android:服务器与客户端的双向开发
Android java web JSON http协议 服务端
在前面的两讲中,我们讲解了JSON数据格式的一些基本知识,以及做一些小Demo,这一讲我们在前面的基础上来做一个综合的可扩展的Demo,主要是针对Android客户端解析服务端传递过来的JSON数据。整个Demo所作的操作如下图所示
1. 服务端
服务端我们需要用到的解析JSON的库是用org.json --> Java --> JSON-lib项目中的库json-lib-2.4-jdk15.jar,这个库还需要附带几个依赖包:commons-beanutils.jar, commons-httpclient.jar, commons- lang.jar, ezmorph.jar,morph-1.0.1.jar。具体的包我会放在源码的lib目录下,读者可以自己去下载。
查看这个项目的api文档:http://json-lib.sourceforge.net/apidocs/jdk15/index.html,我们主要使用的是JSON JSONArray JSONObject JSONSerializer 这几个类,JSONObject这个类可以发现它与org.json这个项目的用法很类似。
1) 先做一个服务端的小实验,就是在服务端实现对Java对象转换成JSON数据格式并且在控制台输出。
Person.java 普通的Person类
[java] view plain copy
- package com.json.domain;
- public class Person {
- private int id;
- private String name;
- private String address;
- public Person(int id, String name, String address) {
- super();
- this.id = id;
- this.name = name;
- this.address = address;
- }
- public Person() {
- // TODO Auto-generated constructor stub
- }
- public int getId() {
- return id;
- }
- public void setId(int id) {
- this.id = id;
- }
- public String getName() {
- return name;
- }
- public void setName(String name) {
- this.name = name;
- }
- public String getAddress() {
- return address;
- }
- public void setAddress(String address) {
- this.address = address;
- }
- }
JsonService.java 服务于Person,给Person对象赋予各种属性
[java] view plain copy
JsonTools.java 工具类
- package com.json.service;
- import java.util.ArrayList;
- import java.util.HashMap;
- import java.util.List;
- import java.util.Map;
- import com.json.domain.Person;
- public class JsonService {
- public JsonService() {
- // TODO Auto-generated constructor stub
- }
- public Person getPerson(){
- Person person = new Person(23, "AHuier", "XIAMEN");
- return person;
- }
- public List
getListPerson(){ - List
list = new ArrayList (); - Person person1 = new Person(1001, "AHuier1", "Beijing");
- Person person2 = new Person(1002, "AHuier2", "shenzheng");
- list.add(person1);
- list.add(person2);
- return list;
- }
- public List
getListString(){ - List
list = new ArrayList (); - list.add("Hello");
- list.add("World");
- list.add("AHuier");
- return list;
- }
- public List
- List
- Map
map1 = new HashMap (); - map1.put("color", "red");
- map1.put("id", 01);
- map1.put("name", "Polu");
- listMap.add(map1);
- Map
map2 = new HashMap (); - map2.put("id", 07);
- map2.put("color", "green");
- map2.put("name", "Zark");
- listMap.add(map2);
- return listMap;
- }
- }
[java] view plain copyJsonTest.java 测试类
- package com.json.tools;
- import net.sf.json.JSONObject;
- /**
- * @author xukunhui
- * 工具类,这里专门处理Java对象转Json字符串的功能
- */
- public class JsonTools {
- public JsonTools() {
- // TODO Auto-generated constructor stub
- }
- /**
- * @param key : JSON 名值对中的的名字
- * @param value :JSON 名值对中的值,值可以有多种类型
- * @return
- */
- // 接受对象转换为JSON数据格式并且作为字符串输出.
