我正在学习如何在Play Framework中使用Ebean ORM，但却遇到了错误。 我有很多课程，但问题出在这两个课程中。
StockItem类：
import com.avaje.ebean.Model;
import com.google.inject.Inject;
import javax.persistence.*;
@Entity
public class StockItem extends Model{
@Id
private Long id;
/*
@ManyToOne
private Warehouse warehouse;
*/
@ManyToOne
private Product product;
private Long quantity;
public static Finder<Long,StockItem> find = new Finder<>(StockItem.class);
public StockItem(){
//left blank
}
public String toString() {
return String.format("%d %s",quantity,product);
}
///gettters and setters
}
仓库类：
import com.avaje.ebean.Model;
import javax.persistence.Entity;
@Entity
public class Warehouse extends Model{
private String name;
/*
@OneToMany(mappedBy="warehouse")
private List<StockItem> stock; // = new ArrayList<>();
*/
private static Finder<Long,Warehouse> find = new Finder<>(Warehouse.class);
public Warehouse(){
//left blank
}
///gettters and setters
}
如果我取消注释多行注释，我会收到此错误：
CreationException: Unable to create injector, see the following errors:
1) Error injecting constructor, java.lang.NullPointerException
at play.db.ebean.EbeanDynamicEvolutions.<init>(EbeanDynamicEvolutions.java:36)
at play.db.ebean.EbeanDynamicEvolutions.class(EbeanDynamicEvolutions.java:33)
while locating play.db.ebean.EbeanDynamicEvolutions
at play.db.ebean.EbeanModule.bindings(EbeanModule.java:23):
Binding(class play.api.db.evolutions.DynamicEvolutions to ConstructionTarget(class play.db.ebean.EbeanDynamicEvolutions) eagerly) (via modules: com.google.inject.util.Modules$OverrideModule -> play.api.inject.guice.GuiceableModuleConversions$$anon$1)
while locating play.api.db.evolutions.DynamicEvolutions
Caused by: java.lang.NullPointerException
at com.avaje.ebeaninternal.server.persist.dmlbind.BindableAssocOne.dmlAppend(BindableAssocOne.java:38)
at com.avaje.ebeaninternal.server.persist.dmlbind.BindableList.dmlAppend(BindableList.java:36)
at com.avaje.ebeaninternal.server.persist.dml.UpdateMeta.genSql(UpdateMeta.java:168)
at com.avaje.ebeaninternal.server.persist.dml.UpdateMeta.<init>(UpdateMeta.java:46)
at com.avaje.ebeaninternal.server.persist.dml.MetaFactory.createUpdate(MetaFactory.java:71)
at com.avaje.ebeaninternal.server.persist.dml.DmlBeanPersisterFactory.create(DmlBeanPersisterFactory.java:25)
at com.avaje.ebeaninternal.server.deploy.BeanManagerFactory.create(BeanManagerFactory.java:22)
at com.avaje.ebeaninternal.server.deploy.BeanDescriptorManager.initialiseAll(BeanDescriptorManager.java:347)
at com.avaje.ebeaninternal.server.deploy.BeanDescriptorManager.deploy(BeanDescriptorManager.java:233)
at com.avaje.ebeaninternal.server.core.InternalConfiguration.<init>(InternalConfiguration.java:119)
at com.avaje.ebeaninternal.server.core.DefaultContainer.createServer(DefaultContainer.java:142)
at com.avaje.ebeaninternal.server.core.DefaultContainer.createServer(DefaultContainer.java:38)
at com.avaje.ebean.EbeanServerFactory.createInternal(EbeanServerFactory.java:81)
at com.avaje.ebean.EbeanServerFactory.create(EbeanServerFactory.java:66)
at play.db.ebean.EbeanDynamicEvolutions.start(EbeanDynamicEvolutions.java:53)
at play.db.ebean.EbeanDynamicEvolutions.<init>(EbeanDynamicEvolutions.java:39)
at play.db.ebean.EbeanDynamicEvolutions$$FastClassByGuice$$52c94231.newInstance(<generated>)
