state;

 }

构造方法：

 　　public PoolEntry(final String id, final T route, final C conn,
             final long timeToLive, final TimeUnit tunit) {
         super();
         Args.notNull(route, "Route");
         Args.notNull(conn, "Connection");
         Args.notNull(tunit, "Time unit");
         this.id = id;
         this.route = route;
         this.conn = conn;
         this.created = System.currentTimeMillis();
         this.updated = this.created;
         if (timeToLive > 0) {
             final long deadline = this.created + tunit.toMillis(timeToLive);
             // If the above overflows then default to Long.MAX_VALUE
             this.validityDeadline = deadline > 0 ? deadline : Long.MAX_VALUE;
         } else {
             this.validityDeadline = Long.MAX_VALUE;
         }
         this.expiry = this.validityDeadline;
     }

更新过期时间：

 　　public synchronized void updateExpiry(final long time, final TimeUnit tunit) {
         Args.notNull(tunit, "Time unit");
         this.updated = System.currentTimeMillis();
         final long newExpiry;
         if (time > 0) {
             newExpiry = this.updated + tunit.toMillis(time);
         } else {
             newExpiry = Long.MAX_VALUE;
         }
         this.expiry = Math.min(newExpiry, this.validityDeadline);
     }

1、http连接池管理一个连接对象，其实管理的是一个PoolEntry实例；

2、什么时候更新PoolEntry实例信息，比如过期时间，状态等？

　　在释放连接的时候会更新实例信息；

　　具体在：PoolingHttpClientConnectionManager.releaseConnection(final HttpClientConnection managedConn, final Object state, final long keepalive, final TimeUnit tunit) 方法中调用；但是这个方法是我们在释放response是调用的。

 　　public void releaseConnection(
             final HttpClientConnection managedConn,
             final Object state,
             final long keepalive, final TimeUnit tunit) {
         Args.notNull(managedConn, "Managed connection");
         synchronized (managedConn) {
             final CPoolEntry entry = CPoolProxy.detach(managedConn);
             if (entry == null) {
                 return;
             }
             final ManagedHttpClientConnection conn = entry.getConnection();
             try {
                 if (conn.isOpen()) {
                     final TimeUnit effectiveUnit = tunit != null ? tunit : TimeUnit.MILLISECONDS;
                     entry.setState(state);
                     entry.updateExpiry(keepalive, effectiveUnit);　　//keepalive 参数表示长连接的过期时间，在客户端通过keepAliveStrategy参数设置
                     if (this.log.isDebugEnabled()) {
                         final String s;
                         if (keepalive > 0) {
                             s = "for " + (double) effectiveUnit.toMillis(keepalive) / 1000 + " seconds";
                         } else {
                             s = "indefinitely";
                         }
                         this.log.debug("Connection " + format(entry) + " can be kept alive " + s);
                     }
                     conn.setSocketTimeout(0);
                 }
             } finally {
                 this.pool.release(entry, conn.isOpen() && entry.isRouteComplete());
                 if (this.log.isDebugEnabled()) {
                     this.log.debug("Connection released: " + format(entry) + formatStats(entry.getRoute()));
                 }
             }
         }
     }

3、PoolingHttpClientConnectionManager 连接池参数 validateAfterInactivity说明：

　　当从连接池中拿到一个poolEntry时，如果validateAfterInactivity参数大于0 且 这个PoolEntry实例的updated加validateAfterInactivity小于等于当前时间，会检查这个连接（httpEntry实例中的con）的连接状态 state 值；

 org.apache.http.impl.BHttpConnectionBase
 　　public boolean isStale() {
         if (!isOpen()) {
             return true;
         }
         try {
             final int bytesRead = fillInputBuffer(1);
             return bytesRead < 0;
         } catch (final SocketTimeoutException ex) {
             return false;
         } catch (final IOException ex) {
             return true;
         }
     }

4、PoolingHttpClientConnectionManager 的关闭空闲超时连接方法：

　　指PoolEntry实例的更新时间加 空闲时间（设置）大于等于 当前时间，表示这个连接超过空闲时间

 　　public void closeIdleConnections(final long idleTimeout, final TimeUnit tunit) {
         if (this.log.isDebugEnabled()) {
             this.log.debug("Closing connections idle longer than " + idleTimeout + " " + tunit);
         }
         this.pool.closeIdle(idleTimeout, tunit);
     }

5、PoolingHttpClientConnectionManager 的关闭过期连接方法：

　　指当前时间大于PoolEntry实例的expiry值

     public void closeExpiredConnections() {
         this.log.debug("Closing expired connections");
         this.pool.closeExpired();
     }

6、closeIdleConnections() 和 closeExpiredConnections() 对外提供，需要用户自己去调用，我们一般维护一个独立的线程去调用，清除空闲的连接和过期连接。