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package javax.el;
import java.util.Iterator;
import java.beans.FeatureDescriptor;
/**
* A convenient class for writing an ELResolver to do custom type conversions.
*
* For example, to convert a String to an instance of MyDate, one can write
*
* ELProcessor elp = new ELProcessor();
* elp.getELManager().addELResolver(new TypeConverter() {
* Object convertToType(ELContext context, Object obj, Class type) {
* if ((obj instanceof String) && type == MyDate.class) {
* context.setPropertyResolved(obj, type);
* return (obj == null)? null: new MyDate(obj.toString());
* }
* return null;
* }
* };
*
*
* @since EL 3.0
*/
public abstract class TypeConverter extends ELResolver {
@Override
public Object getValue(ELContext context,
Object base,
Object property) {
return null;
}
@Override
public Class getType(ELContext context,
Object base,
Object property) {
return null;
}
@Override
public void setValue(ELContext context,
Object base,
Object property,
Object value) {
}
@Override
public boolean isReadOnly(ELContext context,
Object base,
Object property){
return false;
}
@Override
public Iterator getFeatureDescriptors(
ELContext context,
Object base) {
return null;
}
@Override
public Class getCommonPropertyType(ELContext context,
Object base) {
return null;
}
/**
* Converts an object to a specific type.
*
* An ELException is thrown if an error occurs during
* the conversion.
*
* @param context The context of this evaluation.
* @param obj The object to convert.
* @param targetType The target type for the conversion.
* @throws ELException thrown if errors occur.
*/
@Override
abstract public Object convertToType(ELContext context,
Object obj,
Class targetType);
}