at com.google.inject.internal.cglib.reflect.$FastConstructor.newInstance(FastConstructor.java:40)
at com.google.inject.internal.DefaultConstructionProxyFactory$1.newInstance(DefaultConstructionProxyFactory.java:61)
at com.google.inject.internal.ConstructorInjector.provision(ConstructorInjector.java:105)
at com.google.inject.internal.ConstructorInjector.construct(ConstructorInjector.java:85)
at com.google.inject.internal.ConstructorBindingImpl$Factory.get(ConstructorBindingImpl.java:267)
at com.google.inject.internal.ProviderToInternalFactoryAdapter$1.call(ProviderToInternalFactoryAdapter.java:46)
at com.google.inject.internal.InjectorImpl.callInContext(InjectorImpl.java:1103)
at com.google.inject.internal.ProviderToInternalFactoryAdapter.get(ProviderToInternalFactoryAdapter.java:40)
at com.google.inject.internal.SingletonScope$1.get(SingletonScope.java:145)
at com.google.inject.internal.InternalFactoryToProviderAdapter.get(InternalFactoryToProviderAdapter.java:41)
at com.google.inject.internal.FactoryProxy.get(FactoryProxy.java:56)
at com.google.inject.internal.ProviderToInternalFactoryAdapter$1.call(ProviderToInternalFactoryAdapter.java:46)
at com.google.inject.internal.InjectorImpl.callInContext(InjectorImpl.java:1103)
at com.google.inject.internal.ProviderToInternalFactoryAdapter.get(ProviderToInternalFactoryAdapter.java:40)
at com.google.inject.internal.SingletonScope$1.get(SingletonScope.java:145)
at com.google.inject.internal.InternalFactoryToProviderAdapter.get(InternalFactoryToProviderAdapter.java:41)
at com.google.inject.internal.InternalInjectorCreator$1.call(InternalInjectorCreator.java:205)
at com.google.inject.internal.InternalInjectorCreator$1.call(InternalInjectorCreator.java:199)
at com.google.inject.internal.InjectorImpl.callInContext(InjectorImpl.java:1092)
at com.google.inject.internal.InternalInjectorCreator.loadEagerSingletons(InternalInjectorCreator.java:199)
at com.google.inject.internal.InternalInjectorCreator.injectDynamically(InternalInjectorCreator.java:180)
at com.google.inject.internal.InternalInjectorCreator.build(InternalInjectorCreator.java:110)
at com.google.inject.Guice.createInjector(Guice.java:96)
at com.google.inject.Guice.createInjector(Guice.java:73)
at com.google.inject.Guice.createInjector(Guice.java:62)
at play.api.inject.guice.GuiceBuilder.injector(GuiceInjectorBuilder.scala:126)
at play.api.inject.guice.GuiceApplicationBuilder.build(GuiceApplicationBuilder.scala:93)
at play.api.inject.guice.GuiceApplicationLoader.load(GuiceApplicationLoader.scala:21)
at play.core.server.DevServerStart$$anonfun$mainDev$1$$anon$1$$anonfun$get$1$$anonfun$apply$1$$anonfun$1$$anonfun$2.apply(DevServerStart.scala:153)
at play.core.server.DevServerStart$$anonfun$mainDev$1$$anon$1$$anonfun$get$1$$anonfun$apply$1$$anonfun$1$$anonfun$2.apply(DevServerStart.scala:150)
at play.utils.Threads$.withContextClassLoader(Threads.scala:21)
at play.core.server.DevServerStart$$anonfun$mainDev$1$$anon$1$$anonfun$get$1$$anonfun$apply$1$$anonfun$1.apply(DevServerStart.scala:150)
at play.core.server.DevServerStart$$anonfun$mainDev$1$$anon$1$$anonfun$get$1$$anonfun$apply$1$$anonfun$1.apply(DevServerStart.scala:121)
at scala.Option.map(Option.scala:146)
