org.jdesktop.el.Expression Maven / Gradle / Ivy
/*
* Copyright (C) 2007 Sun Microsystems, Inc. All rights reserved. Use is
* subject to license terms.
*/
package org.jdesktop.el;
import java.io.Serializable;
import java.util.List;
/**
* Base class for the expression subclasses {@link ValueExpression} and
* {@link MethodExpression}, implementing characterstics common to both.
*
* All expressions must implement the equals() and
* hashCode() methods so that two expressions can be compared
* for equality. They are redefined abstract in this class to force their
* implementation in subclasses.
*
* All expressions must also be Serializable so that they
* can be saved and restored.
*
* Expressions are also designed to be immutable so
* that only one instance needs to be created for any given expression
* String / {@link FunctionMapper}. This allows a container to pre-create
* expressions and not have to re-parse them each time they are evaluated.
*
* @since JSP 2.1
*/
public abstract class Expression
implements Serializable {
// Debugging
/**
* Returns the original String used to create this Expression,
* unmodified.
*
* This is used for debugging purposes but also for the purposes
* of comparison (e.g. to ensure the expression in a configuration
* file has not changed).
*
* This method does not provide sufficient information to
* re-create an expression. Two different expressions can have exactly
* the same expression string but different function mappings.
* Serialization should be used to save and restore the state of an
* Expression.
*
* @return The original expression String.
*/
public abstract String getExpressionString();
// Comparison
/**
* Determines whether the specified object is equal to this
* Expression.
*
* The result is true if and only if the argument is
* not null, is an Expression object that
* is the of the same type (ValueExpression or
* MethodExpression), and has an identical parsed
* representation.
*
* Note that two expressions can be equal if their expression
* Strings are different. For example, ${fn1:foo()}
* and ${fn2:foo()} are equal if their corresponding
* FunctionMappers mapped fn1:foo and
* fn2:foo to the same method.
*
* @param obj the Object to test for equality.
* @return true if obj equals this
* Expression; false otherwise.
* @see java.util.Hashtable
* @see java.lang.Object#equals(java.lang.Object)
*/
public abstract boolean equals(Object obj);
/**
* Returns the hash code for this Expression.
*
* See the note in the {@link #equals} method on how two expressions
* can be equal if their expression Strings are different. Recall that
* if two objects are equal according to the equals(Object)
* method, then calling the hashCode method on each of the
* two objects must produce the same integer result. Implementations must
* take special note and implement hashCode correctly.
*
* @return The hash code for this Expression.
* @see #equals
* @see java.util.Hashtable
* @see java.lang.Object#hashCode()
*/
public abstract int hashCode();
/**
* Returns whether this expression was created from only literal text.
*
* This method must return true if and only if the
* expression string this expression was created from contained no
* unescaped EL delimeters (${...} or
* #{...}).
*
* @return true if this expression was created from only
* literal text; false otherwise.
*/
public abstract boolean isLiteralText();
public static final class Result {
private final Type type;
private final Object result;
private final List resolvedProperties;
public enum Type {
UNRESOLVABLE,
VALUE
}
public Result(Type type, Object result, List resolvedProperties) {
this.type = type;
this.result = result;
this.resolvedProperties = resolvedProperties;
if (type == null || resolvedProperties == null) {
throw new NullPointerException(
"Type, result and resolvedProperties must be non-null");
}
}
public Type getType() {
return type;
}
public Object getResult() {
return result;
}
public List getResolvedProperties() {
// PENDING: Return a copy?
return resolvedProperties;
}
}
public static final class ResolvedProperty {
private final Object source;
private final Object property;
public ResolvedProperty(Object source, Object property) {
this.source = source;
this.property = property;
if (source == null || property == null) {
throw new IllegalArgumentException(
"Source and property must be non-null");
}
}
public Object getSource() {
return source;
}
public Object getProperty() {
return property;
}
public boolean equals(Object o) {
if (o == this) {
return true;
}
if (o instanceof ResolvedProperty) {
ResolvedProperty orp = (ResolvedProperty)o;
return (orp.source == source &&
((orp.property == null && property == null) ||
(orp.property != null && orp.property.equals(property))));
}
return false;
}
public int hashCode() {
int hash = 17;
hash = 37 * hash + source.hashCode();
hash = 37 * hash + property.hashCode();
return hash;
}
}
}