HttpClient与HttpURLConnection分析

1.HttpClient

　　Android SDK中包含了HttpClient，在Android6.0版本直接删除了HttpClient类库，如果想使用解决方法

是在android studio相应的module下的build.gradle中加入

android {
useLibrary 'org.apache.http.legacy'
}

HttpClient的GET请求

先用DefaultHttpClient类来实例化一个HttpClient，并配置好默认的请求参数：

//创建HttpClient
private HttpClient createHttpClient() {
HttpParams mDefaultHttpParams = new BasicHttpParams();
//设置连接超时
HttpConnectionParams.setConnectionTimeout(mDefaultHttpParams, 10000);
//设置请求超时
HttpConnectionParams.setSoTimeout(mDefaultHttpParams, 10000);
HttpConnectionParams.setTcpNoDelay(mDefaultHttpParams, true);
HttpProtocolParams.setVersion(mDefaultHttpParams, HttpVersion.HTTP_1_1);
HttpProtocolParams.setContentCharset(mDefaultHttpParams, HTTP.UTF_8);
//持续握手
HttpProtocolParams.setUseExpectContinue(mDefaultHttpParams, true);
HttpClient mHttpClient = new DefaultHttpClient(mDefaultHttpParams);
return mHttpClient;
}

然后创建HttpGet和HttpClient，请求网络并得到HttpResponse，并对HttpResponse进行处理：

private void useHttpClientGet(String url) {
HttpGet mHttpGet = new HttpGet(url);
mHttpGet.addHeader("Connection", "Keep-Alive");
try {
HttpClient mHttpClient = createHttpClient();
HttpResponse mHttpResponse = mHttpClient.execute(mHttpGet);
HttpEntity mHttpEntity = mHttpResponse.getEntity();
int code = mHttpResponse.getStatusLine().getStatusCode();
if (null != mHttpEntity) {
InputStream mInputStream = mHttpEntity.getContent();
String respose = converStreamToString(mInputStream);
Log.i("wangshu", "请求状态码:" + code + "\n请求结果:\n" + respose);
mInputStream.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}

converStreamToString方法将请求结果转换成String类型：

private String converStreamToString(InputStream is) throws IOException {
BufferedReader reader = new BufferedReader(new InputStreamReader(is));
StringBuffer sb = new StringBuffer();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
String respose = sb.toString();
return respose;
}

最后我们开启线程访问百度：

new Thread(new Runnable() {
@Override
public void run() {
useHttpClientGet("http://www.baidu.com");
}
}).start();

请求的返回结果，请求状态码为200，结果就是个html页。

GET请求的参数暴露在URL中，这有些不大妥当，而且URL的长度也有限制：长度在2048字符之内，在HTTP 1.1后URL长度才没有限制。一般情况下POST可以替代GET，接下来我们来看看HttpClient的POST请求。

HttpClient的POST请求

post请求和get类似就是需要配置要传递的参数：

private void useHttpClientPost(String url) {
HttpPost mHttpPost = new HttpPost(url);
mHttpPost.addHeader("Connection", "Keep-Alive");
try {
HttpClient mHttpClient = createHttpClient();
List<NameValuePair> postParams = new ArrayList<>();
//要传递的参数
postParams.add(new BasicNameValuePair("username", "moon"));
postParams.add(new BasicNameValuePair("password", "999"));
mHttpPost.setEntity(new UrlEncodedFormEntity(postParams));
HttpResponse mHttpResponse = mHttpClient.execute(mHttpPost);
HttpEntity mHttpEntity = mHttpResponse.getEntity();
int code = mHttpResponse.getStatusLine().getStatusCode();
if (null != mHttpEntity) {
InputStream mInputStream = mHttpEntity.getContent();
String respose = converStreamToString(mInputStream);
Log.i("wangshu", "请求状态码:" + code + "\n请求结果:\n" + respose);
mInputStream.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}

