Spring Data JPA 1.3.0参考文档：查询与自定义扩展

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SpringData JPA 是一个强大的 Java 集成框架，用于简化在 Spring 应用程序中使用 Java Persistence API (JPA) 进行数据访问和操作。此文档是 Spring Data JPA 的参考文档，版本为 1.3.0.RELEASE，由 Oliver Gierke 作为 Senior Consultant，来自 VMware 的 SpringSource 部门编写。版权信息表明，这份文档允许在个人使用和非商业分发的前提下复制，但必须包含版权声明。文档详细介绍了 Spring Data JPA 的核心功能和使用方法，分为多个章节： 1. **项目元数据**：这部分可能涵盖了如何设置项目的基本配置，如 JPA 配置文件、依赖项管理和数据源管理。 2. **Repositories**：这是文档的核心部分，Spring Data JPA 的核心概念围绕 Repository 接口展开。Repository 接口定义了与数据库交互的方法，使得开发者可以通过简单的命名查询（也称为查询方言）来操作数据。这包括： - **Introduction**：介绍Repository接口的概念和其在Spring Data中的作用。 - **Core concepts**：阐述了基本概念，如声明式查询、自动映射和检索策略。 - **Query methods**：讲解如何定义查询方法，包括基本查询、参数化查询和复杂查询构建。 - **Defining repository interfaces**：指导如何创建和定制 Repository 接口，以及如何细化查询查找策略。 - **Query creation**：讨论如何根据具体需求动态创建和执行查询。 - **Special parameter handling**：处理特殊参数的情况，如集合参数、空值处理等。 - **Creating repository instances**：说明如何在应用程序中创建 Repository 实例。 - **XML Configuration** 和 **Java Config**：对比两种不同的配置方式，即基于 XML 的配置和基于 Java 的配置。 3. **Custom implementations**：这部分探讨如何为单个或所有 Repository 实现自定义行为，扩展基础功能。 4. **Extensions**：涵盖了 Spring Data JPA 的扩展点，如领域类（domain classes）、查询事件监听器和自定义查询类型。通过阅读这份参考文档，开发者可以深入理解如何利用 Spring Data JPA 提高开发效率，实现面向对象的数据访问，同时也能掌握如何在实际项目中灵活应用和扩展框架的功能。对于想要在 Spring 应用中集成 JPA 的开发者来说，这是一个不可或缺的参考资料。

please define productname in your docbook file!

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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

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1.3.0.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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Spring Data JPA 1.3.0参考文档：查询与自定义扩展

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