带字符串值的QueryDSL-case表达式

Question

QueryDsl 3.3.4
Hibernate 3.6.10-Final I有两个实体：

public class Document {
    private Confirmation confirmation;
}

public class Confirmation {
    ...
}

SELECT count(d.id), CASE WHEN d.confirmation_id IS NULL then 'NOT_CONFIRMED' else 'CONFIRMED' END as confirmed FROM document d GROUP BY confirmed;

StringExpression confirmExp = new CaseBuilder()
    .when(Expressions.booleanTemplate("confirmation_id is null"))
    .then(Expressions.stringTemplate("NOT_CONFIRMED"))
    .otherwise(Expressions.stringTemplate("CONFIRMED"));

org.hibernate.hql.ast.tree.SelectClause.InitializeExplicitSelectClause(SelectClause.java:156)

Answer 1

如果想要查询中的字符串文本，则需要将其编写为

StringExpression confirmExp = new CaseBuilder()
    .when(Expressions.booleanTemplate("confirmation_id is null"))
    .then(Expressions.stringTemplate("'NOT_CONFIRMED'"))
    .otherwise(Expressions.stringTemplate("'CONFIRMED'"));

StringTemplate并不意味着参数被序列化为字符串文本，而是表示创建的表达式为java.lang.String类型。