QueryDSL 按计算字段排序

Question

在我们的应用程序中，我们使用 querydsl 来获取实体并将它们转换为表示对象。此表示对象具有名为 active 的字段。这是由实体的某个日期是在今天之前（active = false）还是在今天之后（active = true）决定的。这样做一切顺利。问题是在尝试按该表达式 (QEntity.someDate > today) 排序时。这使得休眠抛出这个错误：

org.hibernate.hql.internal.ast.QuerySyntaxException: unexpected AST node: > near line 3, column 40 [select object.someField as someAlias, (object.someDate > ?1) as active, object as objectAlias
from com.example.Object object
order by object.someDate > ?1 asc]

我创建 OrderSpecifier 如下：

    @Override
    public OrderSpecifier<?> getOrderByClause(SortKey sortKey) {
        BooleanExpression expression = getBooleanPath(); // This is the expression: (object.someDate > ?1)
        if (sortKey.getSortOrder() == ESortOrder.ASCENDING) {
            return new OrderSpecifier(Order.ASC, expression);
        }
        return new OrderSpecifier(Order.DESC, expression);
    }

我也这样试过：

    @Override
    public OrderSpecifier<?> getOrderByClause(SortKey sortKey) {
        BooleanExpression expression = getBooleanPath();
        if (sortKey.getSortOrder() == ESortOrder.ASCENDING) {
            return new CaseBuilder().when(expression.isFalse()).then(1).otherwise(2).asc();
        }
        return new CaseBuilder().when(expression.isTrue()).then(1).otherwise(2).desc();
    }

这会导致类似的错误：

org.hibernate.hql.internal.ast.QuerySyntaxException: unexpected AST node: > near line 3, column 40 [select object.someField as someAlias, (object.someDate > ?1) as active, object as objectAlias
from com.example.Object object
order by case when (object.someDate > ?1 = ?2) then ?3 else 2 end asc]

最后像这样：

    @Override
    public OrderSpecifier<?> getOrderByClause(SortKey sortKey) {
        BooleanExpression expression = getBooleanPath();
        if (sortKey.getSortOrder() == ESortOrder.ASCENDING) {
            return new CaseBuilder().when(expression.eq(true)).then(1).otherwise(2).asc();
        }
        return new CaseBuilder().when(expression.eq(true)).then(1).otherwise(2).desc();
    }

抛出与之前相同的错误

Answer 1

通过创建这样的 order 子句修复了它：

    @Override
    public OrderSpecifier<?> getOrderByClause(SortKey sortKey) {
        BooleanPath path = getBooleanPath();
        if (sortKey.getSortOrder() == ESortOrder.ASCENDING) {
            return path.asc();
        }
        return path.desc();
    }

    private BooleanPath getBooleanPath() {
        return Expressions.booleanPath(getFieldName());
    }

其中字段名称是字符串的别名，在我们的例子中是 "active"。

QueryDSL 按计算字段排序

QueryDSL Order by calculated field

java

querydsl