"flexjson.JSONException: Error trying to deepSerialize" confussion

[mbabauer]

I am trying to use the toJsonArray on a list of domain objects and getting this:

2012-02-16 10:06:57,770 [taskScheduler-2] ERROR org.springframework.scheduling.support.MethodInvokingRunnable - Invocation of method 'processPendingMessages' on target class [class com.xyz.art.messaging.MessagingCoordinator] failed
flexjson.JSONException: Error trying to deepSerialize
	at flexjson.transformer.ObjectTransformer.transform(ObjectTransformer.java:61)
	at flexjson.transformer.TransformerWrapper.transform(TransformerWrapper.java:22)
	at flexjson.transformer.ObjectTransformer.transform(ObjectTransformer.java:49)
	at flexjson.transformer.TransformerWrapper.transform(TransformerWrapper.java:22)
	at flexjson.transformer.ObjectTransformer.transform(ObjectTransformer.java:49)
	at flexjson.transformer.TransformerWrapper.transform(TransformerWrapper.java:22)
	at flexjson.transformer.ObjectTransformer.transform(ObjectTransformer.java:49)
	at flexjson.transformer.TransformerWrapper.transform(TransformerWrapper.java:22)
	at flexjson.JSONContext.transform(JSONContext.java:73)
	at flexjson.transformer.IterableTransformer.transform(IterableTransformer.java:29)
	at flexjson.transformer.TransformerWrapper.transform(TransformerWrapper.java:22)
	at flexjson.JSONContext.transform(JSONContext.java:73)
	at flexjson.JSONSerializer.serialize(JSONSerializer.java:377)
	at flexjson.JSONSerializer.serialize(JSONSerializer.java:235)
	at com.xyz.art.domain.Message_Roo_Json.toJsonArray_aroundBody2(Message_Roo_Json.aj:24)
	at com.xyz.art.domain.Message_Roo_Json.ajc$interMethod$com_xyz_art_domain_Message_Roo_Json$com_xyz_art_domain_Message$toJsonArray(Message_Roo_Json.aj:1)
	at com.xyz.art.domain.Message.toJsonArray(Message.java:1)
	at com.xyz.art.domain.Message_Roo_Json.ajc$interMethodDispatch1$com_xyz_art_domain_Message_Roo_Json$com_xyz_art_domain_Message$toJsonArray(Message_Roo_Json.aj)
	at com.xyz.art.messaging.MessagingCoordinator.processPendingMessages(MessagingCoordinator.java:113)
	at sun.reflect.GeneratedMethodAccessor87.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:597)
	at org.springframework.util.MethodInvoker.invoke(MethodInvoker.java:273)
	at org.springframework.scheduling.support.MethodInvokingRunnable.run(MethodInvokingRunnable.java:65)
	at org.springframework.scheduling.support.DelegatingErrorHandlingRunnable.run(DelegatingErrorHandlingRunnable.java:51)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441)
	at java.util.concurrent.FutureTask$Sync.innerRunAndReset(FutureTask.java:317)
	at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:150)
	at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$101(ScheduledThreadPoolExecutor.java:98)
	at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.runPeriodic(ScheduledThreadPoolExecutor.java:180)
	at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:204)
	at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
	at java.lang.Thread.run(Thread.java:680)
Caused by: java.lang.IllegalAccessException: Class flexjson.BeanProperty can not access a member of class sun.util.calendar.CalendarDate with modifiers "private"
	at sun.reflect.Reflection.ensureMemberAccess(Reflection.java:65)
	at java.lang.reflect.Field.doSecurityCheck(Field.java:960)
	at java.lang.reflect.Field.getFieldAccessor(Field.java:896)
	at java.lang.reflect.Field.get(Field.java:358)
	at flexjson.BeanProperty.getValue(BeanProperty.java:104)
	at flexjson.transformer.ObjectTransformer.transform(ObjectTransformer.java:37)
	... 33 more

My class looks like this:

package com.xyz.art.domain;

import java.util.Calendar;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

import javax.persistence.EntityManager;
import javax.persistence.Enumerated;
import javax.persistence.ManyToMany;
import javax.persistence.OneToMany;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
import javax.persistence.TypedQuery;
import javax.validation.constraints.NotNull;
import org.springframework.format.annotation.DateTimeFormat;
import org.springframework.roo.addon.javabean.RooJavaBean;
import org.springframework.roo.addon.jpa.activerecord.RooJpaActiveRecord;
import org.springframework.roo.addon.json.RooJson;
import org.springframework.roo.addon.tostring.RooToString;

