Android用GSon处理Json数据

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如何在Android平台上用GSON反序列化JSON数据, 参考了这篇文章 http://benjii.me/2010/04/deserializing-json-in-android-using-gson/

一. 建立我们包装好的Http请求类文件 WebDataGetApi.java

package com.demo;import java.io.IOException;import java.io.InputStreamReader;import java.io.UnsupportedEncodingException;import org.apache.http.HttpEntity;import org.apache.http.HttpResponse;import org.apache.http.client.methods.HttpGet;import org.apache.http.impl.client.DefaultHttpClient;import org.apache.http.params.BasicHttpParams;import org.apache.http.protocol.HTTP;import android.util.Log;public class WebDataGetApi {    private static final String TAG = "WebDataGetAPI";    private static final String USER_AGENT = "Mozilla/4.5";    protected String getRequest(String url) throws Exception {        return getRequest(url, new DefaultHttpClient(new BasicHttpParams()));    }    protected String getRequest(String url, DefaultHttpClient client)            throws Exception {        String result = null;        int statusCode = 0;        HttpGet getMethod = new HttpGet(url);        Log.d(TAG, "do the getRequest,url=" + url + "");        try {            getMethod.setHeader("User-Agent", USER_AGENT);            // HttpParams params = new HttpParams();            // 添加用户密码验证信息            // client.getCredentialsProvider().setCredentials(            // new AuthScope(null, -1),            // new UsernamePasswordCredentials(mUsername, mPassword));            HttpResponse httpResponse = client.execute(getMethod);            // statusCode == 200 正常            statusCode = httpResponse.getStatusLine().getStatusCode();            Log.d(TAG, "statuscode = " + statusCode);            // 处理返回的httpResponse信息            result = retrieveInputStream(httpResponse.getEntity());        } catch (Exception e) {            Log.e(TAG, e.getMessage());            throw new Exception(e);        } finally {            getMethod.abort();        }        return result;    }    /**     * 处理httpResponse信息,返回String     *      * @param httpEntity     * @return String     */    protected String retrieveInputStream(HttpEntity httpEntity) {        int length = (int) httpEntity.getContentLength();        if (length < 0)            length = 10000;        StringBuffer stringBuffer = new StringBuffer(length);        try {            InputStreamReader inputStreamReader = new InputStreamReader(                    httpEntity.getContent(), HTTP.UTF_8);            char buffer[] = new char[length];            int count;            while ((count = inputStreamReader.read(buffer, 0, length - 1)) > 0) {                stringBuffer.append(buffer, 0, count);            }        } catch (UnsupportedEncodingException e) {            Log.e(TAG, e.getMessage());        } catch (IllegalStateException e) {            Log.e(TAG, e.getMessage());        } catch (IOException e) {            Log.e(TAG, e.getMessage());        }        return stringBuffer.toString();    }}

二. 建立JsonDataGetApi.java

package com.demo;import org.json.JSONArray;import org.json.JSONException;import org.json.JSONObject;public class JsonDataGetApi extends WebDataGetApi {    private static final String BASE_URL = "http://10.0.2.2:82/AccountService/";    private static final String EXTENSION = "Json/";;    public JSONObject getObject(String sbj) throws JSONException, Exception {        return new JSONObject(getRequest(BASE_URL + EXTENSION + sbj));    }    public JSONArray getArray(String sbj) throws JSONException, Exception {        return new JSONArray(getRequest(BASE_URL + EXTENSION + sbj));    }}

三. 建立Android端Account模型Account.java

package com.demo;import java.util.Date;public class Account {    public String Name;    public int Age;    public String Address;    public Date Birthday;}

四. 在我们的主Activity中调用刚才的方法, 在这一步中我们需要引入Google的gson 库gson-1.6.jar至我们的工程(下载地址)

package com.demo;import java.util.Date;import org.json.JSONArray;import org.json.JSONObject;import com.google.gson.Gson;import com.google.gson.GsonBuilder;import android.app.Activity;import android.os.Bundle;import android.util.Log;import android.widget.TextView;import android.widget.Toast;public class WebData extends Activity {    /** Called when the activity is first created. */    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);        getJsonData();    }    public void getJsonData() {        JsonDataGetApi api = new JsonDataGetApi();        JSONArray jArr;        JSONObject jobj;        try {            //调用GetAccountData方法            jArr = api.getArray("GetAccountData");            //从返回的Account Array中取出第一个数据            jobj = jArr.getJSONObject(0);                      GsonBuilder gsonb = new GsonBuilder();            //Json中的日期表达方式没有办法直接转换成我们的Date类型, 因此需要单独注册一个Date的反序列化类.            //DateDeserializer ds = new DateDeserializer();            //给GsonBuilder方法单独指定Date类型的反序列化方法              //gsonb.registerTypeAdapter(Date.class, ds);                        Gson gson = gsonb.create();            Account account = gson.fromJson(jobj.toString(), Account.class);            Log.d("LOG_CAT", jobj.toString());            ((TextView) findViewById(R.id.Name)).setText(account.Name);            ((TextView) findViewById(R.id.Age)).setText(account.Age);            ((TextView) findViewById(R.id.Birthday)).setText(account.Birthday                    .toGMTString());            ((TextView) findViewById(R.id.Address)).setText(account.Address);        } catch (Exception e) {            Toast.makeText(getApplicationContext(), e.getMessage(),                    Toast.LENGTH_LONG).show();            e.printStackTrace();            TextView movie_Address = (TextView) findViewById(R.id.Address);            movie_Address.setText(e.getMessage());        }    }}

