Springboot-单体JSON对象的处理

2021-02-20 MarsHu springboot springboot

---

• json字符格式字段数据返回内容
• 单体JSON对象的映射
• 数组类型JSON与List的映射
• 自定义方法实现JSON到对象之间的转换

json字符格式字段数据返回内容

观察数据库表sku,字段specs的格式为json类型,值格式为如下内容:

[{"key": "颜色", "value": "青蓝色", "key_id": 1, "value_id": 1}, {"key": "尺寸", "value": "7英寸", "key_id": 2, "value_id": 5}]

我们可以观察得出,其值为json格式数组,并且每个元素应该代表一个json对象。我们在Sku实体中是以private String specs;形式去接收的。

当我们访问请求localhost:8080/v1/spu/id/28/detail,因为我们在Spu中设置了关联关系,所以得到如下有关skuList结果片段:

        {
            "id": 43,
            "price": 999.00,
            "discount_price": null,
            "online": true,
            "img": "http://xxx.xxx.xxx/7c462cf2-3874-4ecc-85f9-6b4a0fde4623.png",
            "title": "Ins复古金色落地灯（落地灯）",
            "spu_id": 28,
            "specs": "[{\"key\": \"颜色\", \"value\": \"金色\", \"key_id\": 1, \"value_id\": 27}, {\"key\": \"台灯高低\", \"value\": \"落地灯\", \"key_id\": 8, \"value_id\": 38}]",
            "code": "28$1-27#8-38",
            "stock": 19,
            "category_id": 23,
            "root_category_id": 4
        }

在上面的返回结果中,我们可以看到,我们当前的Sku类的specs字段是以如下形式返回的。该返回结果并不利于实际观察

"specs": "[{\"key\": \"颜色\", \"value\": \"金色\", \"key_id\": 1, \"value_id\": 27}, {\"key\": \"台灯高低\", \"value\": \"落地灯\", \"key_id\": 8, \"value_id\": 38}]",

我们我们实际上是希望该字段能以对象的形式返回结果,Spec类如下,Spec对象对应json数组中每个元素表示的json对象。

package com.zhqx.missyou.model;

import lombok.Getter;
import lombok.Setter;

@Getter
@Setter
public class Spec {
    private Long keyId;
    private String key;
    private Long valueId;
    private String value;
}

为了便于更好的观察单一json字符串与Spec对象的封装转化,我们可以在Sku表中新增一个字段test,字段数据类型为json,并且将第一条数据specs字段的其中一个json对象填入字段内容。

{"key": "颜色", "value": "青蓝色", "key_id": 1, "value_id": 1}

同时,我们修改Sku类,以Map<String, Object> test来接收test字段内容:

package com.zhqx.missyou.model;

import lombok.Getter;
import lombok.Setter;

import javax.persistence.Entity;
import javax.persistence.Id;
import java.math.BigDecimal;
import java.util.Map;

@Getter
@Setter
@Entity
public class Sku extends BaseEntity {
    @Id
    private Long id;
    private BigDecimal price;
    private BigDecimal discountPrice;
    private Boolean online;
    private String img;
    private String title;
    private Long spuId;

    private String specs;
    private Map<String, Object> test;
    private String code;
    private Long stock;
    private Long categoryId;
    private Long rootCategoryId;

}

修改号后,我们会发现代码出错,这是因为我们还没有进行自定义处理,JPA没有办法自动将json数据封装到对象。

单体JSON对象的映射

默认的JPA封装没有办法处理json对象到Map<String, Object>的处理,所以我们需要自定义处理方法MapAndJson.

package com.zhqx.missyou.util;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.zhqx.missyou.exception.http.ServerErrorException;
import org.springframework.beans.factory.annotation.Autowired;

import javax.persistence.AttributeConverter;
import javax.persistence.Converter;
import java.util.HashMap;
import java.util.Map;

