httpclient妙用一 httpclient作为客户端调用webservice	http://aperise.iteye.com/blog/2223454
httpclient妙用二 httpclient保持会话登录	http://aperise.iteye.com/blog/2223470
httpclient连接池	http://aperise.iteye.com/blog/2295153

httpclient连接池

1.连接池原理(待续)

2.httpclient连接池如何保证连接交回至连接池管理器

    2.1 方式一

　　HttpResponse response = (httpMethod);
　　HttpEntity entity = response.getEntity();
　　//这两段代码返回的entity是HttpEntity的实现类BasicManagedEntity。此时与本次请求关联的连接尚未归还至连接管理器。需要调用以下两条语句：
　　InputStream instream = entity.getContent();//获得响应具体内容
　　//处理响应：代码省略
　　instream.close();//关闭输入流同时会将连接交回至连接处理器

     2.2 方式二使用默认的响应处理器BasicResponseHandler

　　httpClient Jar包中提供BasicResponseHandler。如果返回的类型能确定需要解码为String类型的话，推荐使用该响应处理器。
　　该处理器解码http连接响应字节流为String类型，对返回码>=300的响应进行了异常封装，并能够保证连接交还给连接池管理器。
　　该处理器将字节解码为字符的过程依次如下：
　　1)如果响应http报文Head部分由指定的charset，则使用该charset进行解码，否则进行下一步。例如使用UTF-8解码以下响应：DEBUG org.apache.http.headers - $amp;
　　2)如果响应报文未执行charset，则使用传入EntityUntils.toString()时指定的charset进行解码。否则进行下一步
　　3)使用ISO-8859-1进行解码。

 

3.实现连接池（待续）

4.遇到的问题

    4.1 连接池阻塞，频繁的报以下错误信息

pooling post() method executing IOException:java.net.SocketTimeoutException: Read timed out
java.net.SocketTimeoutException: Read timed out
        at java.net.SocketInputStream.socketRead0(Native Method)
        at java.net.SocketInputStream.read(SocketInputStream.java:129)
        at org.apache.http.impl.io.SessionInputBufferImpl.streamRead(SessionInputBufferImpl.java:136)
        at org.apache.http.impl.io.SessionInputBufferImpl.fillBuffer(SessionInputBufferImpl.java:152)
        at org.apache.http.impl.io.SessionInputBufferImpl.readLine(SessionInputBufferImpl.java:270)
        at org.apache.http.impl.conn.DefaultHttpResponseParser.parseHead(DefaultHttpResponseParser.java:140)
        at org.apache.http.impl.conn.DefaultHttpResponseParser.parseHead(DefaultHttpResponseParser.java:57)
        at org.apache.http.impl.io.AbstractMessageParser.parse(AbstractMessageParser.java:260)
        at org.apache.http.impl.DefaultBHttpClientConnection.receiveResponseHeader(DefaultBHttpClientConnection.java:161)
        at sun.reflect.GeneratedMethodAccessor96.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at org.apache.http.impl.conn.CPoolProxy.invoke(CPoolProxy.java:138)
        at com.sun.proxy.$Proxy43.receiveResponseHeader(Unknown Source)
        at org.apache.http.protocol.HttpRequestExecutor.doReceiveResponse(HttpRequestExecutor.java:271)
        at org.apache.http.protocol.HttpRequestExecutor.execute(HttpRequestExecutor.java:123)
        at org.apache.http.impl.execchain.MainClientExec.execute(MainClientExec.java:254)
        at org.apache.http.impl.execchain.ProtocolExec.execute(ProtocolExec.java:195)
        at org.apache.http.impl.execchain.RetryExec.execute(RetryExec.java:85)
        at org.apache.http.impl.execchain.RedirectExec.execute(RedirectExec.java:108)
        at org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java:186)
        at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:72)
        at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:214)
        at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:160)
        at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:136)

 上述问题主要问题是连接池中httpclient连接在遇到异常情况下未正常关闭导致，出问题时候连接池关于回收httpclient连接的代码如下：

	private ResponseHandler<String> responseHandler = new ResponseHandler<String>() {
		public String handleResponse(final HttpResponse response) throws ClientProtocolException, IOException {
			int status = response.getStatusLine().getStatusCode();
			if (status >= HttpStatus.SC_OK && status < HttpStatus.SC_MULTIPLE_CHOICES) {
				HttpEntity entity = response.getEntity();
				
				Charset charset = ContentType.getOrDefault(entity).getCharset();
				if (charset == null) {
					charset = Charset.forName("UTF-8");
				}
				return entity != null ? EntityUtils.toString(entity, charset) : null;
			} else {
                             //注意这里没有告诉连接池要回收连接
				throw new ClientProtocolException("Unexpected response status: " + status);
			}
	};

 修改后的代码如下：

	private ResponseHandler<String> responseHandler = new ResponseHandler<String>() {
		public String handleResponse(final HttpResponse response) throws ClientProtocolException, IOException {

	        final StatusLine statusLine = response.getStatusLine();
	        final HttpEntity entity = response.getEntity();
	        if (statusLine.getStatusCode() >= HttpStatus.SC_MULTIPLE_CHOICES||statusLine.getStatusCode()<HttpStatus.SC_OK) {
	            //主动回收httpclient连接
		    EntityUtils.consume(entity);
	            throw new HttpResponseException(statusLine.getStatusCode(),
	                    statusLine.getReasonPhrase());
	        }
	        Charset charset = ContentType.getOrDefault(entity).getCharset();
			if (charset == null) {
				charset = Charset.forName("UTF-8");
			}
			return entity != null ? EntityUtils.toString(entity, charset) : null;
		}
	};