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

本文介绍了引起：java.lang.ClassCastException：java.lang.Class无法强制转换为java.lang.reflect.ParameterizedType的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我是Java Reflection的新手。

I am new in Java Reflection.

我查了很多论坛，但我找不到合适的解决方案。

I checked a lot of forums, but I haven't found working solution.

错误：

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

当我试图从db获取对象时出现：

comes when I am trying to get object from db:

new Unit().getBy(3L);

方法声明

@MappedSuperclass public abstract class Generic<T extends Generic> { @Transient public Class<T> 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); }

二级延期

@MappedSuperclass public abstract class GenericDictionary<T extends Generic<T>> extends Generic<T> { @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<Unit> { @ManyToOne(fetch=FetchType.LAZY) @JoinColumn(name="parent_id") public Unit parent; }

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，没有任何运行时错误，如这个。这是该实体：

It is quite strange, cause I have other entity where I can use that method without any runtime error like this. Here is that entity:

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

在其他控制器中调用方法：

And the method call in other controller:

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

此代码有效。 我没看到那些型号和控制器之间有任何差异。

This code works. I dont see any differences between that models and controllers.

任何人都可以帮我指出我的错误吗？

Can any one help me pointing my mistakes here?

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完整堆栈跟踪

[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$$anon$1: Execution exception[[PersistenceException: org.hibernate.HibernateException: Javassist Enhancement failed: models.Unit]] at play.api.Application$class.handleError(Application.scala:293) ~[play_2.10-2.2.4.jar:2.2.4] at play.api.DefaultApplication.handleError(Application.scala:399) [play_2.10-2.2.4.jar:2.2.4] at play.core.serverty.PlayDefaultUpstreamHandler$$anonfun$3$$anonfun$applyOrElse$3.apply(PlayDefaultUpstreamHandler.scala:264) [play_2.10-2.2.4.jar:2.2.4] at play.core.serverty.PlayDefaultUpstreamHandler$$anonfun$3$$anonfun$applyOrElse$3.apply(PlayDefaultUpstreamHandler.scala:264) [play_2.10-2.2.4.jar:2.2.4] at scala.Option.map(Option.scala:145) [scala-library.jar:na] at play.core.serverty.PlayDefaultUpstreamHandler$$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$$anonfun$apply$13.apply(routes_routing.scala:317) ~[na:na] Caused by: org.hibernate.HibernateException: Javassist Enhancement failed: models.Unit at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.getProxy(JavassistLazyInitializer.java:143) ~[hibernate-core-4.2.0.CR1.jar:4.2.0.CR1] at org.hibernate.proxy.pojo.javassist.JavassistProxyFactory.getProxy(JavassistProxyFactory.java:73) ~[hibernate-core-4.2.0.CR1.jar:4.2.0.CR1] at org.hibernate.tuple.entity.AbstractEntityTuplizer.createProxy(AbstractEntityTuplizer.java:758) ~[hibernate-core-4.2.0.CR1.jar:4.2.0.CR1] at org.hibernate.persister.entity.AbstractEntityPersister.createProxy(AbstractEntityPersister.java:4396) ~[hibernate-core-4.2.0.CR1.jar:4.2.0.CR1] at org.hibernate.event.internal.DefaultLoadEventListener.createProxyIfNecessary(DefaultLoadEventListener.java:332) ~[hibernate-core-4.2.0.CR1.jar:4.2.0.CR1] at org.hibernate.event.internal.DefaultLoadEventListener.proxyOrLoad(DefaultLoadEventListener.java:258) ~[hibernate-core-4.2.0.CR1.jar:4.2.0.CR1] Caused by: java.lang.ClassCastException: java.lang.Class cannot be cast to java.lang.reflect.ParameterizedType at models.Generic.<init>(Generic.java:40) ~[na:na] at models.GenericDictionary.<init>(GenericDictionary.java:13) ~[na:na] at models.Unit.<init>(Unit.java:30) ~[na:na] at models.Unit_$$_jvst57e_b5.<init>(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

推荐答案

这是解决通用模型的构造函数问题：

Here is constructor for generic model that solves the issue:

@MappedSuperclass public abstract class Generic<T extends Generic> { @Transient protected Class<T> 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])); }