如何编写JPA查询，其中参数是一个集合？ [英] How to write JPA query where parameter is a set?

问题描述

假设以下课程，您如何找到具有特定电子邮件地址的人？

Assuming the following class, how do you find a Person with a particular email address?

public class Person implements Comparable<Person> {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name="id")
    private long id = 0;

    @OneToMany(cascade={CascadeType.PERSIST, CascadeType.MERGE, CascadeType.REMOVE}, fetch=FetchType.LAZY)
    private Set<String> email = new HashSet<String>();
}

这样做是否简单，还是有正确的方法？

Is it as simple as doing just this, or is there a proper way?

select p from Person p where p.email=:email

推荐答案

这并不容易。 JPQL为此提供 IN 运算符：

It's not that easy. JPQL provides the IN operator for this:

select p from Person p, IN(p.email) m where m = :email

'旧'方式（读SQL -like）将是：

The 'old' way (read SQL-like) would be:

select p from Person p join p.email m where m = :email

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