01: /*
02: * Copyright (c) 1998-2008 Caucho Technology -- all rights reserved
03: *
04: * This file is part of Resin(R) Open Source
05: *
06: * Each copy or derived work must preserve the copyright notice and this
07: * notice unmodified.
08: *
09: * Resin Open Source is free software; you can redistribute it and/or modify
10: * it under the terms of the GNU General Public License as published by
11: * the Free Software Foundation; either version 2 of the License, or
12: * (at your option) any later version.
13: *
14: * Resin Open Source is distributed in the hope that it will be useful,
15: * but WITHOUT ANY WARRANTY; without even the implied warranty of
16: * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE, or any warranty
17: * of NON-INFRINGEMENT. See the GNU General Public License for more
18: * details.
19: *
20: * You should have received a copy of the GNU General Public License
21: * along with Resin Open Source; if not, write to the
22: *
23: * Free Software Foundation, Inc.
24: * 59 Temple Place, Suite 330
25: * Boston, MA 02111-1307 USA
26: *
27: * @author Scott Ferguson
28: */
29:
30: package com.caucho.el;
31:
32: import com.caucho.vfs.WriteStream;
33:
34: import javax.el.ELContext;
35: import javax.el.ELException;
36: import java.io.IOException;
37:
38: /**
39: * Represents a null literal expression.
40: */
41: public class NullLiteral extends Expr {
42: /**
43: * Create the literal.
44: */
45: public NullLiteral() {
46: }
47:
48: /**
49: * Returns true if the expression is constant.
50: */
51: @Override
52: public boolean isConstant() {
53: return true;
54: }
55:
56: /**
57: * Evaluate the expression as an object.
58: *
59: * @param env the variable environment
60: *
61: * @return null
62: */
63: @Override
64: public Object getValue(ELContext env) throws ELException {
65: return null;
66: }
67:
68: /**
69: * Evalutes directly to the output.
70: */
71: @Override
72: public boolean print(WriteStream out, ELContext env,
73: boolean isEscaped) throws IOException, ELException {
74: return false;
75: }
76:
77: /**
78: * Prints the code to create an LongLiteral.
79: */
80: @Override
81: public void printCreate(WriteStream os) throws IOException {
82: os.print("new com.caucho.el.NullLiteral()");
83: }
84:
85: /**
86: * Returns true for equal strings.
87: */
88: public boolean equals(Object o) {
89: return (o instanceof NullLiteral);
90: }
91:
92: /**
93: * Returns a printable view.
94: */
95: public String toString() {
96: return "null";
97: }
98: }
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