Android客户端和Servlet服务器端通过JSON交互

本文结构如下：

1. android和servlet之间的直接信息传递（不通过json）

1.1 android端代码

1.2 servlet端代码

2. android和servlet之间通过json进行交互

2.1 android端代码

2.2 servlet端代码

=============================================================

1. android和servlet之间的直接信息传递

在android端通过httpclient去访问服务器，发送request请求，并获取response。

在servlet端只需要简单的定义doGet方法和doPost方法即可。

1.1 android端代码

package com.example.helloworld;


public class MainActivity extends ActionBarActivity {

    private String responseMsg = "";
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
            
        Button button1 = (Button)findViewById(R.id.button1);
        button1.setOnClickListener(new OnClickListener() {
            
            @Override
            public void onClick(View arg0) {                
                Thread loginThread = new Thread(new LoginThread());
                loginThread.start();
            }
        });
        
    }
    
　　//发送请求的主要方法
    private boolean loginServer(){
        boolean loginValidate = false;
        
　　　　　//servlet服务器地址是
        String urlStr = "http://192.168.1.24:8080/servletTest/test";
        HttpPost request = new HttpPost(urlStr);
        
        try {
            HttpClient client = getHttpClient();
            //执行请求
            HttpResponse response = client.execute(request);
　　　　　　　 //response是servlet给出的返回结果
            if(response.getStatusLine().getStatusCode() == 200){
                loginValidate = true;
                responseMsg = EntityUtils.toString(response.getEntity());
            }
        } catch (Exception e) {
            // TODO: handle exception
            e.printStackTrace();
        }
        return loginValidate;
    }
    
    public HttpClient getHttpClient(){
        BasicHttpParams httpParams = new BasicHttpParams();
        HttpConnectionParams.setConnectionTimeout(httpParams, 5*1000);
        HttpConnectionParams.setSoTimeout(httpParams, 10*1000);
        HttpClient client = new DefaultHttpClient(httpParams);
        return client;
    }
    
    class LoginThread implements Runnable{
        public void run(){    
　　　　　　boolean loginValidate = loginServer();  
　　　　　　System.out.println("======================bool is :"+loginValidate+"----------------response: "+responseMsg);
        }
    }
}

1.2 servlet端代码

package cn.dragon.servlet;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;

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

import net.sf.json.JSONArray;
import net.sf.json.JSONObject;

import com.sun.corba.se.pept.transport.Connection;

public class ServletDemoFirst extends HttpServlet{
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
//        response.setContentType("text/html; charset=GB2312");
//        PrintWriter outPrintWriter = response.getWriter();
//        outPrintWriter.println("hello");
//        outPrintWriter.close();
        //Connection conn = null;
　　　　　//首先建立数据库连接
        String driver = "com.mysql.jdbc.Driver";
        String url = "jdbc:mysql://localhost:3306/test";
        String user = "root";
        String password = "admin";
        PrintWriter out = response.getWriter();
        //out.println("welcom");
        try {
            Class.forName(driver);
            java.sql.Connection conn = DriverManager.getConnection(url, user, password);
            //out.println("loading success");


            Statement statement = conn.createStatement();
　　　　　　　//进行数据库查询。
            ResultSet rs = statement.executeQuery("select * from career");
            ArrayList<String> list1 = new ArrayList<String>();
            while(rs.next()){
                //out.println(rs.getString(1));
                list1.add(rs.getString(1));
            }
　　　　　　　//out用来向客户端返回数据。如果用网页访问这个网址，查询数据库的结果就显示在网页上，如果用android访问，就返回给android手机
            out.println(list1.toString());
            rs.close();
            statement.close();
            conn.close();
        } catch (ClassNotFoundException cnfex) {
            //System.err.println("装载 JDBC/ODBC 驱动程序失败。");
            out.println("loading JDBC failed");
            cnfex.printStackTrace();
            System.exit(1); // terminate program
        } catch (SQLException sqlex) {
            //System.err.println("无法连接数据库");
            out.println("can not connect to the database");
            sqlex.printStackTrace();
            System.exit(1); // terminate program
        }
        
