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<>AttributeConverter
javax.persistence.AttributeConverter
开发中有一个问题，有一个业务对象，它的属性是一个JSONObject对象，但是我们希望存入数据库时，存为json字符串。前端在插入和查询时，都是以对象来处理，所以希望能自动转换，即在插入数据库时，转为字符串，查询出来后转为对象。这就用到了今天要说的属性转换器。
第一步：定义一个属性转换器
/** * Copyright (C) zhongda * * @author zx * @date 2019/8/22 0022 10:43 *
@description: */ public class JSONArrayToStringConverter implements
AttributeConverter<JSONArray,String> { @Override public String
convertToDatabaseColumn(JSONArray object) { return object==null?null:object.
toJSONString(); } @Override public JSONArray convertToEntityAttribute(String s)
{ return s==null?null: JSONArray.parseArray(s); } }
这个转换器，实现了javax.persistence.AttributeConverter接口，在存入数据库时，将对象转为字符串，在查询获时，转为实体对象。
第二步：在实体类中标注@Convert注解，并指明转换类。
@Data @AllArgsConstructor @NoArgsConstructor @EqualsAndHashCode(callSuper=false
) @Builder @ToString(callSuper = true) @Entity @Table(name = "t_business_rules")
public class BusinessRules extends BaseEntity { //其他属性... @Convert(converter =
JSONObjectToStringConverter.class) private JSONObject frequency; @Convert(
converter= JSONArrayToStringConverter.class) private JSONArray conditions;
@Convert(converter = JSONObjectToStringConverter.class) private JSONObject
actions; }
这样就ok了，前端参数就可以直接写成JSONObject的格式，就完成了自动转换，当然如果需要其类型的转换，只需要更改转换类的代码即可。
