@Entity
public class Author {
    @Id
    private Long id;

    @OneToMany(mappedBy = "author")
    @BatchSize(size = 10)  // Загружает до 10 книг за один запрос
    private List<Book> books;
}

@Entity
public class Book {
    @Id
    private Long id;

    @ManyToOne(fetch = FetchType.LAZY)
    @BatchSize(size = 5)  // Загружает авторов пачками по 5
    private Author author;
}

SELECT * FROM author WHERE id IN (1, 2, 3, 4, 5)

spring.jpa.properties.hibernate.default_batch_fetch_size=20
Устанавливает глобальный размер пакета для всех ленивых загрузок.

@Entity
@Cacheable
@Cache(usage = CacheConcurrencyStrategy.READ_WRITE, region = "employees")
public class Employee { ... }

@Entity
@Cacheable(true)  // Включено кеширование (по умолчанию true)
public class Product { ... }

spring.jpa.properties.hibernate.cache.use_query_cache=true

spring.jpa.properties.hibernate.cache.use_second_level_cache=true
spring.jpa.properties.hibernate.cache.region.factory_class=org.hibernate.cache.ehcache.EhCacheRegionFactory
(Пример для Ehcache; также поддерживаются Infinispan, Hazelcast, Redis.)

spring.jpa.properties.javax.persistence.sharedCache.mode=ALL
(Варианты: ALL, NONE, ENABLE_SELECTIVE, DISABLE_SELECTIVE.)

<dependency>
    <groupId>org.ehcache</groupId>
    <artifactId>ehcache</artifactId>
</dependency>

И файл ehcache.xml в resources/.

import java.util.function.Function;

public class Task070425 {
    public static void main(String[] args) {
        Function<Integer, Integer> f = x -> x++;
        System.out.println(f.apply(5));
    }
}

@Entity
public class Parent {
    @Id
    private Long id;

    @OneToMany(mappedBy = "parent")
    @Cascade({CascadeType.PERSIST, CascadeType.REMOVE})
    private List<Child> children;
}

@Entity
public class Author {
    @Id
    private Long id;

    @OneToMany(mappedBy = "author")
    @Cascade({CascadeType.MERGE, CascadeType.DELETE_ORPHAN})
    private List<Book> books;
}

@Entity
public class Order {
    @Id
    private Long id;

    @OneToMany(mappedBy = "order")
    @Cascade({CascadeType.LOCK, CascadeType.REPLICATE})
    private List<Item> items;
}

@OneToMany(mappedBy = "parent", cascade = {javax.persistence.CascadeType.PERSIST, javax.persistence.CascadeType.REMOVE})

@OneToMany(mappedBy = "parent")
@Cascade({org.hibernate.annotations.CascadeType.SAVE_UPDATE, org.hibernate.annotations.CascadeType.DELETE_ORPHAN})