    }
    
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
　　　　 doGet(request, response);    
    }

}

 以上就是两部分的代码。都比较好理解，而且也给了一些注释。

==================================================================

2. 通过JSON进行客户端服务器的通讯

2.1 android端

package com.example.helloworld;


public class MainActivity extends ActionBarActivity {

    private String responseMsg = "";
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
            
        Button button1 = (Button)findViewById(R.id.button1);
        button1.setOnClickListener(new OnClickListener() {
            
            @Override
            public void onClick(View arg0) {
                // TODO Auto-generated method stub
                //Intent intent = new Intent(MainActivity.this, InfoActivity.class);
                //startActivity(intent);
                Thread loginThread = new Thread(new LoginThread());
                loginThread.start();
            }
        });
        
    }
   
    public HttpClient getHttpClient(){
        BasicHttpParams httpParams = new BasicHttpParams();
        HttpConnectionParams.setConnectionTimeout(httpParams, 5*1000);
        HttpConnectionParams.setSoTimeout(httpParams, 10*1000);
        HttpClient client = new DefaultHttpClient(httpParams);
        return client;
    }
    
    private void sendJson(){
        //boolean loginValidate = false;
        String urlStr = "http://192.168.1.24:8080/servletTest/test";
        HttpPost post = new HttpPost(urlStr);
        try{
            //向服务器写json
            JSONObject json1 = new JSONObject();
            //Object email = null;
            Object email = "hlelo";
            json1.put("email", email);
            //Object pwd = null;
            Object pwd = "wodls";
            json1.put("password", pwd);
            
            System.out.println("=============="+json.toString());
            //保证json数据不是乱码
            StringEntity se = new StringEntity(json.toString());
            se.setContentEncoding(new BasicHeader(HTTP.CONTENT_TYPE, "application/json"));
            post.setEntity(se);
            
            //发送json给服务器
            HttpClient httpClient = getHttpClient();
            HttpResponse httpResponse = httpClient.execute(post);
            
            /*int httpCode = httpResponse.getStatusLine().getStatusCode();
            if(httpCode == HttpURLConnection.HTTP_OK && httpResponse != null){
                //org.apache.http.Header[] headers = httpResponse.getAllHeaders();
                HttpEntity entity = httpResponse.getEntity();
                //org.apache.http.Header header = httpResponse.getFirstHeader("content-type");
                //读取服务器返回的json
                InputStream inputStream = entity.getContent();
                InputStreamReader inputStreamReader = new InputStreamReader(inputStream);
                BufferedReader reader = new BufferedReader(inputStreamReader);
                String s;
                while((s= reader.readLine())!= null){
                    result.append(s);
                }
                reader.close();
                
                JSONObject jsonObject = new JSONObject(result.toString());
                String nameString = jsonObject.getString("email");
                String passString = jsonObject.getString("password");
                System.out.println("===============email is: "+nameString+", password is: "+passString);*/
        }catch(Exception exception){
            exception.printStackTrace();
        }
    }
    
    class LoginThread implements Runnable{
        public void run(){           
            sendJson();
        }
    }    
 }

2.2 servlet端代码

package cn.dragon.servlet;


public class ServletDemoFirst extends HttpServlet{
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
        doPost(request, response);
    }
    
