java - 无法序列化 HibernateProxy 的对象原因

Question

我从服务器收到以下错误响应。

HTTP Status 500 -

type Exception report

message

descriptionThe server encountered an internal error () that prevented it from fulfilling this request.

exception

javax.servlet.ServletException: java.lang.UnsupportedOperationException: Attempted to serialize java.lang.Class: org.hibernate.proxy.HibernateProxy. Forgot to register a type adapter?

root cause

java.lang.UnsupportedOperationException: Attempted to serialize java.lang.Class: org.hibernate.proxy.HibernateProxy. Forgot to register a type adapter?

来自 Java 调试器:

org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer@7632012e

我正在使用 Gson 将 Java 对象转换为 JSON。下面我粘贴了一些代码。

这是我的资源:

@Stateless
@LocalBean
@Path("/autos")
@Produces(MediaType.APPLICATION_JSON)
public class AutoResource {

    @EJB
    private CarAssembler warehouse;
    @Context
    private UriInfo uriInfo;

    @GET
    public Response allAutos() {
        // Building a context, lots of code...
        // Creating a Gson instance and configures it...

        final Auto auto = warehouse.list(context);
        final String autoJson = gson.toJson(auto);

        return Response.ok(autoJson).build();
    }
}

CarAssembler 只是一个调用存储库的服务。我没有在这里粘贴该服务的代码。

存储库:

@Override
public Question findById(final int id, final FetchType fetchType) {

    final Auto question = getEntityManager().find(Auto.class, id);

    if (fetchType == FetchType.LAZY) {
        return auto;
    }

    Hibernate.initialize(auto.getManufacturer());
    Hibernate.initialize(auto.getAssemblyHouse());

    return auto;
}

如您所见，我提供了对象的延迟加载和急切加载。我使用 Hibernate.initialize 来急切地获取 JPA 关联。但是，问题是如何修复我收到的代理错误。为什么只有AssemblyHouse仍然附加在JavaAssist上，而Manufacturer却没有(我在Java Debugger中看到过这种类型)。我如何知道何时取消代理对象？我应该取消代理该汽车可能具有的所有关联吗？在我的代码的哪一层？当我取消代理时，它会影响我的应用程序的性能吗？还有其他解决方案吗？我从错误消息中看到我可以制作类型适配器。是的，我可以，但是我必须对所有域对象执行此操作，以确保转换正确完成。也许当我尝试将其转换为 JSON 表示形式时，我域中的其他对象也开始失败，但我不知道何时或为何。其他元素都安然无恙只是运气好吗？

这是我取消代理对象的方式，但我还没有实现它，因为我不知道这是好是坏，以及在哪一层执行此操作以及何时执行此操作。我应该一直取消代理对象吗？

public class HibernateUtilities {

    public static <T> T unproxy(T proxy) {
        if (proxy == null) {
            return null;
        }

        if (proxy instanceof HibernateProxy) {
            Hibernate.initialize(proxy);

            HibernateProxy hibernateProxy = (HibernateProxy) proxy;
            T unproxiedObject = (T) hibernateProxy.getHibernateLazyInitializer().getImplementation();

            return unproxiedObject;
        }

        return proxy;
    }
}

<小时/>

根据要求进行堆栈跟踪:

