Gson使用泛型解析
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Gson是Google开发出来的一个快捷解析JSON的工具包，避免了传统的JSONArray、JSONObject的繁琐代码解析，使得程序开发对JSON的解析加快了。
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：
＃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"}]}
通过分析以上 3种约定的JSON返回格式：
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：
{"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：
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}}}
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：
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