如何在Gson中序列化List对象 [英] How to serialize List object in Gson
问题描述
我使用以下方法从数据库返回了数据(方法来自 spark-java框架 ):
get("/data_on_page_load", "application/json", (Request request, Response response) -> {
List<Post> list = Post.findAll(); // NEED TO SERIALIZE THE RESPONSE
System.out.println("list is " + list);
return (list);
}, new JsonTransformer());
从数据库返回的数据:
[Model: com.soul.seeker.models.Post, table: 'post', attributes: {created_at=2017-03-26 04:06:35.0, details=aaa, id=36, title=Eventsa, url=eventsa, userImage=assets/img/spiritual-icon4.png, username=null}]
Post.findAll(); 是 http:中的方法: //javalite.io/record_selection#finding-all-records 来获取所有记录
Model: com.soul.seeker.models.Post
是下面的POJO类:
public class Post extends Model{
private String title;
private String details;
private String username;
private String userImage;
private String url;
private List categories;
//Getters and Setters removed for brevity
}
我正在尝试使用GSON TypeToken 和 TypeAdapter >
ClassTypeAdapterFactory:
public class ClassTypeAdapterFactory implements TypeAdapterFactory {
@Override
public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> typeToken) {
if(!Class.class.isAssignableFrom(typeToken.getRawType())) {
return null;
}
return (TypeAdapter<T>) new ClassTypeAdapter();
}
}
ClassTypeAdapter:
public class ClassTypeAdapter extends TypeAdapter<Class<?>> {
@Override
public void write(JsonWriter jsonWriter, Class<?> clazz) throws IOException {
if(clazz == null){
jsonWriter.nullValue();
return;
}
jsonWriter.value(clazz.getName());
}
@Override
public Class<?> read(JsonReader jsonReader) throws IOException {
if (jsonReader.peek() == JsonToken.NULL) {
jsonReader.nextNull();
return null;
}
Class<?> clazz = null;
try {
clazz = Class.forName(jsonReader.nextString());
} catch (ClassNotFoundException ex) {
ex.printStackTrace();
}
return clazz;
}
}
这里我正在使用JsonTransformer
,它从 spark-java ResponseTransformer接口
public class JsonTransformer implements ResponseTransformer {
private Gson gson = new Gson();
@Override
public String render(Object model) {
GsonBuilder gsonBuilder = new GsonBuilder();
gson = gsonBuilder.registerTypeAdapterFactory(new ClassTypeAdapterFactory()).create();
return gson.toJson(model);
}
}
现在的问题是输出的json还包含序列化类,而不是仅返回pojo类的List对象.我是Java&的新手. Gson序列化.
请问有人可以帮助实现TypeAdapter只返回List对象吗?例如这样的例子:
Type listOfTestObject = new TypeToken<List<TestObject>>(){}.getType();
String s = gson.toJson(list, listOfTestObject);
List<TestObject> list2 = gson.fromJson(s, listOfTestObject);
我认为您无需键入Response Transformer,您可以像在 I have data returned from DB using the below method (method from spark-java framework) below: Data returned from DB: Where Post.findAll(); is method from http://javalite.io/record_selection#finding-all-records to get all records I am trying to serialize the out put using GSON TypeToken and TypeAdapter ClassTypeAdapterFactory: ClassTypeAdapter: Here I am using Now the problem is the json out put also contains serialized class instead of only returning List object of pojo class. I am new to Java & Gson serialization. Can any one please help in implementing TypeAdapter to return only List object? for Example like this:
I think that you won't need to type a Response Transformer, you can use a new Gson object directly like the last snippet at the response transformer documentation. It would end up like this:
这篇关于如何在Gson中序列化List对象的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!get("/data_on_page_load", "application/json", (Request request, Response response) -> {
List<Post> list = Post.findAll(); // NEED TO SERIALIZE THE RESPONSE
System.out.println("list is " + list);
return (list);
}, new JsonTransformer());
[Model: com.soul.seeker.models.Post, table: 'post', attributes: {created_at=2017-03-26 04:06:35.0, details=aaa, id=36, title=Eventsa, url=eventsa, userImage=assets/img/spiritual-icon4.png, username=null}]
Model: com.soul.seeker.models.Post
is the POJO class below:public class Post extends Model{
private String title;
private String details;
private String username;
private String userImage;
private String url;
private List categories;
//Getters and Setters removed for brevity
}
public class ClassTypeAdapterFactory implements TypeAdapterFactory {
@Override
public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> typeToken) {
if(!Class.class.isAssignableFrom(typeToken.getRawType())) {
return null;
}
return (TypeAdapter<T>) new ClassTypeAdapter();
}
}
public class ClassTypeAdapter extends TypeAdapter<Class<?>> {
@Override
public void write(JsonWriter jsonWriter, Class<?> clazz) throws IOException {
if(clazz == null){
jsonWriter.nullValue();
return;
}
jsonWriter.value(clazz.getName());
}
@Override
public Class<?> read(JsonReader jsonReader) throws IOException {
if (jsonReader.peek() == JsonToken.NULL) {
jsonReader.nextNull();
return null;
}
Class<?> clazz = null;
try {
clazz = Class.forName(jsonReader.nextString());
} catch (ClassNotFoundException ex) {
ex.printStackTrace();
}
return clazz;
}
}
JsonTransformer
which implements ResponseTransformer
from spark-java ResponseTransformer interfacepublic class JsonTransformer implements ResponseTransformer {
private Gson gson = new Gson();
@Override
public String render(Object model) {
GsonBuilder gsonBuilder = new GsonBuilder();
gson = gsonBuilder.registerTypeAdapterFactory(new ClassTypeAdapterFactory()).create();
return gson.toJson(model);
}
}
Type listOfTestObject = new TypeToken<List<TestObject>>(){}.getType();
String s = gson.toJson(list, listOfTestObject);
List<TestObject> list2 = gson.fromJson(s, listOfTestObject);
get("/data_on_page_load", (req, res) -> {
res.type("application/json; charset=UTF-8");
List<Post> list = Post.findAll();
System.out.println("list is " + list);
return list;
}, new Gson()::toJson);