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,需要翻墙)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;
    }
}
HttpUtilsJDK

 

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&param2=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;

    }
}
HttpUtilsApache

 

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

 

Java Android HTTP实现总结,,5-wow.com

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