如何将数据库中json格式的列值映射到java对象的属性中
2020/3/7 8:02:19
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前言
mysql5.7版本之后,列值的类型支持json格式,那么如何将json格式的字段类型的值映射到java对象当中呢?以下记录一下转换方法.
数据库展示:
specs列为json格式,现将此列的值映射到java的对象的属性当中
分析json串,需要创建一个VO对象,用于保存json串中的对象
public class Spec implements Serializable { private Integer key_id; private String key; private Integer value_id; private String value; }
创建Pojo对象
@Entity @Table(name = "sku") @Getter @Setter public class SkuEntity extends BaseEntity { @Id private int id; private BigDecimal price; private BigDecimal discountPrice; private byte online; private String img; private String title; private int spuId; //private List<Spec>specs; private String specs; private String code; private int stock; private Integer categoryId; private Integer rootCategoryId;
GenericAndJson工具类代码:
package com.my.sevencell.api.utils; import com.fasterxml.jackson.core.JsonProcessingException; import com.fasterxml.jackson.core.type.TypeReference; import com.fasterxml.jackson.databind.ObjectMapper; import com.my.sevencell.api.exception.http.ServerErrorException; import lombok.extern.slf4j.Slf4j; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Component; import java.io.IOException; /** * @Description: 此工具类进行json的序列化和反序列化 * @Author: my * @CreateDate: 2020/3/5 22:08 * @UpdateUser: * @UpdateDate: 2020/3/5 22:08 * @UpdateRemark: 修改内容 * @Version: 1.0 */ @Component @Slf4j public class GenericAndJson { private static ObjectMapper mapper; /** * 采用set方法自动注入 * @param mapper */ @Autowired public void setMapper(ObjectMapper mapper) { GenericAndJson.mapper = mapper; } public static<T> String objectToJson(T o){ try { String jsonString = mapper.writeValueAsString(o); return jsonString; } catch (JsonProcessingException e) { log.error(e.getMessage()); throw new ServerErrorException(9999); } } public static<T> T jsonToObject(String json, TypeReference<T>typeReference){ try { if (json.isEmpty()){ return null; } T t = mapper.readValue(json, typeReference); return t; } catch (IOException e) { log.error(e.getMessage()); throw new ServerErrorException(9999); } } }
方法一
1.我们将specs列的值当做String类型进行接收
private String specs;
2.编写specs的get/set方法,通过GenericAndJson工具类进行序列化和烦序列化
public List<SpecVO> getSpecs() { if(this.specs.isEmpty()){ return Collections.emptyList(); } List<SpecVO> specs = GenericAndJson.jsonToObject(this.specs, new TypeReference<List<SpecVO>>() { }); return specs; } public void setSpecs(List<SpecVO> specs) { String json = GenericAndJson.objectToJson(specs); this.specs = json; }
测试结果:
{ "id": 1, "price": 3999.00, "discount_price": null, "online": 1, "img": "http://xxxxx", "title": "复古双色沙发(藏青色)", "spu_id": 1, "specs": [ { "key_id": 1, "key": "颜色", "value_id": 2, "value": "藏青色" }, { "key_id": 7, "key": "双色沙发尺寸(非标)", "value_id": 32, "value": "1.5米 x 1米" } ], "code": "1$1-2#7-32", "stock": 89, "category_id": 35, "root_category_id": null }
方法二
1.新建工具类ConveterObjectAndJson,实现AttributeConverter接口
package com.my.sevencell.api.utils; import com.fasterxml.jackson.core.JsonProcessingException; import com.fasterxml.jackson.core.type.TypeReference; import com.fasterxml.jackson.databind.ObjectMapper; import com.my.sevencell.api.exception.http.ServerErrorException; import lombok.extern.slf4j.Slf4j; import org.springframework.beans.factory.annotation.Autowired; import javax.persistence.AttributeConverter; import java.io.IOException; /** * @Description: 实现json的序列化和反序列化,只需要对需要转换的 * 属性打上@convet主机即可 * @Author: my * @CreateDate: 2020/3/6 9:32 * @UpdateUser: * @UpdateDate: 2020/3/6 9:32 * @UpdateRemark: 修改内容 * @Version: 1.0 */ @Slf4j public class ConveterObjectAndJson<T> implements AttributeConverter<T,String> { @Autowired private ObjectMapper objectMapper; @Override public String convertToDatabaseColumn(T t) { try { String jsonString = objectMapper.writeValueAsString(t); return jsonString; } catch (JsonProcessingException e) { log.error(e.getMessage()); throw new ServerErrorException(9999); } } @Override public T convertToEntityAttribute(String s) { try { if(s.isEmpty()){ return null; } T t = objectMapper.readValue(s, new TypeReference<T>() { }); return t; } catch (IOException e) { log.error(e.getMessage()); throw new ServerErrorException(9999); } } }
2.我们将specs列的值当用List集合进行接收,并打上@Convert(converter = ConveterObjectAndJson.class)的注解
注意:
1.specs属性的get/set方法可自动生成,无需进行任何改动.
2.用List<specVo>接收时,idea会报错,不过不影响正常运行,可忽略
3.@Conver是avax.persistence包下的;
@Convert(converter = ConveterObjectAndJson.class) private List<SpecVO> specs;
测试结果:
{ "id": 1, "price": 3999.00, "discount_price": null, "online": 1, "img": "http://xxxx", "title": "复古双色沙发(藏青色)", "spu_id": 1, "specs": [ { "key": "颜色", "value": "藏青色", "key_id": 1, "value_id": 2 }, { "key": "双色沙发尺寸(非标)", "value": "1.5米 x 1米", "key_id": 7, "value_id": 32 } ], "code": "1$1-2#7-32", "stock": 89, "category_id": 35, "root_category_id": null }
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