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  • Android入门:通过JSON数据与服务器进行通信

    我们完成“Android入门:通过XML数据与服务器进行通信“同样的功能,只是数据传输使用JSON而不是XML;

    注意点:

    (1)当返回JSON时,content-type为text/json;

    (2)通过JSON包进行解析JSON格式数据和生成JSON格式数据;

    (3)Android中已经集成了JSON的包;


    一、核心代码介绍


    服务器端核心代码:


    (1)JSONStringer stringer = new JSONStringer();

    (2)stringer.array().endArray();

    (3)stringer.object().key("key").value("value").endObject();

    (4)String str = stringer.toString();


    客户端核心代码:

    (1)JSONArray array = new JSONArray(String str); //将字符串转为JSONArray格式

    (2)JSONObject object = array.getJSONObject(int index);

    (3)int value = object.getInt(String name);

    (4)String value = object.getString(String name);



    二、全部代码


    服务器端:

    ListServlet.java

    package org.xiazdong.servlet;
    
    import java.io.IOException;
    import java.util.ArrayList;
    import java.util.List;
    
    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 org.json.JSONStringer;
    import org.xiazdong.domain.Person;
    
    
    @WebServlet("/ListServlet")
    public class ListServlet extends HttpServlet {
    	private static final long serialVersionUID = 1L;
    
    	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		doPost(request,response);
    	}
    
    	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		List<Person> list = new ArrayList<Person>();
    		for(int i=0;i<4;i++){
    			Person person = new Person(i,"xiazdong-"+i,20+i);
    			list.add(person);
    		}
    		//将List<Person>组织成JSON字符串
    		JSONStringer stringer = new JSONStringer();
    		try{
    			stringer.array();
    			for(Person person:list){
    				stringer.object().key("id").value(person.getId()).key("name").value(person.getName()).key("age").value(person.getAge()).endObject();
    			}
    			stringer.endArray();
    		}
    		catch(Exception e){}
    		response.getOutputStream().write(stringer.toString().getBytes("UTF-8"));
    		response.setContentType("text/json; charset=UTF-8");  //JSON的类型为text/json
    	}
    
    }
    


    在浏览器中访问效果如下:


    客户端:


    MainActivity.java

    package org.xiazdong.personlist;
    
    import java.io.ByteArrayOutputStream;
    import java.io.IOException;
    import java.io.InputStream;
    import java.net.HttpURLConnection;
    import java.net.URL;
    import java.util.ArrayList;
    import java.util.HashMap;
    import java.util.List;
    import java.util.Map;
    
    import org.json.JSONArray;
    import org.json.JSONObject;
    import org.xiazdong.domain.Person;
    import org.xmlpull.v1.XmlPullParser;
    
    import android.app.Activity;
    import android.os.Bundle;
    import android.util.Log;
    import android.util.Xml;
    import android.widget.ListView;
    import android.widget.SimpleAdapter;
    
    public class MainActivity extends Activity {
    	private ListView listView;
    
    	@Override
    	public void onCreate(Bundle savedInstanceState) {
    		super.onCreate(savedInstanceState);
    		setContentView(R.layout.main);
    		listView = (ListView) this.findViewById(R.id.listview);
    		List<Person> persons = null;
    		try {
    			persons = getJSONData();
    		} catch (Exception e) {
    			e.printStackTrace();
    		}
    		List<Map<String, Object>> maps = new ArrayList<Map<String, Object>>();
    		for (Person person : persons) {
    			HashMap<String, Object> map = new HashMap<String, Object>();
    			map.put("id", person.getId());
    			map.put("name", person.getName());
    			map.put("age", person.getAge());
    			maps.add(map);
    		}
    		SimpleAdapter adapter = new SimpleAdapter(this, maps, R.layout.item,
    				new String[] { "id", "name", "age" }, new int[] { R.id.id,
    						R.id.name, R.id.age });
    		listView.setAdapter(adapter);
    	}
    
    	//读取JSON数据并转为List<Person>
    	private List<Person> getJSONData() throws Exception {
    		List<Person> persons = new ArrayList<Person>();
    		URL url = new URL("http://192.168.0.103:8080/Server/ListServlet");
    		HttpURLConnection conn = (HttpURLConnection) url.openConnection();
    		conn.setRequestMethod("GET");
    		if (conn.getResponseCode() == 200) {
    			InputStream in = conn.getInputStream();
    			persons = parseJSON(in);
    		}
    		return persons;
    
    	}
    	private List<Person> parseJSON(InputStream in)throws Exception{
    		List<Person> persons = new ArrayList<Person>();
    		Person person = null;
    		String str = read(in);
    		JSONArray array = new JSONArray(str);
    		int length = array.length();
    		for(int i=0;i<length;i++){
    			JSONObject object = array.getJSONObject(i);
    			person = new Person(object.getInt("id"), object.getString("name"), object.getInt("age"));
    			persons.add(person);
    		}
    		return persons;
    	}
    	private String read(InputStream in) throws IOException {
    		byte[] data;
    		ByteArrayOutputStream bout = new ByteArrayOutputStream();
    		byte[]buf = new byte[1024];
    		int len = 0;
    		while((len = in.read(buf))!=-1){
    			bout.write(buf, 0, len);
    		}
    		data = bout.toByteArray();
    		return new String(data,"UTF-8");
    	}
    }

    总结:

    JSON和XML都是数据传输的两种格式;





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  • 原文地址:https://www.cnblogs.com/xiazdong/p/3058326.html
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