Java Android HTTP实现总结
Java Android HTTP实现总结
Http(Hypertext Transfer Protocol)超文本传输协议，是一个基于请求/响应模式的无状态的协议，Http1.1版给出了持续连接的机制，客户端建立连接之后，可以发送多次请求，当不会再发送时再关闭连接。
Android使用Java，对于Http协议的基本功能有两种实现方案：
1.使用JDK的java.net包下的HttpURLConnection.
2.使用Apache的HttpClient。
关于二者的比较可以看一下：
http://www.cnblogs.com/devinzhang/archive/2012/01/17/2325092.html
Android SDK中集成了Apache的HttpClient模块，也即说Android上两种方法都能用。
之前看一个Android开发者博客(原文链接先空缺，需要FQ)对此的讨论，大意总结如下：
1.HttpClient的功能比较全，更加强大；而HttpURLConnection的功能较简单和原始，但是性能更好。
2.在Android 2.x的版本中使用HttpURLConnection有bug，但是后来高级版本的Android已经将带来的bug修复，并且做了一些进一步优化的工作，所以建议在高级版本的Android系统(Android 2.3之后)使用HttpURLConnection，低版本的系统仍使用HttpClient。
程序实现
下面来讨论一下实现，首先，需要确认Manifest中有权限：
<uses-permission android:name="android.permission.INTERNET" />
使用JDK的HttpURLConnection类
HttpURLConnection参考：
http://developer.android.com/reference/java/net/HttpURLConnection.html
使用这个类的一般步骤：
1.通过URL.openConnection() 方法获取一个HttpURLConnection对象，并且将结果强制转化为HttpURLConnection类型。
2.准备请求(prepare the request)，包括URI，headers中的各种属性等
(Request headers may also include metadata such as credentials, preferred content types, and session cookies.)
3.请求体(optionally)。如果有请求体那么setDoOutput(true)必须为true，然后把输入放在getOutputStream()流中。
4.读取响应。响应的headers一般包括了一些metadata比如响应体的内容类型和长度，修改日期以及session cookies。响应体可以从 getInputStream()流中读出。
5.断开连接。响应体被读出之后，应该调用 disconnect()方法来断开连接。
例子代码：
package com.example.helloandroidhttp; import java.io.ByteArrayOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.io.UnsupportedEncodingException; import java.net.HttpURLConnection; import java.net.MalformedURLException; import java.net.URL; import java.net.URLEncoder; import java.util.Map; import android.util.Log; public class HttpUtilsJDK { private static final String LOG_TAG = "Http->JDK"; private static final int CONNECT_TIME_OUT = 3000; private static final String HEADER_CONTENT_TYPE = "Content-Type"; private static final String HEADER_CONTENT_LENGTH = "Content-Length"; /** * Default encoding for POST or PUT parameters. See * {@link #getParamsEncoding()}. */ private static final String DEFAULT_PARAMS_ENCODING = "UTF-8"; public static String getParamsEncoding() { return DEFAULT_PARAMS_ENCODING; } public static String getBodyContentType() { return "application/x-www-form-urlencoded; charset=" + getParamsEncoding(); } public static String performGetRequest(String baseUrl) { String result = null; HttpURLConnection connection = null; try { URL url = new URL(baseUrl); if (null != url) { // 获取HttpURLConnection类型的对象 connection = (HttpURLConnection) url.openConnection(); // 设置连接的最大等待时间 connection.setConnectTimeout(CONNECT_TIME_OUT); // Sets the maximum time to wait for an input stream read to // complete before giving up. connection.setReadTimeout(3000); // 设置为GET方法 connection.setRequestMethod("GET"); connection.setDoInput(true); if (200 == connection.getResponseCode()) { InputStream inputStream = connection.getInputStream(); result = getResultString(inputStream, getParamsEncoding()); } else { Log.e(LOG_TAG, "Connection failed: " + connection.getResponseCode()); } } } catch (MalformedURLException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } finally { connection.disconnect(); } return result; } public static String performPostRequest(String baseUrl, Map<String, String> params) { String result = null; HttpURLConnection connection = null; try { URL url = new URL(baseUrl); if (null != url) { // 获取HttpURLConnection类型的对象 connection = (HttpURLConnection) url.openConnection(); // 设置响应超时限制 connection.setConnectTimeout(CONNECT_TIME_OUT); // 设置为POST方法 connection.setRequestMethod("POST"); connection.setDoInput(true); // 