[#|2012-11-22T17:17:13.285+0100|WARNING|glassfish3.1.2|javax.enterprise.system.container.web.com.sun.enterprise.web|_ThreadID=71;_ThreadName=Thread-8;|StandardWrapperValve[javax.ws.rs.core.Application]:PWC1406: Servlet.service() for servlet javax.ws.rs.core.Applicationthrew exception java.lang.UnsupportedOperationException: Attempted toserialize java.lang.Class: org.hibernate.proxy.HibernateProxy. Forgotto register a type adapter?    at com.google.gson.internal.bind.TypeAdapters$1.write(TypeAdapters.java:64)    at com.google.gson.internal.bind.TypeAdapters$1.write(TypeAdapters.java:61)    at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.write(TypeAdapterRuntimeTypeWrapper.java:68)    at com.google.gson.internal.bind.ArrayTypeAdapter.write(ArrayTypeAdapter.java:93)    at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.write(TypeAdapterRuntimeTypeWrapper.java:68)    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.write(ReflectiveTypeAdapterFactory.java:89)    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.write(ReflectiveTypeAdapterFactory.java:195)    at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.write(TypeAdapterRuntimeTypeWrapper.java:68)    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.write(ReflectiveTypeAdapterFactory.java:89)    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.write(ReflectiveTypeAdapterFactory.java:195)    at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.write(TypeAdapterRuntimeTypeWrapper.java:68)    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.write(ReflectiveTypeAdapterFactory.java:89)    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.write(ReflectiveTypeAdapterFactory.java:195)    at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.write(TypeAdapterRuntimeTypeWrapper.java:68)    at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.write(CollectionTypeAdapterFactory.java:96)    at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.write(CollectionTypeAdapterFactory.java:60)    at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.write(TypeAdapterRuntimeTypeWrapper.java:68)    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.write(ReflectiveTypeAdapterFactory.java:89)    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.write(ReflectiveTypeAdapterFactory.java:195)    at com.google.gson.Gson.toJson(Gson.java:586)    at com.google.gson.Gson.toJson(Gson.java:565)    at com.google.gson.Gson.toJson(Gson.java:520)    at com.myapp.AutoResource.produceAuto(AutoResource.java:48)    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:601)    at org.glassfish.ejb.security.application.EJBSecurityManager.runMethod(EJBSecurityManager.java:1052)    at org.glassfish.ejb.security.application.EJBSecurityManager.invoke(EJBSecurityManager.java:1124)    at com.sun.ejb.containers.BaseContainer.invokeBeanMethod(BaseContainer.java:5388)    at com.sun.ejb.EjbInvocation.invokeBeanMethod(EjbInvocation.java:619)    at com.sun.ejb.containers.interceptors.AroundInvokeChainImpl.invokeNext(InterceptorManager.java:800)    at com.sun.ejb.EjbInvocation.proceed(EjbInvocation.java:571)    at com.sun.ejb.containers.interceptors.SystemInterceptorProxy.doAround(SystemInterceptorProxy.java:162)    at com.sun.ejb.containers.interceptors.SystemInterceptorProxy.aroundInvoke(SystemInterceptorProxy.java:144)    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:601)    at com.sun.ejb.containers.interceptors.AroundInvokeInterceptor.intercept(InterceptorManager.java:861)    at com.sun.ejb.containers.interceptors.AroundInvokeChainImpl.invokeNext(InterceptorManager.java:800)    at com.sun.ejb.containers.interceptors.InterceptorManager.intercept(InterceptorManager.java:370)    at com.sun.ejb.containers.BaseContainer.__intercept(BaseContainer.java:5360)    at com.sun.ejb.containers.BaseContainer.intercept(BaseContainer.java:5348)    at com.sun.ejb.containers.EJBLocalObjectInvocationHandler.invoke(EJBLocalObjectInvocationHandler.java:214)    at com.sun.ejb.containers.EJBLocalObjectInvocationHandlerDelegate.invoke(EJBLocalObjectInvocationHandlerDelegate.java:89)    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:601)    at com.sun.jersey.spi.container.JavaMethodInvokerFactory$1.invoke(JavaMethodInvokerFactory.java:60)    at com.sun.jersey.server.impl.model.method.dispatch.AbstractResourceMethodDispatchProvider$ResponseOutInvoker._dispatch(AbstractResourceMethodDispatchProvider.java:205)    at com.sun.jersey.server.impl.model.method.dispatch.ResourceJavaMethodDispatcher.dispatch(ResourceJavaMethodDispatcher.java:75)    at com.sun.jersey.server.impl.uri.rules.HttpMethodRule.accept(HttpMethodRule.java:288)    at com.sun.jersey.server.impl.uri.rules.ResourceClassRule.accept(ResourceClassRule.java:108)    at com.sun.jersey.server.impl.uri.rules.RightHandPathRule.accept(RightHandPathRule.java:147)    at com.sun.jersey.server.impl.uri.rules.RootResourceClassesRule.accept(RootResourceClassesRule.java:84)    at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1469)    at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1400)    at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1349)    at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1339)    at com.sun.jersey.spi.container.servlet.WebComponent.service(WebComponent.java:416)    at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:537)    at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:708)    at javax.servlet.http.HttpServlet.service(HttpServlet.java:770)    at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1550)    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:281)    at org.apache.catalina.core.StandardContextValve.__invoke(StandardContextValve.java:175)    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java)    at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:655)    at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:595)    at org.apache.catalina.core.StandardHostValve.__invoke(StandardHostValve.java:161)    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java)    at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:331)    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:231)    at com.sun.enterprise.v3.services.impl.ContainerMapper$AdapterCallable.call(ContainerMapper.java:317)    at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:195)    at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:860)    at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:757)    at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:1056)    at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:229)    at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:137)    at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:104)    at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:90)    at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:79)    at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:54)    at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:59)    at com.sun.grizzly.ContextTask.run(ContextTask.java:71)    at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:532)    at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:513)    at java.lang.Thread.run(Thread.java:722) |#]

