property.java

PIY(Program It Yourself)是一个基于Java的应用程序开发环境

package piy;

import java.lang.reflect.*;
import java.io.Serializable;

/**
* Each getter/setter match in a class can have a Property class modelling it.  This class
* provides information on a particular property a class possesses, and provides standard 
* methods for invoking the methods using low-level reflection.
* @author David Vivash
* @version 1.0, 5/12/00
*/
public class Property implements Serializable
{
	private Object holder;
	private String name;
	private Class type;

	private boolean converted = false;

	/**
	* Construct a property for the specific object, where the property has the particular
	* name and type.  The property must be obtainable using the structure <code>
	* type = holder.get"Name"() </code> and settable using <code> holder.set"Name"(type) </code>
	* @param holder the Object which contains the property
	* @param name the name of the property
	* @param type the type of the property
	*/
	public Property(Object holder, String name, Class type) {
		this.holder	= holder;
		this.name	= name;
		setType(type);
	}

	/**
	* Get the name of the property.
	* @return the name of the property, as provided in the constructor for this object
	*/
	public String getName() { return name; }

	/**
	* Get the holder holding this property.
	* @return the object holding the property
	*/
	public Object getHolder() { return holder; }

	/**
	* Retrieves the value of the property by invoking the get"Name"() method.  The returned
	* Object should be castable to an object of the type specified in the constructor for this
	* class.
	* @return the return value of calling get"Name"() on the holder object
	*/
	public Object getValue() {
		try {
			return holder.getClass().getMethod("get" + name, new Class[0]).invoke(holder, null);
		} catch (Exception e) {
			System.err.println("Unable to get property " + name);
			e.printStackTrace();
		}
		return null;
	}

	/**
	* Sets the property to a new value.  The type of the input variable shold be castable to
	* the type of the property as specified in this constructor.  This method effectively
	* invokes holder.set"Name"(value).
	* @param value the value to set the property to
	*/
	public void setValue(Object value) {
		boolean success = false;

		try {
			
			holder.getClass().getMethod("set" + name, new Class[] { getType() }).invoke(holder, new Object[] { value });
			success = true;
		} catch (Exception e) {
			//don't do anything yet - we'll try again
		}

		if (!success) { //try again with a general Object instead, sometimes works...
			try{
				holder.getClass().getMethod("set" + name, new Class[] { Object.class }).invoke(holder, new Object[] { value });		
			} catch (Exception e) {
				System.err.println("Unable to set property " + name + " on holder " + holder + " with type " + getType());
				e.printStackTrace();
			}
		}
	}
	
	/**
	* This method should only be used by primitive type support classes, to set the
	* type of the property when it has been incorrectly set to a non-primitive
	* wrapper class type.
	* @param type the new primitive type to set the property type to
	*/
	public void setType(Class type) {
		if (type == null) return;
		
		if (type.isPrimitive()) {
			if (type == int.class)		this.type = Integer.class;
			if (type == boolean.class)	this.type = Boolean.class;
			if (type == byte.class)		this.type = Byte.class;
			if (type == char.class)		this.type = Character.class;
			if (type == short.class)	this.type = Short.class;
			if (type == long.class)		this.type = Long.class;
			if (type == float.class)	this.type = Float.class;
			if (type == double.class)	this.type = Double.class;
			if (type == void.class)		this.type = Void.class;
			converted = true;
		} else {
			this.type = type;
			converted = false;
		}
	}

	/**
	* Get the type of the property.
	* @return the type of the property, as provided in the constructor for this object
	*/
	public Class getType() { 
		if (converted) {
			if (type == Integer.class)		return int.class;
			if (type == Boolean.class)		return boolean.class;	
			if (type == Byte.class)			return byte.class;	
			if (type == Character.class)	return char.class;	
			if (type == Short.class)		return short.class;	
			if (type == Long.class)			return long.class;	
			if (type == Float.class)		return float.class;	
			if (type == Double.class)		return double.class;	
			if (type == Void.class)			return void.class;	
		} 
		//else
		return type; 
	}

	public String toString() {
		return "["+holder+", "+name+", "+type+"]";
	}
}