- public static String createJsonString(String key, Object value){
- JSONObject jsonObject = new JSONObject();
- jsonObject.put(key, value);
- return jsonObject.toString(); //就可以转换成Json数据格式
- }
- }
[java] view plain copy
- package com.json.test;
- import com.json.domain.Person;
- import com.json.service.JsonService;
- import com.json.tools.JsonTools;
- /**
- * @author xukunhui
- * 测试类,利用JSON讲Java对象转换成JSON数据格式,并且在控制台中输出
- */
- public class JsonTest {
- public JsonTest() {
- // TODO Auto-generated constructor stub
- }
- /**
- * @param args
- */
- public static void main(String[] args) {
- // TODO Auto-generated method stub
- String msg = "";
- JsonService service = new JsonService();
- // 带有三个属性的person对象
- Person person = service.getPerson();
- msg = JsonTools.createJsonString("person", person);
- System.out.println(msg);
- System.out.println("------------------------------");
- // List中存放两个person对象,这两个对象有各自的三个属性
- msg = JsonTools.createJsonString("persons", service.getListPerson());
- System.out.println(msg);
- System.out.println("------------------------------");
- // List中存放三个字符串
- msg = JsonTools.createJsonString("listString", service.getListString());
- System.out.println(msg);
- System.out.println("------------------------------");
- // List中存放两个Map,两个Map中分别存放三个不同的属性
- msg = JsonTools.createJsonString("listMap", service.getListMaps());
- System.out.println(msg);
- }
- }
编译执行结果:
{"person":{"address":"XIAMEN","id":23,"name":"AHuier"}}
------------------------------
{"persons":[{"address":"Beijing","id":1001,"name":"AHuier1"},{"address":"shenzheng","id":1002,"name":"AHuier2"}]}
------------------------------
{"listString":["Hello","World","AHuier"]}
------------------------------
{"listMap":[{"id":1,"color":"red","name":"Polu"},{"id":7,"color":"green","name":"Zark"}]}【说明】:从这里可以发现在服务端利用JSON很方便的将Java对象转换成JSON数据格式。
【注意】:我们这边需要给加一个person的标示符,作为最外面的一个对象的名,我们在客户端解析数据的时候,其实不加person的标示符也是可以的,但是这样写的目的是把原有的对象转换成JSON数据格式之后,我们在外层再给予封装一层对象,便于后续利用外层的这个对象进行解析。如下图所示:
2) 现在我们将服务端的项目部署到Tomcat服务器(如何部署可以参考前面几篇博文),然后通过在浏览器的地址栏中传递不同的action值来获取相应的JSON数据格式,这样的话浏览器也会显示出请求服务解析好的JSON数据格式。实现好这一步骤之后,我们在服务端的工作也完成了。服务端的项目结构图如下所示:
JsonAction.java Servlet类,处理根浏览器客户端通过不同的参数请求返回JSON数据。
[java] view plain copy程序执行,在浏览器地址栏中输入与浏览器显示如下:
- package com.json.action;
- import java.io.IOException;
- import java.io.PrintWriter;
- import java.nio.charset.Charset;
- import javax.servlet.ServletException;
- import javax.servlet.http.HttpServlet;
- import javax.servlet.http.HttpServletRequest;
- import javax.servlet.http.HttpServletResponse;
- import com.json.service.JsonService;
- import com.json.tools.JsonTools;
- /**
- * @author xukunhui
- * Servlet类,处理根浏览器客户端通过不同的参数请求返回JSON数据。
- */
- public class JsonAction extends HttpServlet {
- private JsonService service;
- /**
- * Constructor of the object.
- */
- public JsonAction() {
- super();
- }
- /**
- * Destruction of the servlet.
- */
- public void destroy() {
- super.destroy(); // Just puts "destroy" string in log
- // Put your code here
- }
- /**
- * The doGet method of the servlet.
- *
- * This method is called when a form has its tag value method equals to get.
- *
- * @param request the request send by the client to the server
- * @param response the response send by the server to the client
- * @throws ServletException if an error occurred
- * @throws IOException if an error occurred
- */
- public void doGet(HttpServletRequest request, HttpServletResponse response)
- throws ServletException, IOException {
- doPost(request, response);
- }
- /**
- * The doPost method of the servlet.
- *
- * This method is called when a form has its tag value method equals to post.
