Was macht Hibernate @Proxy (lazy = false) Annotation?

Ich hatte zwei verschiedene Stack-Traces (siehe unten), als ich versuchte, mein ESRBReading-Objekt, das eine JPA-Entität ist, zu serialisieren. Ich verwende Spring Data JPA. Der Controller hat den Service aufgerufen, der Service heißt Repository. Ich konnte das Problem lösen, indem ich @Proxy (lazy = false) für mein ESRBReating-Objekt hinzufügte.Was macht Hibernate @Proxy (lazy = false) Annotation?

Meine Hauptfrage ist, was macht @Proxy (faul = falsch) eigentlich? Warum funktioniert es beim Hinzufügen? Ist das eine gute Lösung oder wird es Nebenwirkungen wie Leistung/Speicherprobleme haben?

Als Referenz ist dies jetzt meine Klasse ESBRATING.

@Entity 
@Table(name = "esrb_rating", schema = "igdb") 
@JsonIgnoreProperties(ignoreUnknown = true) 
@Proxy(lazy = false) 
public class ESRBRating implements Serializable { 

    private static final long serialVersionUID = 1L; 

    @Id 
    @NotNull 
    @GeneratedValue(strategy = GenerationType.AUTO) 
    @Column(name = "id", nullable = false) 
    private Long id; 

    @NotNull 
    @Size(min = 1, max = 255) 
    @Column(name = "title", nullable = false, length = 255) 
    private String title; 

    @Size(max = 65535) 
    @Column(length = 65535) 
    private String description; 

    @OneToMany(cascade = CascadeType.ALL, mappedBy = "esrbRating") 
    private List<Game> games; 

    public ESRBRating() { 
    } 

    public ESRBRating(Long id, String title, String description) { 
     this.id = id; 
     this.title = title; 
     this.description = description; 
    } 

    public Long getId() { 
     return id; 
    } 

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

    public String getTitle() { 
     return title; 
    } 

    public void setTitle(String title) { 
     this.title = title; 
    } 

    public String getDescription() { 
     return description; 
    } 

    public void setDescription(String description) { 
     this.description = description; 
    } 

    public List<Game> getGames() { 
     return games; 
    } 

    public void setGames(List<Game> games) { 
     this.games = games; 
    } 

    @Override 
    public boolean equals(Object o) { 
     if (this == o) return true; 
     if (o == null || getClass() != o.getClass()) return false; 

     ESRBRating that = (ESRBRating) o; 

     return Objects.equal(this.id, that.id) && 
       Objects.equal(this.title, that.title) && 
       Objects.equal(this.description, that.description); 
    } 

    @Override 
    public int hashCode() { 
     return Objects.hashCode(id, title, description); 
    } 

    @Override 
    public String toString() { 
     return Objects.toStringHelper(this) 
       .add("id", id) 
       .add("title", title) 
       .add("description", description) 
       .toString(); 
    } 
}

Stack Trace:

Caused by: org.hibernate.LazyInitializationException: could not initialize proxy - no Session 
    at org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:165) 
    at org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:286) 
    at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:185) 
    at net.jkratz.igdb.model.ESRBRating_$$_jvst319_0.getId(ESRBRating_$$_jvst319_0.java) 
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) 
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) 
    at java.lang.reflect.Method.invoke(Method.java:606) 
    at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:466) 
    at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:639) 
    ... 76 more

Ich war auch diese Stack-Trace zu bekommen.

