使用gson将嵌套的Java对象与json相互转换 [英] Translating nested Java objects to/from json using gson

问题描述

假设我们有以下两个Java类(省略其他类成员):

Let's assume we have the following two Java Classes (omitting the other class members):

class Book {
    private String name;
    private String[] tags;
    private int price;
    private Author author;
}

class Author {
    private String name;
}

此外，假设我们有以下json对象:

Furthermore, assume we have the following json object:

{"Book": {
    "name": "Bible",
    "price": 20,
    "tags": ["God", "Religion"],
    "writer": {
        "name": "Jesus"
    }
}

我正在尝试找到将Java Book实例转换为json并使用gson返回的最佳方法.为了使示例更有趣，请注意，在json中，我想使用"writer"而不是"Author".你能帮忙吗?理想情况下，我希望看到一个完整的实现.

I am trying to find the best way to convert a Java Book instance to json and back using gson. To make the example more interesting, note that in json, I want to use "writer" instead of "Author". Can you please help? Ideally, I would like to see a complete implementation.

推荐答案

感谢所有答案.我能够弄清楚并使用一些自定义的序列化器和反序列化器来实现它.这是我自己的解决方案:

Thanks for all the answers. I was able to figure it out and implement it using some custom serializer and deserializer. Here is my own solution:

public class JsonTranslator {
    private static Gson gson = null;

    public void test(Book book1) {
        JsonElement je = gson.toJson(book1);  // convert book1 to json
        Book book2 = gson.fromJson(je, Book.class); // convert json to book2
        // book1 and book2 should be equivalent
    }

    public JsonTranslator() {

        GsonBuilder builder = new GsonBuilder();
        builder.registerTypeAdapter(Book.class, new BookTrnaslator());
        builder.registerTypeAdapter(Author.class, new AuthorTrnaslator());
        builder.setPrettyPrinting();
        gson = builder.create();
    }


    private class BookTrnaslator implements JsonDeserializer<Book>, JsonSerializer<Book> {
        public Card deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {
            JsonObject jobj = json.getAsJsonObject();
            Book book = new Book();
            book.setName(jobj.get("name").getAsString());
            book.setTags(jobj.get("tags").getAsJsonArray()); //Assuming setTags(JsonArray ja) exists
            book.setName(jobj.get("price").getAsInt());
            book.setAuthor(gson.fromJson(jobj.get("writer"), Author.class));
            return book;
        }

       public JsonElement serialize(Book src, Type typeOfSrc, JsonSerializationContext context) {
            JsonObject jobj = new JsonObject();
            jobj.addProperty("name", src.getName());
            jobj.add("tags", src.getTagsAsJsonArray());
            jobj.addProperty("price", src.getPrice());
            jobj.add("writer", gson.toJson(src.getAuthor()));
            return jobj;
       }
    }

    private class AuthorTrnaslator implements JsonDeserializer<Author>, JsonSerializer<Author> {
        public Card deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {
            JsonObject jobj = json.getAsJsonObject();
            Author author = new Author();
            author.setName(jobj.get("name").getAsString());
            return author;
        }

       public JsonElement serialize(Author src, Type typeOfSrc, JsonSerializationContext context) {
            JsonObject jobj = new JsonObject();
            jobj.addProperty("name", src.getName());
            return jobj;
       }
    }
}

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