休眠java.lang.NullPointerException

Question

休眠java.lang.NullPointerException

我已经将Set嵌套到我的实体中。这是我的代码：

MyClassA:

@Entity
@Table(name = "aaa")
public class MyClassA {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "id")
    private int id;

    @NotEmpty
    @Size(min = 3, max = 255)
    @Column(name = "name", nullable = false)
    private String name;

    @OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
    private Set<MyClassB> mycollection = new HashSet<MyClassB>();

    public MyClassA() {    
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Set<MyClassB> getMyClassB() {
        return mycollection;
    }

    public void setMyClassB(Set<MyClassB> mycollection) {
        this.mycollection = mycollection;
    }

    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + id;
        result = prime * result + ((name == null) ? 0 : name.hashCode());
        result = prime * result + ((mycollection == null) ? 0 : mycollection.hashCode());
        return result;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        MyClassA other = (MyClassA) obj;
        if (id != other.id)
            return false;
        if (name == null) {
            if (other.name != null)
                return false;
        } else if (!name.equals(other.name))
            return false;
        if (mycollection == null) {
            if (other.mycollection != null)
                return false;
        } else if (!mycollection.equals(other.mycollection))
            return false;
        return true;
    }

    @Override
    public String toString() {
        return "MyClassA [id=" + id + ", name=" + name + ", mycollection=" + mycollection + "]";
    }       
}

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MyClassB:

@Entity
@Table(name = "bbb")
public class MyClassB {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "id")
    private int id;

    @NotEmpty
    @Size(min = 3, max = 255)
    @Column(name = "name", nullable = false)
    private String name;

    @NotEmpty
    @Size(min = 3, max = 255)
    @Column(name = "elementname", nullable = false)
    private String elementname;                

    @NotEmpty
    @Size(min = 3, max = 255)
    @Column(name = "type", nullable = false)
    private String type;

    @OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
    private Set<MyClassC> mycollection = new HashSet<MyClassC>();

    public MyClassB() {    
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getElementname() {
        return elementname;
    }

    public void setElementname(String elementname) {
        this.elementname = elementname;
    }

    public String getType() {
        return type;
    }

    public void setType(String type) {
        this.type = type;
    }

    public Set<MyClassC> getMyCollection() {
        return mycollection;
    }

    public void setMyCollection(Set<MyClassC> mycollection) {
        this.mycollection = mycollection;
    }

    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + ((elementname == null) ? 0 : elementname.hashCode());
        result = prime * result + id;
        result = prime * result + ((name == null) ? 0 : name.hashCode());
Line 79---> result = prime * result + ((mycollection == null) ? 0 : mycollection.hashCode());
        result = prime * result + ((type == null) ? 0 : type.hashCode());
        return result;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        MyClassB other = (MyClassB) obj;
        if (elementname == null) {
            if (other.elementname != null)
                return false;
        } else if (!elementname.equals(other.elementname))
            return false;
        if (id != other.id)
            return false;
        if (name == null) {
            if (other.name != null)
                return false;
        } else if (!name.equals(other.name))
            return false;
        if (mycollection == null) {
            if (other.mycollection != null)
                return false;
        } else if (!mycollection.equals(other.mycollection))
            return false;
        if (type == null) {
            if (other.type != null)
                return false;
        } else if (!type.equals(other.type))
            return false;
        return true;
    }

    @Override
    public String toString() {
        return "MyClassB [id=" + id + ", name=" + name + ", elementname=" + elementname + ", type=" + type + ", mycollection=" + mycollection + "]";
    }       
}

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MyClassC:

@Entity
@Table(name = "ccc")
public class MyClassC {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "id")
    private int id;

    @NotEmpty
    @Size(min = 3, max = 255)
    @Column(name = "name", nullable = false)
    private String name;

    @NotEmpty
    @Size(min = 3, max = 255)
    @Column(name = "value", nullable = false)
    private String value;

    public MyClassC(){          
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getValue() {
        return value;
    }

    public void setValue(String value) {
        this.value = value;
    }

    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + id;
        result = prime * result + ((name == null) ? 0 : name.hashCode());
        result = prime * result + ((value == null) ? 0 : value.hashCode());
        return result;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        MyClassC other = (MyClassC) obj;
        if (id != other.id)
            return false;
        if (name == null) {
            if (other.name != null)
                return false;
        } else if (!name.equals(other.name))
            return false;
        if (value == null) {
            if (other.value != null)
                return false;
        } else if (!value.equals(other.value))
            return false;
        return true;
    }

