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~