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
        //处理json内容
        response.setCharacterEncoding("UTF-8");
        response.setContentType("text/json");
        String acceptjson = "";
        try {
            BufferedReader br = new BufferedReader(new InputStreamReader((ServletInputStream)request.getInputStream(), "utf-8"));
            StringBuffer sb = new StringBuffer("");
            String temp;
            while((temp = br.readLine()) != null){
                sb.append(temp);
            }
            br.close();                     
　　　　　　  //以上的过程都从request中读取json，并将json转换成string，这样可以显示出来。最终String类型的json就是acceptjson　　
            acceptjson = sb.toString();
            System.out.println("=======json is==========="+acceptjson);
            if(acceptjson != ""){
                //System.out.println("get the json successfully");
                JSONObject jo = JSONObject.fromObject(acceptjson);
　　　　　　　　　　//email即是android端发送过来的json当中的一个key，我们使用get方法读取对应的value
                System.out.println(jo.get("email"));
            }
            else{
                System.out.println("get the json failed");
            }
        } catch (Exception e) {
            // TODO: handle exception
            e.printStackTrace();
        }
    }

}

其实应该还有一段内容是servlet将json返还给android端，然后android端再解析出来。关于android端的解析过程在注释掉的部分中，但这段内容我还没有验证。

下面稍微补充一点关于JSONArray的内容——JSONArray如何传输与解析

/**** android: sendJson()      *****/
private void sendJson(){
        //boolean loginValidate = false;
        StringBuilder result = new StringBuilder();
        String urlStr = "http://192.168.1.24:8080/servletTest/test";
        HttpPost post = new HttpPost(urlStr);
        List<NameValuePair> params = new ArrayList<NameValuePair>();
        //params.add(new BasicNameValuePair("name", "this is post"));
        try{
            //向服务器写json
            JSONObject json1 = new JSONObject();
            //Object email = null;
            Object email = "hlelo";
            json1.put("email", email);
            //Object pwd = null;
            Object pwd = "wodls";
            json1.put("password", pwd);
            
            JSONArray jsonArray = new JSONArray();
　　　　　　　 //生成一个JSONARRAY并将上面的json装入其中
            jsonArray.put(0, json1);
            JSONObject json = new JSONObject();
　　　　　　　 //再生成一个JSONObject，将刚才的JSONArray放入其中，再发送到服务器端　
            json.put("dao", jsonArray);
            System.out.println("=============="+json.toString());
            
            //保证json数据不是乱码
            StringEntity se = new StringEntity(json.toString());
            se.setContentEncoding(new BasicHeader(HTTP.CONTENT_TYPE, "application/json"));
            post.setEntity(se);
            
            //发送json给服务器
            HttpClient httpClient = getHttpClient();
            HttpResponse httpResponse = httpClient.execute(post);
            
            
        }catch(Exception exception){
            exception.printStackTrace();
        }    

/***** servlet: doPost()  *****/
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{//处理json内容
        System.out.println("=======json is===========");
        response.setCharacterEncoding("UTF-8");
        response.setContentType("text/json");
        String acceptjson = "";
        try {
            BufferedReader br = new BufferedReader(new InputStreamReader((ServletInputStream)request.getInputStream(), "utf-8"));
            StringBuffer sb = new StringBuffer("");
            String temp;
            while((temp = br.readLine()) != null){
                sb.append(temp);
            }
            br.close();
            acceptjson = sb.toString();
            System.out.println("=======json is==========="+acceptjson);
            if(acceptjson != ""){
                //System.out.println("get the json successfully");
　　　　　　　　　　//先获取json

                JSONObject jo = JSONObject.fromObject(acceptjson);
                //再获取json中包含的jsonarry，dao是刚才android端给出的key
                JSONArray ja = jo.getJSONArray("dao");
　　　　　　　　　　//循环获取jsonarray中的每个json
                for(int i = 0; i < ja.size(); i++){
                    JSONObject object = JSONObject.fromObject(ja.get(i));
　　　　　　　　　　　　 //获取json中的email值，email是json中的key

                    System.out.println("email is: "+object.get("email"));
                }
            }
            else{
                System.out.println("get the json failed");
            }
        } catch (Exception e) {
            // TODO: handle exception
            e.printStackTrace();
        }
    }

Bon Appetite~