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