/*
 * 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 org.springframework.asm.MethodVisitor;
import org.springframework.expression.TypedValue;
import org.springframework.expression.spel.CodeFlow;

/**
 * Expression language AST node that represents null.
 *
 * @author Andy Clement
 * @since 3.0
 */
public class NullLiteral extends Literal {

	public NullLiteral(int pos) {
		super(null,pos);
		this.exitTypeDescriptor = "Ljava/lang/Object";
	}


	@Override
	public TypedValue getLiteralValue() {
		return TypedValue.NULL;
	}

	@Override
	public String toString() {
		return "null";
	}

	@Override
	public boolean isCompilable() {
		return true;
	}
	
	@Override
	public void generateCode(MethodVisitor mv, CodeFlow codeflow) {
		mv.visitInsn(ACONST_NULL);
		codeflow.pushDescriptor(getExitDescriptor());
	}

}
