Android学习13-----网络通信(1) 与WEB服务器交换数据

与Web服务器交互：

如果手机要想与 web 容器交互的话，那么就必须依靠 Http 协议完成。

一、通过地址重新访问动态 Web

首先我们需要建立一个 Web 程序，现在为了说明问题，我们简单见一个 Servlet ，然后返回 true or false 即可

服务器端： AndroidServlet.java

package com.iflytek.demo;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class AndroidServlet
 */
public class AndroidServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;

	/**
	 * Default constructor.
	 */
	public AndroidServlet() {
		// TODO Auto-generated constructor stub
	}

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void doGet(HttpServletRequest request,
			HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		//http://IP:8080/09AndroidWeb/AndroidServlet?name=xdwang&password=1111
		String name = request.getParameter("name");
		String password = request.getParameter("password");
		if ("xdwang".equals(name) && "1111".equals(password)) {
			response.getWriter().println("true");
		} else {
			response.getWriter().println("false");
		}
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void doPost(HttpServletRequest request,
			HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
	}

}

客户端：

Web01_Activity.java

package com.iflytek.demo;

import java.net.HttpURLConnection;
import java.net.URL;

import android.app.Activity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.widget.TextView;

public class Web01_Activity extends Activity {

	private TextView infoTxt;

	public Handler handler = new Handler() {
		@Override
		public void handleMessage(android.os.Message msg) {
			super.handleMessage(msg);
			switch (msg.what) {
			case 1:
				infoTxt.setText(msg.obj.toString());
				break;
			default:
				break;
			}
		}
	};

	/** Called when the activity is first created. */
	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);

		infoTxt = (TextView) super.findViewById(R.id.info);
		this.HttpHelper();

	}

	private void HttpHelper() {
		final AsyncTask<Void, Void, String> task = new AsyncTask<Void, Void, String>() {

			@Override
			protected void onPostExecute(String result) {
				final String temp = result;
				Thread thread = new Thread(new Runnable() {
					@Override
					public void run() {
						Message msg = new Message();
						msg.what = 1;
						msg.obj = temp;
						handler.sendMessage(msg);
					}
				});
				thread.start();
			}

			@Override
			protected void onPreExecute() {
				super.onPreExecute();
			}

			@Override
			protected String doInBackground(Void... arg0) {

				boolean flag = false; // 成功与否的标记
				try {
					URL url = new URL("http", "IP", 8080,
							"/09AndroidWeb/AndroidServlet?name=xdwang&password=1111");
					HttpURLConnection conn = (HttpURLConnection) url
							.openConnection();
					byte data[] = new byte[512];// 开辟一个空间
					int len = conn.getInputStream().read(data); // 输入流读取
					if (len > 0) { // 已经读取到内容
						String temp = new String(data, 0, len).trim();
						flag = Boolean.parseBoolean(temp); // 取出里面的boolean型数据
					}
					conn.getInputStream().close();
				} catch (Exception e) {
					return "WEB服务器连接失败！";
				}
				if (flag) {
					return "用户登录成功！";
				} else {
					return "用户登录失败！";
				}
			}
		};
		task.execute();
	}
}

AndroidManifest.xml需要添加网络访问权限

  <uses-permission android:name="android.permission.INTERNET" />

总结，这种方式是地址重写的方式完成，但是我们知道地址重写是 Get 请求方式，从上面的 Servlet 类的处理也可以看出是 Get 请求，但是这种方式会收到地址传输的限制，所以这时候我们也可以使用 post 请求方式提交。

二、 POST 请求

Get 请求与 Post 请求最大的区别在于一个地址显示，一个不显示，具体可以看我写的 GET 与 POST 请求 。 可是如何在 Android 中实现 post 请求呢？严格来说，之前的程序并不标准，地址重写问题较多。