at play.core.server.DevServerStart$$anonfun$mainDev$1$$anon$1$$anonfun$get$1$$anonfun$apply$1.apply(DevServerStart.scala:121)
at play.core.server.DevServerStart$$anonfun$mainDev$1$$anon$1$$anonfun$get$1$$anonfun$apply$1.apply(DevServerStart.scala:119)
at scala.util.Success.flatMap(Try.scala:230)
at play.core.server.DevServerStart$$anonfun$mainDev$1$$anon$1$$anonfun$get$1.apply(DevServerStart.scala:119)
at play.core.server.DevServerStart$$anonfun$mainDev$1$$anon$1$$anonfun$get$1.apply(DevServerStart.scala:111)
at scala.concurrent.impl.Future$PromiseCompletingRunnable.liftedTree1$1(Future.scala:24)
at scala.concurrent.impl.Future$PromiseCompletingRunnable.run(Future.scala:24)
at java.util.concurrent.ForkJoinTask$RunnableExecuteAction.exec(Unknown Source)
at java.util.concurrent.ForkJoinTask.doExec(Unknown Source)
at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(Unknown Source)
at java.util.concurrent.ForkJoinPool.runWorker(Unknown Source)
at java.util.concurrent.ForkJoinWorkerThread.run(Unknown Source)
2) Error injecting constructor, java.lang.NullPointerException
at play.db.ebean.EbeanDynamicEvolutions.<init>(EbeanDynamicEvolutions.java:36)
at play.db.ebean.EbeanDynamicEvolutions.class(EbeanDynamicEvolutions.java:33)
while locating play.db.ebean.EbeanDynamicEvolutions
at play.db.ebean.EbeanModule.bindings(EbeanModule.java:23):
Binding(class play.api.db.evolutions.DynamicEvolutions to ConstructionTarget(class play.db.ebean.EbeanDynamicEvolutions) eagerly) (via modules: com.google.inject.util.Modules$OverrideModule -> play.api.inject.guice.GuiceableModuleConversions$$anon$1)
while locating play.api.db.evolutions.DynamicEvolutions
while locating play.api.db.evolutions.ApplicationEvolutionsProvider
at play.api.db.evolutions.EvolutionsModule.bindings(EvolutionsModule.scala:22):
Binding(class play.api.db.evolutions.ApplicationEvolutions to ProviderConstructionTarget(class play.api.db.evolutions.ApplicationEvolutionsProvider) eagerly) (via modules: com.google.inject.util.Modules$OverrideModule -> play.api.inject.guice.GuiceableModuleConversions$$anon$1)
while locating play.api.db.evolutions.ApplicationEvolutions
Caused by: java.lang.NullPointerException
at com.avaje.ebeaninternal.server.persist.dmlbind.BindableAssocOne.dmlAppend(BindableAssocOne.java:38)
at com.avaje.ebeaninternal.server.persist.dmlbind.BindableList.dmlAppend(BindableList.java:36)
at com.avaje.ebeaninternal.server.persist.dml.UpdateMeta.genSql(UpdateMeta.java:168)
at com.avaje.ebeaninternal.server.persist.dml.UpdateMeta.<init>(UpdateMeta.java:46)
at com.avaje.ebeaninternal.server.persist.dml.MetaFactory.createUpdate(MetaFactory.java:71)
at com.avaje.ebeaninternal.server.persist.dml.DmlBeanPersisterFactory.create(DmlBeanPersisterFactory.java:25)
at com.avaje.ebeaninternal.server.deploy.BeanManagerFactory.create(BeanManagerFactory.java:22)
at com.avaje.ebeaninternal.server.deploy.BeanDescriptorManager.initialiseAll(BeanDescriptorManager.java:347)
at com.avaje.ebeaninternal.server.deploy.BeanDescriptorManager.deploy(BeanDescriptorManager.java:233)
at com.avaje.ebeaninternal.server.core.InternalConfiguration.<init>(InternalConfiguration.java:119)
at com.avaje.ebeaninternal.server.core.DefaultContainer.createServer(DefaultContainer.java:142)
