Re: [Simple-support] Support for almost-primitive types, Converters in attributes and Arrays in attributes

[Niall G. <gal...@ya...>]

Hi,

Thanks for the contribution, I will take a close look at this and perhaps add it to a future release.

Thanks,
Niall



--- On Tue, 14/6/11, Raphael Jolivet <rap...@gm...> wrote:

From: Raphael Jolivet <rap...@gm...>
Subject: Re: [Simple-support] Support for almost-primitive types, Converters in attributes and Arrays in attributes
To: "Niall Gallagher" <gal...@ya...>
Cc: sim...@li...
Received: Tuesday, 14 June, 2011, 6:25 AM



2011/5/26 Niall Gallagher <gal...@ya...>

Hi,

Yes, it does work for attributes. Check out the test cases, in particular PrimitiveArrayTransformTest.


Niall
Sorry, you were right, it works for attributes. But it works only for arrays ('[]'), not for Lists or Collections. 
However, there should not be any fundamental differences between those two types, they are still "a bunch of something".
This does not work :
	@Attribute(name="group-by", required=false)
	private List<Field> groupBy = new List<Field>();

Also, I have implemented a core Converter and integrated it in the framework so that all objects with a "Constructor(String value)" are serialized out of the box without the need of any further work, annotation, or strategy. I have integrated it only for parsing attributes at the moment; not for elements.

I hope this can be useful to someone.
Regards,Raphael


===== The converter ==================================================================


package org.simpleframework.xml.core;

import java.lang.reflect.Constructor;
import org.simpleframework.xml.stream.InputNode;import org.simpleframework.xml.stream.OutputNode;

/**  * Converter for classes that have a constructor with a single String.
 * It uses this constructor for new instances, and toString for serialiasing.  */

public class StringConstructorConverter implements Converter {

	// ----------------------------------------------------
	// Static method	// ----------------------------------------------------
		static public boolean hasStringConstructor(Class<?> type) {
		return (getStringConstructor(type) != null);	}
		// ----------------------------------------------------
	// Attributes	// ----------------------------------------------------
		Class<?> type;
		// ----------------------------------------------------
	// Private methods	// ----------------------------------------------------
		static private Constructor<?> getStringConstructor(Class<?> type) {
		try {			return type.getConstructor(String.class);
		} catch (NoSuchMethodException e) {			return null;
		}	}
		// ----------------------------------------------------
	// Constructor	// ----------------------------------------------------
		public StringConstructorConverter(Class<?> type) {
		this.type = type;	}
		/** Instantiate the object with the string constructor */
	public Object read(InputNode node) throws Exception {		return getStringConstructor(this.type).newInstance(node.getValue());
	}

	/** Use "toString" as the representation of this object */
	public void write(OutputNode node, Object value) throws Exception {
		node.setValue(value.toString());	}




	/** This should not happen, ginore the existing value */
	public Object read(InputNode node, Object value) throws Exception {		
		return this.read(node);	}

	/** Do not validate, we'll see ... */
	public boolean validate(InputNode node) throws Exception {		return true;
	}	
}
============ Integration into the Framework : AttributeLabel#getConverter ====================

   public Converter getConverter(Context context) throws Exception {
      String ignore = getEmpty(context);      Type type = getContact();
            if(!context.isPrimitive(type)) {
    	  if (!StringConstructorConverter.hasStringConstructor(type.getType())) {
    		  throw new AttributeException("Cannot use %s to represent %s", label, type);
    	  } else {    		  return new StringConstructorConverter(type.getType());
    	  }      }
      return new Primitive(context, type, ignore);   }

=================================================================================================