使用 POST 提交访问动态 WEB 所需要的操作类：

由于 WEB 连接采用的是 HTTP 操作协议进行的，所以用户想要发送请求（ POST 、 GET ）则可以使用 org.apache.http.client.methods.HttpPost 类或者是 org.apache.http.client.methods.HttpGet 类进行。

当用户成功的向 Web Server 端发送请求后，所有返回的数据将使用 org.apache.http.HttpResponse 接口保存。

当用户使用 HttpResponse 的 getEntity() 方法接受所有返回数据之后，可以使用 EntityUtils 类进行处理，而且由于 HttpResponse 是一个接口，所以要想实例化此接口，就要使用 org.apache.http.impl.client.DefaultHttpClient 类完成。

由于在 Web Server 上所提供的方法需要参数的传递，所以所有的参数都要使用 org.apache.http.message.BasicName.ValuePair 类进行封装。

除了处理好参数之外，还需要处理请求时的所需要的编码，通用的编码为 UTF-8 ，而要想指定此编码则必须使用 org.apache.http.client.entry.UrlEncodedFormEntity 类完成。

此时把服务器端的 doPost 中再去调用 doGet 方法：

客户端 Web02_Activity.java

package com.iflytek.demo;

import java.util.ArrayList;
import java.util.List;

import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.protocol.HTTP;
import org.apache.http.util.EntityUtils;

import android.app.Activity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.widget.TextView;

public class Web02_Activity extends Activity {
	private TextView infoTxt = null;
	private static final String URL = "http://IP:8080/09AndroidWeb/AndroidServlet"; // 请求地址

	public Handler handler = new Handler() {
		@Override
		public void handleMessage(android.os.Message msg) {
			super.handleMessage(msg);
			switch (msg.what) {
			case 1:
				infoTxt.setText(msg.obj.toString());
				break;
			default:
				break;
			}
		}
	};

	/** Called when the activity is first created. */
	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		this.infoTxt = (TextView) super.findViewById(R.id.info);
		this.HttpHelper();

	}

	private void HttpHelper() {
		final AsyncTask<Void, Void, String> task = new AsyncTask<Void, Void, String>() {

			@Override
			protected void onPostExecute(String result) {
				final String temp = result;
				Thread thread = new Thread(new Runnable() {
					@Override
					public void run() {
						Message msg = new Message();
						msg.what = 1;
						msg.obj = temp;
						handler.sendMessage(msg);
					}
				});
				thread.start();
			}

			@Override
			protected void onPreExecute() {
				super.onPreExecute();
			}

			@Override
			protected String doInBackground(Void... arg0) {

				boolean flag = false; // 成功与否的标记
				try {
					HttpPost request = new HttpPost(URL);
					List<NameValuePair> params = new ArrayList<NameValuePair>();
					params.add(new BasicNameValuePair("name", "xdwang"));
					params.add(new BasicNameValuePair("password", "1111"));
					request.setEntity(new UrlEncodedFormEntity(params,
							HTTP.UTF_8));
					HttpResponse response = new DefaultHttpClient()
							.execute(request);
					if (response.getStatusLine().getStatusCode() != 404) { // 现在已经发现了数据了
						flag = Boolean.parseBoolean(EntityUtils.toString(
								response.getEntity()).trim());
					}
				} catch (Exception e) {
					return "WEB服务器连接失败！";
				}
				if (flag) {
					return "用户登录成功！";
				} else {
					return "用户登录失败！";
				}
			}
		};
		task.execute();
	}
}

三、网络读取图片

服务器端：

先设计一个返回图片流的工具类

ImageUtil.java

package com.iflytek.util;

import java.awt.image.BufferedImage;
import java.io.FileInputStream;
import java.io.IOException;
import java.text.MessageFormat;

import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletResponse;

public class ImageUtil {

	/**
	 * @descrption
	 * @author xdwang
	 * @create 2012-11-16下午8:35:36
	 * @param response
	 * @param path
	 *            文件路径
	 * @param type
	 *            图片类型
	 */
	public static void showImage(HttpServletResponse response, String path,
			String type) {
		try {
			ServletOutputStream outStream = response.getOutputStream();// 得到向客户端输出二进制数据的对象
			FileInputStream fis = new FileInputStream(path); // 以byte流的方式打开文件
			// 读数据
			byte data[] = new byte[1000];
			while (fis.read(data) > 0) {
				outStream.write(data);
			}
			fis.close();
			response.setContentType(MessageFormat.format("image/{0}", type)); // 设置返回的文件类型
			outStream.write(data); // 输出数据
			outStream.close();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

