用Gson解析单个json条目到多个对象 [英] Parsing single json entry to multiple objects with Gson
问题描述
我有一个json响应，如下所示：
{
id：001，
name：Name，
param_distance：10，
param_sampling：2
}
我有两个类：Teste和Parameters
public class Test {
private int id;
私人字符串名称;
private参数params;
}
public class Parameters {
private double distance;
private int sampling;
$ / code> 我的问题是：有没有办法让Gson明白一些json属性应该去参数类，或者唯一的方法是手动解析这个？
编辑
好吧，只是为了让我在@MyO的回答中的评论更具可读性：
我将一个对象列表添加到json输出中，所以json响应应该看起来像像这样：
{
id：001，
name：Name ，
param_distance：10，
param_sampling：2，
events：[
{
id：01 ，
value：22.5
}，
{
id：02，
value：31.0
}
]
}
Deserializer类看起来像这样：
public class TestDeserializer实现了JsonDeserializer< Test> {
@Override
public Test反序列化（JsonElement json，Type类型，
JsonDeserializationContext上下文）throws JsonParseException {
JsonObject obj = json.getAsJsonObject（）;
Test test = new Test（）;
test.setId（obj.get（id）。getAsInt（））;
test.setName（obj.get（name）。getAsString（））;
参数params = new Parameters（）;
params.setDistance（obj.get（param_distance）。getAsDouble（））;
params.setSampling（obj.get（param_sampling）。getAsInt（））;
test.setParameters（params）;
Gson eventGson = new Gson（）;
Type eventsType = new TypeToken< List< Event>>（）{}。getType（）;
列表< Event> eventList = eventGson.fromJson（obj.get（events），eventsType）;
test.setEvents（eventList）;
return test;
code $
$ b 并做：
GsonBuilder gBuilder = new GsonBuilder（）;
gBuilder.registerTypeAdapter（Test.class，new TestDeserializer（））;
Gson gson = gBuilder.create（）;
Test test = gson.fromJson（reader，Test.class）;
以我想要的方式为我提供测试对象。
解决方案使Gson明白它的方法是通过创建 TypeAdapter来编写自定义反序列化程序为你的 Test 类。您可以在 Gson用户指南 。它不完全是一个手动解析，但它没有什么不同，因为你必须告诉Gson如何处理每个JSON值......
它应该是这样的： private class TestDeserializer实现JsonDeserializer< Test> {
public Test deserialize（JsonElement json，Type typeOfT，JsonDeserializationContext context）
throws JsonParseException {
JsonObject obj = json.getAsJsonObject（）;
int id = obj.get（id）。getAsInt（）;
String name = obj.get（name）。getAsString（）;
double distance = obj.get（param_distance）。getAsDouble（）;
int sampling = obj.get（param_sampling）。getAsInt（）;
//假设你有合适的构造函数...
Test test = new Test（id，name，new Parameters（distance，sampling））;
return test;
然后你必须注册 TypeAdapter with：
GsonBuilder gson = new GsonBuilder（）;
gson.registerTypeAdapter（Test.class，new TestDeserializer（））;
最后，您只需像往常一样解析JSON即可：
gson.fromJson（yourJsonString，Test.class）;
Gson会自动使用您的自定义反序列化器将您的JSON解析到 Test class。
I have a json response that looks like this:
{
"id":"001",
"name":"Name",
"param_distance":"10",
"param_sampling":"2"
}
And I have two classes: Teste and Parameters
public class Test {
private int id;
private String name;
private Parameters params;
}
public class Parameters {
private double distance;
private int sampling;
}
My question is: is there a way to make Gson understand that some of the json attributes should go to the Parameters class, or the only way is to "manually" parse this ?
EDIT
Well, just to make my comment in @MikO's answer more readable:
I'll add a list of an object to the json output, so json response should look like this:
{
"id":"001",
"name":"Name",
"param_distance":"10",
"param_sampling":"2",
"events":[
{
"id":"01",
"value":"22.5"
},
{
"id":"02",
"value":"31.0"
}
]
}
And the Deserializer class would look like this:
public class TestDeserializer implements JsonDeserializer<Test> {
@Override
public Test deserialize(JsonElement json, Type type,
JsonDeserializationContext context) throws JsonParseException {
JsonObject obj = json.getAsJsonObject();
Test test = new Test();
test.setId(obj.get("id").getAsInt());
test.setName(obj.get("name").getAsString());
Parameters params = new Parameters();
params.setDistance(obj.get("param_distance").getAsDouble());
params.setSampling(obj.get("param_sampling").getAsInt());
test.setParameters(params);
Gson eventGson = new Gson();
Type eventsType = new TypeToken<List<Event>>(){}.getType();
List<Event> eventList = eventGson.fromJson(obj.get("events"), eventsType);
test.setEvents(eventList);
return test;
}
}
And doing:
GsonBuilder gBuilder = new GsonBuilder();
gBuilder.registerTypeAdapter(Test.class, new TestDeserializer());
Gson gson = gBuilder.create();
Test test = gson.fromJson(reader, Test.class);
Gives me the test object the way I wanted.
解决方案 The way to make Gson understand it is to write a custom deserializer by creating a TypeAdapter for your Test class. You can find information in Gson's User Guide. It is not exactly a manual parsing, but it is not that different, since you have to tell Gson how to deal with each JSON value...
It should be something like this:
private class TestDeserializer implements JsonDeserializer<Test> {
public Test deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
throws JsonParseException {
JsonObject obj = json.getAsJsonObject();
int id = obj.get("id").getAsInt();
String name = obj.get("name").getAsString();
double distance = obj.get("param_distance").getAsDouble();
int sampling = obj.get("param_sampling").getAsInt();
//assuming you have suitable constructors...
Test test = new Test(id, name, new Parameters(distance, sampling));
return test;
}
}
Then you have to register the TypeAdapter with:
GsonBuilder gson = new GsonBuilder();
gson.registerTypeAdapter(Test.class, new TestDeserializer());
And finally you just have to parse your JSON as usual, with:
gson.fromJson(yourJsonString, Test.class);
Gson will automatically use your custom deserializer to parse your JSON into your Test class.
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