使用GSON和泛型解析约定格式的JSON串(转)

时间紧张，先记一笔，后续优化与完善。

解决的问题：

使用GSON和泛型解析约定格式的JSON串。

背景介绍：

1.使用GSON来进行JSON串与java代码的互相转换。

2.JSON的格式如下三种：

写道

＃第一种：
{"success":true,"data":{"averageStarLevel":4.7,"remarkCount":10}}
＃第二种：
{"success":true,"data":{"page":10,"pageCount":29,"list":[{"starLevel":4,"remarkCotnent":"评价方未及时做出评价，系统默认满意！","remarkTime":"2013-02-27 07:21:48","explainContent":"","postMemberId":"y**f","tpLogoURL":"http://i04.c.aliimg.com/cms/upload/2012/186/684/486681_1232736939.png"},{"starLevel":4,"remarkCotnent":"评价方未及时做出评价，系统默认满意！","remarkTime":"2013-02-27 07:21:48","explainContent":"","postMemberId":"y**f","tpLogoURL":"http://i04.c.aliimg.com/cms/upload/2012/186/684/486681_1232736939.png"}],"statistics":{"star5":20,"star4":40,"star3":30,"star2":10,"star1":0}}}
＃第三种：{"success":true,"data":[{"starLevel":4,"remarkCotnent":"评价方未及时做出评价，系统默认满意！","remarkTime":"2013-02-27 07:21:48","explainContent":"","postMemberId":"y**f","tpLogoURL":"http://i04.c.aliimg.com/cms/upload/2012/186/684/486681_1232736939.png"},{"starLevel":4,"remarkCotnent":"评价方未及时做出评价，系统默认满意！","remarkTime":"2013-02-27 07:21:48","explainContent":"","postMemberId":"y**f","tpLogoURL":"http://i04.c.aliimg.com/cms/upload/2012/186/684/486681_1232736939.png"}]}

分析：

在工作时间中，遇到一种场景，就是在应用中调用多个JSON接口，各接口返回的数据内容不一样，如果逐一解析代码会比较臃肿。JSON串如上所列有三种基本格式。经过分析，发现三种JSON串有一个共同的特点。JSON结构一致：

写道

{"success":true,"data":##} 

success：代表是否访问成功

data:后面跟着所需信息.

基本相同的JSON结构，所以想定义一种通用模型对应到此结构。但是，data中的数据类型不一致。如第一种是简单对象，第二种是对象中嵌套数组，第三种是List。针对data数据类型不一致的情况，使用泛型来解决。

import java.io.Serializable;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;

import com.google.gson.Gson;

public class CommonJson<T> implements Serializable {

    /**
     *
     */
    private static final long serialVersionUID = -3440061414071692254L;

    /**
     * 是否成功
     */
    private Boolean success;

    /**
     * 数据
     */
    private T data;

    public Boolean getSuccess() {
        return success;
    }

    public void setSuccess(Boolean success) {
        this.success = success;
    }

    public T getData() {
        return data;
    }

    public void setData(T data) {
        this.data = data;
    }
}

GSON对于泛型的支持不足，为了使GSON对于泛型进行解析，JSON解析与组装代码如下：

       public static CommonJson fromJson(String json, Class clazz) {
        Gson gson = new Gson();
        Type objectType = type(CommonJson.class, clazz);
        return gson.fromJson(json, objectType);
    }

    public String toJson(Class<T> clazz) {
        Gson gson = new Gson();
        Type objectType = type(CommonJson.class, clazz);
        return gson.toJson(this, objectType);
    }

    static ParameterizedType type(final Class raw, final Type... args) {
        return new ParameterizedType() {
            public Type getRawType() {
                return raw;
            }

            public Type[] getActualTypeArguments() {
                return args;
            }

            public Type getOwnerType() {
                return null;
            }
        };
    }

以上两段代码可以满足第一种和第二种JSON的解析，对于第三种，data是List类型的，无法得到List<>的class，所以，针对第三种格式，实现代码如下：

import java.io.Serializable;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.List;

import com.google.gson.Gson;

public class CommonJson4List<T> implements Serializable {

    /**
     *
     */
    private static final long serialVersionUID = -369558847578246550L;

    /**
     * 是否成功
     */
    private Boolean success;

    /**
     * 数据
     */
    private List<T> data;

    public Boolean getSuccess() {
        return success;
    }

    public void setSuccess(Boolean success) {
        this.success = success;
    }

    public List<T> getData() {
        return data;
    }

    public void setData(List<T> data) {
        this.data = data;
    }

    public static CommonJson4List fromJson(String json, Class clazz) {
        Gson gson = new Gson();
        Type objectType = type(CommonJson4List.class, clazz);
        return gson.fromJson(json, objectType);
    }

    public String toJson(Class<T> clazz) {
        Gson gson = new Gson();
        Type objectType = type(CommonJson4List.class, clazz);
        return gson.toJson(this, objectType);
    }

    static ParameterizedType type(final Class raw, final Type... args) {
        return new ParameterizedType() {
            public Type getRawType() {
                return raw;
            }

            public Type[] getActualTypeArguments() {
                return args;
            }

            public Type getOwnerType() {
                return null;
            }
        };
    }