at com.avaje.ebeaninternal.server.core.DefaultContainer.createServer(DefaultContainer.java:38)
at com.avaje.ebean.EbeanServerFactory.createInternal(EbeanServerFactory.java:81)
at com.avaje.ebean.EbeanServerFactory.create(EbeanServerFactory.java:66)
at play.db.ebean.EbeanDynamicEvolutions.start(EbeanDynamicEvolutions.java:53)
at play.db.ebean.EbeanDynamicEvolutions.<init>(EbeanDynamicEvolutions.java:39)
at play.db.ebean.EbeanDynamicEvolutions$$FastClassByGuice$$52c94231.newInstance(<generated>)
at com.google.inject.internal.cglib.reflect.$FastConstructor.newInstance(FastConstructor.java:40)
at com.google.inject.internal.DefaultConstructionProxyFactory$1.newInstance(DefaultConstructionProxyFactory.java:61)
at com.google.inject.internal.ConstructorInjector.provision(ConstructorInjector.java:105)
at com.google.inject.internal.ConstructorInjector.construct(ConstructorInjector.java:85)
at com.google.inject.internal.ConstructorBindingImpl$Factory.get(ConstructorBindingImpl.java:267)
at com.google.inject.internal.ProviderToInternalFactoryAdapter$1.call(ProviderToInternalFactoryAdapter.java:46)
at com.google.inject.internal.InjectorImpl.callInContext(InjectorImpl.java:1103)
at com.google.inject.internal.ProviderToInternalFactoryAdapter.get(ProviderToInternalFactoryAdapter.java:40)
at com.google.inject.internal.SingletonScope$1.get(SingletonScope.java:145)
at com.google.inject.internal.InternalFactoryToProviderAdapter.get(InternalFactoryToProviderAdapter.java:41)
at com.google.inject.internal.FactoryProxy.get(FactoryProxy.java:56)
at com.google.inject.internal.ProviderToInternalFactoryAdapter$1.call(ProviderToInternalFactoryAdapter.java:46)
at com.google.inject.internal.InjectorImpl.callInContext(InjectorImpl.java:1103)
at com.google.inject.internal.ProviderToInternalFactoryAdapter.get(ProviderToInternalFactoryAdapter.java:40)
at com.google.inject.internal.SingletonScope$1.get(SingletonScope.java:145)
at com.google.inject.internal.InternalFactoryToProviderAdapter.get(InternalFactoryToProviderAdapter.java:41)
at com.google.inject.internal.InjectorImpl$2$1.call(InjectorImpl.java:1016)
at com.google.inject.internal.InjectorImpl.callInContext(InjectorImpl.java:1103)
at com.google.inject.internal.InjectorImpl$2.get(InjectorImpl.java:1012)
at com.google.inject.internal.InjectorImpl.getInstance(InjectorImpl.java:1051)
at play.api.inject.guice.GuiceInjector.instanceOf(GuiceInjectorBuilder.scala:321)
at play.api.inject.guice.GuiceInjector.instanceOf(GuiceInjectorBuilder.scala:316)
at play.api.db.evolutions.ApplicationEvolutionsProvider.get$lzycompute(EvolutionsModule.scala:53)
at play.api.db.evolutions.ApplicationEvolutionsProvider.get(EvolutionsModule.scala:53)
at play.api.db.evolutions.ApplicationEvolutionsProvider.get(EvolutionsModule.scala:44)
at com.google.inject.internal.ProviderInternalFactory.provision(ProviderInternalFactory.java:81)
at com.google.inject.internal.BoundProviderFactory.provision(BoundProviderFactory.java:72)
at com.google.inject.internal.ProviderInternalFactory.circularGet(ProviderInternalFactory.java:61)
at com.google.inject.internal.BoundProviderFactory.get(BoundProviderFactory.java:62)
at com.google.inject.internal.ProviderToInternalFactoryAdapter$1.call(ProviderToInternalFactoryAdapter.java:46)
