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 * Copyright 2002-2018 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
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 *      http://www.apache.org/licenses/LICENSE-2.0
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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;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;

The operator 'instanceof' checks if an object is of the class specified in the right hand operand, in the same way that instanceof does in Java.
Author:Andy Clement
Since:3.0
/** * 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 { @Nullable 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.
Params:
  • state – the expression state
Throws:
Returns:true if the left operand is an instanceof of the right operand, otherwise false
/** * 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 {@code true} if the left operand is an instanceof of the right operand, * otherwise {@code 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; 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()); Assert.state(this.type != null, "No type available"); 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); } }