春休眠：TypedQuery NullPointerException異常

Question

我試圖做一些API Spring MVC中。當我運行clearKoszyk方法時：

$scope.clearKoszyk = function(){ 

        var successCallBack = function(response){ 
         $scope.seans = response.data; 
         }; 

       var errorCallBack = function(response){ 
        $scope.seans = response.status; 
         }; 

         $http.post('http://localhost:8080/kino/koszyk/delete').then(successCallBack, errorCallBack); 

       } 
      }); 

我得到響應狀態500錯誤，所以這是一個內部服務器錯誤。

SEVERE: Servlet.service() for servlet [DispatcherServlet] in context with 
path [/kino] threw exception [Request processing failed; nested exception 
is java.lang.NullPointerException] with root cause 
java.lang.NullPointerException 
at org.hibernate.internal.SessionFactoryImpl.getReturnTypes(SessionFactoryImpl.java:1112) 
at org.hibernate.internal.AbstractQueryImpl.getReturnTypes(AbstractQueryImpl.java:192) 
at org.hibernate.ejb.AbstractEntityManagerImpl.createNamedQuery(AbstractEntityManagerImpl.java:690) 
at sun.reflect.GeneratedMethodAccessor69.invoke(Unknown Source) 
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) 
at java.lang.reflect.Method.invoke(Unknown Source) 
at org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:298) 
at com.sun.proxy.$Proxy43.createNamedQuery(Unknown Source) 
at kino.repositoryImpl.KoszykRepositoryImpl.deleteKoszyk(KoszykRepositoryImpl.java:60) 
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) 
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) 
at java.lang.reflect.Method.invoke(Unknown Source) 
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:333) 
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:190) 
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157) 
at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:99) 
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:282) 
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96) 
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) 
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:213) 
at com.sun.proxy.$Proxy50.deleteKoszyk(Unknown Source) 
at kino.serviceImpl.KoszykServiceImpl.deleteKoszyk(KoszykServiceImpl.java:50) 
at kino.controllers.KoszykController.DeleteKoszyk(KoszykController.java:82) 
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) 
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) 
at java.lang.reflect.Method.invoke(Unknown Source) 

所以我覺得這是NPE這裏：

at kino.repositoryImpl.KoszykRepositoryImpl.deleteKoszyk(KoszykRepositoryImpl.java:60) 

但我真的不知道是什麼導致這個例外它是由引起的。我正在檢查如果EntityManager或用戶爲空。

56 public void deleteKoszyk(User user) throws NullPointerException{ 
57  
58  if(user != null){ 
59   if(emManager != null){ 
60    TypedQuery<Koszyk> query = emManager.createNamedQuery("Koszyk.deleteKoszyk", Koszyk.class); 
      query.setParameter("id", user.getId()); 
      query.executeUpdate(); 
     }else{ 
      throw new NullPointerException("emManager = null"); 
     } 
    }else{ 
     throw new NullPointerException("Podany użytkownik nie istnieje"); 
    } 
} 

這是我的koszyk類。

@Entity 
@NamedQuery(name = "Koszyk.deleteKoszyk", query = "DELETE FROM Koszyk k WHERE k.user.id = :id") 
@Table(name="Koszyk") 
public class Koszyk implements Serializable { 

private static final long serialVersionUID = 1L; 

@Id 
@GeneratedValue 
@Column(name="Koszyk_id") 
private Long id; 
@OneToOne 
private User user; 
@Column(name="Cena") 
private int cena; 
@Column(name="KoszykItems") 
@OneToMany(mappedBy="koszyk", fetch = FetchType.EAGER) 
private List<KoszykItem> koszykItems; 

這個問題只能說明當我嘗試刪除或ID找到koszyk。我可以從這個實體讀取，我可以用正常的方式顯示它。這是我的KoszykRepository類：

@Repository 
@Transactional 
public class KoszykRepositoryImpl implements KoszykRepository { 