有请求体则setDoOutput(true)必须设定 connection.setDoOutput(true); // 为了性能考虑，如果包含请求体，那么最好调用 setFixedLengthStreamingMode(int)或者 // setChunkedStreamingMode(int) // connection.setChunkedStreamingMode(0);// 参数为0时使用默认值 byte[] data = getParamsData(params); connection.setRequestProperty(HEADER_CONTENT_TYPE, getBodyContentType()); if (null != data) { connection.setFixedLengthStreamingMode(data.length); connection.setRequestProperty(HEADER_CONTENT_LENGTH, String.valueOf(data.length)); OutputStream outputStream = connection.getOutputStream(); outputStream.write(data); } // 得到返回值 int responseCode = connection.getResponseCode(); if (200 == responseCode) { result = getResultString(connection.getInputStream(), getParamsEncoding()); } else { Log.e(LOG_TAG, "Connection failed: " + connection.getResponseCode()); } } } catch (MalformedURLException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } finally { connection.disconnect(); } return result; } private static byte[] getParamsData(Map<String, String> params) { byte[] data = null; try { if (null != params && !params.isEmpty()) { StringBuffer buffer = new StringBuffer(); for (Map.Entry<String, String> entry : params.entrySet()) { buffer.append(entry.getKey()) .append("=") .append(URLEncoder.encode(entry.getValue(), getParamsEncoding())).append("&");// 请求的参数之间使用&分割。 } // 最后一个&要去掉 buffer.deleteCharAt(buffer.length() - 1); data = buffer.toString().getBytes(getParamsEncoding()); } } catch (UnsupportedEncodingException e) { e.printStackTrace(); } return data; } private static String getResultString(InputStream inputStream, String encode) { ByteArrayOutputStream outputStream = new ByteArrayOutputStream(); byte[] data = new byte[1024]; int len = 0; String result = ""; if (inputStream != null) { try { while ((len = inputStream.read(data)) != -1) { outputStream.write(data, 0, len); } result = new String(outputStream.toByteArray(), encode); } catch (IOException e) { e.printStackTrace(); } } return result; } }
使用Apache的HttpClient
可以查看官方的Tutorial:
http://hc.apache.org/httpcomponents-client-ga/tutorial/html/index.html
Android有一个实现类AndroidHttpClient，实现了HttpClient：
http://developer.android.com/reference/android/net/http/AndroidHttpClient.html
包装了一些默认的设置。
关于HTTP entity
HTTP消息中可以包含内容实体(content entity)，可以看做消息的报文，包含在请求或者响应中。
HTTP规范规定两种请求方法可以包含内容实体：POST和PUT。
响应则通常是包含内容实体的。
HttpClient会根据内容来源区分三种实体：
1.streamed：内容来源是流，这类里包含了从HTTP响应中获得的实体，流式实体不可重复。
2.self-contained：内容是从内存或者其他方式获得的，即和连接无关，这类实体是可以重复的，多数是用来放在HTTP请求中的实体。
3.wrapping：这类实体是从其他实体获得的。
对于用HttpClient创建的请求实体来说，streamed和self-contained类型的区别其实不太重要，建议把不可重复的实体看作是streamed的，可重复的看作是self-contained的。
创造实体内容
为了发送HTTP的POST请求(当然还有PUT请求也有实体)，需要把一些参数放在实体中，创造实体内容，有四个类型的类可选用：
StringEntity, ByteArrayEntity, InputStreamEntity, FileEntity
注意其中的InputStreamEntity是不可重复的。
UrlEncodedFormEntity这个类是用来把输入数据编码成合适的内容，比如下面这段：
List<NameValuePair> formparams = new ArrayList<NameValuePair>(); formparams.add(new BasicNameValuePair("param1", "value1")); formparams.add(new BasicNameValuePair("param2", "value2")); UrlEncodedFormEntity entity = new UrlEncodedFormEntity(formparams, Consts.UTF_8); HttpPost httppost = new HttpPost("http://localhost/handler.do"); httppost.setEntity(entity);
两个键值对，被UrlEncodedFormEntity实例编码后变为如下内容：
param1=value1¶m2=value2
使用Apache的HttpClient发送HTTP请求的辅助类，例子代码：