Answer 1

您可以使用自定义 TypeAdapter 来手动取消所有内容的代理。大致如下:

/**
 * This TypeAdapter unproxies Hibernate proxied objects, and serializes them
 * through the registered (or default) TypeAdapter of the base class.
 */
public class HibernateProxyTypeAdapter extends TypeAdapter<HibernateProxy> {

    public static final TypeAdapterFactory FACTORY = new TypeAdapterFactory() {
        @Override
        @SuppressWarnings("unchecked")
        public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) {
            return (HibernateProxy.class.isAssignableFrom(type.getRawType()) ? (TypeAdapter<T>) new HibernateProxyTypeAdapter(gson) : null);
        }
    };
    private final Gson context;

    private HibernateProxyTypeAdapter(Gson context) {
        this.context = context;
    }

    @Override
    public HibernateProxy read(JsonReader in) throws IOException {
        throw new UnsupportedOperationException("Not supported");
    }

    @SuppressWarnings({"rawtypes", "unchecked"})
    @Override
    public void write(JsonWriter out, HibernateProxy value) throws IOException {
        if (value == null) {
            out.nullValue();
            return;
        }
        // Retrieve the original (not proxy) class
        Class<?> baseType = Hibernate.getClass(value);
        // Get the TypeAdapter of the original class, to delegate the serialization
        TypeAdapter delegate = context.getAdapter(TypeToken.get(baseType));
        // Get a filled instance of the original class
        Object unproxiedValue = ((HibernateProxy) value).getHibernateLazyInitializer()
                .getImplementation();
        // Serialize the value
        delegate.write(out, unproxiedValue);
    }
}

要使用它，您必须先注册它:

GsonBuilder b = new GsonBuilder();
...
b.registerTypeAdapterFactory(HibernateProxyTypeAdapter.FACTORY);
...
Gson gson = b.create();

请注意，这将递归地初始化对象层次结构中的每个代理；因为无论如何你都必须序列化整个数据，所以无论如何你都应该这样做。

这是如何工作的？

GSON 包含许多 TypeAdapterFactory 实现，适用于各种类型(原始类型、常见类型，如 String 或 Date、列表、数组。 ..)。每个工厂都会被询问是否能够序列化某种 Java 类型(create 的参数是 TypeToken 而不是 Class，以便捕获有关泛型类型的可能信息，而 Class 没有)。如果工厂能够序列化/反序列化类型，它会使用 TypeAdapter 实例进行响应；否则它会返回 null。

HibernateProxyTypeAdapter.FACTORY 验证type是否实现HibernateProxy；在这种情况下，它会返回一个 HibernateProxyTypeAdapter 实例进行序列化。当需要序列化实际对象时，会调用 write 方法；适配器提取底层对象的原始类型，并向 GSON 请求原始类型的标准 TypeAdapter，通常是 ReflectiveTypeAdapter。

然后它检索原始类的实例，而不是直接使用代理。这是必要的，因为 ReflectiveTypeAdapter 访问 directly to fields ，而不是使用 setter/getter ；访问代理对象的字段不起作用，并且是经典的Hibernate pitfall .

作为可能的性能改进，应在 create 方法中获取委托(delegate) TypeAdapter。我发现在代理 Class 上调用 getSuperclass() 似乎会产生原始基类。代码可以变成:

public static final TypeAdapterFactory FACTORY = new TypeAdapterFactory() {
    @Override
    @SuppressWarnings("unchecked")
    public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) {
        return (HibernateProxy.class.isAssignableFrom(type.getRawType())
                ? (TypeAdapter<T>) new HibernateProxyTypeAdapter((TypeAdapter)gson.getAdapter(TypeToken.get(type.getRawType().getSuperclass()))) 
     : null);
    }
};
private final TypeAdapter<Object> delegate;

private HibernateProxyTypeAdapter(TypeAdapter<Object> delegate) {
    this.delegate = delegate;
}

@SuppressWarnings({"rawtypes", "unchecked"})
@Override
public void write(JsonWriter out, HibernateProxy value) throws IOException {
    if (value == null) {
        out.nullValue();
        return;
    }
    delegate.write(out, ((HibernateProxy) value).getHibernateLazyInitializer()
            .getImplementation());
}