JPA CriteriaBuilder案例查询 [英] JPA CriteriaBuilder case query

问题描述

任何人都可以提供如何使用CriteriaBuilder编写案例查询的示例吗?

Can anyone provide an example of how to write a case query using CriteriaBuilder?

推荐答案

以下是使用CriteriaBuilder的示例案例表达式(在JPA 2中有效):

What follows is a sample case expression using CriteriaBuilder (this works in JPA 2):

Hashtable caseTable = new Hashtable(3);
caseTable.put("Bob", "Bobby");
caseTable.put("Susan", "Susie");
caseTable.put("Eldrick", "Tiger");
Expression expression = builder.get("firstName").caseStatement(caseTable, "NoNickname").equal("Bobby");

它将生成以下SQL查询:

"CASE t1.firstName WHEN 'Bob' THEN 'Bobby' WHEN 'Susan' THEN 'Susie' WHEN 'Eldrick' THEN 'Tiger' ELSE 'NoNickname' END = 'Bobby'"

有关更多信息，请参见 JPA 2.0案例表达式.

For more info please see JPA 2.0 Case Expressions.

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