@Converter
public class MapAndJson implements AttributeConverter<Map<String, Object>, String> {

    @Autowired
    private ObjectMapper mapper;

    @Override
    public String convertToDatabaseColumn(Map<String, Object> stringObjectMap) {
        try {
            return mapper.writeValueAsString(stringObjectMap);
        } catch (JsonProcessingException e) {
            e.printStackTrace();
            throw new ServerErrorException(9999);
        }
    }

    @Override
    public Map<String, Object> convertToEntityAttribute(String s) {
        try {
            return mapper.readValue(s, HashMap.class);
        } catch (JsonProcessingException e) {
            e.printStackTrace();
            throw new ServerErrorException(9999);
        }
    }
}

ServerErrorException类:

package com.zhqx.missyou.exception.http;

public class ServerErrorException extends HttpException {
    public ServerErrorException(int code) {
        this.code = code;
        this.httpStatusCode = 500;
    }
}

exception-code.properties配置类中配置ServerErrorException异常对应的信息

zhqx.codes[9999] = 服务器未知异常O(∩_∩)O哈哈~

zhqx.codes[10000]= 通用异常
zhqx.codes[10001]= 通用参数异常

zhqx.codes[30003]= 商品信息不存在
zhqx.codes[30006]= Spu类的资源不存在

在Sku类中指定转换方法:

package com.zhqx.missyou.model;

import com.zhqx.missyou.util.MapAndJson;
import lombok.Getter;
import lombok.Setter;

import javax.persistence.Convert;
import javax.persistence.Entity;
import javax.persistence.Id;
import java.math.BigDecimal;
import java.util.Map;

@Getter
@Setter
@Entity
public class Sku extends BaseEntity {
    @Id
    private Long id;
    private BigDecimal price;
    private BigDecimal discountPrice;
    private Boolean online;
    private String img;
    private String title;
    private Long spuId;

    private String specs;
    @Convert(converter = MapAndJson.class)
    private Map<String, Object> test;
    private String code;
    private Long stock;
    private Long categoryId;
    private Long rootCategoryId;

}

由于我们修改的Sku数据的spu对应的id为1,所以访问:localhost:8080/v1/spu/id/1/detail,的到如下结果:

{
    "id": 1,
    "title": "青锋大碗",
    "subtitle": "大碗主要用来盛宽面，凡凡倾情推荐",
    "category_id": 28,
    "root_category_id": 27,
    "online": true,
    "price": "12.99",
    "sketch_spec_id": 1,
    "default_sku_id": null,
    "img": "http://xxx.xxx.xxx/32ba82d0-4fbe-4bbb-b833-fdc8d397bb34.png",
    "discount_price": "11.11",
    "description": null,
    "tags": "林白推荐",
    "is_test": true,
    "for_theme_img": "http://xxx.xxx.xxx/c38dd758-e07a-46d4-a1be-3a4601f886f9.png",
    "sku_list"
}{
    "code": 9999,
    "message": "服务器异常",
    "request": "GET /v1/spu/id/1/detail"
}

在当前Spu的private List skuList;属性使用的是懒加载模式,即程序用到skuList时,才会查询结果。在Springboot2.5.2中,会出现如上结果,如果改为Springboot2.2.2,则只会出现如下结果

{
    "code": 9999,
    "message": "服务器异常",
    "request": "GET /v1/spu/id/1/detail"
}

或者对Spu类中采取热加载模式时

@OneToMany(fetch = FetchType.EAGER)
@JoinColumn(name = "spuId")
private List<Sku> skuList;

也只会出现如下结果:

{
    "code": 9999,
    "message": "服务器异常",
    "request": "GET /v1/spu/id/1/detail"
}

备注:在Springboot2.3.2(不包括)以后的版本中,应该做了相关返回数据的改动,导致统一异常处理没能拦截到全部数据。

这所以会出现这样的错误,是因为数据库中的数据没有补全,我们将Sku表中Spu的id与第一条相同的sku数据的test字段填充上内容。

修改正常后,我们再次访问时,可以看到对应数据格式片段如下:

