Android - 服务器json数据交互.

一,服务器端

　　服务器端使用的是Servlet,封装json对象使用的 'json-lib-2.2.2-jdk15.jar,ezmorph-1.0.4.jar,commons-logging-1.1.jar,commons-lang-2.4.jar,commons-collections-3.2.jar,commons-beanutils-1.7.0.jar' 6个jar包.可在 json封装的jar包中下载,我也不懂最近什么情况,使用Firefox总是很难下载****资源,可以使用ie.

1.首先是使用一个Person进行原始数据的封装:

package spt.src;

public class Person {
	private String name;
	private int age;
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}

	public Person(String name, int age) {
		this.name = name;
		this.age = age;
	}
}

2.然后是两个服务类PersonService和JsonService,分别提供Person对象和将Person对象转换为json格式的字符串的服务类.

package spt.service;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import spt.src.Person;

/**
 * 该类用于产生Person对象的服务类.
 *
 * @author Administrator 2015-1-29
 */
public class PersonService {
	public Person getAPerson() {
		return new Person("莉莉", 21);
	}

	public List<Person> getListPersons() {
		List<Person> persons = new ArrayList<Person>();
		persons.add(new Person("李静", 23));
		persons.add(new Person("lucy", 20));
		persons.add(new Person("小气", 22));
		return persons;
	}

	/**获取 id-Person对应的Map列表.
	 * @return
	 */
	public List<Map<String, Person>> getListMaps() {
		List<Map<String, Person>> maps = new ArrayList<Map<String,Person>>();

		Map<String, Person> map01 = new HashMap<String, Person>();
		map01.put("a01", new Person("王静", 19));
		map01.put("a02", new Person("json", 26));

		Map<String, Person> map02 = new HashMap<String, Person>();
		map01.put("b01", new Person("okay", 19));
		map01.put("b02", new Person("小琴", 24));

		maps.add(map01);
		maps.add(map02);

		return maps;
	}
}

package spt.service;

import net.sf.json.JSONObject;

/**将对象映射为json格式数据的服务类.
 * @author Administrator
 *2015-1-29
 */
public class JsonService {
	public String getJsonStr(String key, Object value) {
		JSONObject jsonObject = new JSONObject();
		jsonObject.put(key, value);
		return jsonObject.toString();
	}
}

3.HttpServlet的子类JsonServlet,用于响应客户端的Servlet的核心处理类.

package spt.servlet;

import java.io.IOException;

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

import spt.service.JsonService;
import spt.service.PersonService;

@WebServlet("/JsonAction")
public class JsonServlet extends HttpServlet{
	/**
	 *
	 */
	private static final long serialVersionUID = 1L;

	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

		//get person data.
		PersonService personService = new PersonService();

		//change person as json.
		JsonService jsonService = new JsonService();

		String action = req.getParameter("action");
		String json = null;
		if("p".equalsIgnoreCase(action))
			json = jsonService.getJsonStr("p", personService.getAPerson());
		else if("plst".equalsIgnoreCase(action))
			json = jsonService.getJsonStr("plst", personService.getListPersons());
		else if("plstMap".equalsIgnoreCase(action))
			json = jsonService.getJsonStr("plstMap", personService.getListMaps());

		System.out.println(json);
	}

	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		doPost(req, resp);	//Get的处理方式和POST的处理方式一样.
	}
}

4.另外的一个类是处理不同响应的编码的统一类:

package spt.servlet.filter;

import java.io.IOException;
import java.io.UnsupportedEncodingException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;

//filter all servlets.
@WebFilter("/*")
public class EncodingFilter  implements Filter {

	public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
		HttpServletRequest httpReq = (HttpServletRequest) servletRequest;
		//由于HttpServletRequest.setCharacterEncoding()对get方式不起作用,所以要单独编码.
		if ("GET".equals(httpReq.getMethod()))
			filterChain.doFilter(new HttpServletRequestEncodingWrapper(httpReq), servletResponse);
		else {
			//use utf encoding for none-get request.
			httpReq.setCharacterEncoding("utf-8");
			filterChain.doFilter(httpReq, servletResponse);
		}
	}

	public void init(FilterConfig filterConfig) throws ServletException {

	}

	/**inner class dealing for 'GET' method.
	 * @author Administrator
	 *2015-1-27
	 */
	private class HttpServletRequestEncodingWrapper extends HttpServletRequestWrapper {

		public HttpServletRequestEncodingWrapper(HttpServletRequest request) {
			super(request);
		}

		@Override
		public String getParameter(String name) {
			//encode with 'iso', and than decode with 'utf'.
			String val = super.getRequest().getParameter(name);
			if (null != val) {
				try {
					return new String(val.getBytes("iso8859-1"), "utf-8");
				} catch (UnsupportedEncodingException e) {
					e.printStackTrace();
				}
			}
			return super.getParameter(name);
		}
	}

	public void destroy() {

	}

}

到此,服务器端已经基本完成,启动服务器后,可在浏览器中输入不同请求参数的url获取不同的json字符串,例如

http://192.168.1.101:8080/ReceiveAndroid/JsonAction?action=Plst

可获得

{"plst":[{"age":23,"name":"李静"},{"age":20,"name":"lucy"},{"age":22,"name":"小气"}]}

