使用Set上的@DBRef注释引用文档

Question

我有以下类，它是更大域结构的一部分。换句话说，Squad不是文档的基础：

public class Squad {

  @DBRef
  private final Set<Player> players;

  public Squad(Set<Player> players) {
    this.players = ImmutableSet.copyOf(Objects.requireNonNull(players));
  }

  public Set<Player> getPlayers() {
    return players;
  }

}

Player的外观与问题无关。

我正在使用Spring Data MongoDB版本 1.10.1 ，这允许我使用@DBRef作为单独的文档引用Player。

存储和阅读我正在扩展的文件MongoRepository。

我在存储文档时没有问题，但是当从数据库中读取文档时，Spring Data会尝试使用Squad构造函数创建List。

我尽量保持我的域名清洁，因为一个小队应该包含独特的玩家，Set会有所作为。另外，我想避免使用构造函数（例如默认构造函数）来混乱我的类，只是为了使它工作。作为旁注，我试图保持我的域不可变。

如何让Spring Data MongoDB了解如何在从数据库中读取Squad时使用Player来实例化Set？或者这就是MongoDB的方式作品？ （我更熟悉关系数据库/ JPA，其中Collection可以像这样使用）

我想让构造函数接受Collection作为参数可行，但正如我所说，我想避免这种情况。我也尝试使用私有构造函数接受java.lang.IllegalArgumentException: argument type mismatch at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.8.0_121] at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) ~[na:1.8.0_121] at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[na:1.8.0_121] at java.lang.reflect.Constructor.newInstance(Constructor.java:423) ~[na:1.8.0_121] at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:142) ~[spring-beans-4.3.7.RELEASE.jar:4.3.7.RELEASE] at org.springframework.data.convert.ReflectionEntityInstantiator.createInstance(ReflectionEntityInstantiator.java:76) ~[spring-data-commons-1.13.1.RELEASE.jar:na] at org.springframework.data.convert.ClassGeneratingEntityInstantiator.createInstance(ClassGeneratingEntityInstantiator.java:83) ~[spring-data-commons-1.13.1.RELEASE.jar:na] at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:257) ~[spring-data-mongodb-1.10.1.RELEASE.jar:na] at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:237) ~[spring-data-mongodb-1.10.1.RELEASE.jar:na] at org.springframework.data.mongodb.core.convert.MappingMongoConverter.readValue(MappingMongoConverter.java:1214) ~[spring-data-mongodb-1.10.1.RELEASE.jar:na] at org.springframework.data.mongodb.core.convert.MappingMongoConverter.access$200(MappingMongoConverter.java:84) ~[spring-data-mongodb-1.10.1.RELEASE.jar:na] at org.springframework.data.mongodb.core.convert.MappingMongoConverter$MongoDbPropertyValueProvider.getPropertyValue(MappingMongoConverter.java:1162) ~[spring-data-mongodb-1.10.1.RELEASE.jar:na] at org.springframework.data.mongodb.core.convert.MappingMongoConverter$MongoDbPropertyValueProvider.getPropertyValue(MappingMongoConverter.java:1125) ~[spring-data-mongodb-1.10.1.RELEASE.jar:na] at org.springframework.data.mapping.model.PersistentEntityParameterValueProvider.getParameterValue(PersistentEntityParameterValueProvider.java:78) ~[spring-data-commons-1.13.1.RELEASE.jar:na] at org.springframework.data.mapping.model.SpELExpressionParameterValueProvider.getParameterValue(SpELExpressionParameterValueProvider.java:63) ~[spring-data-commons-1.13.1.RELEASE.jar:na] at org.springframework.data.convert.ReflectionEntityInstantiator.createInstance(ReflectionEntityInstantiator.java:71) ~[spring-data-commons-1.13.1.RELEASE.jar:na] at org.springframework.data.convert.ClassGeneratingEntityInstantiator.createInstance(ClassGeneratingEntityInstantiator.java:83) ~[spring-data-commons-1.13.1.RELEASE.jar:na] at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:257) ~[spring-data-mongodb-1.10.1.RELEASE.jar:na] at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:237) ~[spring-data-mongodb-1.10.1.RELEASE.jar:na] at org.springframework.data.mongodb.core.convert.MappingMongoConverter.readValue(MappingMongoConverter.java:1214) ~[spring-data-mongodb-1.10.1.RELEASE.jar:na] at org.springframework.data.mongodb.core.convert.MappingMongoConverter.access$200(MappingMongoConverter.java:84) ~[spring-data-mongodb-1.10.1.RELEASE.jar:na] at org.springframework.data.mongodb.core.convert.MappingMongoConverter$MongoDbPropertyValueProvider.getPropertyValue(MappingMongoConverter.java:1162) ~[spring-data-mongodb-1.10.1.RELEASE.jar:na] at org.springframework.data.mongodb.core.convert.MappingMongoConverter$MongoDbPropertyValueProvider.getPropertyValue(MappingMongoConverter.java:1125) ~[spring-data-mongodb-1.10.1.RELEASE.jar:na] at org.springframework.data.mapping.model.PersistentEntityParameterValueProvider.getParameterValue(PersistentEntityParameterValueProvider.java:78) ~[spring-data-commons-1.13.1.RELEASE.jar:na] at org.springframework.data.mapping.model.SpELExpressionParameterValueProvider.getParameterValue(SpELExpressionParameterValueProvider.java:63) ~[spring-data-commons-1.13.1.RELEASE.jar:na] at org.springframework.data.convert.ReflectionEntityInstantiator.createInstance(ReflectionEntityInstantiator.java:71) ~[spring-data-commons-1.13.1.RELEASE.jar:na] at org.springframework.data.convert.ClassGeneratingEntityInstantiator.createInstance(ClassGeneratingEntityInstantiator.java:83) ~[spring-data-commons-1.13.1.RELEASE.jar:na] at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:257) ~[spring-data-mongodb-1.10.1.RELEASE.jar:na] at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:237) ~[spring-data-mongodb-1.10.1.RELEASE.jar:na] at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:197) ~[spring-data-mongodb-1.10.1.RELEASE.jar:na] at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:193) ~[spring-data-mongodb-1.10.1.RELEASE.jar:na] at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:84) ~[spring-data-mongodb-1.10.1.RELEASE.jar:na] at org.springframework.data.mongodb.core.MongoTemplate$ReadDbObjectCallback.doWith(MongoTemplate.java:2313) ~[spring-data-mongodb-1.10.1.RELEASE.jar:na] at org.springframework.data.mongodb.core.MongoTemplate.executeFindMultiInternal(MongoTemplate.java:1966) ~[spring-data-mongodb-1.10.1.RELEASE.jar:na] at org.springframework.data.mongodb.core.MongoTemplate.doFind(MongoTemplate.java:1784) ~[spring-data-mongodb-1.10.1.RELEASE.jar:na] at org.springframework.data.mongodb.core.MongoTemplate.doFind(MongoTemplate.java:1767) ~[spring-data-mongodb-1.10.1.RELEASE.jar:na] at org.springframework.data.mongodb.core.MongoTemplate.find(MongoTemplate.java:641) ~[spring-data-mongodb-1.10.1.RELEASE.jar:na] at org.springframework.data.mongodb.repository.support.SimpleMongoRepository.findAll(SimpleMongoRepository.java:359) ~[spring-data-mongodb-1.10.1.RELEASE.jar:na] at org.springframework.data.mongodb.repository.support.SimpleMongoRepository.findAll(SimpleMongoRepository.java:197) ~[spring-data-mongodb-1.10.1.RELEASE.jar:na] at