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package jsp2_1.examples.elresolver;
import java.util.Arrays;
import java.util.Iterator;
import javax.el.ELContext;
import javax.el.ELException;
import javax.el.ELResolver;
import javax.el.PropertyNotWritableException;
/**
* Introduces a new ${Color} implicit object and resolves properties
* on that object.
*
* <p>Features include:
* <ul>
* <li>Look up common colors by name, e.g. ${Color.MintCream}</li>
* <li>Look up colors by hex, e.g. ${Color["#f0f0f0"]}</li>
* <li>Specify r, g, and b values numerically, e.g.
* ${Color[240][255][255]}</li>
* <li>Retrieve red, green, or blue individually, e.g. ${myColor.red}</li>
* <li>Retrieve HTML-style hex value for a color, e.g. ${myColor.hex}</li>
* <li>Retrieve java.awt.Color object for a color, e.g. ${myColor.color}</li>
* <li>Retrieve brigter and darker colors, e.g.
* ${Color.AliceBlue.darker.hex}</li>
* </ul>
* </p>
*
* @author Mark Roth
*/
public class ColorELResolver
extends ELResolver
{
public Object getValue(ELContext context, Object base, Object property)
throws ELException
{
if(context == null) throw new NullPointerException();
Object result = null;
if(base == null) {
// Resolving first variable (e.g. ${Color}).
// We only handle "Color"
String propertyName = (String)property;
if(propertyName.equals("Color")) {
result = new ColorImplicitObject();
context.setPropertyResolved(true);
}
}
else if(base instanceof ColorImplicitObject) {
// Resolving a property on ${Color}
ColorImplicitObject color = (ColorImplicitObject)base;
if(property instanceof Long) {
// Handle ${Color[100]}
int red = ((Long)property).intValue();
result = new ColorImplicitObject.ColorR(red);
context.setPropertyResolved(true);
}
else {
String colorName = property.toString();
if(colorName.startsWith("#")) {
// Handle ${Color['#f0f0f0']}
result = ColorImplicitObject.fromHex(colorName);
context.setPropertyResolved(true);
}
else {
// Handle ${Color.MintCream}
result = ColorImplicitObject.fromName(colorName);
context.setPropertyResolved(true);
}
}
}
else if(base instanceof ColorImplicitObject.ColorRGB) {
ColorImplicitObject.ColorRGB rgb =
(ColorImplicitObject.ColorRGB)base;
// The rest is handled by the BeanPropertyResolver.
}
else if(base instanceof ColorImplicitObject.ColorRG) {
ColorImplicitObject.ColorRG rg = (ColorImplicitObject.ColorRG)base;
if(property instanceof Long) {
// Handle ${Color[100][150][200]}
int blue = ((Long)property).intValue();
result = new ColorImplicitObject.ColorRGB(rg.getRed(),
rg.getGreen(), blue);
context.setPropertyResolved(true);
}
}
else if(base instanceof ColorImplicitObject.ColorR) {
ColorImplicitObject.ColorR r = (ColorImplicitObject.ColorR)base;
if(property instanceof Long) {
// Handle ${Color[100][150]}
int green = ((Long)property).intValue();
result = new ColorImplicitObject.ColorRG(r.getRed(), green);
context.setPropertyResolved(true);
}
}
return result;
}
public Class getType(ELContext context, Object base, Object property)
throws ELException
{
Class result = null;
if(context == null) throw new NullPointerException();
if(base == null) {
// We don't handle setting top-level implicit objects.
}
else if(base instanceof ColorImplicitObject) {
// None of the properties of the ${Color} implicit object are
// ever writable.
context.setPropertyResolved(true);
}
else if(
(base instanceof ColorImplicitObject.ColorR)
|| (base instanceof ColorImplicitObject.ColorRG))
{
// Don't allow setting of
// ${Color[100][150]} or ${Color[100][150][200]}
if(property instanceof Long) {
context.setPropertyResolved(true);
}
}
// The rest is handled by BeanELResolver, etc.
return result;
}
public void setValue(ELContext context, Object base, Object property,
Object value)
throws ELException
{
if(context == null) throw new NullPointerException();
if(base == null) {
// We don't handle setting top-level implicit objects.
}
else if(base instanceof ColorImplicitObject) {
// None of the properties of the ${Color} implicit object are
// ever writable.
throw new PropertyNotWritableException();
}
else if(
(base instanceof ColorImplicitObject.ColorR)
|| (base instanceof ColorImplicitObject.ColorRG))
{
// Don't allow setting of
// ${Color[100][150]} or ${Color[100][150][200]}
if(property instanceof Long) {
throw new PropertyNotWritableException();
}
}
}
public boolean isReadOnly(ELContext context, Object base,
Object property)
throws ELException
{
boolean result = false;
if(context == null) throw new NullPointerException();
if(base == null) {
// We don't handle setting top-level implicit objects.
}
else if(base instanceof ColorImplicitObject) {
// None of the properties of the ${Color} implicit object are
// ever writable.
result = false;
context.setPropertyResolved(true);
}
else if(
(base instanceof ColorImplicitObject.ColorR)
|| (base instanceof ColorImplicitObject.ColorRG))
{
// Don't allow setting of
// ${Color[100][150]} or ${Color[100][150][200]}
if(property instanceof Long) {
result = false;
context.setPropertyResolved(true);
}
}
return result;
}
public Iterator getFeatureDescriptors(ELContext context, Object base) {
Iterator result = null;
if(context == null) throw new NullPointerException();
if(base == null) {
result = Arrays.asList(new String[] {"Color"}).iterator();
}
else if(base instanceof ColorImplicitObject) {
// Return all color names
result = ColorImplicitObject.colorNameIterator();
// XXX - There's no way to say we also accept 0-255
}
else if(
(base instanceof ColorImplicitObject.ColorR)
|| (base instanceof ColorImplicitObject.ColorRG)
|| (base instanceof ColorImplicitObject.ColorRGB))
{
// We accept integers 0-255, but don't enumerate them.
// The tool will call getCommonPropertyType() instead.
result = null;
}
// BeanELResolver will add to this iterator with the bean properties.
return result;
}
public Class getCommonPropertyType(ELContext context,
Object base)
{
Class result = null;
if(base == null) {
// Resolving first variable (e.g. ${Color}).
// We only handle "Color"
result = String.class;
}
else if(base instanceof ColorImplicitObject) {
// We handle either integers or strings, so return Object
result = Object.class;
}
else if(base instanceof ColorImplicitObject.ColorR) {
// We handle only integers in this case.
result = Long.class;
}
else if(base instanceof ColorImplicitObject.ColorRG) {
// We handle only integers in this case.
result = Long.class;
}
else if(base instanceof ColorImplicitObject.ColorRGB) {
// We don't do anything with these - the BeanELResolver
// takes it from here.
}
return result;
}
}
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