此版本仍在开发中，尚未被视为稳定版本。对于最新的稳定版本，请使用 Spring Data Commons 3.4.4！spring-doc.cadn.net.cn

查询方法

标准 CRUD 功能存储库通常对底层数据存储进行查询。 使用 Spring Data，声明这些查询将成为一个四步过程：spring-doc.cadn.net.cn

  1. 声明一个扩展 Repository 的接口或其子接口之一，并将其键入到它应该处理的域类和 ID 类型，如以下示例所示：spring-doc.cadn.net.cn

    interface PersonRepository extends Repository<Person, Long> { … }

  2. 在接口上声明查询方法。spring-doc.cadn.net.cn

    interface PersonRepository extends Repository<Person, Long> {
  List<Person> findByLastname(String lastname);
}

  3. 设置 Spring 以使用 JavaConfig 或 XML 配置为这些接口创建代理实例。spring-doc.cadn.net.cn

    import org.springframework.data.….repository.config.EnableJpaRepositories;

@EnableJpaRepositories
class Config { … }
    <?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xmlns:jpa="http://www.springframework.org/schema/data/jpa"
   xsi:schemaLocation="http://www.springframework.org/schema/beans
     https://www.springframework.org/schema/beans/spring-beans.xsd
     http://www.springframework.org/schema/data/jpa
     https://www.springframework.org/schema/data/jpa/spring-jpa.xsd">

   <repositories base-package="com.acme.repositories"/>

</beans>

    The JPA namespace is used in this example. If you use the repository abstraction for any other store, you need to change this to the appropriate namespace declaration of your store module. In other words, you should exchange jpa in favor of, for example, mongodb.spring-doc.cadn.net.cn

    Note that the JavaConfig variant does not configure a package explicitly, because the package of the annotated class is used by default. To customize the package to scan, use one of the basePackage… attributes of the data-store-specific repository’s @EnableJpaRepositories-annotation.spring-doc.cadn.net.cn

  4. Inject the repository instance and use it, as shown in the following example:spring-doc.cadn.net.cn

    class SomeClient {

  private final PersonRepository repository;

  SomeClient(PersonRepository repository) {
    this.repository = repository;
  }

  void doSomething() {
    List<Person> persons = repository.findByLastname("Matthews");
  }
}

The sections that follow explain each step in detail:spring-doc.cadn.net.cn