    @Override
    public String toString() {
        return "MyClassC [id=" + id + ", name=" + name + ", value=" + value + "]";
    }

}

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当我尝试在控制器中获取所有MyClassA对象时，出现以下异常：

2016-09-28 10:10:46调试DefaultHandlerExceptionResolver：134-从处理程序[公共org.springframework.http.ResponseEntity> com.example.controller.MyController.listAllMyClassA（）]中解析异常：java.lang.NullPointerException 2016-09 -28 10:10:46 DEBUG DispatcherServlet：989-无法在org.hibernate.event.spi.AbstractCollectionEvent处完成请求org.hibernate.engine.internal.StatefulPersistenceContext.getLoadedCollectionOwnerOrNull（StatefulPersistenceContext.java:756）的java.lang.NullPointerException org.hibernate.event.spi.InitializeCollectionEvent。（InitializeCollectionEvent.java:36）处的.getLoadedOwnerOrNull（AbstractCollectionEvent.java:75）org.hibernate.internal.SessionImpl.initializeCollection（SessionImpl.java:1931）处的org.hibernate.collection 。内部。org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded（AbstractPersistentCollection.java:261）处的org.hibernate.collection.internal.AbstractPersistentCollection.initialize（AbstractPersistentCollection.java:555）处的AbstractPersistentCollection $ 4.doWork（AbstractPersistentCollection.java:559） org.hibernate.collection.internal.PersistentSet.toString（PersistentSet.java:316）上的org.hibernate.collection.internal.AbstractPersistentCollection.read（AbstractPersistentCollection.java:143）在com.example.model.MyClassB.hashCode（MyClassB。的java.util.HashMap.hash（HashMap.java:338）的java：79）的java.util.HashSet.add（HashSet.java:219）的java.util.HashMap.put（HashMap.java:611）的Java java.util.AbstractCollection.addAll（AbstractCollection。org.hibernate.collection.internal.PersistentSet.endRead（PersistentSet.java:344）处org.hibernate.engine.loading.internal.CollectionLoadContext.endLoadingCollection（CollectionLoadContext.java:251）处org.hibernate.engine org.hibernate.engine.loading.internal.CollectionLoadContext.endLoadingCollections（CollectionLoadContext.java:211）的org.hibernate.loader.Loader.Loader.endCollectionLoad（Loader.java）的.loading.internal.CollectionLoadContext.endLoadingCollections（CollectionLoadContext.java:238）：1157），位于org.hibernate.loader.Loader.doQuery（Loader.org）的org.hibernate.loader.Loader.processResultSet（Loader.java:973），位于org.hibernate.loader.Loader.initializeEntitiesAndCollections（Loader.java:1126）。 java：921）上的org.hibernate.loader.Loader。org.hibernate.loader.Loader.doList（Loader.java:2554）的org.hibernate.loader.Loader.doList（Loader.java:2540）的org.hibernate.loader.doList（Loader.java:2540）的org.hibernate.loader.Loader的doQueryAndInitializeNonLazyCollections（Loader.java:355） org.hibernate.loader.Loader.list（Loader.java:2365）的.listIgnoreQueryCache（Loader.java:2370）org.hibernate的org.hibernate.loader.criteria.CriteriaLoader.list（CriteriaLoader.java:126）的.listIgnoreQueryCache（Loader.java:2370） com.example.dao.MyClassADaoImpl.findAllGroupQuestions（MyClassADaoImpl.java:42）上org.hibernate.internal.CriteriaImpl.list（CriteriaImpl.java:380）上的internal.SessionImpl.list（SessionImpl.java:1718） .service.MyClassAImpl.findAllGroupQuestions（MyClassAImpl.java:41）位于sun.reflect.NativeMethodAccessorImpl.invoke0（原生方法），位于sun.reflect。org.springframework.aop.support上java.lang.reflect.Method.invoke（Method.java:497）上的sun.reflect.DelegatingMethodAccessorImpl.invoke（NlegantMethodAccessorImpl.java:43）上的NativeMethodAccessorImpl.invoke（NativeMethodAccessorImpl.java:62） org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint（ReflectiveMethodInvocation.java:190）的org.springframework.aop.framework.ReflectiveMethodInvocation.proceed（ReflectiveMethodInvocation。 org.springframework.transaction.interceptor.TransactionInterceptor $ 1.proceedWithInvocation（TransactionInterceptor.java:99）在org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction（TransactionAspectSupport.java：281）在org.springframework.aop.framework.JdkDynamicAopProxy（org.springframework.transaction.interceptor.TransactionInterceptor.invoke（TransactionInterceptor.java:96）在org.springframework.aop.framework.ReflectiveMethodInvocation.proceed（ReflectiveMethodInvocation.java:179）在org.springframework.aop.framework.JdkDynamicAopProxy .com.sun.proxy上的.invoke（JdkDynamicAopProxy.java:207）.gr.citystore.helios.controller.QuestionaireController.listAllGroupQuestions（QuestionaireController.java:212）上的com.sun.proxy。