- *
- * @param request the request send by the client to the server
- * @param response the response send by the server to the client
- * @throws ServletException if an error occurred
- * @throws IOException if an error occurred
- */
- public void doPost(HttpServletRequest request, HttpServletResponse response)
- throws ServletException, IOException {
- response.setContentType("text/html; Charset=utf-8");
- request.setCharacterEncoding("utf-8");
- response.setCharacterEncoding("utf-8");
- PrintWriter out = response.getWriter();
- /*
- * 如果是以下这种方式直接在浏览器地址栏中用 http://192.168.0.112:8080/JsonProject/servlet/JsonAction 请求即可
- * String jsonString = JsonTools.createJsonString("person", service.getListPerson());
- * out.print(jsonString); // 从服务端提取数据,并且输出的浏览器客户端。
- */
- // 根据不同的参数输出不同的JSON数据
- String jsonString = "";
- String action_flag = request.getParameter("action_flag");
- if(action_flag.equals("person")) {
- jsonString = JsonTools.createJsonString("person", service.getPerson());
- } else if(action_flag.equals("persons")){
- jsonString = JsonTools.createJsonString("persons", service.getListPerson());
- } else if(action_flag.equals("listString")) {
- jsonString = JsonTools.createJsonString("listString", service.getListString());
- } else if(action_flag.equals("listMap")){
- jsonString = JsonTools.createJsonString("listMap", service.getListMaps());
- }
- out.print(jsonString);
- out.flush();
- out.close();
- }
- /**
- * Initialization of the servlet.
- *
- * @throws ServletException if an error occurs
- */
- public void init() throws ServletException {
- // Put your code here
- service = new JsonService();
- }
- }
输入: http://192.168.0.112:8080/JsonProject/servlet/JsonAction?action_flag=person
输出: {"person":{"address":"XIAMEN","id":23,"name":"AHuier"}}输入:http://192.168.0.112:8080/JsonProject/servlet/JsonAction?action_flag=persons
输出: {"persons":[{"address":"Beijing","id":1001,"name":"AHuier1"},{"address":"shenzheng","id":1002,"name":"AHuier2"}]}输入:http://192.168.0.112:8080/JsonProject/servlet/JsonAction?action_flag=listString
输出: {"listString":["Hello","World","AHuier"]}输入:http://192.168.0.112:8080/JsonProject/servlet/JsonAction?action_flag=listMap
输出: {"listMap":[{"id":1,"color":"red","name":"Polu"},{"id":7,"color":"green","name":"Zark"}]}【备注】:自此,我们服务端模块的内容已经实现的差不多了,在服务端我们通常还结合JDBC进行操作。可以把JDBC的数据提取出来,提取出来的肯定是单条记录,或者是某一个集合。也就是服务端从JDBC数据库中提取到数据只要转换成JSON的数据格式后提供客户端进行显示。如下图所示:
2. 客户端
上面我们已经写好了服务端的代码,现在我们开始进行Android客户端的操作。JSON的解析有一个规则就是服务端把对象转换成一个JSON的数据格式,而客户端需要把JSON格式换成对象,客户端主要是通过Http协议向服务端发出请求获得服务端的JSON数据。
客户端项目结构如下图所示:
1. 客户端需要通过网络去向服务端请求数据,所以需要在 manifest.xml 清单文件中定义好访问网络的属性
[html] view plain copy2. HttpUtils.java 负责从服务器请求获取到JSON数据格式的字符串 [java] view plain copy
- <uses-permission android:name="android.permission.INTERNET"/>
3. JSONTools.java 完成对从服务端请求获得的JSON数据的解析成指定的对象. [java] view plain copy
- package com.android.jsonproject.http;
- import java.io.ByteArrayOutputStream;
- import java.io.InputStream;
- import java.net.HttpURLConnection;
- import java.net.URL;
- /**
- * @author xukunhui 从服务器请求获取到JSON数据格式的字符串
- */
- public class HttpUtils {
- public HttpUtils() {
- // TODO Auto-generated constructor stub
- }
- public static String getJsonContent(String url_path) {
- try {
- URL url = new URL(url_path);
- HttpURLConnection connection = (HttpURLConnection) url.openConnection();
- connection.setConnectTimeout(3000); // 请求超时时间3s
- connection.setRequestMethod("GET");