}

测试代码如下：

import java.util.ArrayList;
import java.util.List;

import com.alibaba.asc.sharewood.common.http.CommonJson;
import com.alibaba.asc.sharewood.common.http.CommonJson4List;
import com.alibaba.asc.sharewood.external.service.model.AverageStarLevelAndCount;
import com.alibaba.asc.sharewood.external.service.model.Evalution;
import com.alibaba.asc.sharewood.external.service.model.EvalutionProfile;
import com.alibaba.asc.sharewood.external.service.model.StarLevelStatistics;

public class Test {

    @SuppressWarnings("unchecked")
    public static void main(String[] args) {

        CommonJson<AverageStarLevelAndCount> cj = new CommonJson<AverageStarLevelAndCount>();
        AverageStarLevelAndCount data = new AverageStarLevelAndCount();
        data.setAverageStarLevel(4.7f);
        data.setRemarkCount(10);

        cj.setSuccess(Boolean.TRUE);
        cj.setData(data);

        String res1 = cj.toJson(AverageStarLevelAndCount.class);

        System.out.println(res1);

        CommonJson<AverageStarLevelAndCount> cj2 = CommonJson.fromJson(res1,
                AverageStarLevelAndCount.class);

        System.out.println(cj2.getSuccess());
        System.out.println(cj2.getData().getAverageStarLevel());

        EvalutionProfile p = new EvalutionProfile();
        p.setPage(10);
        p.setPageCount(29);

        StarLevelStatistics s = new StarLevelStatistics();
        s.setStar1(0);
        s.setStar2(10);
        s.setStar3(30);
        s.setStar4(40);
        s.setStar5(20);

        p.setStatistics(s);

        Evalution e1 = new Evalution();

        e1.setStarLevel(4);
        e1.setRemarkTime("2013-02-27 07:21:48");
        e1.setRemarkCotnent("评价方未及时做出评价，系统默认满意！");
        e1.setTpLogoURL("http://i04.c.aliimg.com/cms/upload/2012/186/684/486681_1232736939.png");
        e1.setExplainContent("");
        e1.setPostMemberId("y**f");

        Evalution e2 = new Evalution();

        e2.setStarLevel(4);
        e2.setRemarkTime("2013-02-27 07:21:48");
        e2.setRemarkCotnent("评价方未及时做出评价，系统默认满意！");
        e2.setTpLogoURL("http://i04.c.aliimg.com/cms/upload/2012/186/684/486681_1232736939.png");
        e2.setExplainContent("");
        e2.setPostMemberId("y**f");

        List<Evalution> le = new ArrayList<Evalution>();
        le.add(e1);
        le.add(e2);

        p.setList(le);

        CommonJson<EvalutionProfile> ce = new CommonJson<EvalutionProfile>();

        ce.setSuccess(Boolean.TRUE);
        ce.setData(p);

        String res2 = ce.toJson(EvalutionProfile.class);

        System.out.println(res2);

        String ps = "{\"data\":{\"pageCount\":29,\"page\":\"1\",\"list\":[{\"starLevel\":4,\"remarkTime\":\"2013-04-10 05:17:42\",\"explainTime\":\"\",\"remarkContent\":\"评价方未及时做出评价，系统默认满意！\",\"tpLogoURL\":\"\",\"explainContent\":\"\",\"postMemberId\":\"b**6\"},{\"starLevel\":4,\"remarkTime\":\"2013-04-05 04:42:40\",\"explainTime\":\"\",\"remarkContent\":\"评价方未及时做出评价，系统默认满意！\",\"tpLogoURL\":\"\",\"explainContent\":\"\",\"postMemberId\":\"b**8\"},{\"starLevel\":4,\"remarkTime\":\"2013-03-20 00:52:18\",\"explainTime\":\"\",\"remarkContent\":\"评价方未及时做出评价，系统默认满意！\",\"tpLogoURL\":\"\",\"explainContent\":\"\",\"postMemberId\":\"b**5\"},{\"starLevel\":4,\"remarkTime\":\"2013-03-07 01:51:01\",\"explainTime\":\"\",\"remarkContent\":\"评价方未及时做出评价，系统默认满意！\",\"tpLogoURL\":\"\",\"explainContent\":\"\",\"postMemberId\":\"b**7\"},{\"starLevel\":4,\"remarkTime\":\"2013-03-06 03:38:57\",\"explainTime\":\"\",\"remarkContent\":\"评价方未及时做出评价，系统默认满意！\",\"tpLogoURL\":\"\",\"explainContent\":\"\",\"postMemberId\":\"z**2\"},{\"starLevel\":4,\"remarkTime\":\"2013-03-06 03:17:33\",\"explainTime\":\"\",\"remarkContent\":\"评价方未及时做出评价，系统默认满意！\",\"tpLogoURL\":\"\",\"explainContent\":\"\",\"postMemberId\":\"b**2\"},{\"starLevel\":4,\"remarkTime\":\"2013-03-03 01:40:17\",\"explainTime\":\"\",\"remarkContent\":\"评价方未及时做出评价，系统默认满意！\",\"tpLogoURL\":\"\",\"explainContent\":\"\",\"postMemberId\":\"a**6\"},{\"starLevel\":4,\"remarkTime\":\"2013-03-01 02:41:31\",\"explainTime\":\"\",\"remarkContent\":\"评价方未及时做出评价，系统默认满意！\",\"tpLogoURL\":\"\",\"explainContent\":\"\",\"postMemberId\":\"b**4\"},{\"starLevel\":4,\"remarkTime\":\"2013-02-28 03:20:45\",\"explainTime\":\"\",\"remarkContent\":\"评价方未及时做出评价，系统默认满意！\",\"tpLogoURL\":\"\",\"explainContent\":\"\",\"postMemberId\":\"t**y\"},{\"starLevel\":4,\"remarkTime\":\"2013-02-27 07:21:48\",\"explainTime\":\"\",\"remarkContent\":\"评价方未及时做出评价，系统默认满意！\","
                + "\"tpLogoURL\":\""
                + "http://i04.c.aliimg.com/cms/upload/2012/186/684/486681_1232736939.png\",\"explainContent\":\"\",\"postMemberId\":\"y**f\"}],"
                + "\"statistics\":{\"star5\":59,\"star4\":38,\"star3\":2,\"star2\":1,\"star1\":0}},\"success\":true}";

