字面常量使用字串
使用以下JPQL查詢時：
SELECT e FROM Employee e WHERE e.name = 'Rose'
等價於使用以下Criteria API查詢，且行8顯示否定用法：
@Test
public void Criteria_EqualString() {
EntityManager em = emf.createEntityManager();
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery sql = cb.createQuery(Employee.class);
Root emp = sql.from(Employee.class);
Expression expr = cb.equal(emp.get(Employee_.name), "Rose");
// Expression expr = cb.equal(emp.get(Employee_.name), "Rose").not();
sql.select(emp).where(expr);
TypedQuery tq = em.createQuery(sql);
List resultList = tq.getResultList();
resultList.forEach(System.out::println);
assertThat(resultList, containsInAnyOrder(employee2));
}
字面常量使用數字
使用以下JPQL查詢時：
SELECT e FROM Employee e WHERE e.salary > 2000.0
等價於使用以下Criteria API查詢。比較數字使用方法gt()表示greater-than：
@Test
public void Criteria_GreaterNumber() {
EntityManager em = emf.createEntityManager();
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery sql = cb.createQuery(Employee.class);
Root emp = sql.from(Employee.class);
Expression expr = cb.gt(emp.get(Employee_.salary), 2000.0);
sql.select(emp).where(expr);
TypedQuery typedQuery = em.createQuery(sql);
List resultList = typedQuery.getResultList();
resultList.forEach(System.out::println);
assertThat(resultList, containsInAnyOrder(employee1, employee2));
}
字面常量使用enum
使用以下JPQL查詢時：
SELECT e FROM Employee e WHERE e.role = entity.Role.IT
等價於使用以下Criteria API查詢。Entity欄位型態為enum可以直接使用equal()方法：
@Test
public void Criteria_EqualEnum() {
EntityManager em = emf.createEntityManager();
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery sql = cb.createQuery(Employee.class);
Root emp = sql.from(Employee.class);
Expression expr = cb.equal(emp.get(Employee_.role), Role.IT);
sql.select(emp).where(expr);
TypedQuery tq = em.createQuery(sql);
List resultList = tq.getResultList();
resultList.forEach(System.out::println);
assertThat(resultList, containsInAnyOrder(employee1, employee3));
}
字面常量使用日期
使用以下JPQL查詢時：
SELECT e FROM Employee e WHERE e.joinDate > '2017-05-01'
等價於使用以下Criteria API查詢。比較日期時，無法直接比較日期格式如Timestamp，必須借助CriteriaBuilder的literal()方法轉換為Expression<Timestamp>後再套用到greaterThanOrEqualTo()，如範例程式碼行7~10：
@Test
public void Criteria_GreaterDate() {
EntityManager em = emf.createEntityManager();
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery sql = cb.createQuery(Employee.class);
Root emp = sql.from(Employee.class);
Expression timestampExpr =
cb.literal( localToTimeStamp(LocalDate.of(2017, 05, 01)) );
Expression expr =
cb.greaterThanOrEqualTo(emp.get(Employee_.joinDate), timestampExpr);
sql.select(emp).where(expr);
TypedQuery typedQuery = em.createQuery(sql);
List resultList = typedQuery.getResultList();
resultList.forEach(System.out::println);
assertThat(resultList, containsInAnyOrder(employee4, employee2));
}
字面常量使用boolean
使用以下JPQL查詢時：
SELECT e FROM Employee e WHERE e.fullTime = true
等價於使用以下Criteria API查詢。若Entity的Boolean欄位為true，可以使用範例程式碼行9的方法isTrue()或行10直接省略，兩者效果相同；若欄位值要求為false則使用行11的方法isFalse()：
@Test
public void Criteria_BooleanField() {
EntityManager em = emf.createEntityManager();
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery sql = cb.createQuery(Employee.class);
Root emp = sql.from(Employee.class);
Expression adultExpression = emp.get(Employee_.fullTime);
sql.select(emp)
.where(cb.isTrue(adultExpression));
// .where(adultExpression);
// .where(cb.isFalse(adultExpression));
TypedQuery typedQuery = em.createQuery(sql);
List resultList = typedQuery.getResultList();
resultList.forEach(System.out::println);
assertThat(resultList, hasItems(employee1));
assertThat(resultList, hasItems(employee3));
}