- connection.setDoInput(true);
- int code = connection.getResponseCode(); // 返回状态码
- if (code == 200) {
- // 或得到输入流,此时流里面已经包含了服务端返回回来的JSON数据了,此时需要将这个流转换成字符串
- return changeInputStream(connection.getInputStream());
- }
- } catch (Exception e) {
- // TODO: handle exception
- }
- return "";
- }
- private static String changeInputStream(InputStream inputStream) {
- // TODO Auto-generated method stub
- String jsonString = "";
- ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
- int length = 0;
- byte[] data = new byte[1024];
- try {
- while (-1 != (length = inputStream.read(data))) {
- outputStream.write(data, 0, length);
- }
- // inputStream流里面拿到数据写到ByteArrayOutputStream里面,
- // 然后通过outputStream.toByteArray转换字节数组,再通过new String()构建一个新的字符串。
- jsonString = new String(outputStream.toByteArray());
- } catch (Exception e) {
- // TODO: handle exception
- }
- return jsonString;
- }
- }
4. Person.java 配合客户端将JSON数据转换成Java对象,服务端有Person对象,所以客户端需要相应的Person对象 [java] view plain copy
- package com.android.jsonproject.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.JSONObject;
- import com.android.jsonproject.domain.Person;
- /**
- * @author xukunhui
- * 完成对从服务端请求获得的JSON数据的解析成指定的对象.
- */
- public class JSONTools {
- public JSONTools() {
- // TODO Auto-generated constructor stub
- }
- // 此时从服务端取下来的数据是:{"person":{"address":"XIAMEN","id":23,"name":"AHuier"}}
- public static Person getPerson(String key, String jsonString){
- Person person = new Person();
- try {
- // 在Android官方文档中,org.json 这是Android提供给我们的解析json数据格式的包,
- // 我们比较常用的是JSONArray 和 JSONObject这个两个类
- JSONObject jsonObject = new JSONObject(jsonString);
- JSONObject personObject = jsonObject.getJSONObject(key);
- person.setId(personObject.getInt("id"));
- person.setAddress(personObject.getString("address"));
- person.setName(personObject.getString("name"));
- } catch (Exception e) {
- // TODO: handle exception
- }
- return person;
- }
- //{"persons":[{"address":"Beijing","id":1001,"name":"AHuier1"},{"address":"shenzheng","id":1002,"name":"AHuier2"}]}
- public static List
getPersons(String key, String jsonString){ - List
list = new ArrayList (); - try {
- JSONObject jsonObject = new JSONObject(jsonString);
- //返回json的数组
- JSONArray jsonArray = jsonObject.getJSONArray(key);
- for(int i = 0; i < jsonArray.length(); i++){
- JSONObject jsonObject2 = jsonArray.getJSONObject(i);
- Person person = new Person();
- person.setId(jsonObject2.getInt("id"));
- person.setName(jsonObject2.getString("name"));
- person.setAddress(jsonObject2.getString("address"));
- list.add(person);
- }
- } catch (Exception e) {
- // TODO: handle exception
- }
- return list;
- }
- //{"listString":["Hello","World","AHuier"]}
- public static List
getListString(String key, String jsonString){ - List
listString = new ArrayList (); - try {
- JSONObject jsonObject = new JSONObject(jsonString);
- //返回JSON的数组
- JSONArray jsonArray = jsonObject.getJSONArray(key);
- for(int i = 0; i < jsonArray.length(); i++){
- String msg = jsonArray.getString(i);
- listString.add(msg);
- }
- } catch (Exception e) {
- // TODO: handle exception
- }
- return listString;
- }
- // 此时从服务端取下来的数据是:{"listMap":[{"id":1,"color":"red","name":"Polu"},{"id":7,"color":"green","name":"Zark"}]}
- public static List
> getListMaps(String key, String jsonString){ - List
> listMap = new ArrayList >(); - try {
- JSONObject jsonObject = new JSONObject(jsonString);
