IllegalArgumentException：为TypedQuery 指定的类型与查询返回类型不兼容

我在为Generic类型创建TypedQuery时遇到了这种间歇性错误。 我的方法是：

public List findByEmail(Class type, String email_id){ String query = "SELECT t FROM " + type.getSimpleName() + " t WHERE t.email =:"+email_id; TypedQuery typedQuery =em.createQuery(query, type); return (List) typedQuery.getResultList(); } 

如果我重新启动服务器，则错误不会重新出现并正确获取结果。

 play.api.Application$$anon$1: Execution exception[[IllegalArgumentException: Type specified for TypedQuery [model.User] is incompatible with query return type [class model.User]]] at play.api.Application$class.handleError(Application.scala:296) ~[play_2.11-2.3.7.jar:2.3.7] at play.api.DefaultApplication.handleError(Application.scala:402) [play_2.11-2.3.7.jar:2.3.7] at play.core.server.netty.PlayDefaultUpstreamHandler$$anonfun$3$$anonfun $applyOrElse$4.apply(PlayDefaultUpstreamHandler.scala:320) [play_2.11-2.3.7.jar: 2.3.7] at play.core.server.netty.PlayDefaultUpstreamHandler$$anonfun$3$$anonfun $applyOrElse$4.apply(PlayDefaultUpstreamHandler.scala:320) [play_2.11-2.3.7.jar:2.3.7] at scala.Option.map(Option.scala:145) [scala-library-2.11.1.jar:na] Caused by: java.lang.IllegalArgumentException: Type specified for TypedQuery [model.User] is incompatible with query return type [class model.User] at org.hibernate.jpa.spi.AbstractEntityManagerImpl.resultClassChecking(AbstractEntityManagerImpl.java:387) ~[hibernate-entitymanager-4.3.6.Final.jar:4.3.6.Final] at org.hibernate.jpa.spi.AbstractEntityManagerImpl.createQuery(AbstractE ntityManagerImpl.java:344) ~[hibernate-entitymanager-4.3.6.Final.jar:4.3.6.Final ] at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8. 0_25] at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl. java:62) ~[na:1.8.0_25] at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAcces sorImpl.java:43) ~[na:1.8.0_25] 

Answer 1

问题是

 TypedQuery typedQuery =em.createQuery(query.toString(), type); 

这里var类型是一个Class Object而不是User类，你需要做这样的事情。

 TypedQuery typedQuery =em.createQuery(query.toString(), Class.forName(type.getSimpleName())); 

这将返回一个Class，TypedQuery将在运行时变为TypedQuery