java - 使用Spring Data Rest从自定义JpaRepository方法返回投影列表

我有一个简单的Spring Boot应用程序，其中包含Spring Data JPA和Spring Data Rest模块。

Spring Data Rest会自动公开JPA存储库，但是当我向存储库中的自定义搜索方法发送HTTP GET请求时，该方法返回一个投影列表，我得到Couldn't find PersistentEntity for type class com.sun.proxy.$Proxy117!。当我将方法的返回类型从投影列表更改为仅投影时，它可以正常工作。

人实体类

@Entity
public class Person {
    @Id
    @GeneratedValue
    private Long id;

    @Column
    private String name;

    @Column
    private String surname;
}

人资料库

public interface PersonRepository extends JpaRepository<Person, Long> {
    List<NameProjection> findByNameContains(@Param(value = "name") String name);
}

投影

@Projection(name = "nameProjection", types = {Person.class})
public interface NameProjection {
    String getName();
}

网址:http://localhost:8080/persons/search/findByNameContains?name=a

堆栈跟踪:

java.lang.IllegalArgumentException: Couldn't find PersistentEntity for type class com.sun.proxy.$Proxy117!
    at org.springframework.data.mapping.context.PersistentEntities.lambda$getRequiredPersistentEntity$2(PersistentEntities.java:78) ~[spring-data-commons-2.0.6.RELEASE.jar:2.0.6.RELEASE]
    at java.util.Optional.orElseThrow(Optional.java:290) ~[na:1.8.0_161]
    at org.springframework.data.mapping.context.PersistentEntities.getRequiredPersistentEntity(PersistentEntities.java:77) ~[spring-data-commons-2.0.6.RELEASE.jar:2.0.6.RELEASE]
    at org.springframework.data.rest.webmvc.PersistentEntityResourceAssembler.wrap(PersistentEntityResourceAssembler.java:72) ~[spring-data-rest-webmvc-3.0.6.RELEASE.jar:3.0.6.RELEASE]
    at org.springframework.data.rest.webmvc.PersistentEntityResourceAssembler.toResource(PersistentEntityResourceAssembler.java:55) ~[spring-data-rest-webmvc-3.0.6.RELEASE.jar:3.0.6.RELEASE]
    at org.springframework.data.rest.webmvc.AbstractRepositoryRestController.entitiesToResources(AbstractRepositoryRestController.java:110) ~[spring-data-rest-webmvc-3.0.6.RELEASE.jar:3.0.6.RELEASE]
    at org.springframework.data.rest.webmvc.AbstractRepositoryRestController.toResources(AbstractRepositoryRestController.java:80) ~[spring-data-rest-webmvc-3.0.6.RELEASE.jar:3.0.6.RELEASE]
    at org.springframework.data.rest.webmvc.RepositorySearchController.lambda$toResource$1(RepositorySearchController.java:209) ~[spring-data-rest-webmvc-3.0.6.RELEASE.jar:3.0.6.RELEASE]
    at java.util.Optional.map(Optional.java:215) ~[na:1.8.0_161]
    at org.springframework.data.rest.webmvc.RepositorySearchController.toResource(RepositorySearchController.java:206) ~[spring-data-rest-webmvc-3.0.6.RELEASE.jar:3.0.6.RELEASE]
    at org.springframework.data.rest.webmvc.RepositorySearchController.executeSearch(RepositorySearchController.java:190) ~[spring-data-rest-webmvc-3.0.6.RELEASE.jar:3.0.6.RELEASE]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_161]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_161]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_161]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_161]
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:209) ~[spring-web-5.0.5.RELEASE.jar:5.0.5.RELEASE]
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:136) ~[spring-web-5.0.5.RELEASE.jar:5.0.5.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:102) ~[spring-webmvc-5.0.5.RELEASE.jar:5.0.5.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:877) ~[spring-webmvc-5.0.5.RELEASE.jar:5.0.5.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:783) ~[spring-webmvc-5.0.5.RELEASE.jar:5.0.5.RELEASE]

https://github.com/mahsumdemir/projection-demo上有一个示例项目来显示错误。启动项目后，转到http://localhost:8080/persons/search/findByNameContains?name=i url，您将看到错误。

更新

我想返回List<NameProjection>，因为Spring Data JPA使用存储库方法的返回类型来确定将在数据库上执行的SQL。调用返回类型为List<Person>的方法将在数据库上执行select * from person;。但是，调用返回类型为List<NameProjection>的方法会在数据库上执行select name from person;。对于Person实体，从数据库收集的额外数据不是问题。但是，在具有多媒体列的实体上操作时，这是一个大问题。

更新2

相关吉拉问题:https://jira.spring.io/browse/DATAREST-1237

最佳答案

Spring Data REST 允许多个投影。您可以通过url参数传递所需的投影

例如:/ persons / search / nickname？name = r＆ projection =姓

因此，在您的存储库中，您无需重新运行 NameProjection ，只需返回人员

 public interface PersonRepository extends JpaRepository<Person, Long> {
  List<Person> findByNameContains(@Param(value = "name") String name);
 }

并致电/ persons / search / findByNameContains？name = a＆ projection = nameProjection ，就可以了。

看看这个demo