Spring Data JPA 1.3.2参考文档：查询与扩展详解

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SpringData JPA Reference Documentation 是一个详细的指南，专为Spring框架下的JPA（Java Persistence API）开发者设计，特别关注于1.3.2.RELEASE版本。该文档由Oliver Gierke撰写，他是SpringSource的高级顾问，版权归属2008-2013年原创作者。这份文档允许个人复制和分发，但需确保免费且包含版权声明，无论是纸质还是电子形式。文档主要分为以下几个部分： 1. **项目元数据**：这部分可能介绍了项目的背景、目标以及使用Spring Data JPA的目的，帮助读者理解整体架构。 2. **参考文档**： - **Repositories（仓库）**：是Spring Data的核心，这里是文档的重点。首先，它概述了仓库的概念，解释如何通过定义接口来访问和操作数据库。核心概念包括查询方法的定义和调用，如查询查找策略的选择和自定义查询的创建。 - **定义仓库接口**：讲解如何编写符合Repository接口规范的类，以便Spring Data能够理解和管理这些接口与数据库之间的交互。 - **细化仓库定义**：讨论如何优化仓库接口的设计，可能涉及参数处理和查询参数化。 - **查询方法**：涵盖了如何创建和使用不同的查询方式，如CRUD（Create, Read, Update, Delete）操作，以及可能的特殊查询处理。 - **创建仓库实例**：介绍如何在Spring配置中创建和注入这些仓库实例，支持XML配置和Java配置两种方式。 - **定制实现**：讨论如何为单个仓库或所有仓库添加额外的行为，如事务管理或错误处理。 - **扩展性**：这部分可能会涉及如何与其他Spring模块集成，如领域模型（domain classes）和Spring Boot等的整合。文档提供了一个清晰的结构，使开发人员能系统地学习和使用Spring Data JPA进行数据库操作，无论是初级开发者还是经验丰富的技术专家都能从中受益。通过阅读和实践文档中的内容，用户可以更好地理解和掌握Spring框架在JPA上的应用，提高开发效率并遵循最佳实践。

please define productname in your docbook file!

1.3.2.RELEASE

Spring Data JPA -

Reference Documentation 4

public interface PersonRepository extends Repository<User, Long> { … }

2. Declare query methods on the interface.

List<Person> findByLastname(String lastname);

3. Setup Spring to create proxy instances for those interfaces.

<?xml version="1.0" encoding="UTF-8"?>

<beans:beans xmlns:beans="http://www.springframework.org/schema/beans"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xmlns="http://www.springframework.org/schema/data/jpa"

xsi:schemaLocation="http://www.springframework.org/schema/beans

http://www.springframework.org/schema/beans/spring-beans.xsd

http://www.springframework.org/schema/data/jpa

http://www.springframework.org/schema/data/jpa/spring-jpa.xsd">

</beans>

Note

Note that we use the JPA namespace here just by example. If you're using the repository

abstraction for any other store you need to change this to the appropriate namespace

declaration of your store module which should be exchanging jpa in favor of e.g. mongodb.

4. Get the repository instance injected and use it.

public class SomeClient {

@Autowired

private PersonRepository repository;

public void doSomething() {

List<Person> persons = repository.findByLastname("Matthews");

}

At this stage we barely scratched the surface of what's possible with the repositories but the general

approach should be clear. Let's go through each of these steps and figure out details and various options

that you have at each stage.

Defining repository interfaces

As a very first step you define a domain class specific repository interface. It's got to extend Repository

and be typed to the domain class and an ID type. If you want to expose CRUD methods for that domain

type, extend CrudRepository instead of Repository.

Fine tuning repository definition

Usually you will have your repository interface extend Repository, CrudRepository or

PagingAndSortingRepository. If you don't like extending Spring Data interfaces at all you can also

annotate your repository interface with @RepositoryDefinition. Extending CrudRepository will

expose a complete set of methods to manipulate your entities. If you would rather be selective about

please define productname in your docbook file!

1.3.2.RELEASE

Spring Data JPA -

Reference Documentation 5

the methods being exposed, simply copy the ones you want to expose from CrudRepository into

your domain repository.

interface MyBaseRepository<T, ID extends Serializable> extends Repository<T, ID> {

T findOne(ID id);

T save(T entity);

}

interface UserRepository extends MyBaseRepository<User, Long> {

User findByEmailAddress(EmailAddress emailAddress);

}

Example 1.3 Selectively exposing CRUD methods

In the first step we define a common base interface for all our domain repositories and expose

findOne(…) as well as save(…).These methods will be routed into the base repository implementation

of the store of your choice because they are matching the method signatures in CrudRepository.

So our UserRepository will now be able to save users, find single ones by id as well as triggering

a query to find Users by their email address.

Defining query methods

Query lookup strategies

The next thing we have to discuss is the definition of query methods. There are two main ways that the

repository proxy is able to come up with the store specific query from the method name. The first option

is to derive the query from the method name directly, the second is using some kind of additionally

created query. What detailed options are available pretty much depends on the actual store, however,

there's got to be some algorithm that decides what actual query is created.

There are three strategies available for the repository infrastructure to resolve the query. The strategy

to be used can be configured at the namespace through the query-lookup-strategy attribute.

However, It might be the case that some of the strategies are not supported for specific datastores.

Here are your options:

CREATE

This strategy will try to construct a store specific query from the query method's name. The general

approach is to remove a given set of well-known prefixes from the method name and parse the rest of

the method. Read more about query construction in the section called “Query creation”.

USE_DECLARED_QUERY

This strategy tries to find a declared query which will be used for execution first. The query could be

defined by an annotation somewhere or declared by other means. Please consult the documentation

of the specific store to find out what options are available for that store. If the repository infrastructure

does not find a declared query for the method at bootstrap time it will fail.

CREATE_IF_NOT_FOUND (default)

This strategy is actually a combination of CREATE and USE_DECLARED_QUERY. It will try to lookup a

declared query first but create a custom method name based query if no declared query was found. This

is the default lookup strategy and thus will be used if you don't configure anything explicitly. It allows

quick query definition by method names but also custom tuning of these queries by introducing declared

queries as needed.

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