org.springframework.data.mongodb.repository.support.SimpleMongoRepository.findAll(SimpleMongoRepository.java:51) ~[spring-data-mongodb-1.10.1.RELEASE.jar:na] at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_121] at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_121] at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_121] at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_121] at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.executeMethodOn(RepositoryFactorySupport.java:504) ~[spring-data-commons-1.13.1.RELEASE.jar:na] at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.doInvoke(RepositoryFactorySupport.java:489) ~[spring-data-commons-1.13.1.RELEASE.jar:na] at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.invoke(RepositoryFactorySupport.java:461) ~[spring-data-commons-1.13.1.RELEASE.jar:na] at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) ~[spring-aop-4.3.7.RELEASE.jar:4.3.7.RELEASE] at org.springframework.data.projection.DefaultMethodInvokingMethodInterceptor.invoke(DefaultMethodInvokingMethodInterceptor.java:61) ~[spring-data-commons-1.13.1.RELEASE.jar:na] at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) ~[spring-aop-4.3.7.RELEASE.jar:4.3.7.RELEASE] at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92) ~[spring-aop-4.3.7.RELEASE.jar:4.3.7.RELEASE] at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) ~[spring-aop-4.3.7.RELEASE.jar:4.3.7.RELEASE] at org.springframework.data.repository.core.support.SurroundingTransactionDetectorMethodInterceptor.invoke(SurroundingTransactionDetectorMethodInterceptor.java:57) ~[spring-data-commons-1.13.1.RELEASE.jar:na] at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) ~[spring-aop-4.3.7.RELEASE.jar:4.3.7.RELEASE] at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:213) ~[spring-aop-4.3.7.RELEASE.jar:4.3.7.RELEASE] at com.sun.proxy.$Proxy67.findAll(Unknown Source) ~[na:na] at my.package.TestController.getAllTeams(TestController.java:39) ~[classes/:na] at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_121] at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_121] at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_121] at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_121] at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE] at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:133) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE] at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:116) ~[spring-webmvc-4.3.7.RELEASE.jar:4.3.7.RELEASE] at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827) ~[spring-webmvc-4.3.7.RELEASE.jar:4.3.7.RELEASE] at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738) ~[spring-webmvc-4.3.7.RELEASE.jar:4.3.7.RELEASE] at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85) ~[spring-webmvc-4.3.7.RELEASE.jar:4.3.7.RELEASE] at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:963) ~[spring-webmvc-4.3.7.RELEASE.jar:4.3.7.RELEASE] at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:897) ~[spring-webmvc-4.3.7.RELEASE.jar:4.3.7.RELEASE] at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970) ~[spring-webmvc-4.3.7.RELEASE.jar:4.3.7.RELEASE] at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861) ~[spring-webmvc-4.3.7.RELEASE.jar:4.3.7.RELEASE] at javax.servlet.http.HttpServlet.service(HttpServlet.java:622) ~[tomcat-embed-core-8.5.11.jar:8.5.11] at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846) ~[spring-webmvc-4.3.7.RELEASE.jar:4.3.7.RELEASE] at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) ~[tomcat-embed-core-8.5.11.jar:8.5.11] at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:230) ~[tomcat-embed-core-8.5.11.jar:8.5.11] at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.11.jar:8.5.11] at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) ~[tomcat-embed-websocket-8.5.11.jar:8.5.11] at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) ~[tomcat-embed-core-8.5.11.jar:8.5.11] at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.11.jar:8.5.11] at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE] at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE] at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) ~[tomcat-embed-core-8.5.11.jar:8.5.11] at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.11.jar:8.5.11] at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:105) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE] at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE] at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) ~[tomcat-embed-core-8.5.11.jar:8.5.11] at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.11.jar:8.5.11] at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:81) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE] at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE] at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) ~[tomcat-embed-core-8.5.11.jar:8.5.11] at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.11.jar:8.5.11] at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:197) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE] at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE] at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) ~[tomcat-embed-core-8.5.11.jar:8.5.11] at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.11.jar:8.5.11] at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198) ~[tomcat-embed-core-8.5.11.jar:8.5.11] at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-8.5.11.jar:8.5.11] at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:474) [tomcat-embed-core-8.5.11.jar:8.5.11] at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) [tomcat-embed-core-8.5.11.jar:8.5.11] at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) [tomcat-embed-core-8.5.11.jar:8.5.11] at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) [tomcat-embed-core-8.5.11.jar:8.5.11] at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:349) [tomcat-embed-core-8.5.11.jar:8.5.11] at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:783) [tomcat-embed-core-8.5.11.jar:8.5.11] at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-8.5.11.jar:8.5.11] at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:798) [tomcat-embed-core-8.5.11.jar:8.5.11] at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1434) [tomcat-embed-core-8.5.11.jar:8.5.11] at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-8.5.11.jar:8.5.11] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_121] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_121] at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-8.5.11.jar:8.5.11] at java.lang.Thread.run(Thread.java:745) [na:1.8.0_121] ，但是Spring Data期望一个没有参数的构造函数（我猜是因为找到了两个构造函数）。

