Re: [json-lib-user] Converting GregorianCalendar object, Java to JSON and back

[Andres A. <aal...@ya...>]

What about this (pseudo) Java code ;-)

class Bean {
   String name
}


class BeanFactory {
   Bean newBean( String name ){ new Bean(name: name) }
}

class MyNewBeanInstanceFactory extends NewBeanInstanceFactory.DEFAULT {
    BeanFactory factory = new BeanFactory()
    public Object newInstance( Class target, JSONObject source ){
      if( Bean.class.isAssignableFrom(target) ) {
         return factory.newBean( source.get("name") )
      }else{
         super.newInstance(target,source)
      }
   }
}

JsonConfig jsonConfig = new JsonConfig()
jsonConfig.setNewBeanInstanceStrategy( new MyNewBeanInstanceFactory() )
...


----- Original Message ----
From: Darlene Wong <dar...@gm...>
To: Andres Almiray <aal...@ya...>
Cc: jso...@li...
Sent: Tuesday, June 10, 2008 6:52:27 PM
Subject: Re: [json-lib-user] Converting GregorianCalendar object, Java to JSON and back

Thanks Andres.  I will give this a shot.  Can you point me to some sample code that creates a custom strategy?

thanks,
Darlene


On Fri, Jun 6, 2008 at 4:15 PM, Andres Almiray <aal...@ya...> wrote:

Hi Darlene,

There is indeed a restriction on the classes that can be used when serializing back to Java, they must adhere to the JavaBeans conventions (no-arg constructor, getters/setters, etc). It looks like GregorianCalendar follows suit still it throws an exception. Well no worries as you may register a NewBeanInstanceStrategy with JsonConfig. The default strategy follows the JavaBeans convention (no-arg constructor), with a custom strategy you are free to instantiate the class as you see fit, for example using a factory.

http://json-lib.sourceforge.net/xref/net/sf/json/util/NewBeanInstanceStrategy.html

Cheers,
Andres

 -------------------------------------------
http://jroller.com/aalmiray
http://www.linkedin.com/in/aalmiray
--
What goes up, must come down. Ask any system administrator.
There are 10 types of people in the world: Those who understand binary, and those who don't.
To understand recursion, we must first understand recursion.



----- Original Message ----
From: Darlene Wong <dar...@gm...>
To: jso...@li...
Sent: Friday, June 6, 2008 3:08:30 PM
Subject: [json-lib-user] Converting GregorianCalendar object, Java to JSON and back

Hi, I'm new to json-lib.  I want to convert a Java class into JSONObject and then back again.  I am able to do this conversion with a Date class.  However, the class I want to convert contains a nested XMLGregorianCalendar object, which has issues when converting from JSONObject to Java.   

I've tried to create a simple test case that converts only a GregorianCalendar object (http://java.sun.com/javase/6/docs/api/java/util/GregorianCalendar.html).
This works fine when converting from Java to JSONObject, but the reverse conversion gives an InstantiationException error when calling toJava().  Here is my sample code:


            GregorianCalendar gc = DateUtil.getCalendar(-7);
            System.out.println(gc.toString());

            // Convert object to JSON
            JSONObject jsonObject = (JSONObject) JSONSerializer.toJSON(gc);
            System.out.println(jsonObject.toString());


            // Convert JSON object back into Java object
            GregorianCalendar gc2;
            JsonConfig jsonConfig = new JsonConfig();
            jsonConfig.setRootClass(GregorianCalendar.class);
            gc2 = (GregorianCalendar) JSONSerializer.toJava(jsonObject, jsonConfig);
            System.out.println(gc2.toString());


The output is as follows:
java.util.GregorianCalendar[time=1212788878236,areFieldsSet=true,areAllFieldsSet=true,lenient=true,zone=java.util.SimpleTimeZone[id=GMT-07:00,offset=-25200000,dstSavings=3600000,useDaylight=true,startYear=0,startMode=3,startMonth=3,startDay=1,startDayOfWeek=1,startTime=7200000,startTimeMode=0,endMode=2,endMonth=9,endDay=-1,endDayOfWeek=1,endTime=7200000,endTimeMode=0],firstDayOfWeek=1,minimalDaysInFirstWeek=1,ERA=1,YEAR=2008,MONTH=5,WEEK_OF_YEAR=23,WEEK_OF_MONTH=1,DAY_OF_MONTH=6,DAY_OF_YEAR=158,DAY_OF_WEEK=6,DAY_OF_WEEK_IN_MONTH=1,AM_PM=1,HOUR=3,HOUR_OF_DAY=15,MINUTE=47,SECOND=58,MILLISECOND=236,ZONE_OFFSET=-25200000,DST_OFFSET=3600000]
{"firstDayOfWeek":1,"gregorianChange":{"date":4,"day":4,"hours":16,"minutes":0,"month":9,"seconds":0,"time":-12219292800000,"timezoneOffset":480,"year":-318},"lenient":true,"minimalDaysInFirstWeek":1,"time":{"date":6,"day":5,"hours":14,"minutes":47,"month":5,"seconds":58,"time":1212788878236,"timezoneOffset":420,"year":108},"timeInMillis":1212788878236,"timeZone":{"DSTSavings":3600000,"ID":"GMT-07:00","displayName":"GMT-07:00","rawOffset":-25200000}}
net.sf.json.JSONException: java.lang.InstantiationException
    at net.sf.json.JSONObject.toBean(JSONObject.java:304)
    at net.sf.json.JSONObject.toBean(JSONObject.java:420)
    at net.sf.json.JSONSerializer.toJava(JSONSerializer.java:69)

...

Like I said, I am able to get the same code to work on other objects, such as Date objects, so what am I missing?  Is there a limitation on the types of objects that can be converted to JSONObject and back?  

Any help or pointers is greatly appreciated!

Darlene