java - 需要最佳的实体和查询设计来获取具有多个关联的对象

Question

我有一个实体，它有多个 @ManyToOne 关联对象。目前，我将所有关联的对象获取类型建模为 LAZY。

实际上我正在编写REST API来支持各种功能，例如

1. 获取带有 @ManytoOne 注释的实体，仅解析为 ID
2. 获取带有解析整个对象的 @ManytoOne 注释的实体
3. 获取带有解析为部分对象的 @ManytoOne 注释的实体
4. 使用 @ManytoOne 注释获取仅解析为 ID 的实体

我的应用程序是使用 spring-boot jpa 存储库构建的。显然，REST API 中的上述变化可以通过为每个 API 编写命名查询来解决。如果我这样做，在某一时刻，每个关联对象都会有多个命名查询。但我期待有更好的方法来建模和查询实体。

如有任何建议，我们将不胜感激。

Answer 1

根据我的理解，你应该使用 Query by Example

The Query by Example API consists of three parts:

• Probe: The actual example of a domain object with populated fields.
• ExampleMatcher: The ExampleMatcher carries details on how to match particular fields. It can be reused across multiple Examples.
• Example: An Example consists of the probe and the ExampleMatcher. It is used to create the query.

Query by Example is well suited for several use cases:

• Querying your data store with a set of static or dynamic constraints.
• Frequent refactoring of the domain objects without worrying about breaking existing queries.
• Working independently from the underlying data store API.

Query by Example also has several limitations:

• No support for nested or grouped property constraints, such as firstname = ?0 or (firstname = ?1 and lastname = ?2).
• Only supports starts/contains/ends/regex matching for strings and exact matching for other property types.