Release Connection in Apache HttpComponents

分析家

　　原文：http://blog.blacklee.net/tech/707-release-connection-in-apache-httpcomponents
　　自从HttpClient升级到HttpComponent后，HttpMethod提供的方法releaseConnection()就被丢弃了。

转而改成另外相对麻烦点的维护一个连接池的处理方式。
　　When you replace Apache Commons HttpClient
with Apache HttpComponents
.

if you haven’t release connection in your codes, you may found exception traces like:

java.lang.IllegalStateException: Invalid use of SingleClientConnManager: connection still allocated.


Make sure to release the connection before allocating another one.


        
at org.apache.http.impl.conn.SingleClientConnManager.getConnection(SingleClientConnManager.java:199)


        
at org.apache.http.impl.conn.SingleClientConnManager$1.getConnection(SingleClientConnManager.java:173)


        
at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:390)


        
at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:641)


        
at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:576)


        
at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:554)










But HttpComponents
doesn’t provide method like void org.apache.commons.httpclient.HttpMethod.releaseConnection()
.　　It provides another method to do this work. And it’s more complex then before. Sample codes I wrote below:

public class Test {
public static void main(String[] args) throws Exception {
System.setProperty("org.apache.commons.logging.simplelog.log.httpclient.wire", "debug");
System.setProperty("org.apache.commons.logging.simplelog.log.org.apache.commons.httpclient", "debug");
System.setProperty("org.apache.commons.logging.Log", "org.apache.commons.logging.impl.SimpleLog");
System.setProperty("org.apache.commons.logging.simplelog.showdatetime", "true");
System.setProperty("org.apache.commons.logging.simplelog.log.org.apache.http", "debug");
HttpParams httpParams = new BasicHttpParams();
httpParams.setIntParameter(ConnManagerPNames.MAX_TOTAL_CONNECTIONS, 20);
SchemeRegistry schreg = new SchemeRegistry();
schreg.register(new Scheme("http", PlainSocketFactory.getSocketFactory(), 80));
schreg.register(new Scheme("https", PlainSocketFactory.getSocketFactory(), 443));
ThreadSafeClientConnManager connManager = new ThreadSafeClientConnManager(httpParams, schreg);
//        connManager.setMaxTotal(20);
DefaultHttpClient client = new DefaultHttpClient(connManager, httpParams);
String url = "http://www.google.com/";
HttpGet get = new HttpGet(url);
sendRequest(get, client);
System.out.println("------------------2------------------");
sendRequest(get, client);
System.out.println("------------------3------------------");
sendRequest(get, client);
System.out.println("------------------4------------------");
sendRequest(get, client);
System.out.println("------------------5------------------");
sendRequest(get, client);
}
private static void sendRequest(HttpGet get, DefaultHttpClient client) throws InterruptedException {
HttpResponse resp = null;
try {
resp = client.execute(get);
// get response content here
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
resp.getEntity().getContent().close(); //!!!IMPORTANT
} catch (Exception e) {
// go to hell
}
}
}
}
 　　Here are some notes:

• HC4.1 may deprecated some methods/properties.
  
• 
  DON’T FORGET TO CLOSE THE RESPONSE STREAM