Spring Data REST的QueryDSL集成，用于查询实体中集合映射的子属性

进行了一些重要的挖掘，以确定使用query-dsl的spring-data-rest可以让REST API客户端轻松过滤实体的大多数属性 .

这个问题也很有用：Can Spring Data REST's QueryDSL integration be used to perform more complex queries?

正如Dennis Laumen已经提到的那样， QueryDslPredicateExecutor 和 QuerydslBinderCustomizer 提供了一些壮观的功能，但缺乏文档 .

我试图破解的具体功能是：

我有一个User实体，其中@ManyToMany映射到UserGroup实体

public class User {

    @Id
    @GeneratedValue
    private Long id;

    @Column(name = "user_name")
    private String username;

    @ManyToMany
    @JoinTable(name = "fs_user_group_map", joinColumns = { @JoinColumn(name = "user_id") }, inverseJoinColumns = { @JoinColumn(name = "group_id") })
    private List<UserGroup> userGroups;
}

我正在尝试获取所有用户，其userGroup的名称之一应与文本匹配：

所以我想要点击的URI是： /users?userGroups.name=Admin

但是这个错误了 .

19:08:04.423|ERROR|o.s.d.r.w.RepositoryRestExceptionHandler|null
    java.lang.NullPointerException: null
    at org.springframework.util.ReflectionUtils.getField(ReflectionUtils.java:143) ~[spring-core-4.2.4.RELEASE.jar:4.2.4.RELEASE]
    at org.springframework.data.querydsl.binding.QuerydslPredicateBuilder.reifyPath(QuerydslPredicateBuilder.java:185) ~[spring-data-commons-1.11.2.RELEASE.jar:na]
    at org.springframework.data.querydsl.binding.QuerydslPredicateBuilder.reifyPath(QuerydslPredicateBuilder.java:188) ~[spring-data-commons-1.11.2.RELEASE.jar:na]
    at org.springframework.data.querydsl.binding.QuerydslPredicateBuilder.getPath(QuerydslPredicateBuilder.java:167) ~[spring-data-commons-1.11.2.RELEASE.jar:na]
    at org.springframework.data.querydsl.binding.QuerydslPredicateBuilder.invokeBinding(QuerydslPredicateBuilder.java:136) ~[spring-data-commons-1.11.2.RELEASE.jar:na]
    at org.springframework.data.querydsl.binding.QuerydslPredicateBuilder.getPredicate(QuerydslPredicateBuilder.java:111) ~[spring-data-commons-1.11.2.RELEASE.jar:na]
    at org.springframework.data.rest.webmvc.config.QuerydslAwareRootResourceInformationHandlerMethodArgumentResolver.postProcess(QuerydslAwareRootResourceInformationHandlerMethodArgumentResolver.java:91) ~[spring-data-rest-webmvc-2.4.2.RELEASE.jar:na]
    at org.springframework.data.rest.webmvc.config.RootResourceInformationHandlerMethodArgumentResolver.resolveArgument(RootResourceInformationHandlerMethodArgumentResolver.java:92) ~[spring-data-rest-webmvc-2.4.2.RELEASE.jar:na]
    at org.springframework.data.rest.webmvc.config.RootResourceInformationHandlerMethodArgumentResolver.resolveArgument(RootResourceInformationHandlerMethodArgumentResolver.java:40) ~[spring-data-rest-webmvc-2.4.2.RELEASE.jar:na]
    at org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:78) ~[spring-web-4.2.4.RELEASE.jar:4.2.4.RELEASE]
    at org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:162) ~[spring-web-4.2.4.RELEASE.jar:4.2.4.RELEASE]
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:129) ~[spring-web-4.2.4.RELEASE.jar:4.2.4.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:110) ~[spring-webmvc-4.2.4.RELEASE.jar:4.2.4.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:814) ~[spring-webmvc-4.2.4.RELEASE.jar:4.2.4.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:737) ~[spring-webmvc-4.2.4.RELEASE.jar:4.2.4.RELEASE]
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85) ~[spring-webmvc-4.2.4.RELEASE.jar:4.2.4.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:959) ~[spring-webmvc-4.2.4.RELEASE.jar:4.2.4.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893) ~[spring-webmvc-4.2.4.RELEASE.jar:4.2.4.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:969) [spring-webmvc-4.2.4.RELEASE.jar:4.2.4.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:860) [spring-webmvc-4.2.4.RELEASE.jar:4.2.4.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:687) [javax.servlet-api-3.1.0.jar:3.1.0]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:845) [spring-webmvc-4.2.4.RELEASE.jar:4.2.4.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:790) [javax.servlet-api-3.1.0.jar:3.1.0]
    at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:812) [jetty-servlet-9.2.14.v20151106.jar:9.2.14.v20151106]

围绕QuerydslPredicateBuilder.reifyPath的一些调试让我理解userGroups是 ListPath 并且尝试使用反射来查找它上面的属性'name' . 但我真正需要的query-dsl路径是 user.userGroups.any().name

尝试在URL上使用任何其他语法虽然在 QuerydslPredicateBuilder.getPredicate 中似乎没有被识别为有效 PropertyPath .

这是一个错误吗？