SpringData JPA 官方英文参考文档PDF

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SpringData JPA 是一个强大的 Java 框架，它与 Java Persistence API (JPA) 集成，简化了在企业级应用程序中管理和操作数据库的操作。此参考文档（1.4.2.RELEASE 版本）由 Oliver Gierke 和 Thomas Darimont 两位软件工程师编撰，他们是 GoPivotal GmbH 的成员，版权日期涵盖 2008-2013 年。该文档的核心内容分为两大部分： 1. **Project metadata**：这部分介绍了文档的基本信息，包括作者、许可条款（允许复制和分发，但需保留版权声明），以及对文档中产品名称的要求，提示读者在自己的文档中定义明确的产品名称。 2. **Reference Documentation**： - **Working with SpringData Repositories**: 这是文档的主要部分，详细讲解如何在项目中有效地使用 SpringData JPA。首先，涵盖了 **Core concepts**，即 SpringData JPA 的核心概念，如Repository接口、查询方法和数据映射。 - **Defining repository interfaces**: 如何定义带有查询方法的 Repository 接口，这是实现数据访问的关键。用户可以自定义查询方法，包括查询策略、参数处理和返回结果的属性表达式。 - **Fine-tuning repository definition**: 提供了对 Repository 定义的进一步优化选项，比如查询创建和处理特殊参数的方式。 - **Query creation and lookup strategies**: 讨论了如何创建和选择查询执行策略，确保高效的数据检索。 - **Property expressions**: 关注如何使用属性表达式来指定查询条件，提高代码的可读性和灵活性。 - **Special parameter handling**: 专门探讨在处理复杂查询时，如何处理特殊参数，如数组或集合。 - **Creating repository instances**: 描述了如何在 Spring 应用上下文中创建和配置 Repository 实例，支持 XML 配置和 Java Configuration。 - **Standalone usage**: 提供了如何在不依赖 Spring 容器的情况下单独使用 SpringData JPA 的指导。通过阅读这份官方文档，开发人员可以深入了解如何利用 SpringData JPA 提升 Java 应用程序的数据库访问效率，以及如何遵循最佳实践来设计和扩展 Repository 接口。无论是在开发新项目还是优化现有系统，这份文档都是不可或缺的参考资料。

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1.4.2.RELEASE

Spring Data JPA -

Reference Documentation 5

Query lookup strategies

The following strategies are available for the repository infrastructure to resolve the query. You can

configure the strategy at the namespace through the query-lookup-strategy attribute. Some

strategies may not be supported for particular datastores.

CREATE

CREATE attempts to construct a store-specific query from the query method 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

USE_DECLARED_QUERY tries to find a declared query and will throw an exception in case it can't find

one. The query can be defined by an annotation somewhere or declared by other means. Consult the

documentation of the specific store to find available options for that store. If the repository infrastructure

does not find a declared query for the method at bootstrap time, it fails.

CREATE_IF_NOT_FOUND (default)

CREATE_IF_NOT_FOUND combines CREATE and USE_DECLARED_QUERY. It looks up a declared query

first, and if no declared query is found, it creates a custom method name-based query. This is the default

lookup strategy and thus will be used if you do not configure anything explicitly. It allows quick query

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

as needed.

Query creation

The query builder mechanism built into Spring Data repository infrastructure is useful for building

constraining queries over entities of the repository. The mechanism strips the prefixes find…By, read…

By, and get…By from the method and starts parsing the rest of it. The introducing clause can contain

further expressions such as a Distinct to set a distinct flag on the query to be created. However, the

first By acts as delimiter to indicate the start of the actual criteria. At a very basic level you can define

conditions on entity properties and concatenate them with And and Or .

public interface PersonRepository extends Repository<User, Long> {

List<Person> findByEmailAddressAndLastname(EmailAddress emailAddress, String lastname);

// Enables the distinct flag for the query

List<Person> findDistinctPeopleByLastnameOrFirstname(String lastname, String firstname);

List<Person> findPeopleDistinctByLastnameOrFirstname(String lastname, String firstname);

// Enabling ignoring case for an individual property

List<Person> findByLastnameIgnoreCase(String lastname);

// Enabling ignoring case for all suitable properties

List<Person> findByLastnameAndFirstnameAllIgnoreCase(String lastname, String firstname);

// Enabling static ORDER BY for a query

List<Person> findByLastnameOrderByFirstnameAsc(String lastname);

List<Person> findByLastnameOrderByFirstnameDesc(String lastname);

}

Example 1.4 Query creation from method names

The actual result of parsing the method depends on the persistence store for which you create the query.

However, there are some general things to notice.

please define productname in your docbook file!

1.4.2.RELEASE

Spring Data JPA -

Reference Documentation 6

• The expressions are usually property traversals combined with operators that can be concatenated.

You can combine property expressions with AND and OR. You also get support for operators such as

Between, LessThan, GreaterThan, Like for the property expressions. The supported operators

can vary by datastore, so consult the appropriate part of your reference documentation.

• The method parser supports setting an IgnoreCase flag for individual properties, for

example,findByLastnameIgnoreCase(…)) or for all properties of a type that support ignoring case

(usually Strings, for example, findByLastnameAndFirstnameAllIgnoreCase(…)). Whether

ignoring cases is supported may vary by store, so consult the relevant sections in the reference

documentation for the store-specific query method.

• You can apply static ordering by appending an OrderBy clause to the query method that references

a property and by providing a sorting direction (Asc or Desc). To create a query method that supports

dynamic sorting, see the section called “Special parameter handling”.

Property expressions

Property expressions can refer only to a direct property of the managed entity, as shown in the preceding

example. At query creation time you already make sure that the parsed property is a property of the

managed domain class. However, you can also define constraints by traversing nested properties.

Assume Persons have Addresses with ZipCodes. In that case a method name of

List<Person> findByAddressZipCode(ZipCode zipCode);

creates the property traversal x.address.zipCode. The resolution algorithm starts with interpreting

the entire part (AddressZipCode) as the property and checks the domain class for a property with

that name (uncapitalized). If the algorithm succeeds it uses that property. If not, the algorithm splits

up the source at the camel case parts from the right side into a head and a tail and tries to find the

corresponding property, in our example, AddressZip and Code. If the algorithm finds a property with

that head it takes the tail and continue building the tree down from there, splitting the tail up in the way

just described. If the first split does not match, the algorithm move the split point to the left (Address,

ZipCode) and continues.

Although this should work for most cases, it is possible for the algorithm to select the wrong property.

Suppose the Person class has an addressZip property as well. The algorithm would match in the first

split round already and essentially choose the wrong property and finally fail (as the type of addressZip

probably has no code property). To resolve this ambiguity you can use _ inside your method name to

manually define traversal points. So our method name would end up like so:

List<Person> findByAddress_ZipCode(ZipCode zipCode);

Special parameter handling

To handle parameters to your query you simply define method parameters as already seen in the

examples above. Besides that the infrastructure will recognize certain specific types like Pageable and

Sort to apply pagination and sorting to your queries dynamically.

Page<User> findByLastname(String lastname, Pageable pageable);

List<User> findByLastname(String lastname, Sort sort);

List<User> findByLastname(String lastname, Pageable pageable);

Example 1.5 Using Pageable and Sort in query methods

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