"test": {
            "key_id": 1,
            "value_id": 1,
            "value": "青蓝色",
            "key": "颜色"
        },

数组类型JSON与List的映射

自定义处理方法ListAndJson.

package com.zhqx.missyou.util;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.zhqx.missyou.exception.http.ServerErrorException;
import org.springframework.beans.factory.annotation.Autowired;

import javax.persistence.AttributeConverter;
import javax.persistence.Converter;
import java.util.List;

@Converter
public class ListAndJson implements AttributeConverter<List<Object>, String> {
    @Autowired
    private ObjectMapper mapper;

    @Override
    public String convertToDatabaseColumn(List<Object> objects) {
        try {
            return mapper.writeValueAsString(objects);
        } catch (JsonProcessingException e) {
            e.printStackTrace();
            throw new ServerErrorException(9999);
        }
    }

    @Override
    public List<Object> convertToEntityAttribute(String s) {
        try {
            if(s == null){
                return null;
            }
            List<Object> t = mapper.readValue(s, List.class);
            return t;
        } catch (Exception e) {
            e.printStackTrace();
            throw new ServerErrorException(9999);
        }
    }
}

修改Sku类:

@Convert(converter = ListAndJson.class)
private List<Object> specs;

再次访问上面的请求地址,可以得到如下的代码片段:

"specs": [
            {
                "key": "颜色",
                "value": "青蓝色",
                "key_id": 1,
                "value_id": 1
            },
            {
                "key": "尺寸",
                "value": "7英寸",
                "key_id": 2,
                "value_id": 5
            }
        ],

自定义方法实现JSON到对象之间的转换

自定义通用转化工具类GenericAndJson:

package com.zhqx.missyou.util;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.zhqx.missyou.exception.http.ServerErrorException;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

@Component
public class GenericAndJson {
    private static ObjectMapper mapper;

    @Autowired
    public void setMapper(ObjectMapper mapper) {
        GenericAndJson.mapper = mapper;
    }

    public static <T> String objectToJson(T o) {
        try {
            return GenericAndJson.mapper.writeValueAsString(o);
        } catch (Exception e) {
            e.printStackTrace();
            throw new ServerErrorException(9999);
        }
    }

    public static <T> T jsonToObject(String s,  TypeReference<T> tr) {
        if (s == null) {
            return null;
        }
        try {
            T o = GenericAndJson.mapper.readValue(s, tr);
            return o;
        } catch (JsonProcessingException e) {
            e.printStackTrace();
            throw new ServerErrorException(9999);
        }
    }
}

修改实体的setter和getter方法:

package com.zhqx.missyou.model;

import com.fasterxml.jackson.core.type.TypeReference;
import com.zhqx.missyou.util.GenericAndJson;
import lombok.Getter;
import lombok.Setter;

import javax.persistence.Entity;
import javax.persistence.Id;
import java.math.BigDecimal;
import java.util.Collections;
import java.util.List;

@Getter
@Setter
@Entity
public class Sku extends BaseEntity {
    @Id
    private Long id;
    private BigDecimal price;
    private BigDecimal discountPrice;
    private Boolean online;
    private String img;
    private String title;
    private Long spuId;
    private String specs;
    private String code;
    private Long stock;
    private Long categoryId;
    private Long rootCategoryId;

    public List<Spec> getSpecs() {
        if (this.specs == null) {
            return Collections.emptyList();
        }
        return GenericAndJson.jsonToObject(this.specs, new TypeReference<List<Spec>>(){});
    }

    public void setSpecs(List<Spec> specs) {
        if(specs.isEmpty()){
            return;
        }
        this.specs = GenericAndJson.objectToJson(specs);
    }

}

原文链接: https://marshucheng1.github.io/2021/02/20/springboot-qiyue-6/

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