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我正在使用EL,当我运行下面的查询时,我一直收到0。我想知道当前有效的申请人数(AP)。子实体申请人是Person,我想避免查询Person的所有元素?JPA EclipseLink getCount子实体
@RooJavaBean
@RooToString
@RooEntity(identifierColumn = "personID", inheritanceType = "SINGLE_TABLE")
@DiscriminatorColumn(name = "TYPE", discriminatorType = DiscriminatorType.STRING, length = 20)
@DiscriminatorValue("P")
public class Person {
@NotNull
@Size(min = 1, max = 50)
private String FirstName;
@NotNull
@Size(min = 1, max = 50)
private String LastName;
}
子实体 '申请人'
@RooJavaBean
@RooToString
@RooEntity
@DiscriminatorValue("AP")
public class Applicant extends Person{
private String major;
private String nativeLanguage;
private String ethnicity;
private String hispanic;
}
我的查询尝试:
/**
*
* @return
*/
public int getCountActiveApplicants(){
EntityManager entityManager = factory.createEntityManager();
int value = entityManager.createQuery("select count(distinct o) from Person o where o.TYPE = \"AP\" AND o.active = \"Yes\" ").getFirstResult();
System.out.println("wowzer " + value + "\n");
return value;
}
它实际上不是一个布尔字段我想将它设置为“是”或“否”,但它可能不是一个很好的事情时,我可以使用真或假。我会立即尝试这个查询。谢谢 – Warz
得到这个实体经理的计数,我应该使用getFirstResult()? – Warz
不可以。您应该使用getSingleResult():http://docs.oracle.com/javaee/6/api/javax/persistence/Query.html#getSingleResult%28%29。 getFirstResult()返回setFirstResult()设置的内容。 –