JPA 连表查询

最新推荐文章于 2025-07-03 09:50:45 发布

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最新推荐文章于 2025-07-03 09:50:45 发布

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文章标签： java

原文链接：http://www.cnblogs.com/hanjun0612/p/10343151.html

本文详细介绍了如何在Java持久化API(JPA)中实现A表和B表的关联查询，通过示例代码展示了如何在实体类中定义一对一关联关系，并在DAO层使用Specification和@Query注解进行复杂查询。

A表和B表

@Entity
@Table(name = "A", schema = "kps", catalog = "kps")
@DynamicUpdate
public class A implements java.io.Serializable {

private String aUUID;
//关联B
private B b;

@OneToOne(fetch = FetchType.EAGER, optional = true)
@NotFound(action = NotFoundAction.IGNORE)
@JoinColumn(name = "aUUID", referencedColumnName = "aUUID", insertable = false, updatable = false)
public B getB() {
return b;
}

public void setB(B b) {
this.b= b;
}


}

@Entity
@Table(name = "B", schema = "kps", catalog = "kps")
@DynamicUpdate
public class B implements java.io.Serializable {

private String bUUID;
private Integer age;


}

JPA查询时

@Override
public PageResult<A> pagedListForVaild(A entity, Integer currentPage, Integer pageSize,
Order... orders) throws Exception {
// 构建查询条件
Specification<A> sf = new Specification<A>() {
@Override
public Predicate toPredicate(Root<A> root, CriteriaQuery<?> query, CriteriaBuilder cb) {
List<Predicate> list = new ArrayList<Predicate>();
Join<A, B> join = root.join("b", JoinType.INNER);
list.add(cb.equal(join.<String>get("age"), Age));
return cb.and(list.toArray(p));
}
};

return super.gerPageResult(currentPage, pageSize, sf, orders);

}