接触json数据不是很多,不过很奇怪的是,为什么获得Map列表的时候,我在调试的时候,获得的Map的size()是2,但是在使用url为:

http://192.168.1.101:8080/ReceiveAndroid/JsonAction?action=plstMap

的时候,获取的json字符串为:

{"plstMap":[{"b01":{"age":19,"name":"okay"},"a01":{"age":19,"name":"王静"},"a02":{"age":26,"name":"json"},"b02":{"age":24,"name":"小琴"}},{}]}

末尾有一个成员为空的'{}'.

二,接下来写Android客户端

　　1.首先,记得加 Internet permission.

　　2.Activity代码:

package spt.http.activity;

import java.lang.ref.WeakReference;

import spt.http.get.activity.R;
import spt.http.post.PostSender;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends Activity {
	//view.
	private EditText edt_param = null;
	private Button btn_ok = null;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		initView();
		initListener();
	}

	/**
	 * 初始化View.
	 */
	private void initView() {
		edt_param = (EditText)findViewById(R.id.edt_para);
		btn_ok = (Button)findViewById(R.id.btn_ok);

		//test:
		edt_param.setText("plstMap");
	}

	/**使用静态内部类,解决'This Handler class should be static or leaks might occur',以免造成内存泄露.
	 * @author Administrator
	 *
	 */
	private static class StatusHandler extends Handler {
		WeakReference<MainActivity>  iMainActivity = null;

		public StatusHandler(MainActivity mainActivity) {
			iMainActivity = new WeakReference<MainActivity>(mainActivity);
		}

		@Override
		public void handleMessage(Message msg) {
			switch (msg.what) {
			case PostSender.SEND_SUCCESS:
				//有iMainActivity.get()和iMainActivity.getClass().
				Toast.makeText(iMainActivity.get(), "发送成功", Toast.LENGTH_SHORT).show();
				break;
			case PostSender.SEND_FAIL:
				Toast.makeText(iMainActivity.get(), "发送失败", Toast.LENGTH_SHORT).show();
				break;
			default:
				throw new RuntimeException("未知的发送结果!");
			}
		}
	}

	/**
	 * 处理发送是否成功的状态的Handler.
	 */
	private final  Handler handler = new StatusHandler(this);

	/**
	 * 初始化监听器.
	 */
	private void initListener() {
		//点击按钮,往服务器端发送数据.
		btn_ok.setOnClickListener(new Button.OnClickListener() {

			@Override
			public void onClick(View v) {
				String name = edt_param.getText().toString();
				if(name.isEmpty()) {
					Toast.makeText(MainActivity.this, "参数不能为空", Toast.LENGTH_SHORT).show();
					return;
				}
				new PostSender(handler).send(name);
			}
		});
	}
}

　　3.使用Apache提供的HTTPClient进行POST请求的业务逻辑层类:

package spt.http.post;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;

import org.apache.http.HttpResponse;
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.json.JSONException;

import spt.json.JsonParser;
import spt.src.Person;
import android.os.Handler;
import android.util.Log;

/**
 * 用户向服务器端发送数据的类(使用post)方法.
 *
 * @author Administrator
 *
 */
public class PostSender {
	// 连接服务器的url.
	private static final String URL = "http://192.168.1.101:8080/ReceiveAndroid/JsonAction";
	// 标识是否连接到服务器成功.
	public static final int SEND_SUCCESS = 1;
	public static final int SEND_FAIL = 0;

	private Handler handler = null;	//新线程关联的Handler,用于将是否发送成功的标识Message放到消息队列中.

	public PostSender(Handler handler) {
		this.handler = handler;
	}

	/**
	 * 往服务器发送数据.
	 *
	 * @param param
	 * @param pwd
	 */
	public void send(String param) {
		// 这里params要传递到另外一个方法,加final为了防止被修改.
		final Map<String, String> params = new HashMap<String, String>();
		params.put("action", param);

		// 启动新的线程连接服务器.
		new Thread(new Runnable() {

			@Override
			public void run() {
				// 请求连接.
				try {
					if (postSend(params, URL, "utf-8"))
						handler.sendEmptyMessage(SEND_SUCCESS);
					else
						handler.sendEmptyMessage(SEND_FAIL);
				} catch (MalformedURLException e) {
					Log.d("sysout", "run:MalformedURLException" + e.getMessage());
				} catch (IOException e) {
					Log.d("sysout", "run:IOException" + e.getMessage());
				}
			}
		}).start();
	}

