參考父對象反序列化使用GSON

Question

考慮下面的JSON一個JSON：

{ 
    "authors": [{ 
     "name": "Stephen King", 
     "books": [{ 
      "title": "Carrie" 
     }, { 
      "title": "The Shining" 
     }, { 
      "title": "Christine" 
     }, { 
      "title": "Pet Sematary" 
     }] 
    }] 
} 

這個對象結構：

public class Author { 
    private List<Book> books; 
    private String name; 
} 

public class Book { 
    private transient Author author; 
    private String title; 
} 

有沒有一種方法，使用谷歌的Java庫GSON，反序列化JSON並且書籍對象具有對「父」作者對象的引用？

是否有可能使用自定義解串器的而不使用？

• 如果是：如何？
• 如果否：是否仍然可以使用自定義解串器來做到這一點？

Answer 1

在這種情況下，我將實現父對象的自定義JsonDeserializer，並傳播Author信息，像這樣：

public class AuthorDeserializer implements JsonDeserializer<Author> { 
    @Override 
    public Author deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException { 
     final JsonObject authorObject = json.getAsJsonObject(); 

     Author author = new Author(); 
     author.name = authorObject.get("name").getAsString(); 

     Type booksListType = new TypeToken<List<Book>>(){}.getType(); 
     author.books = context.deserialize(authorObject.get("books"), booksListType); 

     for(Book book : author.books) { 
      book.author = author; 
     } 

     return author; 
    } 
} 

請注意，我的例子中省略了錯誤檢查。你會使用它，像這樣：

Gson gson = new GsonBuilder() 
    .registerTypeAdapter(Author.class, new AuthorDeserializer()) 
    .create(); 

要顯示它的工作，我脫下只是「作者」從你的例子關鍵JSON，讓我做到這一點：

JsonElement authorsJson = new JsonParser().parse(json).getAsJsonObject().get("authors"); 

Type authorList = new TypeToken<List<Author>>(){}.getType(); 
List<Author> authors = gson.fromJson(authorsJson, authorList); 
for(Author a : authors) { 
    System.out.println(a.name); 
    for(Book b : a.books) { 
     System.out.println("\t " + b.title + " by " + b.author.name); 
    } 
} 

打印了：

Stephen King 
    Carrie by Stephen King 
    The Shining by Stephen King 
    Christine by Stephen King 
    Pet Sematary by Stephen King