/*
* FreeMarker: a tool that allows Java programs to generate HTML
* output using templates.
* Copyright (C) 1998-2004 Benjamin Geer
* Email: beroul@users.sourceforge.net
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*/
package freemarker.template.expression;
import java.io.IOException;
import java.io.InvalidObjectException;
import java.io.ObjectInputStream;
import java.io.ObjectStreamException;
import java.io.Serializable;
import freemarker.template.TemplateException;
import freemarker.template.TemplateHashModel;
import freemarker.template.TemplateModel;
import freemarker.template.TemplateModelException;
import freemarker.template.TemplateWriteableHashModel;
/**
* The dot operator. Used to reference items inside a
* {@link freemarker.template.TemplateHashModel}. It associates with other
* {@link Variable} expressions to its left.
*
* @version $Id: Dot.java 1123 2005-10-04 10:48:25Z run2000 $
*/
public final class Dot implements Unary, Variable, Serializable {
/**
* @serial The identifier following the dot
*/
private final Identifier identifier;
/**
* @serial The variable preceding the dot
*/
private Variable target;
/** Serialization UUID for this class. */
private static final long serialVersionUID = -5994615948590817642L;
/**
* Create a new <code>Dot</code> instruction.
*
* @param id
* the identifier to the right of the dot.
* @throws NullPointerException
* the identifier is null
*/
public Dot(Identifier id) {
if (id == null) {
throw new NullPointerException("Identifier for Dot operator cannot be null");
}
identifier = id;
}
/**
* Retrieve the name of this portion of the variable.
*
* @param modelRoot
* the model to be used in cases where the variable is the result
* of an {@link freemarker.template.expression.Expression}.
*/
public String getName(TemplateWriteableHashModel modelRoot) {
return identifier.getName();
}
/**
* Are both the target and the identifier specified?
*
* @return <code>true</code> if the target and identifier are both
* specified, otherwise <code>false</code>
*/
public boolean isComplete() {
return (target != null);
}
/**
* Determine the type of result that can be calculated by this expression.
* This is in the form of an integer constant ored together from values in
* the {@link ExpressionUtils} class.
*/
public int getType() {
return ExpressionUtils.EXPRESSION_TYPE_VARIABLE;
}
/**
* Determine whether result calculated by this expression is a constant
* value.
*/
public boolean isConstant() {
return false;
}
/**
* The {@link freemarker.template.TemplateModel} value of this
* <code>Expression</code>.
*
* @param modelRoot
* the template model that will be evaluated by the expression
* @throws TemplateException
* the expression could not be evaluated for some reason
*/
public TemplateModel getAsTemplateModel(TemplateWriteableHashModel modelRoot) throws TemplateException {
TemplateModel leftModel = target.getAsTemplateModel(modelRoot);
if ((leftModel == null) || (leftModel.isEmpty())) {
return null;
}
TemplateModel referent;
if (leftModel instanceof TemplateHashModel) {
TemplateHashModel leftHash = (TemplateHashModel) leftModel;
try {
referent = leftHash.get(identifier.getName());
} catch (TemplateModelException e) {
throw new TemplateException("Couldn't get referent of " + identifier.getName(), e);
}
} else {
throw new TemplateException(target.getName(modelRoot) + " is not a TemplateHashModel, it's a " + leftModel.getClass().getName());
}
return referent;
}
/**
* Implements a write of the given value to a writeable hash model.
*
* @param modelRoot
* the root model, for determining context
* @param value
* the value to be assigned
* @throws TemplateException
* there was a problem performing the assignment
*/
public void setTemplateModel(TemplateWriteableHashModel modelRoot, TemplateModel value) throws TemplateException {
TemplateModel leftModel = target.getAsTemplateModel(modelRoot);
if (leftModel == null) {
throw new TemplateException(target.getName(modelRoot) + " is a null model");
}
if (leftModel instanceof TemplateWriteableHashModel) {
TemplateWriteableHashModel leftHash = (TemplateWriteableHashModel) leftModel;
try {
leftHash.put(identifier.getName(), value);
} catch (TemplateModelException e) {
throw new TemplateException("Couldn't get referent of " + identifier.getName(), e);
}
} else {
throw new TemplateException(target.getName(modelRoot) + " is not a TemplateHashModel, it's a " + leftModel.getClass().getName());
}
}
/**
* Retrieve the operator association for this operator.
*
* @return <code>POSTFIX</code>.
*/
public int getAssociationType() {
return POSTFIX;
}
/**
* Sets the target of this <code>Dot</code> operator.
*
* @throws IllegalArgumentException
* the target is of the wrong type for this operator.
*/
public void setTarget(Expression target) {
if (!(target instanceof Variable) || !(target.isComplete())) {
throw new IllegalArgumentException("Syntax error in expression");
}
this.target = (Variable) target;
}
/**
* Return the precedence for this operator to the caller. Used for
* associating operators according to precedence.
*
* @return an integer indicating the precedence of this operator
*/
public int getPrecedence() {
return ExpressionBuilder.PRECEDENCE_VARIABLE;
}
/**
* For serialization purposes, resolve a deserialized instance to an
* instance in the expression cache.
*/
private Object readResolve() throws ObjectStreamException {
if (isComplete()) {
return ExpressionCache.cacheExpression(this);
}
return this;
}
/**
* For serialization, read this object normally, then check whether the
* identifier has been deserialized to null.
*
* @param stream
* the input stream to read serialized objects from
*/
private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException {
stream.defaultReadObject();
if (identifier == null) {
throw new InvalidObjectException("Cannot create an Dot with a null identifier");
}
}
/**
* Returns a string representation of the object.
*
* @return a <code>String</code> representation of this expression
*/
public String toString() {
StringBuffer buffer = new StringBuffer();
if (target == null) {
buffer.append("???");
} else {
buffer.append(target);
}
buffer.append('.');
buffer.append(identifier);
return buffer.toString();
}
/**
* Determines whether this object is equal to the given object.
*
* @param o
* the object to be compared with
* @return <code>true</code> if the objects are equal, otherwise
* <code>false</code>
*/
public boolean equals(Object o) {
if (this == o) {
return true;
}
if (!(o instanceof Dot)) {
return false;
}
final Dot dot = (Dot) o;
if (!identifier.equals(dot.identifier)) {
return false;
}
if (target == null) {
return dot.target == null;
}
return target.equals(dot.target);
}
/**
* Returns the hash code for this operator.
*
* @return the hash code of this object
*/
public int hashCode() {
int result;
result = identifier.hashCode();
result = 29 * result + (target != null ? target.hashCode() : 0);
return result;
}
/**
* Resolves the current expression, possibly into a different expression
* object. This is loosely equivalent to the serialization protocol's
* <code>readResolve</code> method. Situations where this may be used are:
* <ul>
* <li>Caching frequently-used expression objects</li>
* <li>Evaluating constant expressions, and returning a constant reference</li>
* </ul>
*/
public Expression resolveExpression() {
return ExpressionCache.cacheExpression(this);
}
}