¿Cómo serializar una lista en AutoBean (GWT)?

Question

Estoy tratando de averiguar cómo serializar una lista usando AutoBean en GWT, pero sigo obteniendo una excepción de puntero nulo.

Esto es lo que tengo:

GuideCreatorFactory beanFactory = AutoBeanFactorySource.create(GuideCreatorFactory.class); 

    List<Guide> guides = new LinkedList<Guide>(); 
    Guide guide = new Guide(); 
    guide.setText("this is the text"); 
    guide.setTitle("this is the title"); 
    guides.add(guide); 

    GuideCreatorList<Guide> impl = new GuideCreatorListImpl(); 
    impl.setGuides(guides); 

    System.out.println("Serializing the given parameter to JSON"); 

    // Fails on the below lines w/ NPE 
    AutoBean<GuideCreatorList> bean = beanFactory.create(GuideCreatorList.class, impl); 
    String json = AutoBeanCodex.encode(bean).getPayload(); 
    System.out.println("guides as json: " + json); 

¿Puede alguien ayudarme a apuntar en la dirección correcta? Muchas gracias.

He aquí las clases de apoyo e interfaces:

public interface GuideCreatorFactory extends AutoBeanFactory { 
    AutoBean<GuideCreator> createGuide(); 

    AutoBean<GuideCreatorList> createGuideList(); 
} 


public interface GuideCreator { 

    public String getText(); 

    public void setText(String text); 

    public String getTitle(); 

    public void setTitle(String title); 

} 


public interface GuideCreatorList<T extends GuideCreator> { 
    public List<T> getGuides(); 

    public void setGuides(List<T> guides); 
} 



class GuideCreatorListImpl implements GuideCreatorList<Guide> { 
    private List<Guide> guides; 

    public GuideCreatorListImpl() { 

    } 

    @Override 
    public List<Guide> getGuides() { 
     return guides; 
    } 

    @Override 
    public void setGuides(List<Guide> guides) { 
     this.guides = guides; 
    } 
    }; 

Aquí está la NPE:

java.lang.NullPointerException 
    at com.google.web.bindery.autobean.shared.impl.AutoBeanCodexImpl.doEncode(AutoBeanCodexImpl.java:558) 
    at com.google.web.bindery.autobean.shared.impl.AutoBeanCodexImpl$ObjectCoder.encode(AutoBeanCodexImpl.java:321) 
    at com.google.web.bindery.autobean.shared.impl.AutoBeanCodexImpl$CollectionCoder.encode(AutoBeanCodexImpl.java:163) 
    at com.google.web.bindery.autobean.shared.impl.AutoBeanCodexImpl$PropertyGetter.encodeProperty(AutoBeanCodexImpl.java:413) 
    at com.google.web.bindery.autobean.shared.impl.AutoBeanCodexImpl$PropertyGetter.visitReferenceProperty(AutoBeanCodexImpl.java:389) 
    at com.google.web.bindery.autobean.shared.AutoBeanVisitor.visitCollectionProperty(AutoBeanVisitor.java:229) 
    at com.google.web.bindery.autobean.vm.impl.ProxyAutoBean.traverseProperties(ProxyAutoBean.java:300) 
    at com.google.web.bindery.autobean.shared.impl.AbstractAutoBean.traverse(AbstractAutoBean.java:166) 
    at com.google.web.bindery.autobean.shared.impl.AbstractAutoBean.accept(AbstractAutoBean.java:101) 
    at com.google.web.bindery.autobean.shared.impl.AutoBeanCodexImpl.doEncode(AutoBeanCodexImpl.java:558) 
    at com.google.web.bindery.autobean.shared.AutoBeanCodex.encode(AutoBeanCodex.java:83) 
    at com.districthp.core.ui.client.review.JsonSerializationText.testMyObject(JsonSerializationText.java:82) 
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) 
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) 
    at java.lang.reflect.Method.invoke(Method.java:597) 
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44) 
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15) 
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41) 
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20) 
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28) 
    at org.junit.runners.BlockJUnit4ClassRunner.runNotIgnored(BlockJUnit4ClassRunner.java:79) 
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:71) 
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:49) 
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193) 
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52) 
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191) 
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42) 
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184) 
    at org.junit.runners.ParentRunner.run(ParentRunner.java:236) 
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50) 
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38) 
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467) 
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683) 
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390) 
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197) 

Answer 1

Desgraciadamente, esto es un problema conocido: https://github.com/gwtproject/gwt/issues/6903

El problema es que los elementos de la lista no están incluidos en AutoBean s así que AutoBeanUtils#getAutoBean en AutoBeanCodexImpl.ObjectCoder#encode devuelve null, gallina ce el NPE en AutoBeanCodexImpl#doEncode.

La solución consiste en reemplazar los elementos de la lista con AutoBean s que ajustan el valor real.