1 /*
2 * Copyright 2002-2014 the original author or authors.
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 package org.springframework.expression.spel.ast;
18
19 import org.springframework.asm.MethodVisitor;
20 import org.springframework.expression.TypedValue;
21 import org.springframework.expression.spel.CodeFlow;
22
23 /**
24 * Expression language AST node that represents null.
25 *
26 * @author Andy Clement
27 * @since 3.0
28 */
29 public class NullLiteral extends Literal {
30
31 public NullLiteral(int pos) {
32 super(null,pos);
33 this.exitTypeDescriptor = "Ljava/lang/Object";
34 }
35
36
37 @Override
38 public TypedValue getLiteralValue() {
39 return TypedValue.NULL;
40 }
41
42 @Override
43 public String toString() {
44 return "null";
45 }
46
47 @Override
48 public boolean isCompilable() {
49 return true;
50 }
51
52 @Override
53 public void generateCode(MethodVisitor mv, CodeFlow cf) {
54 mv.visitInsn(ACONST_NULL);
55 cf.pushDescriptor(this.exitTypeDescriptor);
56 }
57
58 }