1 /*
2 * #%L
3 * UnaryExpression.java - mongodb-async-driver - Allanbank Consulting, Inc.
4 * %%
5 * Copyright (C) 2011 - 2014 Allanbank Consulting, Inc.
6 * %%
7 * Licensed under the Apache License, Version 2.0 (the "License");
8 * you may not use this file except in compliance with the License.
9 * You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing, software
14 * distributed under the License is distributed on an "AS IS" BASIS,
15 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16 * See the License for the specific language governing permissions and
17 * limitations under the License.
18 * #L%
19 */
20 package com.allanbank.mongodb.builder.expression;
21
22 import java.io.StringWriter;
23
24 import com.allanbank.mongodb.bson.Element;
25 import com.allanbank.mongodb.bson.ElementAssignable;
26 import com.allanbank.mongodb.bson.element.DocumentElement;
27 import com.allanbank.mongodb.bson.element.JsonSerializationVisitor;
28
29 /**
30 * UnaryExpression provides an implementation of an {@link Expression} with 1
31 * operand.
32 *
33 * @api.no This class is <b>NOT</b> part of the drivers API. This class may be
34 * mutated in incompatible ways between any two releases of the driver.
35 * @copyright 2012-2013, Allanbank Consulting, Inc., All Rights Reserved
36 */
37 public class UnaryExpression implements Expression, ElementAssignable {
38
39 /** The sub expression. */
40 protected final Expression myExpression;
41
42 /** The operator. */
43 protected final String myOperator;
44
45 /**
46 * Creates a new NaryExpression.
47 *
48 * @param operator
49 * The operator this object represents.
50 * @param expression
51 * The sub expression.
52 */
53 public UnaryExpression(final String operator, final Expression expression) {
54 myOperator = operator;
55 myExpression = expression;
56 }
57
58 /**
59 * {@inheritDoc}
60 * <p>
61 * Overridden to return the sub expressions as an element:
62 * </p>
63 * <blockquote>
64 *
65 * <pre>
66 * <code>
67 * "$op" : expression
68 * </code>
69 * </pre>
70 *
71 * </blockquote>
72 */
73 @Override
74 public Element asElement() {
75 return myExpression.toElement(myOperator);
76 }
77
78 /**
79 * {@inheritDoc}
80 * <p>
81 * Overridden to return the sub expressions as a document with a nested
82 * array element:
83 * </p>
84 * <blockquote>
85 *
86 * <pre>
87 * <code>
88 * { <name> : { "$op" : expression } }
89 * </code>
90 * </pre>
91 *
92 * </blockquote>
93 */
94 @Override
95 public DocumentElement toElement(final String name) {
96 return new DocumentElement(name, myExpression.toElement(myOperator));
97 }
98
99 /**
100 * {@inheritDoc}
101 * <p>
102 * Overridden to return the expression in JSON format.
103 * </p>
104 * <blockquote>
105 *
106 * <pre>
107 * <code>
108 * "$op" : expression
109 * </code>
110 * </pre>
111 *
112 * </blockquote>
113 */
114 @Override
115 public String toString() {
116 final StringWriter sink = new StringWriter();
117 final JsonSerializationVisitor json = new JsonSerializationVisitor(
118 sink, true);
119
120 asElement().accept(json);
121
122 return sink.toString();
123 }
124 }