/*
* Copyright 2004-2012 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.binding.expression.el;
import javax.el.ELContext;
import javax.el.ELException;
import javax.el.ValueExpression;
import org.springframework.binding.expression.EvaluationException;
import org.springframework.binding.expression.Expression;
import org.springframework.binding.expression.PropertyNotFoundException;
import org.springframework.util.Assert;
/**
* Evaluates a parsed EL expression.
*
* @author Jeremy Grelle
* @author Scott Andrews
*/
public class ELExpression implements Expression {
private ELContextFactory elContextFactory;
private ValueExpression valueExpression;
/**
* Creates a new el expression
* @param factory the el context factory for creating the EL context that will be used during expression evaluation
* @param valueExpression the value expression to evaluate
*/
public ELExpression(ELContextFactory factory, ValueExpression valueExpression) {
Assert.notNull(factory, "The ELContextFactory is required to evaluate EL expressions");
Assert.notNull(valueExpression, "The EL ValueExpression is required for evaluation");
this.elContextFactory = factory;
this.valueExpression = valueExpression;
}
public Object getValue(Object context) throws EvaluationException {
ELContext ctx = elContextFactory.getELContext(context);
try {
Object result = valueExpression.getValue(ctx);
if (result == null && !ctx.isPropertyResolved()) {
if (getExpressionString().equals("null")) {
// special case for handling reserved null keyword
return null;
} else {
throw new EvaluationException(context.getClass(), getExpressionString(), "The expression '"
+ getExpressionString() + "' did not resolve... is the base variable '" + getBaseVariable()
+ "' spelled correctly?");
}
}
return result;
} catch (javax.el.PropertyNotFoundException e) {
throw new PropertyNotFoundException(context.getClass(), getExpressionString(), e);
} catch (ELException e) {
throw new EvaluationException(context.getClass(), getExpressionString(),
"An ELException occurred getting the value for expression '" + getExpressionString()
+ "' on context [" + context.getClass() + "]", e);
}
}
public void setValue(Object context, Object value) throws EvaluationException {
ELContext ctx = elContextFactory.getELContext(context);
try {
valueExpression.setValue(ctx, value);
if (!ctx.isPropertyResolved()) {
throw new EvaluationException(context.getClass(), getExpressionString(), "The expression '"
+ getExpressionString() + "' did not resolve... is the base variable ''" + getBaseVariable()
+ "' spelled correctly?");
}
} catch (javax.el.PropertyNotFoundException e) {
throw new PropertyNotFoundException(context.getClass(), getExpressionString(), e);
} catch (ELException e) {
throw new EvaluationException(context.getClass(), getExpressionString(),
"An ELException occurred setting the value of expression '" + getExpressionString()
+ "' on context [" + context.getClass() + "] to [" + value + "]", e);
}
}
public Class<?> getValueType(Object context) {
ELContext ctx = elContextFactory.getELContext(context);
try {
return valueExpression.getType(ctx);
} catch (javax.el.PropertyNotFoundException e) {
throw new PropertyNotFoundException(context.getClass(), getExpressionString(), e);
} catch (ELException e) {
throw new EvaluationException(context.getClass(), getExpressionString(),
"An ELException occurred getting the value type for expression '" + getExpressionString()
+ "' on context [" + context.getClass() + "]", e);
}
}
public String getExpressionString() {
return valueExpression.getExpressionString();
}
private String getBaseVariable() {
String expressionString = getExpressionString();
int firstDot = expressionString.indexOf('.');
if (firstDot == -1) {
return expressionString;
} else {
return expressionString.substring(0, firstDot);
}
}
public int hashCode() {
return valueExpression.hashCode();
}
public boolean equals(Object o) {
if (!(o instanceof ELExpression)) {
return false;
}
ELExpression other = (ELExpression) o;
return valueExpression.equals(other.valueExpression);
}
public String toString() {
return getExpressionString();
}
}