        CommonJson<EvalutionProfile> re = CommonJson.fromJson(ps,
                EvalutionProfile.class);

        System.out.println(re.getData().getStatistics().getStar5());

        System.out.println(re.getData().getPageCount());

        System.out.println(re.getData().getList().get(0).getPostMemberId());

        CommonJson4List<Evalution> cjl = new CommonJson4List<Evalution>();

        cjl.setSuccess(Boolean.TRUE);
        cjl.setData(le);

        System.out.println("###" + cjl.toJson(Evalution.class));

        String sList = "{\"data\":[{\"starLevel\":4,\"remarkCotnent\":\"评价方未及时做出评价，系统默认满意！\",\"remarkTime\":\"2013-02-27 07:21:48\",\"explainContent\":\"\",\"postMemberId\":\"y**f\",\"tpLogoURL\":\"http://i04.c.aliimg.com/cms/upload/2012/186/684/486681_1232736939.png\"},{\"starLevel\":4,\"remarkCotnent\":\"评价方未及时做出评价，系统默认满意！\",\"remarkTime\":\"2013-02-27 07:21:48\",\"explainContent\":\"\",\"postMemberId\":\"y**f\",\"tpLogoURL\":\"http://i04.c.aliimg.com/cms/upload/2012/186/684/486681_1232736939.png\"}],\"success\":true}";

        CommonJson4List<Evalution> cjle = CommonJson4List.fromJson(sList,
                Evalution.class);

        System.out.println("***"
                + cjle.getData().get(0).getPostMemberId());

    }
}

执行结果如下：

{"success":true,"data":{"averageStarLevel":4.7,"remarkCount":10}}
true
4.7
{"success":true,"data":{"page":10,"pageCount":29,"list":[{"starLevel":4,"remarkCotnent":"评价方未及时做出评价，系统默认满意！","remarkTime":"2013-02-27 07:21:48","explainContent":"","postMemberId":"y**f","tpLogoURL":"http://i04.c.aliimg.com/cms/upload/2012/186/684/486681_1232736939.png"},{"starLevel":4,"remarkCotnent":"评价方未及时做出评价，系统默认满意！","remarkTime":"2013-02-27 07:21:48","explainContent":"","postMemberId":"y**f","tpLogoURL":"http://i04.c.aliimg.com/cms/upload/2012/186/684/486681_1232736939.png"}],"statistics":{"star5":20,"star4":40,"star3":30,"star2":10,"star1":0}}}
59
29
b**6
{"success":true,"data":[{"starLevel":4,"remarkCotnent":"评价方未及时做出评价，系统默认满意！","remarkTime":"2013-02-27 07:21:48","explainContent":"","postMemberId":"y**f","tpLogoURL":"http://i04.c.aliimg.com/cms/upload/2012/186/684/486681_1232736939.png"},{"starLevel":4,"remarkCotnent":"评价方未及时做出评价，系统默认满意！","remarkTime":"2013-02-27 07:21:48","explainContent":"","postMemberId":"y**f","tpLogoURL":"http://i04.c.aliimg.com/cms/upload/2012/186/684/486681_1232736939.png"}]}
y**f

Ps：文中说到Gson对泛型的支持不足，其实是不正确的，Gson对泛型做了以下支持：

public static CommonJson4List fromJson(String json, Class clazz) {
        Gson gson = new Gson();
        Type objectType = new TypeToken<CommonJson4List<clazz>>() {}.getType();
        return gson.fromJson(json, objectType);
    }  

只需将获取类型的泛型类作为TypeToken的泛型参数构造一个匿名的子类，就可以通过getType方法获取一个parameterized类型，结果与type方法一致。