引起：java.lang.ClassCastException：java.lang.Class无法强制转换为java.lang.reflect.ParameterizedType

我是Java Reflection的新手。

我检查了很多论坛，但我还没有找到合适的解决方案。

错误：

Caused by: java.lang.ClassCastException: java.lang.Class cannot be cast to java.lang.reflect.ParameterizedType 

当我试图从db获取对象时：

  new Unit().getBy(3L); 

方法声明

 @MappedSuperclass public abstract class Generic { @Transient public Class entityClass; Generic() { entityClass = ((Class) ((Class) ((ParameterizedType) getClass().getGenericSuperclass()).getActualTypeArguments()[0])); } @Id @GeneratedValue(strategy = GenerationType.TABLE) public Long id; public T getBy(Long id) { return JPA.em().find(entityClass, id); } 

二级扩展

 @MappedSuperclass public abstract class GenericDictionary<T extends Generic> extends Generic { @Required public String name; @Required public boolean active = true; public String getName() { return name; } public void setName(String name) { this.name = name; } public boolean getActive() { return active; } public void setActive(boolean stat) { this.active = stat; } 

实体类：

 @Entity @Table(name="common__Unit") public class Unit extends GenericDictionary { @ManyToOne(fetch=FetchType.LAZY) @JoinColumn(name="parent_id") public Unit parent; } 

和控制器中的方法调用：

 new Unit().getBy(3L); 

这很奇怪，因为我有其他实体，我可以使用该方法没有像这样的任何运行时错误。 这是实体：

 @Entity @Table(name="common__Clinic") public class Clinic extends GenericDictionary { @ManyToMany(cascade = CascadeType.PERSIST) public List unit; 

并在其他控制器中调用方法：

  Clinic clinic = new Clinic().getBy(3L); 

这段代码有效。 我没有看到模型和控制器之间的任何差异。

任何人都可以帮我指出我的错误吗？

—————————————-编辑——— —————————–

全栈跟踪

 [error] play - Cannot invoke the action, eventually got an error: javax.persistence.PersistenceException: org.hibernate.HibernateException: Javassist Enhancement failed: models.Unit [error] application - ! @6kb72hhpo - Internal server error, for (POST) [/SupraADMIN/oddzialy/zapisz] -> play.api.Application$$anon$1: Execution exception[[PersistenceException: org.hibernate.HibernateException: Javassist Enhancement failed: models.Unit]] at play.api.Application$class.handleError(Application.scala:293) ~[play_2.10-2.2.4.jar:2.2.4] at play.api.DefaultApplication.handleError(Application.scala:399) [play_2.10-2.2.4.jar:2.2.4] at play.core.server.netty.PlayDefaultUpstreamHandler$$anonfun$3$$anonfun$applyOrElse$3.apply(PlayDefaultUpstreamHandler.scala:264) [play_2.10-2.2.4.jar:2.2.4] at play.core.server.netty.PlayDefaultUpstreamHandler$$anonfun$3$$anonfun$applyOrElse$3.apply(PlayDefaultUpstreamHandler.scala:264) [play_2.10-2.2.4.jar:2.2.4] at scala.Option.map(Option.scala:145) [scala-library.jar:na] at play.core.server.netty.PlayDefaultUpstreamHandler$$anonfun$3.applyOrElse(PlayDefaultUpstreamHandler.scala:264) [play_2.10-2.2.4.jar:2.2.4] Caused by: javax.persistence.PersistenceException: org.hibernate.HibernateException: Javassist Enhancement failed: models.Unit at org.hibernate.ejb.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1387) ~[hibernate-entitymanager-4.2.0.CR1.jar:4.2.0.CR1] at org.hibernate.ejb.AbstractEntityManagerImpl.find(AbstractEntityManagerImpl.java:838) ~[hibernate-entitymanager-4.2.0.CR1.jar:4.2.0.CR1] at org.hibernate.ejb.AbstractEntityManagerImpl.find(AbstractEntityManagerImpl.java:781) ~[hibernate-entitymanager-4.2.0.CR1.jar:4.2.0.CR1] at models.Generic.getBy(Generic.java:62) ~[na:na] at controllers.admin.CMS.UnitsSubmit(CMS.java:477) ~[na:na] at admin.Routes$$anonfun$routes$1$$anonfun$applyOrElse$13$$anonfun$apply$13.apply(routes_routing.scala:317) ~[na:na] Caused by: org.hibernate.HibernateException: Javassist Enhancement failed: models.Unit at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.getProxy(JavassistLazyInitializer.java:143) ~[hibernate-core-4.2.0.CR1.jar:4.2.0.CR1] at org.hibernate.proxy.pojo.javassist.JavassistProxyFactory.getProxy(JavassistProxyFactory.java:73) ~[hibernate-core-4.2.0.CR1.jar:4.2.0.CR1] at org.hibernate.tuple.entity.AbstractEntityTuplizer.createProxy(AbstractEntityTuplizer.java:758) ~[hibernate-core-4.2.0.CR1.jar:4.2.0.CR1] at org.hibernate.persister.entity.AbstractEntityPersister.createProxy(AbstractEntityPersister.java:4396) ~[hibernate-core-4.2.0.CR1.jar:4.2.0.CR1] at org.hibernate.event.internal.DefaultLoadEventListener.createProxyIfNecessary(DefaultLoadEventListener.java:332) ~[hibernate-core-4.2.0.CR1.jar:4.2.0.CR1] at org.hibernate.event.internal.DefaultLoadEventListener.proxyOrLoad(DefaultLoadEventListener.java:258) ~[hibernate-core-4.2.0.CR1.jar:4.2.0.CR1] Caused by: java.lang.ClassCastException: java.lang.Class cannot be cast to java.lang.reflect.ParameterizedType at models.Generic.(Generic.java:40) ~[na:na] at models.GenericDictionary.(GenericDictionary.java:13) ~[na:na] at models.Unit.(Unit.java:30) ~[na:na] at models.Unit_$$_jvst57e_b5.(Unit_$$_jvst57e_b5.java) ~[na:na] at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.7.0_65] at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57) ~[na:1.7.0_65] [error] application - REGUEST: POST /SupraADMIN/oddzialy/zapisz GENERATED ERROR: @6kb72hhpo: Execution exception in /home/user/Aplikacje/Eclipse/SVP/modules/common/app/models/Generic.java:62 

Answer 1

使用复杂类型层次结构时， getGenericSuperclass方法不起作用。 相反，您可以尝试使用TypeTools ：

 Generic() { entityClass = (Class)TypeResolver.resolveRawArgument(Generic.class, getClass()); } 

Answer 2

这是解决问题的通用模型的构造函数：

 @MappedSuperclass public abstract class Generic { @Transient protected Class entityClass; public Generic() { Class obtainedClass = getClass(); Type genericSuperclass = null; for(;;) { genericSuperclass = obtainedClass.getGenericSuperclass(); if(genericSuperclass instanceof ParameterizedType) { break; } obtainedClass = obtainedClass.getSuperclass(); } ParameterizedType genericSuperclass_ = (ParameterizedType) genericSuperclass; entityClass = ((Class) ((Class) genericSuperclass_.getActualTypeArguments()[0])); } 

Answer 3

在您的Generic类中请用户：

 private Class persistentClass; @SuppressWarnings("unchecked") public AbstractGenericDAOImpl() { this.persistentClass = (Class) ((ParameterizedType) getClass().getGenericSuperclass()).getActualTypeArguments()[0]; }