Spring data JPA 自定义仓库，如何应用逻辑

Without spring-data normally, I define a DAO method with input parameter FilterPatient, so I build a query based on parameter not null and then I substitute parameter with query.setString method. In this way I write one generic method, is it possible with Spring-data and JPA repositories?

编辑

用户查询示例

SELECT FROM Patient p WHERE p.name = :name
AND p.surname = :surname
AND p.cf = :cf

以及其他可能的配置，例如FilterPatient的cf属性为NULL，查询会变成:

and other possible configuration, for example, in cf property of FilterPatient IS NULL, the query will become:

SELECT FROM Patient p WHERE p.name = :name
AND p.surname = :surname

推荐答案

您正在寻找的是与 Spring Data JPA 相关的规范模式:

What you are looking for is the Specification pattern which is discussed in relation to Spring Data JPA at the following:

https://spring.io/blog/2011/04/26/advanced-spring-data-jpa-specifications-and-querydsl/

以及关于每个查询都有一个查询方法的注意事项:

and which notes with reference to having a query method per query:

虽然这种方法真的很方便(你甚至不必编写一行实现代码来获取查询执行)它有两个缺点:第一，查询方法的数量可能会因更大的应用程序而增长 - 这是第二个point - 查询定义了一组固定的标准.为了避免这些两个缺点，如果你能想出一套不是很酷您可以动态组合以构建您的原子谓词查询?

Although this approach is really convenient (you don’t even have to write a single line of implementation code to get the queries executed) it has two drawbacks: first, the number of query methods might grow for larger applications because of - and that’s the second point - the queries define a fixed set of criterias. To avoid these two drawbacks, wouldn’t it be cool if you could come up with a set of atomic predicates that you could combine dynamically to build your query?

您可以使用 JPA 标准 API 或使用 QueryDSL 来实现规范模式.使用后者就像让您的存储库扩展以下接口一样简单:

You can implement the Specification pattern using either the JPA criteria API or using QueryDSL. Using the latter this is as easy as having your repository extend the following interface:

http://docs.spring.io/spring-data/commons/docs/current/api/org/springframework/data/querydsl/QueryDslPredicateExecutor.html

并为您的项目添加对 Querydsl 的支持.对于 Maven 项目，您只需将以下配置添加到您的 POM.该插件将自动生成构造谓词所需的查询类，然后您可以使用任意参数组合调用存储库的以下方法:

and adding support for Querydsl to your project. For a Maven project you simply need to add the configuration below to your POM. The plugin will auto generate the Query classes required to construct the predicates and you can then call the following methods of your Repository with any combination of parameters:

Iterable<T> findAll(com.querydsl.core.types.OrderSpecifier<?>... orders)
Iterable<T> findAll(com.querydsl.core.types.Predicate predicate)
Iterable<T> findAll(com.querydsl.core.types.Predicate predicate, com.querydsl.core.types.OrderSpecifier<?>... orders)
Page<T> findAll(com.querydsl.core.types.Predicate predicate, Pageable pageable)
Iterable<T> findAll(com.querydsl.core.types.Predicate predicate, Sort sort)
T   findOne(com.querydsl.core.types.Predicate predicate)

使用这种方法，您的 PatientRepository 变得简单:

With this approach then your PatientRepository becomes simply:

PatientRepository extends JpaRepository<Patient, Long>, QueryDslLPredicateExecutor<Patient> {
   // no query methods needed
}

请注意，Spring Data Gosling 版本还添加了对自动将 HTTP 参数绑定到 QueryDSL 谓词的支持，因此您还可以删除过滤器并让 Spring Data 端到端处理所有内容.

Note that the Spring Data Gosling release also added support for automatically binding HTTP params to a QueryDSL Predicate so you could also remove your Filter and have Spring Data handle everything end-to-end.

https://spring.io/blog/2015/09/04/what-s-new-in-spring-data-release-gosling#querydsl-web-support

这里有一些示例显示了使用各种参数调用的 1 个查询方法:

There are some examples here showing 1 query method being called with various parameters:

https://stackoverflow.com/a/26450224/1356423

Maven 设置:

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    .....

    <properties>
        <querydsl.version>4.1.3</querydsl.version>
    </properties>

    <dependencies>

        .....

        <dependency>
            <groupId>com.querydsl</groupId>
            <artifactId>querydsl-jpa</artifactId>
            <version>${querydsl.version}</version>
        </dependency>
        <dependency>
            <groupId>com.querydsl</groupId>
            <artifactId>querydsl-apt</artifactId>
            <version>${querydsl.version}</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>

           ....

            <plugin>
                <groupId>com.mysema.maven</groupId>
                <artifactId>apt-maven-plugin</artifactId>
                <version>1.1.3</version>
                <executions>
                    <execution>
                        <goals>
                            <goal>process</goal>
                        </goals>
                        <configuration>
                            <outputDirectory>target/generated-sources/java</outputDirectory>
                            <processor>com.querydsl.apt.jpa.JPAAnnotationProcessor</processor>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>

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