我没有执行代码,但给了正确的导入语句,至少编译。根据您的实体定义,某些属性可能需要进行调整,无论如何,您应该了解如何处理此问题。
我的条件查询是基于以下SQL:
SELECT * FROM TERMINAL
WHERE ID IN (
SELECT TERMINAL_FK FROM TERMINAL_PROPERTIES
WHERE (KEY = 'key1' AND VALUE = 'value1')
OR (KEY = 'key2' AND VALUE = 'value2')
...
GROUP BY TERMINAL_FK
HAVING COUNT(*) = 42
)
在那里你列出每个名称/值对和42
仅仅代表名称/值对的数目。
所以我假设你定义的存储库这样的:
public interface TerminalRepository extends CrudRepository<Terminal, Long>, JpaSpecificationExecutor {
}
它,以便利用标准API的扩展JpaSpecificationExecutor
是很重要的。
然后你就可以建立一个标准,这样的查询:
public class TerminalService {
private static Specification<Terminal> hasProperties(final Map<String, String> properties) {
return new Specification<Terminal>() {
@Override
public Predicate toPredicate(Root<Terminal> root, CriteriaQuery<?> query, CriteriaBuilder builder) {
// SELECT TERMINAL_FK FROM TERMINAL_PROPERTIES
Subquery<TerminalProperty> subQuery = query.subquery(TerminalProperty.class);
Root propertyRoot = subQuery.from(TerminalProperty.class);
subQuery.select(propertyRoot.get("terminal.id"));
Predicate whereClause = null;
for (Map.Entry<String, String> entry : properties.entrySet()) {
// (KEY = 'key1' AND VALUE = 'value1')
Predicate predicate = builder.and(builder.equal(propertyRoot.get("key"),
entry.getKey()), builder.equal(propertyRoot.get("value"), entry.getValue()));
if (whereClause == null) {
whereClause = predicate;
} else {
// (...) OR (...)
whereClause = builder.or(whereClause, predicate);
}
}
subQuery.where(whereClause);
// GROUP BY TERMINAL_FK
subQuery.groupBy(propertyRoot.get("terminal.id"));
// HAVING COUNT(*) = 42
subQuery.having(builder.equal(builder.count(propertyRoot), properties.size()));
// WHERE ID IN (...)
return query.where(builder.in(root.get("id")).value(subQuery)).getRestriction();
}
};
}
@Autowired
private TerminalRepository terminalRepository;
public Iterable<Terminal> findTerminalsWith(Map<String, String> properties) {
// this works only because our repository implements JpaSpecificationExecutor
return terminalRepository.findAll(hasProperties(properties));
}
}
可以很明显的替代Map<String, String>
与Iterable<TerminalProperty>
,但因为他们似乎被绑定到特定的Terminal
会感到奇怪。
我希望避免规范和编程建立查询,但显然这是不可能的。非常感谢您的详细解答。 – Ismail 2013-04-24 07:03:37
不客气。如果您希望避免使用'Specification',但您想使用Spring Data JPA,则您可以直接使用JPA标准API? – skirsch 2013-04-24 07:27:14