Json--Android中数据文件解析（Json解析--从服务器端获取数据并且解析，显示在客户端上面)

  前面学习过了使用SAX解析XML数据(点击进入:SAX解析XML数据),今天学习Json解析；

      首先说一下Json数据的最基本的特点，Json数据是一系列的键值对的集合,和XML数据来比，Json数据的体积更加小，传输效率高，易解析，不过可读性不高;

      因为这次要从服务器端得到Json数据，并且通过解析之后把解析后的数据显示在Android客户端中，首先部署服务器端代码(直接使用Jsp/Servlet):

       构造的Json数据如下:

     [{"name":"张三","address":"北京","age":20},{"name":"李四","address":"上海","age":30},{"name":"王五","address":"深圳","age":35}]

[一]服务器端(Person.java省略):

     ①:数据构造JsonService.java

<span style="font-size: 16px; ">public class JsonService {
    public static List<Person> getListPerson() {
        List<Person> mLists = new ArrayList<Person>();
        mLists.add(new Person("张三", "北京", 20));
        mLists.add(new Person("李四", "上海", 30));
        mLists.add(new Person("王五", "深圳", 35));
        return mLists;
    }</span>

         ②:Servlet的代码（包括构造Json数据，没有使用Json数据转换方法）JsonServlet.java

<span style="font-size: 16px; ">public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html");
        response.setCharacterEncoding("UTF-8");
        PrintWriter out = response.getWriter();
        List<Person> persons = JsonService.getListPerson();
        StringBuffer sb = new StringBuffer();
        sb.append('[');
        for (Person person : persons) {
            sb.append('{').append(""name":").append("""+person.getName()+""").append(
                    ",");
            sb.append(""address":").append("""+person.getAddress()+""").append(",");
            sb.append(""age":").append(person.getAge());
            sb.append('}').append(",");
        }
        sb.deleteCharAt(sb.length() - 1);
        sb.append(']');
        out.write(new String(sb));
        out.flush();
        out.close();
    }</span>

<span style="font-size: 16px; ">
</span>

         ③:部署到Tomact 浏览器输入http://localhost/JsonWeb/JsonServlet直接访问结果如下:

       至此服务器端代码编码完成，下面进行客户端代码编写;

  

  (二)客户端(Person类，和展示数据的布局文件因为简单省去)

      ①:获取服务器端的Json数据并且解析的工具类JsonParse.java

  必要的需要导入的包省去   

<span style="font-size:18px;">public class JsonParse {
    /**
     * 解析Json数据
     *
     * @param urlPath
     * @return mlists
     * @throws Exception
     */
    public static List<Person> getListPerson(String urlPath) throws Exception {
        List<Person> mlists = new ArrayList<Person>();
        byte[] data = readParse(urlPath);
        JSONArray array = new JSONArray(new String(data));
        for (int i = 0; i < array.length(); i++) {
            JSONObject item = array.getJSONObject(i);
            String name = item.getString("name");
            String address = item.getString("address");
            int age = item.getInt("age");
            mlists.add(new Person(name, address, age));
        }
        return mlists;
    }
    /**
     * 从指定的url中获取字节数组
     *
     * @param urlPath
     * @return 字节数组
     * @throws Exception
     */
    public static byte[] readParse(String urlPath) throws Exception {
        ByteArrayOutputStream outStream = new ByteArrayOutputStream();
        byte[] data = new byte[1024];
        int len = 0;
        URL url = new URL(urlPath);
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        InputStream inStream = conn.getInputStream();
        while ((len = inStream.read(data)) != -1) {
            outStream.write(data, 0, len);
        }
        inStream.close();
        return outStream.toByteArray();
    }
}</span>

    ②:主Activity类

<pre code_snippet_id="216479" snippet_file_name="blog_20140304_5_9107204" name="code" class="java">public class MainActivity extends Activity {
    private Button mButton;
    private ListView mListView;
    //使用IP不能使用localhost或者127.0.0.1，因为android模拟器默认绑定这个IP，这里应该访问局域网IP
    private static final String urlPath = "http://10.16.31.207/JsonWeb/JsonServlet";
    private static final String TAG = "MainActivity";
    private List<Person> persons;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        mButton = (Button) findViewById(R.id.button1);
        mListView = (ListView) findViewById(R.id.listView1);
        mButton.setOnClickListener(new MyOnClickListener());
    }

    private class MyOnClickListener implements OnClickListener {
        @Override
        public void onClick(View v) {
            try {
                // 得到Json解析成功之后数据
                persons = JsonParse.getListPerson(urlPath);
                List<HashMap<String, Object>> data = new ArrayList<HashMap<String, Object>>();
                for (int i = 0; i < persons.size(); i++) {
                    HashMap<String, Object> map = new HashMap<String, Object>();
                    map.put("name", persons.get(i).getName());
                    map.put("address", persons.get(i).getAddress());
                    map.put("age", persons.get(i).getAge());
                    data.add(map);
                }
                //初始化适配器，并且绑定数据
                SimpleAdapter _Adapter = new SimpleAdapter(MainActivity.this,
                        data, R.layout.listview_item, new String[] { "name",
                                "address", "age" }, new int[] { R.id.textView1,
                                R.id.textView2, R.id.textView3 });
                mListView.setAdapter(_Adapter);
            } catch (Exception e) {
                Toast.makeText(MainActivity.this, "解析失败", 2000).show();
                Log.i(TAG, e.toString());

            }
        }
    }</pre><br>