/*
 * Copyright 2002-2019 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
 *
 *      https://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
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package org.springframework.expression.spel.ast;

import java.lang.reflect.Modifier;

import org.springframework.asm.MethodVisitor;
import org.springframework.expression.EvaluationContext;
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.lang.Nullable;

Represents a variable reference, eg. #someVar. Note this is different to a *local* variable like $someVar
Author:Andy Clement
Since:3.0
/** * Represents a variable reference, eg. #someVar. Note this is different to a *local* * variable like $someVar * * @author Andy Clement * @since 3.0 */
public class VariableReference extends SpelNodeImpl { // Well known variables: private static final String THIS = "this"; // currently active context object private static final String ROOT = "root"; // root context object private final String name; public VariableReference(String variableName, int startPos, int endPos) { super(startPos, endPos); this.name = variableName; } @Override public ValueRef getValueRef(ExpressionState state) throws SpelEvaluationException { if (this.name.equals(THIS)) { return new ValueRef.TypedValueHolderValueRef(state.getActiveContextObject(),this); } if (this.name.equals(ROOT)) { return new ValueRef.TypedValueHolderValueRef(state.getRootContextObject(),this); } TypedValue result = state.lookupVariable(this.name); // a null value will mean either the value was null or the variable was not found return new VariableRef(this.name,result,state.getEvaluationContext()); } @Override public TypedValue getValueInternal(ExpressionState state) throws SpelEvaluationException { if (this.name.equals(THIS)) { return state.getActiveContextObject(); } if (this.name.equals(ROOT)) { TypedValue result = state.getRootContextObject(); this.exitTypeDescriptor = CodeFlow.toDescriptorFromObject(result.getValue()); return result; } TypedValue result = state.lookupVariable(this.name); Object value = result.getValue(); if (value == null || !Modifier.isPublic(value.getClass().getModifiers())) { // If the type is not public then when generateCode produces a checkcast to it // then an IllegalAccessError will occur. // If resorting to Object isn't sufficient, the hierarchy could be traversed for // the first public type. this.exitTypeDescriptor = "Ljava/lang/Object"; } else { this.exitTypeDescriptor = CodeFlow.toDescriptorFromObject(value); } // a null value will mean either the value was null or the variable was not found return result; } @Override public void setValue(ExpressionState state, @Nullable Object value) throws SpelEvaluationException { state.setVariable(this.name, value); } @Override public String toStringAST() { return "#" + this.name; } @Override public boolean isWritable(ExpressionState expressionState) throws SpelEvaluationException { return !(this.name.equals(THIS) || this.name.equals(ROOT)); } @Override public boolean isCompilable() { return (this.exitTypeDescriptor != null); } @Override public void generateCode(MethodVisitor mv, CodeFlow cf) { if (this.name.equals(ROOT)) { mv.visitVarInsn(ALOAD,1); } else { mv.visitVarInsn(ALOAD, 2); mv.visitLdcInsn(this.name); mv.visitMethodInsn(INVOKEINTERFACE, "org/springframework/expression/EvaluationContext", "lookupVariable", "(Ljava/lang/String;)Ljava/lang/Object;",true); } CodeFlow.insertCheckCast(mv, this.exitTypeDescriptor); cf.pushDescriptor(this.exitTypeDescriptor); } private static class VariableRef implements ValueRef { private final String name; private final TypedValue value; private final EvaluationContext evaluationContext; public VariableRef(String name, TypedValue value, EvaluationContext evaluationContext) { this.name = name; this.value = value; this.evaluationContext = evaluationContext; } @Override public TypedValue getValue() { return this.value; } @Override public void setValue(@Nullable Object newValue) { this.evaluationContext.setVariable(this.name, newValue); } @Override public boolean isWritable() { return true; } } }