1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the
7 * "License"); you may not use this file except in compliance
8 * with the License. You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing,
13 * software distributed under the License is distributed on an
14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15 * KIND, either express or implied. See the License for the
16 * specific language governing permissions and limitations
17 * under the License.
18 *
19 */
20 package org.apache.mina.filter.codec.prefixedstring;
21
22 import org.apache.mina.core.buffer.IoBuffer;
23 import org.apache.mina.core.session.IoSession;
24 import org.apache.mina.filter.codec.ProtocolEncoderAdapter;
25 import org.apache.mina.filter.codec.ProtocolEncoderOutput;
26 import org.apache.mina.filter.codec.ProtocolEncoder;
27
28 import java.nio.charset.Charset;
29
30 /**
31 * A {@link ProtocolEncoder} which encodes a string
32 * using a fixed-length length prefix.
33 *
34 * @author <a href="http://mina.apache.org">Apache MINA Project</a>
35 */
36 public class PrefixedStringEncoder extends ProtocolEncoderAdapter {
37 /** The default length for the prefix */
38 public static final int DEFAULT_PREFIX_LENGTH = 4;
39
40 /** The default maximum data length */
41 public static final int DEFAULT_MAX_DATA_LENGTH = 2048;
42
43 private final Charset charset;
44
45 private int prefixLength = DEFAULT_PREFIX_LENGTH;
46
47 private int maxDataLength = DEFAULT_MAX_DATA_LENGTH;
48
49 /**
50 * Creates a new PrefixedStringEncoder instance
51 *
52 * @param charset the {@link Charset} to use for encoding
53 * @param prefixLength the length of the prefix
54 * @param maxDataLength maximum number of bytes allowed for a single String
55 */
56 public PrefixedStringEncoder(Charset charset, int prefixLength, int maxDataLength) {
57 this.charset = charset;
58 this.prefixLength = prefixLength;
59 this.maxDataLength = maxDataLength;
60 }
61
62 /**
63 * Creates a new PrefixedStringEncoder instance
64 *
65 * @param charset the {@link Charset} to use for encoding
66 * @param prefixLength the length of the prefix
67 */
68 public PrefixedStringEncoder(Charset charset, int prefixLength) {
69 this(charset, prefixLength, DEFAULT_MAX_DATA_LENGTH);
70 }
71
72 /**
73 * Creates a new PrefixedStringEncoder instance
74 *
75 * @param charset the {@link Charset} to use for encoding
76 */
77 public PrefixedStringEncoder(Charset charset) {
78 this(charset, DEFAULT_PREFIX_LENGTH);
79 }
80
81 /**
82 * Creates a new PrefixedStringEncoder instance
83 */
84 public PrefixedStringEncoder() {
85 this(Charset.defaultCharset());
86 }
87
88 /**
89 * Sets the number of bytes used by the length prefix
90 *
91 * @param prefixLength the length of the length prefix (1, 2, or 4)
92 */
93 public void setPrefixLength(int prefixLength) {
94 if (prefixLength != 1 && prefixLength != 2 && prefixLength != 4) {
95 throw new IllegalArgumentException("prefixLength: " + prefixLength);
96 }
97 this.prefixLength = prefixLength;
98 }
99
100 /**
101 * Gets the length of the length prefix (1, 2, or 4)
102 *
103 * @return length of the length prefix
104 */
105 public int getPrefixLength() {
106 return prefixLength;
107 }
108
109 /**
110 * Sets the maximum number of bytes allowed for encoding a single String
111 * (including the prefix)
112 * <p>
113 * The encoder will throw a {@link IllegalArgumentException} when more bytes
114 * are needed to encode a String value.
115 * The default value is {@link PrefixedStringEncoder#DEFAULT_MAX_DATA_LENGTH}.
116 * </p>
117 *
118 * @param maxDataLength maximum number of bytes allowed for encoding a single String
119 */
120 public void setMaxDataLength(int maxDataLength) {
121 this.maxDataLength = maxDataLength;
122 }
123
124 /**
125 * Gets the maximum number of bytes allowed for encoding a single String *
126 *
127 * @return maximum number of bytes allowed for encoding a single String (prefix included)
128 */
129 public int getMaxDataLength() {
130 return maxDataLength;
131 }
132
133 /**
134 * {@inheritDoc}
135 */
136 @Override
137 public void encode(IoSession session, Object message, ProtocolEncoderOutput out) throws Exception {
138 String value = (String) message;
139 IoBuffer buffer = IoBuffer.allocate(value.length()).setAutoExpand(true);
140 buffer.putPrefixedString(value, prefixLength, charset.newEncoder());
141 if (buffer.position() > maxDataLength) {
142 throw new IllegalArgumentException("Data length: " + buffer.position());
143 }
144 buffer.flip();
145 out.write(buffer);
146 }
147 }