	/**
	 * 发送post请求的方法.
	 *
	 * @param params
	 *            请求参数的键-值对.
	 * @param url
	 * @param encoding
	 *            使用指定编码对参数值进行编码.
	 * @return
	 * @throws MalformedURLException
	 * @throws IOException
	 */
	private boolean postSend(Map<String, String> params, String url,
			String encoding) throws MalformedURLException, IOException {
		// 封装请求参数的键值对.
		List<BasicNameValuePair> pairs = new ArrayList<BasicNameValuePair>();
		for (Entry<String, String> param : params.entrySet()) {
			pairs.add(new BasicNameValuePair(param.getKey(), param.getValue()));
		}
		//封装请求参数的实体.
		UrlEncodedFormEntity entity = new UrlEncodedFormEntity(pairs, encoding);
		//使用post请求.
		HttpPost post = new HttpPost(url);
		post.setEntity(entity);
		//使用DefaultHttpClient指定请求,以获取响应信息.
		DefaultHttpClient client = new DefaultHttpClient();
		HttpResponse response = client.execute(post);
		BufferedReader reader = new BufferedReader(new InputStreamReader(response.getEntity().getContent(), "utf-8"));
		String ln = null;
		while((ln = reader.readLine()) != null) {
//			Log.d("sysout", ln);
			try {
				List<Map<String, Person>> maps = JsonParser.getListPersonMap("plstMap", ln);
				for (Map<String, Person> map : maps) {
					for (Entry<String, Person> en : map.entrySet()) {
						Person p = en.getValue();
						Log.d("sysout", "k:" + en.getKey() + "->" + p.getName() + "," + p.getAge());
					}
				}
			} catch (JSONException e) {
				Log.d("sysout", "postSend::readLine:JSONException" + e.getMessage());
				e.printStackTrace();
			}
		}
		return response.getStatusLine().getStatusCode() == 200; // 等于200表示发送成功.
	}
}

　　4.在客户端定义一个对象类,与服务器端的一致,用来封装json数据.

package spt.src;

/**用于将json数据转换的目标对象的类.
 * @author Administrator
 *
 */
public class Person {
	private String name;
	private int age;
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}

	public Person(String name, int age) {
		this.name = name;
		this.age = age;
	}
}

　　5.解析json数据为目标类对象的辅助类:

package spt.json;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import spt.src.Person;

/**
 * 解析从服务器端获取的json数据,并封装为对象.
 *
 * @author Administrator
 *
 */
public class JsonParser {
	public static Person getPerson(String key, String jsonStr)
			throws JSONException {
		JSONObject jObj = new JSONObject(jsonStr);
		JSONObject personObj = jObj.getJSONObject(key);
		return new Person(personObj.getString("name"), personObj.getInt("age"));
	}

	/**
	 * 根据json数据,返回对象列表.
	 *
	 * @param key
	 * @param jsonStr
	 * @return
	 * @throws JSONException
	 */
	public static List<Person> getPersonList(String key, String jsonStr)
			throws JSONException {
		JSONObject jsonObject = new JSONObject(jsonStr);
		JSONArray jArr = jsonObject.getJSONArray(key);

		List<Person> persons = new ArrayList<Person>(); // 存储返回对象.
		JSONObject jObj = null;
		for (int j = 0; j < jArr.length(); j++) {
			jObj = jArr.getJSONObject(j);
			persons.add(new Person(jObj.getString("name"), jObj.getInt("age")));
		}
		return persons;
	}

	/**
	 * 根据json数据,返回对象构成的键值对的列表.
	 *
	 * @param key
	 * @param jsonStr
	 * @return
	 * @throws JSONException
	 */
	public static List<Map<String, Person>> getListPersonMap(String key,
			String jsonStr) throws JSONException {
		JSONObject jsonObject = new JSONObject(jsonStr);
		List<Map<String, Person>> personMaps = new ArrayList<Map<String, Person>>(); // 存储返回对象构成的键值对.
		//Map<String, Person>构成的数组.
		JSONArray jArr = jsonObject.getJSONArray(key);
		JSONObject jObj = null;
		for (int j = 0; j < jArr.length(); j++) {
			jObj = jArr.getJSONObject(j);
			//迭代每一个Map<String, Person>.
			Map<String, Person> personMap = new HashMap<String, Person>();
			@SuppressWarnings("unchecked")
			Iterator<String> ks = jObj.keys();
			JSONObject jPersonObj = null;	//一个Person对象对应的json.
			String k = null;	//Person对象对应的键.
			while(ks.hasNext()) {
				k = ks.next();
				jPersonObj = (JSONObject)jObj.get(k);
				//将Person对象封装到Map中.
				personMap.put(k, new Person(jPersonObj.getString("name"), jPersonObj.getInt("age")));
			}
			//将Map<String, Person>封装成数组.
			personMaps.add(personMap);
		}
		return personMaps;
	}
}

客户端可以运行,在这里偷懒一下,对于不同解析,如何遍历List<Person> 和显示Person单独对象,相对简单,所以就省略了.

json api: http://json-lib.sourceforge.net/apidocs/jdk15/