/*
* Copyright 2002-2014 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 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;
/**
* 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 pos) {
super(pos);
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, 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));
}
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(Object newValue) {
this.evaluationContext.setVariable(this.name, newValue);
}
@Override
public boolean isWritable() {
return true;
}
}
@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(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);
}
}