自从我迁移到 Hibernate 6（5.4.30.Final 到 6.2.0.Final）后，我的一些查询没有正确翻译。
这是基于本教程的最小复制项目：
实体（省略getters/setters）：
@Entity
public class Author {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int id;
private String name;
}
@Entity
public class PublishingHouse {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int id;
private String name;
}
一本书有作者和出版社的外键：
@Entity
public class Book {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int id;
private String title;
@ManyToOne
private Author author;
@ManyToOne
private PublishingHouse publishingHouse;
}
我的主要方法添加实体，然后尝试查找所有以“Stephen king”为作者或以“Simon & Schuster”为出版社的书籍：
public static void main(String[] args) {
Transaction transaction = null;
PublishingHouse phSimonSchuster = null;
Author stephenKing = null;
try (Session session = HibernateUtil.getSessionFactory().openSession()) {
transaction = session.beginTransaction();
/**
* Add Publishing houses
*/
phSimonSchuster = new PublishingHouse();
phSimonSchuster.setName("Simon & Schuster");
session.persist(phSimonSchuster);
var phHarperCollins = new PublishingHouse();
phHarperCollins.setName("HarperCollins");
session.persist(phHarperCollins);
/**
* Add Authors
*/
stephenKing = new Author();
stephenKing.setName("Stephen King");
session.persist(stephenKing);
var hpLovecraft = new Author();
hpLovecraft.setName("Howard Phillips Lovecraft");
session.persist(hpLovecraft);
/**
* Add Books
*/
var bShining = new Book();
bShining.setTitle("Shining");
bShining.setAuthor(stephenKing);
bShining.setPublishingHouse(phSimonSchuster);
session.persist(bShining);
var bColorOutOfSpace = new Book();
bColorOutOfSpace.setTitle("The Colour Out of Space");
bColorOutOfSpace.setAuthor(hpLovecraft);
bColorOutOfSpace.setPublishingHouse(phHarperCollins);
session.persist(bColorOutOfSpace);
transaction.commit();
}
try (Session session = HibernateUtil.getSessionFactory().openSession()) {
var hql = "SELECT book "
+ "FROM Book book "
+ " LEFT JOIN book.author author "
+ " WITH author.id = :stephenKingId "
+ " LEFT JOIN book.publishingHouse publishingHouse "
+ " WITH publishingHouse.id = :simonSchusterId "
+ "WHERE author IS NOT NULL OR publishingHouse IS NOT NULL ";
List<Book> books = session.createQuery(hql, Book.class)
.setParameter("stephenKingId", stephenKing.getId())
.setParameter("simonSchusterId", phSimonSchuster.getId())
.list();
books.forEach(b -> {
System.out.println("Book found: " + b.getTitle());
});
}
}
我的主要方法的输出是：
找到的书：闪亮
找到的书：空间之外的颜色
但是《The Color Out of Space》不是斯蒂芬·金写的，也不是“Simon & Schuster”出版的，我插入数据的时候可以看到，所以这本书不应该通过这个查询得到。
问题是这个hql:
SELECT book
FROM Book book
LEFT JOIN book.author author
WITH author.id = :stephenKingId
LEFT JOIN book.publishingHouse publishingHouse
WITH publishingHouse.id = :simonSchusterId
WHERE author IS NOT NULL OR publishingHouse IS NOT NULL
翻译错了：
SELECT b1_0.id,
b1_0.author_id,
b1_0.publishinghouse_id,
b1_0.title
FROM book b1_0
LEFT JOIN author a1_0
ON a1_0.id = b1_0.author_id
AND b1_0.author_id = ?
LEFT JOIN publishinghouse p1_0
ON p1_0.id = b1_0.publishinghouse_id
AND b1_0.publishinghouse_id = ?
WHERE b1_0.author_id IS NOT NULL
OR b1_0.publishinghouse_id IS NOT NULL
为什么错了？因为 WHERE 条件正在测试
author_idpublishinghouse_idBookauthor_idpublishinghouse_idFROM book book
LEFT JOIN book.author author
WITH author.id = :stephenKingId
应该是：
FROM book b1_0
LEFT JOIN author a1_0
ON a1_0.id = b1_0.author_id
AND a1_0.id = ?
而不是：
FROM book b1_0
LEFT JOIN author a1_0
ON a1_0.id = b1_0.author_id
AND b1_0.author_id = ?
最后，正确的查询应该是：
SELECT b1_0.id,
b1_0.author_id,
b1_0.publishinghouse_id,
b1_0.title
FROM book b1_0
LEFT JOIN author a1_0
ON a1_0.id = b1_0.author_id
AND a1_0.id = ?
LEFT JOIN publishinghouse p1_0
ON p1_0.id = b1_0.publishinghouse_id
AND p1_0.id = ?
WHERE a1_0.id IS NOT NULL OR p1_0.id IS NOT NULL
此查询仅查找作者为“Stephen king”或出版社为“Simon & Schuster”的书籍
我的休眠版本没有这个问题< 6.0
我的意思是，如果我理解正确的话，您正在尝试使用
is not null为什么不首先使用内连接编写查询？
任一：
SELECT book
FROM Book book
JOIN book.author author
WITH author.id = :stephenKingId
JOIN book.publishingHouse publishingHouse
WITH publishingHouse.id = :simonSchusterId
甚至只是：
SELECT book
FROM Book book
JOIN book.author author
JOIN book.publishingHouse publishingHouse
WHERE author.id = :stephenKingId
AND publishingHouse.id = :simonSchusterId
我的意思是，我只是不确定为什么会在这里使用外部连接。
我建议一个更简单的查询：
SELECT b.id, b.author.id, b.publishingHouse.id, b.title
FROM Book b
LEFT JOIN b.author a
LEFT JOIN b.publishingHouse p
WHERE a.id = :authorId OR p.id = :publishingHouseId
你可以使用 WITH:
SELECT b.id, b.author.id, b.publishingHouse.id, b.title
FROM Book b
LEFT JOIN b.author a WITH a.id = :authorId
LEFT JOIN b.publishingHouse p WITH p.id = :publishingHouseId
WHERE a.id IS NOT NULL OR p.id IS NOT NULL
或者，明确指定连接条件：
SELECT b.id, b.author.id, b.publishingHouse.id, b.title
FROM Book b
LEFT JOIN b.author a ON a.id = :authorId
LEFT JOIN b.publishingHouse p ON p.id = :publishingHouseId
WHERE a.id IS NOT NULL OR p.id IS NOT NULL