spring Ternary 源码

spring Ternary 代码

文件路径：/spring-expression/src/main/java/org/springframework/expression/spel/ast/Ternary.java

/*
 * 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
 * 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;
import org.springframework.util.Assert;
import org.springframework.util.ObjectUtils;

/**
 * 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.
	 * @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 supertype
				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);
	}

}

相关信息

spring 源码目录

相关文章

spring Assign 源码

spring AstUtils 源码

spring BeanReference 源码

spring BooleanLiteral 源码

spring CompoundExpression 源码

spring ConstructorReference 源码

spring Elvis 源码

spring FloatLiteral 源码

spring FormatHelper 源码

spring FunctionReference 源码