	/**
	 * @descrption
	 * @author xdwang
	 * @create 2012-11-16下午8:35:48
	 * @param response
	 * @param data
	 *            byte数组
	 * @param type
	 *            图片类型
	 */
	public static void showImage(HttpServletResponse response, byte[] data,
			String type) {
		try {
			ServletOutputStream outStream = response.getOutputStream();// 得到向客户端输出二进制数据的对象
			// 读数据
			outStream.write(data);
			response.setContentType(MessageFormat.format("image/{0}", type)); // 设置返回的文件类型
			outStream.write(data); // 输出数据
			outStream.close();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

}

AndroidServlet.java

package com.iflytek.servlet;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.iflytek.util.ImageUtil;

/**
 * Servlet implementation class AndroidServlet
 */
public class AndroidServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;

	/**
	 * Default constructor.
	 */
	public AndroidServlet() {
		// TODO Auto-generated constructor stub
	}

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void doGet(HttpServletRequest request,
			HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void doPost(HttpServletRequest request,
			HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		ImageUtil.showImage(response,
				getServletContext().getRealPath("Java.jpg"), "jpeg");
	}

}

Android客户端：
Web03_Activity.java

package com.iflytek.demo;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.widget.ImageView;

public class Web03_Activity extends Activity {

	private ImageView iamgeView = null;
	private static final String PATH = "http://IP:8080/09AndroidWeb/Java.jpg"; // 请求地址

	private Bitmap bitmap;

	public Handler handler = new Handler() {
		@Override
		public void handleMessage(android.os.Message msg) {
			super.handleMessage(msg);
			switch (msg.what) {
			case 1:
				try {
					iamgeView.setImageBitmap(bitmap);
				} catch (Exception e) {
				}
				break;
			default:
				break;
			}
		}
	};

	/** Called when the activity is first created. */
	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		this.iamgeView = (ImageView) super.findViewById(R.id.img);
		this.HttpHelper();

	}

	private void HttpHelper() {
		final AsyncTask<Void, Void, String> task = new AsyncTask<Void, Void, String>() {

			@Override
			protected void onPostExecute(String result) {
				Thread thread = new Thread(new Runnable() {
					@Override
					public void run() {
						Message msg = new Message();
						msg.what = 1;
						handler.sendMessage(msg);
					}
				});
				thread.start();
			}

			@Override
			protected void onPreExecute() {
				super.onPreExecute();
			}

			@Override
			protected String doInBackground(Void... arg0) {

				ByteArrayOutputStream bos = null; // 内存操作流完成
				try {
					URL url = new URL(PATH);

					HttpURLConnection conn = (HttpURLConnection) url
							.openConnection();
					conn.connect();
					InputStream input = conn.getInputStream();
					bitmap = BitmapFactory.decodeStream(input);
					// bos = new ByteArrayOutputStream();
					// byte data[] = new byte[1024];
					// int len = 0;
					// while ((len = input.read(data)) != -1) {
					// bos.write(data, 0, len);
					// }
					// byte resultData[] = bos.toByteArray();
					// bitmap = BitmapFactory.decodeByteArray(resultData, 0,
					// resultData.length); // 把二进制变为图片
				} catch (Exception e) {
				} finally {
					if (bos != null) {
						try {
							bos.close();
						} catch (IOException e) {
							e.printStackTrace();
						}
					}
				}
				return null;
			}
		};
		task.execute();
	}

}