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 * 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
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 *      https://www.apache.org/licenses/LICENSE-2.0
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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;
import org.springframework.util.Assert;
import org.springframework.util.ObjectUtils;

Represents a ternary expression, for example: "someCheck()?true:false".
Author:Andy Clement, Juergen Hoeller
Since:3.0
/** * 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 startPos, int endPos, SpelNodeImpl... args) { super(startPos, endPos, args); }
Evaluate the condition and if true evaluate the first alternative, otherwise evaluate the second alternative.
Params:
  • 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
/** * 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 (ObjectUtils.nullSafeEquals(leftDescriptor, 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); String lastDesc = cf.lastDescriptor(); Assert.state(lastDesc != null, "No last descriptor"); if (!CodeFlow.isPrimitive(lastDesc)) { CodeFlow.insertUnboxInsns(mv, 'Z', lastDesc); } 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)) { lastDesc = cf.lastDescriptor(); Assert.state(lastDesc != null, "No last descriptor"); CodeFlow.insertBoxIfNecessary(mv, lastDesc.charAt(0)); } cf.exitCompilationScope(); mv.visitJumpInsn(GOTO, endOfIf); mv.visitLabel(elseTarget); cf.enterCompilationScope(); this.children[2].generateCode(mv, cf); if (!CodeFlow.isPrimitive(this.exitTypeDescriptor)) { lastDesc = cf.lastDescriptor(); Assert.state(lastDesc != null, "No last descriptor"); CodeFlow.insertBoxIfNecessary(mv, lastDesc.charAt(0)); } cf.exitCompilationScope(); mv.visitLabel(endOfIf); cf.pushDescriptor(this.exitTypeDescriptor); } }