Android网络(4):HttpClient必经之路----使用线程安全的单例模式HttpClient，及HttpClient和Application的融合

时间：2022-04-17 02:03:45

上文简介了HttpClient和Tomcatserver的交互，主角是HttpClient,然后它跟server交互有两种方式即get和post。所以这个HttpClient就相似于电脑上用的浏览器。当我打开多个网页的时候，并不须要开一个网页就开一个浏览器，而是一个浏览器上面开了好几个网页。相应于HttpClient，即无需连接一次就new一个HttpClient。一般，我们希望一个应用里就一个HttpClient就ok了，就像我们的手机或PC，没人会呼呼的装好几个浏览器。本文即解决此问题，代码能够直接拿过去复用。

1、自然而然想到单例。

public class MyHttpClient {
private static HttpClient mHttpClient = null;
private static final String CHARSET = HTTP.UTF_8;
//将构造函数封掉，仅仅能通过对外接口来获取HttpClient实例
private MyHttpClient(){

}
public static HttpClient getHttpClient(){
if(mHttpClient == null){
mHttpClient = new DefaultHttpClient();
}
return mHttpClient;
}
}

上面是最简单的一种单例，确实能够满足须要。但不能满足多线程的要求，即当同一时候完毕多个Http请求时，就出马蛋了。

2、线程安全的HttpClient

幸运的是android已经提供了能够创建线程安全的HttpClient，即通过ClientConnectionManager 来完毕。以下贴出完整代码：

package org.yanzi.webutil;

import org.apache.http.HttpVersion;

import org.apache.http.client.HttpClient;

import org.apache.http.conn.ClientConnectionManager;

import org.apache.http.conn.params.ConnManagerParams;

import org.apache.http.conn.scheme.PlainSocketFactory;

import org.apache.http.conn.scheme.Scheme;

import org.apache.http.conn.scheme.SchemeRegistry;

import org.apache.http.conn.ssl.SSLSocketFactory;

import org.apache.http.impl.client.DefaultHttpClient;

import org.apache.http.impl.conn.tsccm.ThreadSafeClientConnManager;

import org.apache.http.params.BasicHttpParams;

import org.apache.http.params.HttpConnectionParams;

import org.apache.http.params.HttpParams;

import org.apache.http.params.HttpProtocolParams;

import org.apache.http.protocol.HTTP;

public class MyHttpClient {

	private static HttpClient mHttpClient = null;

	private static final String CHARSET = HTTP.UTF_8;

	//将构造函数封掉，仅仅能通过对外接口来获取HttpClient实例

	private MyHttpClient(){

	}

	public static HttpClient getHttpClient(){

		if(mHttpClient == null){

			mHttpClient = new DefaultHttpClient();

		}

		return mHttpClient;

	}

	public static synchronized HttpClient getSaveHttpClient(){

		if(mHttpClient == null){

			HttpParams params = new BasicHttpParams();

			//设置基本參数

			HttpProtocolParams.setVersion(params, HttpVersion.HTTP_1_1);

			HttpProtocolParams.setContentCharset(params, CHARSET);

			HttpProtocolParams.setUseExpectContinue(params, true);

			//超时设置

			/*从连接池中取连接的超时时间*/

			ConnManagerParams.setTimeout(params, 1000);

			/*连接超时*/

			HttpConnectionParams.setConnectionTimeout(params, 2000);

			/*请求超时*/

			HttpConnectionParams.setSoTimeout(params, 4000);

			//设置HttpClient支持HTTp和HTTPS两种模式

			SchemeRegistry schReg = new SchemeRegistry();

			schReg.register(new Scheme("http", PlainSocketFactory.getSocketFactory(), 80));

			schReg.register(new Scheme("https", SSLSocketFactory.getSocketFactory(), 443));

			//使用线程安全的连接管理来创建HttpClient

			ClientConnectionManager conMgr = new ThreadSafeClientConnManager(params, schReg);

			mHttpClient = new DefaultHttpClient(conMgr, params);

		}

		return mHttpClient;

	}

}

方法getSaveHttpClient()就可以获得线程安全的单例httpClient，凝视非常具体了啥都不说了，能够直接使用。

3、已经非常完美了，还能不能再优化呢?