@RooJavaBean
@RooToString
@RooJpaActiveRecord
@RooJson
public class Message {
    @NotNull
    @Enumerated
    private MessageDisplayType displayType;

    @NotNull
    private String title;

    @NotNull
    private String message;
    
    @ManyToMany
    private Set<SiteAuthority> destinationAuthorities = new HashSet<SiteAuthority>();
    
    /**
     * If ackRequired == true, the message will continue to be sent until it is acknowledged.
     * If ackRequired == false, the message is auto-ack'ed when it is sent, as we don't care 
     * about guaranteed delivery.
     */
    private boolean ackRequired = false;
    
    @NotNull
    @Temporal(TemporalType.TIMESTAMP)
    @DateTimeFormat(style = "MM")
    private Calendar createdOn = Calendar.getInstance();
    
    @Temporal(TemporalType.TIMESTAMP)
    @DateTimeFormat(style = "MM")
    private Calendar sentOn;
    
    @Temporal(TemporalType.TIMESTAMP)
    @DateTimeFormat(style = "MM")
    private Calendar start;
    
    @Temporal(TemporalType.TIMESTAMP)
    @DateTimeFormat(style = "MM")
    private Calendar expiration;
}

Nothing overly crazy. What I am confused about is why it's complaining about serializing the Calendar objects? Aren't all the values marked "private"? I have use the Object.toJsonArray many times, and never had a problem with other class members that were marked as "private".

Anyone know why it might be complaining now?

[Vito Meuli]

I have the exact same problem as mbabauer.
Googling hasn't helped so far.
Any hint?

[mbabauer]

Yeah, I haven't figured it out yet, either. Its sort of blocking my development at the moment.

For additional information, what I have is a class that has a method setup with a simple Scheduler. When kicked off, it uses a find to get a bunch of these Message objects out of the DB, which is returned as a TypedQuery. It then uses getResultList() to get it as a list, does some processing to convert that to a HashMap, then iterates the keys of the HashMap, creating a third list of Messages that need acting on. This list is what is being serialized via the Message.toJsonArray(). I have broke at the spot where the serialization occurs, and the list looks fine. I can see the Message objects, can click the various parts, etc.

From the error message, though, I am lead to believe this might not be in the Message class at all, though, given the phrase "deepSerialize". So, it may be one of the linked objects. My next step will be to start looking at those more closely to see if I can figure out why this is happening.

[Vito Meuli]

I'm trying to debug the FlexJson JSONSerializer().serialize() (difficult task for me).
The first weird thing is that maybe it has problems with the Calendar type we are using; it has a map of transformers, and the Calendar type isn't in it! It has a GregorianCalendar and a JulianCalendar one, and a java.util.Date one, but not the abstract Calendar...

I have to dig into it more.
I'll keep you posted.

[Vito Meuli]

If I use a java.util.Date field the serializer works without exceptions...but it outputs a Long instead of a date, and there are other problems with the scaffolded MVC controller, the jspx has problems in formatting such Long.
I guess Roo is built to use a Calendar and not a Date.
----------------------
I tryed using a GregorianCalendar: it gives the same exception as before, but now it is thrown on my own class containing the date field, and not on the Calendar anymore.

The ObjectTransformer is looking for a Calendar field named "modifyDate", but it can't find one!
The one that is in there is a GregorianCalendar indeed.

ObjectTransformer:

BeanAnalyzer analyzer = BeanAnalyzer.analyze( resolveClass(object) );
TypeContext typeContext = context.writeOpenObject();
for( BeanProperty prop : analyzer.getProperties() ) {
	String name = prop.getName();
	path.enqueue(name);
	if( context.isIncluded(prop) ) {
		Object value = prop.getValue( object ); // <<<<< exception here!
		if (!context.getVisits().contains(value)) {

			TransformerWrapper transformer = (TransformerWrapper)context.getTransformer(value);

			if(!transformer.isInline()) {
				if (!typeContext.isFirst()) context.writeComma();

BeanProperty:

public Object getValue(Object instance) throws InvocationTargetException, IllegalAccessException {
	Method rm = getReadMethod();
	if (rm != null ) {
		return rm.invoke(instance, (Object[]) null);
	} else if (property != null) {
		return property.get(instance);  // <<<<< exception here!
	} else {
		return null;
	}
}

Maybe I should ask such questions on the FlexJason list.

[Vito Meuli]

I think my former guesses were wrong: there's no problem in finding a transformer for a GregorianCalendar.
The field that cannot be read from Calendar (GregorianCalendar in my case) is "locale", which has no getter as per its API. Let's go ahead tomorrow...