org.springframework.http.converter.HttpMessageNotWritableException: Could not write content: No serializer found for class org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS)) (through reference chain: net.jkratz.igdb.model.ESRBRating_$$_jvstb5c_0["handler"]); nested exception is com.fasterxml.jackson.databind.JsonMappingException: No serializer found for class org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS)) (through reference chain: net.jkratz.igdb.model.ESRBRating_$$_jvstb5c_0["handler"]) 
    at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.writeInternal(AbstractJackson2HttpMessageConverter.java:238) 
    at org.springframework.http.converter.AbstractHttpMessageConverter.write(AbstractHttpMessageConverter.java:208) 
    at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:158) 
    at org.springframework.web.servlet.mvc.method.annotation.HttpEntityMethodProcessor.handleReturnValue(HttpEntityMethodProcessor.java:138) 
    at org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:71) 
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:122) 
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:781) 
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:721) 
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:83) 
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:943) 
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:877) 
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:966) 
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:857) 
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:620) 
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:842) 
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:727) 
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303) 
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208) 
    at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:77) 
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) 
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241) 
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208) 
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) 
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241) 
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
    at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:118) 
    at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:84) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342) 
    at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:113) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342) 
    at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:103) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342) 
    at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:113) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342) 
    at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:154) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342) 
    at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:45) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342) 
    at org.springframework.security.web.authentication.www.BasicAuthenticationFilter.doFilter(BasicAuthenticationFilter.java:150) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342) 
    at org.springframework.security.web.authentication.ui.DefaultLoginPageGeneratingFilter.doFilter(DefaultLoginPageGeneratingFilter.java:155) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342) 
    at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:199) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342) 
    at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:110) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342) 
    at org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:50) 
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342) 
    at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:87) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342) 
    at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:192) 
    at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:160) 
    at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:344) 
    at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:261) 
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241) 
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208) 
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220) 
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122) 
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501) 
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171) 
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) 
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950) 
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116) 
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408) 
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1040) 
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:607) 
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:314) 
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) 
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) 
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) 
    at java.lang.Thread.run(Thread.java:745) 
Caused by: com.fasterxml.jackson.databind.JsonMappingException: No serializer found for class org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS)) (through reference chain: net.jkratz.igdb.model.ESRBRating_$$_jvstb5c_0["handler"]) 
    at com.fasterxml.jackson.databind.ser.impl.UnknownSerializer.failForEmpty(UnknownSerializer.java:59) 
    at com.fasterxml.jackson.databind.ser.impl.UnknownSerializer.serialize(UnknownSerializer.java:26) 
    at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:505) 
    at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:639) 
    at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:152) 
    at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.serializeValue(DefaultSerializerProvider.java:114) 
    at com.fasterxml.jackson.databind.ObjectMapper.writeValue(ObjectMapper.java:1887) 
    at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.writeInternal(AbstractJackson2HttpMessageConverter.java:231) 
    ... 72 more

Verweis auf meine ursprüngliche Frage und Ausgabe: JsonMappingException: could not initialize proxy - no Session

Quelle

2014-11-18 greyfox

@Proxy(lazy=false) wird die Standard-träges Laden für eine bestimmte Einheit deaktivieren. Dies bedeutet, dass Sie die initialisierte Entität immer dann erhalten, wenn auf diese Entität von anderen Entitäten verwiesen wird.

Die Verwendung dieser Annotation ist normalerweise ein "Code-Geruch". Wenn ich Sie wäre, würde ich es entfernen und laden Sie einfach alle Entity-Zuordnungen mit der join fetch Direktive wie in this article erläutert.

Quelle

2014-11-18 19:14:42

Also wird @Proxy (lazy = false) dazu führen, dass Spiele in meiner ESRBRating-Klasse jedes Mal automatisch geladen werden? Das wäre definitiv ein Problem, denn jedes ESRBRating wird Tausende von Spielen haben. Oder verstehe ich das nicht richtig? Wenn ich fetch = FETCHTYPE.LAZY in @OneToMany setzen würde, würde es das überschreiben? Beim Abrufen des ESRBReating von der REST-API würden die Spiele niemals in der Realität zurückgegeben. – greyfox

Alle ToMany-Verknüpfungen sind standardmäßig faul, daher werden nicht unbedingt die Spiele-Sammlungen abgerufen. Es ist das ESRBRating, das immer dann abgerufen wird, wenn du es von anderen Entitäten referenzierst, etwa wenn ein Spiel eine @ManyToOne-ESBR-Association hat. In diesem Fall wird Game.ESRBReating kein Proxy sein, sondern ein tatsächlich abgeholtes Objekt. –

Ahhh okay, das macht Sinn, wenn also die Game-Entity @ManyToOne (optional = false, fetch = FetchType.LAZY) für die esrbRating und/oder der Getter ein @JSONIgnore hat, wird das ESRBReating-Objekt trotzdem abgerufen? – greyfox

Was macht Hibernate @Proxy (lazy = false) Annotation?

Antwort

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