五.我们开始构建UI

打开layout下的main.xml

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:orientation="vertical" android:layout_width="fill_parent"    android:layout_height="fill_parent">    <TextView android:id="@+id/Name" android:layout_width="fill_parent"        android:layout_height="wrap_content" />    <TextView android:id="@+id/Age" android:layout_width="fill_parent"        android:layout_height="wrap_content" />    <TextView android:id="@+id/Birthday" android:layout_width="fill_parent"        android:layout_height="wrap_content" />    <TextView android:id="@+id/Address" android:layout_width="fill_parent"        android:layout_height="wrap_content" /></LinearLayout>

在配置好RunConfiguration之后,我们开始运行程序, 查看Log发现有以下错误,

意思是说访问被禁止，也就是未授权访问, 其意思并不是我们的服务未授权, 因为Andriod具有很好的很好很好的安全机制, 我们要访问网络必须要经过授权才可以;

我们打开res目录下AndroidManifest.xml, 注意字体加粗放大的那句, 就是给我们的程序加入Internet的访问授权.

<?xml version="1.0" encoding="utf-8"?><manifest xmlns:android="http://schemas.android.com/apk/res/android"      package="com.demo"      android:versionCode="1"      android:versionName="1.0">            <uses-permission android:name="android.permission.INTERNET"></uses-permission>    <application android:icon="@drawable/icon" android:label="@string/app_name">        <activity android:name=".WebData"                  android:label="@string/app_name">            <intent-filter>                <action android:name="android.intent.action.MAIN" />                <category android:name="android.intent.category.LAUNCHER" />            </intent-filter>        </activity>    </application></manifest>

再次运行程序，会发现显示如下:

从上图中的statuscode = 200来看,说明我们的请求已经成功, 问题出现在Json Parse(Json数据转换/反序列化/格式化)的过程中, 我们现在把从服务器传过来的数据拿出来看看, 在浏览器输入我们的服务地址: http://localhost:82/AccountService/Json/GetAccountData

[ {     "Address": "YouYi East Road",     "Age": 56,     "Birthday": "/Date(1298605481453+0800)/",     "Name": "Bill Gates" }, {     "Address": "YouYi West Road",     "Age": 57,     "Birthday": "/Date(1298605481453+0800)/",     "Name": "Steve Paul Jobs" }, {     "Address": "YouYi North Road",     "Age": 65,     "Birthday": "/Date(1298605481453+0800)/",     "Name": "John D. Rockefeller" }]

我们发现其中的Birthday的结果并非我们想象中yyyy-mm-dd HH:mm:ss类型, 究其原因可以查看MSDN文章《JavaScript 和 .NET 中的 JavaScript Object Notation (JSON) 简介》

现在我们给我们的GsonBuilder指定Date的序列化方法, 先增加一个Date反序列化的类DateDeserializer.java

package com.demo;import java.lang.reflect.Type;import java.util.Date;import java.util.regex.Matcher;import java.util.regex.Pattern;import com.google.gson.JsonDeserializationContext;import com.google.gson.JsonDeserializer;import com.google.gson.JsonElement;import com.google.gson.JsonParseException;public class DateDeserializer implements JsonDeserializer<Date> {    public Date deserialize(JsonElement json, Type typeOfT,            JsonDeserializationContext context) throws JsonParseException {        String JSONDateToMilliseconds = "\\/(Date\\((.*?)(\\+.*)?\\))\\/";        Pattern pattern = Pattern.compile(JSONDateToMilliseconds);        Matcher matcher = pattern.matcher(json.getAsJsonPrimitive()                .getAsString());        String result = matcher.replaceAll("$2");        return new Date(new Long(result));    }}

其次修改Activity类中的GetDate方法如下, 注意其中加粗的部分.

    public void getJsonData() {        JsonDataGetApi api = new JsonDataGetApi();        JSONArray jArr;        JSONObject jobj;        try {            //调用GetAccountData方法            jArr = api.getArray("GetAccountData");            //从返回的Account Array中取出第一个数据            jobj = jArr.getJSONObject(0);                        GsonBuilder gsonb = new GsonBuilder();            //Json中的日期表达方式没有办法直接转换成我们的Date类型, 因此需要单独注册一个Date的反序列化类.            DateDeserializer ds = new DateDeserializer();            //给GsonBuilder方法单独指定Date类型的反序列化方法              gsonb.registerTypeAdapter(Date.class, ds);                        Gson gson = gsonb.create();            Account account = gson.fromJson(jobj.toString(), Account.class);            Log.d("LOG_CAT", jobj.toString());            ((TextView) findViewById(R.id.Name)).setText(account.Name);            ((TextView) findViewById(R.id.Age)).setText(String.valueOf(account.Age)）;            ((TextView) findViewById(R.id.Birthday)).setText(account.Birthday                    .toGMTString());            ((TextView) findViewById(R.id.Address)).setText(account.Address);        } catch (Exception e) {            Toast.makeText(getApplicationContext(), e.getMessage(),                    Toast.LENGTH_LONG).show();            e.printStackTrace();        }    }}

我们现在再运行程序：

执行成功.

示例下载