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Spring Expression Language (SpEL)
/*
* Copyright 2002-2017 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.Label;
import org.springframework.asm.MethodVisitor;
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;
/**
* Represents a ternary expression, for example: "someCheck()?true:false".
*
* @author Andy Clement
* @author Juergen Hoeller
* @since 3.0
*/
public class Ternary extends SpelNodeImpl {
public Ternary(int pos, SpelNodeImpl... args) {
super(pos, args);
}
/**
* Evaluate the condition and if true evaluate the first alternative, otherwise
* evaluate the second alternative.
* @param state the expression state
* @throws EvaluationException if the condition does not evaluate correctly to
* a boolean or there is a problem executing the chosen alternative
*/
@Override
public TypedValue getValueInternal(ExpressionState state) throws EvaluationException {
Boolean value = this.children[0].getValue(state, Boolean.class);
if (value == null) {
throw new SpelEvaluationException(getChild(0).getStartPosition(),
SpelMessage.TYPE_CONVERSION_ERROR, "null", "boolean");
}
TypedValue result = this.children[value ? 1 : 2].getValueInternal(state);
computeExitTypeDescriptor();
return result;
}
@Override
public String toStringAST() {
return getChild(0).toStringAST() + " ? " + getChild(1).toStringAST() + " : " + getChild(2).toStringAST();
}
private void computeExitTypeDescriptor() {
if (this.exitTypeDescriptor == null && this.children[1].exitTypeDescriptor != null &&
this.children[2].exitTypeDescriptor != null) {
String leftDescriptor = this.children[1].exitTypeDescriptor;
String rightDescriptor = this.children[2].exitTypeDescriptor;
if (leftDescriptor.equals(rightDescriptor)) {
this.exitTypeDescriptor = leftDescriptor;
}
else {
// Use the easiest to compute common super type
this.exitTypeDescriptor = "Ljava/lang/Object";
}
}
}
@Override
public boolean isCompilable() {
SpelNodeImpl condition = this.children[0];
SpelNodeImpl left = this.children[1];
SpelNodeImpl right = this.children[2];
return (condition.isCompilable() && left.isCompilable() && right.isCompilable() &&
CodeFlow.isBooleanCompatible(condition.exitTypeDescriptor) &&
left.exitTypeDescriptor != null && right.exitTypeDescriptor != null);
}
@Override
public void generateCode(MethodVisitor mv, CodeFlow cf) {
// May reach here without it computed if all elements are literals
computeExitTypeDescriptor();
cf.enterCompilationScope();
this.children[0].generateCode(mv, cf);
if (!CodeFlow.isPrimitive(cf.lastDescriptor())) {
CodeFlow.insertUnboxInsns(mv, 'Z', cf.lastDescriptor());
}
cf.exitCompilationScope();
Label elseTarget = new Label();
Label endOfIf = new Label();
mv.visitJumpInsn(IFEQ, elseTarget);
cf.enterCompilationScope();
this.children[1].generateCode(mv, cf);
if (!CodeFlow.isPrimitive(this.exitTypeDescriptor)) {
CodeFlow.insertBoxIfNecessary(mv, cf.lastDescriptor().charAt(0));
}
cf.exitCompilationScope();
mv.visitJumpInsn(GOTO, endOfIf);
mv.visitLabel(elseTarget);
cf.enterCompilationScope();
this.children[2].generateCode(mv, cf);
if (!CodeFlow.isPrimitive(this.exitTypeDescriptor)) {
CodeFlow.insertBoxIfNecessary(mv, cf.lastDescriptor().charAt(0));
}
cf.exitCompilationScope();
mv.visitLabel(endOfIf);
cf.pushDescriptor(this.exitTypeDescriptor);
}
}