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

zz:http://blog.csdn.net/yanzi1225627/article/details/24937439

上文简单介绍了HttpClient和Tomcat服务器的交互，主角是HttpClient,然后它跟服务器交互有两种方式即get和post。所以这个HttpClient就类似于电脑上用的浏览器。当我打开多个网页的时候，并不需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。对应于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，代码可以直接拿过去复用。

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，只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，确实能够满足需要。但不能满足多线程的要求，即当同时完成多个Http请求时，就出马蛋了。

2、线程安全的HttpClient

幸运的是android已经提供了可以创建线程安全的HttpClient，即通过ClientConnectionManager 来完成。下面贴出完整代码：

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<span style="font-family:Comic Sans MS;font-size:18px;">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，只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();

//设置基本参数

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;

}

}

</span>

方法getSaveHttpClient()即可获得线程安全的单例httpClient，注释很详细了啥都不说了，可以直接使用。

3、已经很完美了，还能不能再优化呢?

可以使用Application来进一步优化创建HttpClient的时机及其他配置。Application的相关知识参见:链接

新建包名org.yanzi.application，在里面新建MyApplication.java，完整代码如下:

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<span style="font-family:Comic Sans MS;font-size:18px;">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();

//设置基本参数

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;

}

}

</span>

然后再AndroidManifest.xml理添加：

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

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<span style="font-family:Comic Sans MS;font-size:18px;"> <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></span>

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

mMyApplication.getHttpClient()得到HttpClient就可以使用了。

可以看到在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里更优。