带有子类的抽象集合中的JPA条件搜索属性

Question

我正在使用Spring数据规范编写一个使用JPA标准API的标准查询。

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在数据库中，类层次结构是用一个连接的继承策略存储的，如下（5个表）：

• 特性（id+某些常用字段）
• integer_spearchitecture（外键+INT值）
• decimal_spearchitecture（外键+十进制值）
• 字符串特性（外键+VARCHAR值）
• boolean_spearchitecture（外键+TINYINT值）

我需要使用JPA标准API来搜索所有至少具有指定值的特性的东西。

SELECT DISTINCT thing.id
FROM   thing 
       LEFT OUTER JOIN thing_has_characteristic has_c 
                    ON ( has_c.thing_id = thing.id ) 
       LEFT OUTER JOIN characteristic c 
                    ON ( c.id = has_c.characteristic_id ) 
       LEFT OUTER JOIN integer_characteristic integer_c 
                    ON ( integer_c.characteristic_id = c.id ) 
       LEFT OUTER JOIN string_characteristic string_c 
                    ON ( string_c.characteristic_id = c.id ) 
       LEFT OUTER JOIN boolean_characteristic boolean_c 
                    ON ( boolean_c.characteristic_id = c.id ) 
       LEFT OUTER JOIN decimal_characteristic decimal_c 
                    ON ( decimal_c.characteristic_id = c.id ) 
WHERE  integer_c.value = "9694" 
        OR string_c.value = "9694"
        OR decimal_c.value = "9694" 
        OR boolean_c.value = "9694";

private Specification<Thing> buildSearchSpecificationByCharacteristicValue(String value) {

    return (Specification<Thing>) (root, query, builder) -> {

        SetJoin<Thing,IntegerCharacteristic> integers = root.<Thing,IntegerCharacteristic>joinSet("characteristics", JoinType.LEFT );
        Predicate isInteger;
        try{
            isInteger = builder.equal(integers.get("value"), Integer.parseInt(value));
        }catch(NumberFormatException e){
            isInteger = builder.disjunction();
        }

        SetJoin<Thing,StringCharacteristic> strings = root.<Thing,StringCharacteristic>joinSet("characteristics", JoinType.LEFT);
        Predicate isString = builder.equal(strings.get("value"), value);

        return builder.or(
            isInteger,
            isString
        );
    };
}

org.springframework.dao.InvalidDataAccessApiUsageException: 
Unable to locate Attribute  with the the given name [value] on this 
ManagedType [com.xxxxxxxx.common.domain.DomainObject];
 nested exception is java.lang.IllegalArgumentException: 
Unable to locate Attribute  with the the given name [value] 
on this ManagedType [com.xxxxxxxx.common.domain.DomainObject]

Answer 1

好了，我找到了解决问题的办法：

下面是一个示例，其中只包含了整数类型的条件，但隐式地说明了如何对其他类型执行这些条件。

return (Specification<Thing>) (root, query, builder) -> {

    Path<Characteristic> characteristics = root.join("characteristics", JoinType.LEFT);

    query.distinct(true);

    Subquery<IntegerCharacteristic> integerSub = query.subquery(IntegerCharacteristic.class);
    Root integerRoot = integerSub.from(IntegerCharacteristic.class);
    integerSub.select(integerRoot);
    integerSub.where(builder.equal(integerRoot.get("value"),Integer.parseInt(value)));

    return builder.in(characteristics).value(integerSub);

};