$ Proxy63.findAllGroupQuestions（未知源），在sun.reflect.NativeMethodAccessorImpl。调用sun.reflect.NativeMethodAccessorImpl.invoke（NativeMethodAccessorImpl.java:62）上的invoke0（本机方法），调用java.lang.reflect.Method.invoke（Method。org.springframework.web.method.support.InvocableHandlerMethod.doInvoke（InvocableHandlerMethod.java:221）处org.springframework.web.method.support.InvocableHandlerMethod.java:221）org.springframework.web.method.support.InvocableHandlerMethod.java org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod（RequestMappingHandlerAdapter.java:776）上的.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle（ServletInvocableHandlerMethod.java:110） org.org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle（AbstractHandlerMethodAdapter.java:85）处的.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal（RequestMappingHandlerAdapter.java:705）org.springframework.web.servlet.DispatcherServlet.doService（DispatcherServlet.java:893）上的springframework.web.servlet.DispatcherServlet.doDispatch（DispatcherServlet.java:959）org.springframework.web.servlet.FrameworkServlet.processRequest（FrameworkServlet。 org.springframework.web.servlet.FrameworkServlet.doGet（FrameworkServlet.java:857）处org.springframework.web.servlet.FrameworkServlet处javax.servlet.http.HttpServlet.service（HttpServlet.java:622）处org.apache.catalina.core.ApplicationFilterChain.internalDoFilter（ApplicationFilterChain.java:291）的javax.servlet.http.HttpServlet.service（HttpServlet.java:729）的.service（FrameworkServlet.java:842） catalina.core.ApplicationFilterChain.doFilter（ApplicationFilterChain.java：206），位于org.apache.catalina.core的org.apache.tomcat.websocket.server.WsFilter.doFilter（WsFilter.java:52），位于org.apache.catalina.core的ApplicationFilterChain.internalDoFilter（ApplicationFilterChain.java:239） org.springframework.security.web.FilterChainProxy $ VirtualFilterChain.doFilter（FilterChainProxy.java:316）上的.ApplicationFilterChain.doFilter（ApplicationFilterChain.java:206）在org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke（FilterSecurityInterceptor） .java：126），位于org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter（FilterSecurityInterceptor.java:90），位于org.springframework.security.web.FilterChainProxy $ VirtualFilterChain.doFilter（FilterChainProxy.java:330） org.springframework.security.web.access。org.springframework.security.web.session.SessionManagementFilter.doFilter（SessionManagementFilter.java：org.springframework.security.web.FilterChainProxy $ VirtualFilterChain.doFilter（FilterChainProxy.java:330）处的ExceptionTranslationFilter.doFilter（ExceptionTranslationFilter.java:114）： 122）在org.springframework.security.web.FilterChainProxy $ VirtualFilterChain.doFilter（FilterChainProxy.java:330）在org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter（AnonymousAuthenticationFilter.java:111）在org.springframework.security org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter（SecurityContextHolderAwareRequestFilter.java处的.web.FilterChainProxy $ VirtualFilterChain.doFilter（FilterChainProxy.java:330）：168）在org.springframework.security.web.FilterChainProxy $ VirtualFilterChain.doFilter（FilterChainProxy.java:330）在org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter（RequestCacheAwareFilter.java:48）在org.springframework.security org.springframework.security.web.FilterChainProxy $ VirtualFilterChain.doFilter上的.web.FilterChainProxy $ VirtualFilterChain.doFilter（FilterChainProxy.java:330）在org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter（AbstractAuthenticationProcessingFilter.java:205）（FilterChainProxy.java:330）在org.springframework.security.web.authentication.logout.LogoutFilter.doFilter（LogoutFilter.java:120）在org.springframework.security.web.FilterChainProxy $ VirtualFilterChain。