@PersistenceContext 
private EntityManager emManager; 

public KoszykRepositoryImpl(){ 

} 

@Override 
public void update(Koszyk koszyk) { 
    emManager.merge(koszyk); 

} 

@Override 
public Koszyk deleteKoszykItem(KoszykItem koszykItem, User user) { 

    Koszyk koszyk = read(user); 
    List<KoszykItem> listaItemow = koszyk.getKoszykItems(); 
    listaItemow.remove(koszykItem); 
    koszyk.setKoszykItems(listaItemow); 
    update(koszyk); 

    return koszyk; 

} 
@Override 
public void deleteKoszyk(User user) throws NullPointerException{ 

    if(user != null){ 
     if(emManager != null){ 
      TypedQuery<Koszyk> query = emManager.createNamedQuery("Koszyk.deleteKoszyk", Koszyk.class); 
      query.setParameter("id", user.getId()); 
      query.executeUpdate(); 
     }else{ 
      throw new NullPointerException("emManager = null"); 
     } 
    }else{ 
     throw new NullPointerException("Podany użytkownik nie istnieje"); 
    } 
} 

@Override 
public void create(User user, Koszyk koszykDoZapisu) { 

    List<Koszyk> ListaKoszykow = read(); 
    boolean zapisz = true; 

    if(user == null){ 
     throw new NullPointerException("Zaloguj się!"); 
    }else if(!ListaKoszykow.isEmpty() && ListaKoszykow != null){ 
      for(Koszyk koszyk: ListaKoszykow){ 
       if(koszyk.getUser().getId() == user.getId()){ 
        zapisz = false; 
        break; 
       }  
      } 
     } 

     if(zapisz){ 
      koszykDoZapisu.setUser(user); 
      emManager.persist(koszykDoZapisu); 
     } 
    } 


@Override 
public List<Koszyk> read() { 

    return emManager.createQuery("SELECT k FROM Koszyk k", Koszyk.class).getResultList(); 
} 

@Override 
public Koszyk read(User user) { 

    List<Koszyk> ListaKoszykow = read(); 
    Koszyk zwracany = new Koszyk(); 

    if(user == null){ 
     throw new NullPointerException("Zaloguj się!"); 
    } 

    if(ListaKoszykow.isEmpty() || ListaKoszykow == null){ 
      throw new NullPointerException("Dany użytkownik nie ma jeszcze przypisanego koszyka"); 
     }else{ 
      for(Koszyk koszyk: ListaKoszykow){ 
       if(koszyk.getUser().equals(user)){ 
        zwracany = koszyk; 
        //Hibernate.initialize(zwracany.getKoszykItems()); 
       } 
      } 
    } 

    return zwracany; 
} 

}

[編輯]

我已經改變了刪除功能，這一點：

public void deleteKoszyk(User user) throws NullPointerException{ 

    if(user != null){ 
     if(emManager != null){ 
      final Query query = emManager.createNamedQuery("Koszyk.deleteKoszyk"); 
      query.setParameter("id", user.getId()); 
63    final int executeUpdate = query.executeUpdate(); 
     }else{ 
      throw new NullPointerException("emManager = null"); 
     } 
    }else{ 
     throw new NullPointerException("Podany użytkownik nie istnieje"); 
    } 
} 