能够使用Application来进一步优化创建HttpClient的时机及其它配置。Application的相关知识參见:链接

新建包名org.yanzi.application，在里面新建MyApplication.java，完整代码例如以下:

package org.yanzi.application;

import org.apache.http.HttpVersion;

import org.apache.http.client.HttpClient;

import org.apache.http.conn.ClientConnectionManager;

import org.apache.http.conn.params.ConnManagerParams;

import org.apache.http.conn.scheme.PlainSocketFactory;

import org.apache.http.conn.scheme.Scheme;

import org.apache.http.conn.scheme.SchemeRegistry;

import org.apache.http.conn.ssl.SSLSocketFactory;

import org.apache.http.impl.client.DefaultHttpClient;

import org.apache.http.impl.conn.tsccm.ThreadSafeClientConnManager;

import org.apache.http.params.BasicHttpParams;

import org.apache.http.params.HttpConnectionParams;

import org.apache.http.params.HttpParams;

import org.apache.http.params.HttpProtocolParams;

import org.apache.http.protocol.HTTP;

import android.app.Application;

public class MyApplication extends Application {

	private HttpClient mHttpClient = null;

	private static final String CHARSET = HTTP.UTF_8;

	@Override

	public void onCreate() {

		// TODO Auto-generated method stub

		super.onCreate();

		mHttpClient = this.createHttpClient();

	}

	@Override

	public void onTerminate() {

		// TODO Auto-generated method stub

		super.onTerminate();

		this.shutdownHttpClient();

	}

	@Override

	public void onLowMemory() {

		// TODO Auto-generated method stub

		super.onLowMemory();

		this.shutdownHttpClient();

	}

	/**创建HttpClient实例

	 * @return

	 */

	private HttpClient createHttpClient(){

		HttpParams params = new BasicHttpParams();

		//设置基本參数

		HttpProtocolParams.setVersion(params, HttpVersion.HTTP_1_1);

		HttpProtocolParams.setContentCharset(params, CHARSET);

		HttpProtocolParams.setUseExpectContinue(params, true);

		//超时设置

		/*从连接池中取连接的超时时间*/

		ConnManagerParams.setTimeout(params, 1000);

		/*连接超时*/

		HttpConnectionParams.setConnectionTimeout(params, 2000);

		/*请求超时*/

		HttpConnectionParams.setSoTimeout(params, 4000);

		//设置HttpClient支持HTTp和HTTPS两种模式

		SchemeRegistry schReg = new SchemeRegistry();

		schReg.register(new Scheme("http", PlainSocketFactory.getSocketFactory(), 80));

		schReg.register(new Scheme("https", SSLSocketFactory.getSocketFactory(), 443));

		//使用线程安全的连接管理来创建HttpClient

		ClientConnectionManager conMgr = new ThreadSafeClientConnManager(params, schReg);

		HttpClient client = new DefaultHttpClient(conMgr, params);

		return client;

	}

	private void shutdownHttpClient(){

		if(mHttpClient != null && mHttpClient.getConnectionManager() != null){

			mHttpClient.getConnectionManager().shutdown();

		}

	}

	public HttpClient getHttpClient(){

		return mHttpClient;

	}

}

然后再AndroidManifest.xml理加入：

android:name="org.yanzi.application.MyApplication"

    <application

        android:name="org.yanzi.application.MyApplication"

        android:allowBackup="true"

        android:icon="@drawable/ic_launcher"

        android:label="@string/app_name"

        android:theme="@style/AppTheme" >

        <activity

            android:name="org.yanzi.testtomecat.MainActivity"

            android:label="@string/app_name" >

            <intent-filter>

                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />

            </intent-filter>

        </activity>

    </application>

然后再Activity里，通过mMyApplication = (MyApplication)getApplication();

mMyApplication.getHttpClient()得到HttpClient就能够使用了。

能够看到在Application的onCreate里就实例化了HttpClient，且在低内存和关闭时关闭连接管理器，释放资源，比2中的写到一个普通文件中更优。

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