org处org.springframework.security.web.csrf.CsrfFilter.doFilterInternal（CsrfFilter.java:96）处的doFilter（FilterChainProxy.java:330）org org.org.springframework.web.filter.OncePerRequestFilter.doFilter（OncePerRequestFilter.java:107） org.springframework.security.web.header.HeaderWriterFilter.doFilterInternal（HeaderWriterFilter.java:64）上的.springframework.security.web.FilterChainProxy $ VirtualFilterChain.doFilter（FilterChainProxy.java:330）在org.springframework.web.filter.OncePerRequestFilter org.springframework.security.web.FilterChainProxy $ VirtualFilterChain.doFilter（FilterChainProxy.java:330）的org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter（SecurityContextPersistenceFilter.java:91的.doFilter（OncePerRequestFilter.java:107））在org。org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal（WebAsyncManagerIntegrationFilter.java:53）上的springframework.security.web.FilterChainProxy $ VirtualFilterChain.doFilter（FilterChainProxy.java:330）在org.springframework.web上。 org.springframework.security.web.FilterChainProxy.doFilterInternal（FilterChainProxy.java）处的filter.OncePerRequestFilter.doFilter（OncePerRequestFilter.java:107）在org.springframework.security.web.FilterChainProxy $ VirtualFilterChain.doFilter（FilterChainProxy.java:330）在org.springframework.security.web.FilterChainProxy.doFilterInternal（FilterChainProxy.java： 213），位于org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate（DelegatingFilterProxy.java:344），位于org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate（DelegatingFilterProxy.java:344），位于org.springframework.web.filter。org上的org.apache.catalina.core.ApplicationFilterChain.internalDoFilter（ApplicationFilterChain.java:239）的org.org.apache.catalina.core.ApplicationFilterChain.doFilter（ApplicationFilterChain.java:206）的DelegatingFilterProxy.doFilter（DelegatingFilterProxy.java:261） org.apache.catalina.core.StandardContextValve.invoke（StandardContextValve.java:106）上的.apache.catalina.core.StandardWrapperValve.invoke（StandardWrapperValve.java:212）org.apache.catalina.authenticator.AuthenticatorBase.invoke（AuthenticatorBase .java：502）位于org.apache.catalina.core.StandardHostValve.invoke（StandardHostValve.java:141）位于org.apache.catalina.valves.ErrorReportValve.invoke（ErrorReportValve.java:79）位于org.apache.catalina。 valve.AbstractAccessLogValve.invoke（AbstractAccessLogValve.java：616）在org.apache.catalina.connector.CoyoteAdapter.service（CoyoteAdapter.java:521）在org.apache.catalina.connector.CoyoteAdapter.service（CocoteAdapter.java:521）在org.apache.coyote.http11.AbstractHttp11Processor org.apache.coyote.AbstractProtocol $ AbstractConnectionHandler.process（AbstractProtocol.java:674）的.process（AbstractHttp11Processor.java:1096）org.apache.tomcat.util.net.AprEndpoint $ SocketProcessor.doRun（AprEndpoint.java:2500处的。）在org.apache.tomcat.util.net.AprEndpoint $ SocketProcessor.run（AprEndpoint.java:2489）在java.util.concurrent.ThreadPoolExecutor.runWorker（ThreadPoolExecutor.java:1142）在java.util.concurrent.ThreadPoolExecutor $ org.apache.tomcat.util.threads.TaskThread $ WrappingRunnable上的Worker.run（ThreadPoolExecutor.java:617）。在java.lang.Thread.run（Thread.java:745）上运行（TaskThread.java:61）

MyClassADaoImpl:

@SuppressWarnings("unchecked")
public List<MyClassA> findAllMyClassAs() {
    Criteria criteria = createEntityCriteria();
    criteria.setResultTransformer(CriteriaSpecification.DISTINCT_ROOT_ENTITY);
    return (List<MyClassA>) criteria.list();
}

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最后，我的服务实现MyClassAImpl：

public List<MyClassA> findAllMyClassAs() {
        return dao.findAllMyClassAs();
    }

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我的Hibernate版本是4.3.11.Final。如果您需要其他任何信息，请告诉我！谢谢

Answer 1

Osc*_*sta 6

查看您的stacktrace，我相信此问题的根源在您的hashCode方法中：

com.example.model.MyClassB.hashCode（MyClassB.java:79）在

尝试从您的hashCode方法中删除sets属性。我认为这对于计算类的哈希值不是必需的。在大多数情况下，您使用业务密钥（即标识对象的唯一属性）。

https://docs.jboss.org/hibernate/stable/core.old/reference/en/html/persistent-classes-equalshashcode.html

注意安全！:)

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