Gson無法反序列化List <Serializable>

Question

我試圖將從服務器獲取的JSON反序列化爲其原始POJO表單。我知道原始對象（我有服務器代碼的來源），但似乎我錯過了一些東西。

這裏是最小的代碼示例我可以組裝，說明我的問題：

package mycompany.mypackage; 
import java.io.Serializable; 
import java.lang.reflect.Type; 
import java.util.ArrayList; 
import java.util.List; 
import com.google.gson.Gson; 
import com.google.gson.GsonBuilder; 
import com.google.gson.InstanceCreator; 

public class GsonSerializeTest { 

    /* main method to illustrate the problem */ 
    public static void main(String[] args) { 
     Serializable[] identifiers= {"ITEM",12345678,"abc.def.ghijkl.mnopqr",87654321}; 
     EntityUid uid = new GsonSerializeTest().new EntityUid(identifiers); 
     Gson converter = new GsonBuilder().registerTypeAdapter(Serializable.class, new GsonSerializeTest().new SerializableInstanceCreator()).create(); 
     String json = converter.toJson(uid); 
     System.out.println("Converted to string: " + json); 
     EntityUid uid2 = converter.fromJson(json, EntityUid.class); // ERROR 
     System.out.println("Converted back to object: " + uid2); 
    } 

    /* the POJO that gets serialized and fails while deserializing */ 
    public class EntityUid implements Serializable { 
     private final List<Serializable> identifier = new ArrayList<Serializable>(); 

     public EntityUid(final Serializable... identifier) { 
      for (Serializable partialIdentifier : identifier) { 
       this.identifier.add(partialIdentifier); 
      } 
     } 
    } 

    /* Class for generating Serializable instances */ 
    public class SerializableInstanceCreator implements InstanceCreator<Serializable> { 
     public Serializable createInstance(Type arg0) { 
      return new String(); 
     } 
    } 
} 

這準備EntityUid對象，將其序列（就像服務器一樣）變成這樣：

Converted to string: {"identifier":["ITEM",12345678,"abc.def.ghijkl.mnopqr",87654321]} 

然後嘗試將其反序列化爲原始對象，但是會失敗，如下所示：

Exception in thread "main" com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was STRING at line 1 column 17 
    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:176) 
    at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.read(TypeAdapterRuntimeTypeWrapper.java:40) 
    at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:81) 
    at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:60) 
    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.read(ReflectiveTypeAdapterFactory.java:93) 
    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:172) 
    at com.google.gson.Gson.fromJson(Gson.java:803) 
    at com.google.gson.Gson.fromJson(Gson.java:768) 
    at com.google.gson.Gson.fromJson(Gson.java:717) 
    at com.google.gson.Gson.fromJson(Gson.java:689) 
    at mycompany.mypackage.GsonSerializeTest.main(GsonSerializeTest.java:19) 
Caused by: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was STRING at line 1 column 17 
    at com.google.gson.stream.JsonReader.beginObject(JsonReader.java:374) 
    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:165) 
    ... 10 more 

請問有人請給我一個指示，指出我可能錯過了什麼？提前感謝！

Answer 1

請閱讀Serializing and Deserializing Collection with Objects of Arbitrary Types。

下面的代碼可以工作。

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

import com.google.gson.Gson; 
import com.google.gson.GsonBuilder; 

public class GsonSerializeTest { 

    /* main method to illustrate the problem */ 
    public static void main(String[] args) { 
     Object[] identifiers= {12345678,"ITEM","abc.def.ghijkl.mnopqr",87654321}; 
     EntityUid uid = new EntityUid(identifiers); 
     Gson converter = new GsonBuilder().create(); 
     String json = converter.toJson(uid); 
     System.out.println("Converted to string: " + json); 
     EntityUid uid2 = converter.fromJson(json, EntityUid.class); // ERROR 
     System.out.println("Converted back to object: " + uid2); 
    } 

    /* the POJO that gets serialized and fails while deserializing */ 
    public static class EntityUid { 
     private final List<Object> identifier = new ArrayList<Object>(); 

     public EntityUid(final Object... identifier) { 
      for (Object partialIdentifier : identifier) { 
       this.identifier.add(partialIdentifier); 
      } 
     } 

     @Override 
     public String toString() { 
      return "EntityUid [identifier=" + identifier + "]"; 
     } 


    } 
}