2.HttpURLConnection

Android 2.2版本之前，HttpURLConnection一直存在着一些令人厌烦的bug。比如说对一个可读的InputStream调用close()方法时，就有可能会导致连接池失效了。那么我们通常的解决办法就是直接禁用掉连接池的功能：

private void disableConnectionReuseIfNecessary() {
// 这是一个2.2版本之前的bug
if (Integer.parseInt(Build.VERSION.SDK) < Build.VERSION_CODES.FROYO) {
System.setProperty("http.keepAlive", "false");
}
}

所以在Android 2.2版本以及之前的版本使用HttpClient是较好的选择，而在Android 2.3版本及以后，HttpURLConnection则是最佳的选择，它的API简单，体积较小，因而非常适用于Android项目。压缩和缓存机制可以有效地减少网络访问的流量，在提升速度和省电方面也起到了较大的作用。另外在Android 6.0版本中，HttpClient库被移除了，HttpURLConnection则是以后我们唯一的选择。

HttpURLConnection的POST请求

因为会了HttpURLConnection的POST请求那GET请求也就会了，所以我这里只举出POST的例子

首先我们创建一个UrlConnManager类，然后里面提供getHttpURLConnection()方法用于配置默认的参数并返回HttpURLConnection：

public static HttpURLConnection getHttpURLConnection(String url){
HttpURLConnection mHttpURLConnection=null;
try {
URL mUrl=new URL(url);
mHttpURLConnection=(HttpURLConnection)mUrl.openConnection();
//设置链接超时时间
mHttpURLConnection.setConnectTimeout(15000);
//设置读取超时时间
mHttpURLConnection.setReadTimeout(15000);
//设置请求参数
mHttpURLConnection.setRequestMethod("POST");
//添加Header
mHttpURLConnection.setRequestProperty("Connection","Keep-Alive");
//接收输入流
mHttpURLConnection.setDoInput(true);
//传递参数时需要开启
mHttpURLConnection.setDoOutput(true);
} catch (IOException e) {
e.printStackTrace();
}
return mHttpURLConnection ;
}

因为我们要发送POST请求，所以在UrlConnManager类中再写一个postParams()方法用来组织一下请求参数并将请求参数写入到输出流中：

public static void postParams(OutputStream output,List<NameValuePair>paramsList) throws IOException{
StringBuilder mStringBuilder=new StringBuilder();
for (NameValuePair pair:paramsList){
if(!TextUtils.isEmpty(mStringBuilder)){
mStringBuilder.append("&");
}
mStringBuilder.append(URLEncoder.encode(pair.getName(),"UTF-8"));
mStringBuilder.append("=");
mStringBuilder.append(URLEncoder.encode(pair.getValue(),"UTF-8"));
}
BufferedWriter writer=new BufferedWriter(new OutputStreamWriter(output,"UTF-8"));
writer.write(mStringBuilder.toString());
writer.flush();
writer.close();
}

接下来我们添加请求参数，调用postParams()方法将请求的参数组织好传给HttpURLConnection的输出流，请求连接并处理返回的结果：

private void useHttpUrlConnectionPost(String url) {
InputStream mInputStream = null;
HttpURLConnection mHttpURLConnection = UrlConnManager.getHttpURLConnection(url);
try {
List<NameValuePair> postParams = new ArrayList<>();
//要传递的参数
postParams.add(new BasicNameValuePair("username", "moon"));
postParams.add(new BasicNameValuePair("password", "123"));
UrlConnManager.postParams(mHttpURLConnection.getOutputStream(), postParams);
mHttpURLConnection.connect();
mInputStream = mHttpURLConnection.getInputStream();
int code = mHttpURLConnection.getResponseCode();
String respose = converStreamToString(mInputStream);
Log.i("wangshu", "请求状态码:" + code + "\n请求结果:\n" + respose);
mInputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}

最后开启线程请求网络：

private void useHttpUrlConnectionGetThread() {
new Thread(new Runnable() {
@Override
public void run() {
useHttpUrlConnectionPost("http://www.baidu.com");
}
}).start();
}

Fiddler和HTTP协议分析的请查看HTTP协议分析。