package com.example.helloandroidhttp; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.io.UnsupportedEncodingException; import java.net.URLEncoder; import java.util.ArrayList; import java.util.List; import java.util.Map; import org.apache.http.HttpEntity; import org.apache.http.HttpResponse; import org.apache.http.NameValuePair; import org.apache.http.client.HttpClient; import org.apache.http.client.entity.UrlEncodedFormEntity; import org.apache.http.client.methods.HttpGet; import org.apache.http.client.methods.HttpPost; import org.apache.http.entity.ByteArrayEntity; import org.apache.http.entity.StringEntity; import org.apache.http.impl.client.DefaultHttpClient; import org.apache.http.message.BasicNameValuePair; import org.apache.http.params.BasicHttpParams; import org.apache.http.params.HttpConnectionParams; import org.apache.http.params.HttpParams; import android.util.Log; public class HttpUtilsApache { private static final String LOG_TAG = "Http->Apache"; private static final String HEADER_CONTENT_TYPE = "Content-Type"; /** * Default encoding for POST or PUT parameters. See * {@link #getParamsEncoding()}. */ private static final String DEFAULT_PARAMS_ENCODING = "UTF-8"; /** * Returns which encoding should be used when converting POST or PUT * parameters returned by {@link #getParams()} into a raw POST or PUT body. * * <p> * This controls both encodings: * <ol> * <li>The string encoding used when converting parameter names and values * into bytes prior to URL encoding them.</li> * <li>The string encoding used when converting the URL encoded parameters * into a raw byte array.</li> * </ol> */ public static String getParamsEncoding() { return DEFAULT_PARAMS_ENCODING; } public static String getBodyContentType() { return "application/x-www-form-urlencoded; charset=" + getParamsEncoding(); } public static String performGetRequest(String url) { String result = null; // 生成一个请求对象 HttpGet httpGet = new HttpGet(url); // 1.生成一个Http客户端对象(带参数的) HttpParams httpParameters = new BasicHttpParams(); HttpConnectionParams.setConnectionTimeout(httpParameters, 10 * 1000);// 设置请求超时10秒 HttpConnectionParams.setSoTimeout(httpParameters, 10 * 1000); // 设置等待数据超时10秒 HttpConnectionParams.setSocketBufferSize(httpParameters, 8192); HttpClient httpClient = new DefaultHttpClient(httpParameters); // 此时构造DefaultHttpClient时将参数传入 // 2.默认实现： // HttpClient httpClient = new DefaultHttpClient(); httpGet.addHeader(HEADER_CONTENT_TYPE, getBodyContentType()); // 下面使用Http客户端发送请求，并获取响应内容 HttpResponse httpResponse = null; try { // 发送请求并获得响应对象 httpResponse = httpClient.execute(httpGet); final int statusCode = httpResponse.getStatusLine().getStatusCode(); if (200 == statusCode) { result = getResponseString(httpResponse); } else { Log.e(LOG_TAG, "Connection failed: " + statusCode); } } catch (Exception e) { e.printStackTrace(); } finally { } return result; } public static String performPostRequest(String baseURL, String postData) { String result = ""; HttpResponse response = null; try { // URL使用基本URL即可，其中不需要加参数 HttpPost httpPost = new HttpPost(baseURL); // 设置ContentType httpPost.addHeader(HEADER_CONTENT_TYPE, getBodyContentType()); // 将请求体内容加入请求中 HttpEntity requestHttpEntity = prepareHttpEntity(postData); if (null != requestHttpEntity) { httpPost.setEntity(requestHttpEntity); } // 需要客户端对象来发送请求 HttpClient httpClient = new DefaultHttpClient(); // 发送请求 response = httpClient.execute(httpPost); final int statusCode = response.getStatusLine().getStatusCode(); if (200 == statusCode) { // 显示响应 result = getResponseString(response); } else { Log.e(LOG_TAG, "Connection failed: " + statusCode); } } catch (Exception e) { e.printStackTrace(); } finally { } return result; } /** * 直接利用String生成HttpEntity，String应该已经是key=value&key2=value2的形式 * * @param postData * @return */ private static HttpEntity prepareHttpEntity(String postData) { HttpEntity requestHttpEntity = null; try { if (null != postData) { // 去掉所有的换行 postData = postData.replace("\n", ""); // one way // requestHttpEntity = new ByteArrayEntity( // postData.getBytes(getParamsEncoding())); // another way requestHttpEntity = new StringEntity(postData, getParamsEncoding()); ((StringEntity) requestHttpEntity) .setContentEncoding(getParamsEncoding()); ((StringEntity) requestHttpEntity) .setContentType(getBodyContentType()); } } catch (Exception e) { e.printStackTrace(); } return requestHttpEntity; } /** * 利用Map结构的参数生成HttpEntity，使用UrlEncodedFormEntity对参数对进行编码 * * @param params * @return */ private static HttpEntity prepareHttpEntity1(Map<String, String> params) { // 需要将String里面的key value拆分出来 HttpEntity requestHttpEntity = null; try { if (null != params) { List<NameValuePair> pairList = new ArrayList<NameValuePair>( params.size()); for (Map.Entry<String, String> entry : params.entrySet()) { NameValuePair pair = new BasicNameValuePair(entry.getKey(), entry.getValue()); pairList.add(pair); } requestHttpEntity = new UrlEncodedFormEntity(pairList, getParamsEncoding()); } } catch (UnsupportedEncodingException e) { e.printStackTrace(); } return requestHttpEntity; } /** * 利用Map结构的参数生成HttpEntity，使用自己的方法对参数进行编码合成字符串 * * @param params * @return */ private static HttpEntity prepareHttpEntity2(Map<String, String> params) { // 需要将String里面的key value拆分出来 HttpEntity requestHttpEntity = null; byte[] body = encodeParameters(params, getParamsEncoding()); requestHttpEntity = new ByteArrayEntity(body); return requestHttpEntity; } /** * Converts <code>params</code> into an application/x-www-form-urlencoded * encoded string. */ private static byte[] encodeParameters(Map<String, String> params, String paramsEncoding) { StringBuilder encodedParams = new StringBuilder(); try { for (Map.Entry<String, String> entry : params.entrySet()) { encodedParams.append(URLEncoder.encode(entry.getKey(), paramsEncoding)); encodedParams.append('='); encodedParams.append(URLEncoder.encode(entry.getValue(), paramsEncoding)); encodedParams.append('&'); } return encodedParams.toString().getBytes(paramsEncoding); } catch (UnsupportedEncodingException uee) { throw new RuntimeException("Encoding not supported: " + paramsEncoding, uee); } } public static String getResponseString(HttpResponse response) { String result = null; if (null == response) { return result; } HttpEntity httpEntity = response.getEntity(); InputStream inputStream = null; try { inputStream = httpEntity.getContent(); BufferedReader reader = new BufferedReader(new InputStreamReader( inputStream)); result = ""; String line = ""; while (null != (line = reader.readLine())) { result += line; } } catch (Exception e) { e.printStackTrace(); } finally { try { if (null != inputStream) { inputStream.close(); } } catch (IOException e) { e.printStackTrace(); } } return result; } }
参考资料
本博客HTTP标签下相关文章，比如这个：
http://www.cnblogs.com/mengdd/p/3144599.html
Apache HttpClient：
http://hc.apache.org/httpcomponents-client-ga/
http://hc.apache.org/httpcomponents-client-ga/tutorial/html/fundamentals.html#d5e49
Android之网络编程 系列博文：
http://www.cnblogs.com/devinzhang/category/349642.html
Http Header详解：
http://kb.cnblogs.com/page/92320/
Android--Apache HttpClient：
http://www.cnblogs.com/plokmju/p/Android_apacheHttpClient.html
推荐项目
Android网络通信框架Volley：
https://github.com/mengdd/android-volley
Android Asynchronous Http Client：A Callback-Based Http Client Library for Android
https://github.com/mengdd/android-async-http
也即：http://loopj.com/android-async-http/
本文项目地址(目前还是个挺简陋的Demo，有待完善)：
https://github.com/mengdd/HelloAndroidHttpUtils