也许不相关，但这是我得到的堆栈跟踪：

{
  "timestamp": 1491657302229,
  "status": 500,
  "error": "Internal Server Error",
  "exception": "org.springframework.data.mapping.model.MappingInstantiationException",
  "message": "Failed to instantiate my.package.team.Squad using constructor public my.package.team.Squad(java.util.Set) with arguments [my.package.person.player.Player@2afde45b, my.package.person.player.Player@7f87e2e6, my.package.person.player.Player@337d278d, my.package.person.player.Player@3637e725, my.package.person.player.Player@732d0284, my.package.person.player.Player@337d5ed5, my.package.person.player.Player@69665678, my.package.person.player.Player@60e19abe, my.package.person.player.Player@7b439d04, my.package.person.player.Player@2211ef4f, my.package.person.player.Player@799fb8e3, my.package.person.player.Player@1547f904, my.package.person.player.Player@728bed15, my.package.person.player.Player@5fcd1f9c, my.package.person.player.Player@5b91ec26, my.package.person.player.Player@7134b189, my.package.person.player.Player@5cfa19ff, my.package.person.player.Player@6bfcdc03, my.package.person.player.Player@3fd8fd86, my.package.person.player.Player@6bb4ab0d]",
  "path": "/club"
}

我的测试控制器返回的内容：

require 'Slim/Slim.php';
\Slim\Slim::registerAutoloader();

$name_outside = '';

$app = new \Slim\Slim();
$app->get('/session/program_name/{name}', function ($args) use($app) {
    $name_outside = $args['name'];
    echo $args['name'];
});
$app->run();

Answer 1

字段和属性访问器映射都可以正常工作，并使用spring的集合转换器转换为Set<Player>。

这对于不可变部分没有帮助。

看起来与bean创建相关的代码是将DBRef批量提取到List中，然后将其传递给bean创建，并在此过程中丢失目标类型Set。

已记录下面的jira以涵盖更改以允许集合类型进入构造函数创建。

https://jira.spring.io/browse/DATAMONGO-1666

现在，解决方法是更改​​构造函数以接受您已找到的Collection类型。