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Elizaveta
Asked:2022-02-04 22:19:19 +0000 UTC2022-02-04 22:19:19 +0000 UTC

Gson + List<> 如何序列化层次结构

  • 772

我有以下层次结构：

产品：

import com.google.gson.annotations.Expose;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.io.Serializable;
import java.util.Objects;
import java.util.concurrent.atomic.AtomicLong;

@Data
@NoArgsConstructor
public class Product implements Serializable {

    private static final AtomicLong counter = new AtomicLong(1L);

    @Expose
    private long id;

    @Expose
    private String name;

    @Expose
    private long priceInCents;

    @Expose
    private int rate;

    public Product(String name, long priceInCents, int rate) {

        this.id = counter.getAndIncrement();

        this.name = name;
        this.priceInCents = priceInCents;
        this.rate = rate;
    }

    public Product(long id, String name, long priceInCents, int rate) {
        this.id = id;
        this.name = name;
        this.priceInCents = priceInCents;
        this.rate = rate;
    }

    public Product(long id) {
        this.id = id;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Product product = (Product) o;
        return id == product.id;
    }

    @Override
    public int hashCode() {
        return Objects.hash(id);
    }
}

产品类别：

import coherentsolutions.nastyabakhshieva.model.products.Product;
import com.google.gson.annotations.Expose;
import lombok.Data;

import java.io.Serializable;
import java.util.List;
import java.util.Objects;
import java.util.concurrent.atomic.AtomicLong;

@Data
public abstract class Category implements Serializable {

    private static final AtomicLong counter = new AtomicLong(1L);

    @Expose
    protected long id;

    @Expose
    protected String title;

    @Expose
    protected List<Product> products;

    public Category(long id) {
        this.id = id;
    }

    public Category() {
        this.id = counter.getAndIncrement();
    }

    @Override
    public String toString() {
        return "Category{" +
                "title='" + title + '\'' +
                ", products=" + products +
                '}';
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Category category = (Category) o;
        return id == category.id;
    }

    @Override
    public int hashCode() {
        return Objects.hash(id);
    }
}

还有一个包含所有类别的目录：

@Data
@AllArgsConstructor
@NoArgsConstructor
public class Catalog implements Serializable {

    private List<Category> categories;

}

我知道可以为列表获取适配器 ---> Type itemsListType = new TypeToken<List<GoodsItem>>() {}.getType();，但我的情况并不完全相同（请帮助，我该如何发送？

我也尝试通过方法简单地序列化，gson.toJson(catalog)但这来到了前面{}

java

2 个回答

  1. Best Answer

    您的 Catalog 类中没有 Expose 注释。因此，Json 是空的，因为。您已明确阻止在没有此注释的情况下对字段进行序列化。有必要删除此禁令或添加注释

    • 1

  2. 结果比我想象的要容易 - 我只需要在文档中爬一点。希望它可以帮助某人！）

    import coherentsolutions.nastyabakhshieva.model.catalog.Catalog;
import coherentsolutions.nastyabakhshieva.model.categories.Category;
import com.google.gson.TypeAdapter;
import com.google.gson.stream.JsonReader;
import com.google.gson.stream.JsonWriter;
import lombok.extern.slf4j.Slf4j;

import java.io.IOException;

@Slf4j
public class CatalogTypeAdapter extends TypeAdapter<Catalog> {

    @Override
    public void write(JsonWriter jsonWriter, Catalog catalog) throws IOException {
        jsonWriter.beginObject();
        jsonWriter.name("categories");
        jsonWriter.beginArray();

        for (Category category : catalog.getCategories()) {
            jsonWriter.beginObject();
            jsonWriter.name("id");
            jsonWriter.value(category.getId());
            jsonWriter.name("title");
            jsonWriter.value(category.getTitle());
            jsonWriter.name("products");

            jsonWriter.beginArray();
            category.getProducts().forEach(product -> {
                try {
                    jsonWriter.beginObject();

                    jsonWriter.name("id");
                    jsonWriter.value(product.getId());
                    jsonWriter.name("name");
                    jsonWriter.value(product.getName());
                    jsonWriter.name("price in cents");
                    jsonWriter.value(product.getPriceInCents());
                    jsonWriter.name("rate");
                    jsonWriter.value(product.getRate());

                    jsonWriter.endObject();

                } catch (IOException e) {
                    log.error("IN write - {}", e.getMessage());
                }
            });
            jsonWriter.endArray();

            jsonWriter.endObject();
        }

        jsonWriter.endArray();
        jsonWriter.endObject();
    }

    @Override
    public Catalog read(JsonReader jsonReader) throws IOException {
        //do nothing
        return null;
    }
}

    控制台输出：

    {
  "categories": [
    {
      "id": 1,
      "title": "Clothes category",
      "products": [
        {
          "id": 1,
          "name": "Sweater",
          "price in cents": 65458,
          "rate": 45
        },
        {
          "id": 2,
          "name": "Jacket",
          "price in cents": 11111,
          "rate": 89
        },
        {
          "id": 3,
          "name": "Coat",
          "price in cents": 9999,
          "rate": 36
        },
        {
          "id": 4,
          "name": "Vest",
          "price in cents": 1200,
          "rate": 68
        },
        {
          "id": 5,
          "name": "Shorts",
          "price in cents": 45000,
          "rate": 90
        },
        {
          "id": 6,
          "name": "Casual dress",
          "price in cents": 36500,
          "rate": 79
        }
      ]
    },
    {
      "id": 2,
      "title": "Food category",
      "products": [
        {
          "id": 7,
          "name": "Meet",
          "price in cents": 2132,
          "rate": 100
        },
        {
          "id": 8,
          "name": "Cookies",
          "price in cents": 1111,
          "rate": 90
        },
        {
          "id": 9,
          "name": "Bread",
          "price in cents": 777,
          "rate": 85
        },
        {
          "id": 10,
          "name": "Apples",
          "price in cents": 454,
          "rate": 32
        },
        {
          "id": 11,
          "name": "Ice cream",
          "price in cents": 873,
          "rate": 79
        }
      ]
    },
    {
      "id": 3,
      "title": "Toys category",
      "products": [
        {
          "id": 13,
          "name": "Barbie",
          "price in cents": 12345,
          "rate": 80
        },
        {
          "id": 14,
          "name": "Cycle",
          "price in cents": 65432,
          "rate": 90
        },
        {
          "id": 15,
          "name": "Lorry",
          "price in cents": 10000,
          "rate": 55
        },
        {
          "id": 16,
          "name": "Little hare",
          "price in cents": 6400,
          "rate": 97
        },
        {
          "id": 17,
          "name": "Bricks",
          "price in cents": 1500,
          "rate": 100
        },
        {
          "id": 18,
          "name": "Rocking horse",
          "price in cents": 10999,
          "rate": 10
        }
      ]
    }
  ]
}
    • 0

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