001/* 002 * Copyright 2002-2017 the original author or authors. 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); 005 * you may not use this file except in compliance with the License. 006 * You may obtain a copy of the License at 007 * 008 * https://www.apache.org/licenses/LICENSE-2.0 009 * 010 * Unless required by applicable law or agreed to in writing, software 011 * distributed under the License is distributed on an "AS IS" BASIS, 012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 013 * See the License for the specific language governing permissions and 014 * limitations under the License. 015 */ 016 017package org.springframework.expression.spel.ast; 018 019import org.springframework.asm.MethodVisitor; 020import org.springframework.expression.TypedValue; 021import org.springframework.expression.spel.CodeFlow; 022 023/** 024 * Expression language AST node that represents null. 025 * 026 * @author Andy Clement 027 * @since 3.0 028 */ 029public class NullLiteral extends Literal { 030 031 public NullLiteral(int pos) { 032 super(null, pos); 033 this.exitTypeDescriptor = "Ljava/lang/Object"; 034 } 035 036 037 @Override 038 public TypedValue getLiteralValue() { 039 return TypedValue.NULL; 040 } 041 042 @Override 043 public String toString() { 044 return "null"; 045 } 046 047 @Override 048 public boolean isCompilable() { 049 return true; 050 } 051 052 @Override 053 public void generateCode(MethodVisitor mv, CodeFlow cf) { 054 mv.visitInsn(ACONST_NULL); 055 cf.pushDescriptor(this.exitTypeDescriptor); 056 } 057 058}