和stacktree是完全地不同：

SEVERE: Servlet.service() for servlet [DispatcherServlet] in context with 
path [/kino] threw exception [Request processing failed; nested exception is 
javax.persistence.PersistenceException: 
org.hibernate.exception.ConstraintViolationException: Cannot delete or 
update a parent row: a foreign key constraint fails (`marcin`.`koszykitem`, 
CONSTRAINT `FK8F90CFF02AE8E273` FOREIGN KEY (`koszyk_Koszyk_id`) REFERENCES 
`koszyk` (`Koszyk_id`))] with root cause 
com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: 
Cannot delete or update a parent row: a foreign key constraint fails 
(`marcin`.`koszykitem`, CONSTRAINT `FK8F90CFF02AE8E273` FOREIGN KEY 
(`koszyk_Koszyk_id`) REFERENCES `koszyk` (`Koszyk_id`)) 
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) 
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source) 
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source) 
at java.lang.reflect.Constructor.newInstance(Unknown Source) 
at com.mysql.jdbc.Util.handleNewInstance(Util.java:404) 
at com.mysql.jdbc.Util.getInstance(Util.java:387) 
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:932) 
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3878) 
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3814) 
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2478) 
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2625) 
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2551) 
at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1861) 
at com.mysql.jdbc.PreparedStatement.executeUpdateInternal(PreparedStatement.java:2073) 
at com.mysql.jdbc.PreparedStatement.executeUpdateInternal(PreparedStatement.java:2009) 
at com.mysql.jdbc.PreparedStatement.executeLargeUpdate(PreparedStatement.java:5094) 
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:1994) 
at sun.reflect.GeneratedMethodAccessor66.invoke(Unknown Source) 
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) 
at java.lang.reflect.Method.invoke(Unknown Source) 
at org.hibernate.engine.jdbc.internal.proxy.AbstractStatementProxyHandler.continueInvocation(AbstractStatementProxyHandler.java:122) 
at org.hibernate.engine.jdbc.internal.proxy.AbstractProxyHandler.invoke(AbstractProxyHandler.java:81) 
at com.sun.proxy.$Proxy51.executeUpdate(Unknown Source) 
at org.hibernate.hql.internal.ast.exec.BasicExecutor.execute(BasicExecutor.java:95) 
at org.hibernate.hql.internal.ast.QueryTranslatorImpl.executeUpdate(QueryTranslatorImpl.java:413) 
at org.hibernate.engine.query.spi.HQLQueryPlan.performExecuteUpdate(HQLQueryPlan.java:283) 
at org.hibernate.internal.SessionImpl.executeUpdate(SessionImpl.java:1135) 
at org.hibernate.internal.QueryImpl.executeUpdate(QueryImpl.java:116) 
at org.hibernate.ejb.QueryImpl.internalExecuteUpdate(QueryImpl.java:183) 
at org.hibernate.ejb.AbstractQueryImpl.executeUpdate(AbstractQueryImpl.java:99) 
at kino.repositoryImpl.KoszykRepositoryImpl.deleteKoszyk(KoszykRepositoryImpl.java:63) 
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) 
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) 
at java.lang.reflect.Method.invoke(Unknown Source) 
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:333) 
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:190) 
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157) 
at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:99) 
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:282) 
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96) 
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) 
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:213) 
at com.sun.proxy.$Proxy48.deleteKoszyk(Unknown Source) 
at kino.serviceImpl.KoszykServiceImpl.deleteKoszyk(KoszykServiceImpl.java:50) 
at kino.controllers.KoszykController.DeleteKoszyk(KoszykController.java:91) 
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) 
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) 
at java.lang.reflect.Method.invoke(Unknown Source) 

Answer 1

很難猜測NPE來自哪裏，而沒有進行調試，可能沒有User分配給您的Koszyk實例。您的@OneToOne映射不會阻止在此處運行，因爲默認值爲optional = true。如果你想調整一下，那麼這個約束會幫助你至少避免這種情況。

更令人困惑的是，你沒有得到另一種類型的錯誤。我希望是這樣的：

...更新/刪除查詢無法鍵入......

因爲更新/刪除查詢，RESP。 executeUpdate()方法只是返回一個更新計數int值，沒有實例。

你應該把它變成：

final Query query = emManager.createNamedQuery("Koszyk.deleteKoszyk"); 
query.setParameter("id", user.getId()); 
final int executeUpdate = query.executeUpdate(); 

更新：

因爲我們現在有真正的根源，這個問題似乎很清楚。只要它的id被用作另一個實體的外鍵，就不能刪除實體。先刪除引用此Koszyk的實體。