/*
* Copyright 2002-2016 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.expression.spel.ast;
import org.springframework.asm.MethodVisitor;
import org.springframework.asm.Type;
import org.springframework.expression.EvaluationException;
import org.springframework.expression.TypedValue;
import org.springframework.expression.spel.CodeFlow;
import org.springframework.expression.spel.ExpressionState;
import org.springframework.expression.spel.SpelEvaluationException;
import org.springframework.expression.spel.SpelMessage;
import org.springframework.expression.spel.support.BooleanTypedValue;
/**
* The operator 'instanceof' checks if an object is of the class specified in the right
* hand operand, in the same way that {@code instanceof} does in Java.
*
* @author Andy Clement
* @since 3.0
*/
public class OperatorInstanceof extends Operator {
private Class<?> type;
public OperatorInstanceof(int pos, SpelNodeImpl... operands) {
super("instanceof", pos, operands);
}
/**
* Compare the left operand to see it is an instance of the type specified as the
* right operand. The right operand must be a class.
* @param state the expression state
* @return true if the left operand is an instanceof of the right operand, otherwise
* false
* @throws EvaluationException if there is a problem evaluating the expression
*/
@Override
public BooleanTypedValue getValueInternal(ExpressionState state) throws EvaluationException {
SpelNodeImpl rightOperand = getRightOperand();
TypedValue left = getLeftOperand().getValueInternal(state);
TypedValue right = rightOperand.getValueInternal(state);
Object leftValue = left.getValue();
Object rightValue = right.getValue();
BooleanTypedValue result = null;
if (rightValue == null || !(rightValue instanceof Class)) {
throw new SpelEvaluationException(getRightOperand().getStartPosition(),
SpelMessage.INSTANCEOF_OPERATOR_NEEDS_CLASS_OPERAND,
(rightValue == null ? "null" : rightValue.getClass().getName()));
}
Class<?> rightClass = (Class<?>) rightValue;
if (leftValue == null) {
result = BooleanTypedValue.FALSE; // null is not an instanceof anything
}
else {
result = BooleanTypedValue.forValue(rightClass.isAssignableFrom(leftValue.getClass()));
}
this.type = rightClass;
if (rightOperand instanceof TypeReference) {
// Can only generate bytecode where the right operand is a direct type reference,
// not if it is indirect (for example when right operand is a variable reference)
this.exitTypeDescriptor = "Z";
}
return result;
}
@Override
public boolean isCompilable() {
return (this.exitTypeDescriptor != null && getLeftOperand().isCompilable());
}
@Override
public void generateCode(MethodVisitor mv, CodeFlow cf) {
getLeftOperand().generateCode(mv, cf);
CodeFlow.insertBoxIfNecessary(mv, cf.lastDescriptor());
if (this.type.isPrimitive()) {
// always false - but left operand code always driven
// in case it had side effects
mv.visitInsn(POP);
mv.visitInsn(ICONST_0); // value of false
}
else {
mv.visitTypeInsn(INSTANCEOF,Type.getInternalName(this.type));
}
cf.pushDescriptor(this.exitTypeDescriptor);
}
}