- JSONArray jsonArray = jsonObject.getJSONArray(key);
- for(int i = 0; i < jsonArray.length(); i++){
- JSONObject jsonObject2 = jsonArray.getJSONObject(i);
- Map
map = new HashMap (); - // 通过org.json中的迭代器来取Map中的值。
- Iterator
iterator = jsonObject2.keys(); - while(iterator.hasNext()) {
- String jsonKey = iterator.next();
- Object jsonValue = jsonObject2.get(jsonKey);
- //JSON的值是可以为空的,所以我们也需要对JSON的空值可能性进行判断。
- if(jsonValue == null){
- jsonValue = "";
- }
- map.put(jsonKey, jsonValue);
- }
- listMap.add(map);
- }
- } catch (Exception e) {
- // TODO: handle exception
- }
- return listMap;
- }
- }
5. Android 客户端主界面代码,这里主要是定义四个按钮分别处理解析不同类型的JSON数据格式,布局文件这里不再贴出. [java] view plain copy
- package com.android.jsonproject.domain;
- public class Person {
- private int id;
- private String name;
- private String address;
- public Person(int id, String name, String address) {
- super();
- this.id = id;
- this.name = name;
- this.address = address;
- }
- public Person() {
- // TODO Auto-generated constructor stub
- }
- @Override
- public String toString() {
- return "Person [id=" + id + ", name=" + name + ", address=" + address + "]";
- }
- public int getId() {
- return id;
- }
- public void setId(int id) {
- this.id = id;
- }
- public String getName() {
- return name;
- }
- public void setName(String name) {
- this.name = name;
- }
- public String getAddress() {
- return address;
- }
- public void setAddress(String address) {
- this.address = address;
- }
- }
客户端编译执行结果:
- @Override
- public void onClick(View v) {
- // TODO Auto-generated method stub
- switch (v.getId()) {
- case R.id.person:
- String path = "http://192.168.0.112:8080/JsonProject/servlet/JsonAction?action_flag=person";
- String jsonString = HttpUtils.getJsonContent(path);
- Log.i(TAG, "The jsonString:" + jsonString);
- Person person = JSONTools.getPerson("person", jsonString);
- Log.i(TAG, "The person:" + person.toString());
- break;
- case R.id.persons:
- String path2 = "http://192.168.0.112:8080/JsonProject/servlet/JsonAction?action_flag=persons";
- String jsonString2 = HttpUtils.getJsonContent(path2);
- Log.i(TAG, "The jsonString:" + jsonString2);
- List
list2 = JSONTools.getPersons("persons", jsonString2); - Log.i(TAG, "The persons:" + list2.toString());
- break;
- case R.id.liststring:
- String path3 = "http://192.168.0.112:8080/JsonProject/servlet/JsonAction?action_flag=listString";
- String jsonString3 = HttpUtils.getJsonContent(path3);
- Log.i(TAG, "The jsonString:" + jsonString3);
- List
list3 = JSONTools.getListString("listString", jsonString3); - Log.i(TAG, "The listString:" + list3.toString());
- break;
- case R.id.listmap:
- String path4 = "http://192.168.0.112:8080/JsonProject/servlet/JsonAction?action_flag=listMap";
- String jsonString4 = HttpUtils.getJsonContent(path4);
- Log.i(TAG, "The jsonString:" + jsonString4);
- List
> list4 = JSONTools.getListMaps("listMap", jsonString4); - Log.i(TAG, "The listMap:" + list4.toString());
- break;
- }
- }
1. 点击解析person数据按钮
2. 点击解析List嵌套person数据
3. 点击List嵌套String数据
4. 点击List嵌套Map数据
自此,Android客户端与服务之间的JSON数据交互的Demo就完成了,下面附上源代码,读者可以自行编译执行
服务端: MyEclipse + Tomcat + Servlet
客户端: Eclipse + Android(模拟器和真机都可以,但是必须保证通过IP地址可以访问)
源码下载:http://download.csdn.net/detail/xukunhui2/6546095
服务端(符JSON开源项目包路径:JsonProject\WebRoot\WEB-INF\lib):
客户端:http://download.csdn.net/detail/xukunhui2/6546117
接下去,我们会学习一下google-gson的数据格式的解析,敬请关注。
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