1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache license, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the license for the specific language governing permissions and
15 * limitations under the license.
16 */
17
18 package org.apache.commons.text.lookup;
19
20 import java.io.BufferedInputStream;
21 import java.io.InputStreamReader;
22 import java.io.StringWriter;
23 import java.net.URL;
24
25 import org.apache.commons.lang3.StringUtils;
26
27 /**
28 * Looks up keys from an XML document.
29 * <p>
30 * Looks up the value for a given key in the format "Charset:URL".
31 * </p>
32 * <p>
33 * For example: "UTF-8:https://www.apache.org".
34 * </p>
35 *
36 * @since 1.5
37 */
38 final class UrlStringLookup extends AbstractStringLookup {
39
40 /**
41 * Defines the singleton for this class.
42 */
43 static final UrlStringLookup INSTANCE = new UrlStringLookup();
44
45 /**
46 * No need to build instances for now.
47 */
48 private UrlStringLookup() {
49 // empty
50 }
51
52 /**
53 * Looks up the value for the key in the format "DocumentPath:URL".
54 * <p>
55 * For example: "UTF-8:https://www.apache.org".
56 * </p>
57 *
58 * @param key the key to be looked up, may be null
59 * @return The value associated with the key.
60 */
61 @Override
62 public String lookup(final String key) {
63 if (key == null) {
64 return null;
65 }
66 final String[] keys = key.split(SPLIT_STR);
67 final int keyLen = keys.length;
68 if (keyLen < 2) {
69 throw IllegalArgumentExceptions.format("Bad URL key format [%s]; expected format is DocumentPath:Key.",
70 key);
71 }
72 final String charsetName = keys[0];
73 final String urlStr = StringUtils.substringAfter(key, SPLIT_CH);
74 try {
75 final URL url = new URL(urlStr);
76 final int size = 8192;
77 final StringWriter writer = new StringWriter(size);
78 final char[] buffer = new char[size];
79 try (BufferedInputStream bis = new BufferedInputStream(url.openStream());
80 InputStreamReader reader = new InputStreamReader(bis, charsetName)) {
81 int n;
82 while (-1 != (n = reader.read(buffer))) {
83 writer.write(buffer, 0, n);
84 }
85 }
86 return writer.toString();
87 } catch (final Exception e) {
88 throw IllegalArgumentExceptions.format(e, "Error looking up URL [%s] with Charset [%s].", urlStr,
89 charsetName);
90 }
91 }
92
93 }