at com.google.inject.internal.InjectorImpl.callInContext(InjectorImpl.java:1103)
at com.google.inject.internal.ProviderToInternalFactoryAdapter.get(ProviderToInternalFactoryAdapter.java:40)
at com.google.inject.internal.SingletonScope$1.get(SingletonScope.java:145)
at com.google.inject.internal.InternalFactoryToProviderAdapter.get(InternalFactoryToProviderAdapter.java:41)
at com.google.inject.internal.InternalInjectorCreator$1.call(InternalInjectorCreator.java:205)
at com.google.inject.internal.InternalInjectorCreator$1.call(InternalInjectorCreator.java:199)
at com.google.inject.internal.InjectorImpl.callInContext(InjectorImpl.java:1092)
at com.google.inject.internal.InternalInjectorCreator.loadEagerSingletons(InternalInjectorCreator.java:199)
at com.google.inject.internal.InternalInjectorCreator.injectDynamically(InternalInjectorCreator.java:180)
at com.google.inject.internal.InternalInjectorCreator.build(InternalInjectorCreator.java:110)
at com.google.inject.Guice.createInjector(Guice.java:96)
at com.google.inject.Guice.createInjector(Guice.java:73)
at com.google.inject.Guice.createInjector(Guice.java:62)
at play.api.inject.guice.GuiceBuilder.injector(GuiceInjectorBuilder.scala:126)
at play.api.inject.guice.GuiceApplicationBuilder.build(GuiceApplicationBuilder.scala:93)
at play.api.inject.guice.GuiceApplicationLoader.load(GuiceApplicationLoader.scala:21)
at play.core.server.DevServerStart$$anonfun$mainDev$1$$anon$1$$anonfun$get$1$$anonfun$apply$1$$anonfun$1$$anonfun$2.apply(DevServerStart.scala:153)
at play.core.server.DevServerStart$$anonfun$mainDev$1$$anon$1$$anonfun$get$1$$anonfun$apply$1$$anonfun$1$$anonfun$2.apply(DevServerStart.scala:150)
at play.utils.Threads$.withContextClassLoader(Threads.scala:21)
at play.core.server.DevServerStart$$anonfun$mainDev$1$$anon$1$$anonfun$get$1$$anonfun$apply$1$$anonfun$1.apply(DevServerStart.scala:150)
at play.core.server.DevServerStart$$anonfun$mainDev$1$$anon$1$$anonfun$get$1$$anonfun$apply$1$$anonfun$1.apply(DevServerStart.scala:121)
at scala.Option.map(Option.scala:146)
at play.core.server.DevServerStart$$anonfun$mainDev$1$$anon$1$$anonfun$get$1$$anonfun$apply$1.apply(DevServerStart.scala:121)
at play.core.server.DevServerStart$$anonfun$mainDev$1$$anon$1$$anonfun$get$1$$anonfun$apply$1.apply(DevServerStart.scala:119)
at scala.util.Success.flatMap(Try.scala:230)
at play.core.server.DevServerStart$$anonfun$mainDev$1$$anon$1$$anonfun$get$1.apply(DevServerStart.scala:119)
at play.core.server.DevServerStart$$anonfun$mainDev$1$$anon$1$$anonfun$get$1.apply(DevServerStart.scala:111)
at scala.concurrent.impl.Future$PromiseCompletingRunnable.liftedTree1$1(Future.scala:24)
at scala.concurrent.impl.Future$PromiseCompletingRunnable.run(Future.scala:24)
at java.util.concurrent.ForkJoinTask$RunnableExecuteAction.exec(Unknown Source)
at java.util.concurrent.ForkJoinTask.doExec(Unknown Source)
at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(Unknown Source)
at java.util.concurrent.ForkJoinPool.runWorker(Unknown Source)
at java.util.concurrent.ForkJoinWorkerThread.run(Unknown Source)
2 errors
任何帮助将不胜感激。
答案 0 :(得分：7)
我找到了解决方案。为其他遇到同样问题的人添加它。
我没有在Warehouse类中添加id变量。
将以下内容添加到Warehouse类中。
@Id
private Long id;