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1 package com.thaiopensource.util;
2
3 import java.util.Enumeration  ;
4 import java.util.NoSuchElementException ;
5 import java.util.Vector ;
6 import java.io.Reader ;
7 import java.io.InputStream ;
8 import java.io.InputStreamReader ;
9 import java.io.BufferedReader ;
10 import java.io.IOException ;
11 import java.io.UnsupportedEncodingException ;
12 import java.net.URL ;
13
14 public class Service {
15 private final Class serviceClass;
16 private final Enumeration configFiles;
17 private Enumeration classNames = null;
18 private final Vector providers = new Vector ();
19 private Loader loader;
20
21 private class ProviderEnumeration implements Enumeration {
22 private int nextIndex = 0;
23
24 public boolean hasMoreElements() {
25 return nextIndex < providers.size() || moreProviders();
26 }
27
28 public Object nextElement() {
29 try {
30 return providers.elementAt(nextIndex++);
31 }
32 catch (ArrayIndexOutOfBoundsException e) {
33 throw new NoSuchElementException ();
34 }
35 }
36 }
37
38 private static class Singleton implements Enumeration {
39 private Object obj;
40 private Singleton(Object obj) {
41 this.obj = obj;
42 }
43
44 public boolean hasMoreElements() {
45 return obj != null;
46 }
47
48 public Object nextElement() {
49 if (obj == null)
50 throw new NoSuchElementException ();
51 Object tem = obj;
52 obj = null;
53 return tem;
54 }
55 }
56
57 private static class Loader {
59 Enumeration getResources(String resName) {
60 ClassLoader cl = Loader.class.getClassLoader();
61 URL url;
62 if (cl == null)
63 url = ClassLoader.getSystemResource(resName);
64 else
65 url = cl.getResource(resName);
66 return new Singleton(url);
67 }
68
69 Class loadClass(String name) throws ClassNotFoundException {
70 return Class.forName(name);
71 }
72 }
73
74 private static class Loader2 extends Loader {
76 private ClassLoader cl;
77
78 Loader2() {
79 cl = Loader2.class.getClassLoader();
80 ClassLoader clt = Thread.currentThread().getContextClassLoader();
85 for (ClassLoader tem = clt; tem != null; tem = tem.getParent())
86 if (tem == cl) {
87 cl = clt;
88 break;
89 }
90 }
91
92 Enumeration getResources(String resName) {
93 try {
94 Enumeration resources = cl.getResources(resName);
95 if (resources.hasMoreElements())
96 return resources;
97 return new Singleton(cl.getResource(resName));
100 }
101 catch (IOException e) {
102 return new Singleton(null);
103 }
104 }
105
106 Class loadClass(String name) throws ClassNotFoundException {
107 return Class.forName(name, true, cl);
108 }
109 }
110
111 public Service(Class cls) {
112 try {
113 loader = new Loader2();
114 }
115 catch (NoSuchMethodError e) {
116 loader = new Loader();
117 }
118 serviceClass = cls;
119 String resName = "META-INF/services/" + serviceClass.getName();
120 configFiles = loader.getResources(resName);
121 }
122
123 public Enumeration getProviders() {
124 return new ProviderEnumeration();
125 }
126
127 synchronized private boolean moreProviders() {
128 for (;;) {
129 while (classNames == null) {
130 if (!configFiles.hasMoreElements())
131 return false;
132 classNames = parseConfigFile((URL )configFiles.nextElement());
133 }
134 while (classNames.hasMoreElements()) {
135 String className = (String )classNames.nextElement();
136 try {
137 Class cls = loader.loadClass(className);
138 Object obj = cls.newInstance();
139 if (serviceClass.isInstance(obj)) {
140 providers.addElement(obj);
141 return true;
142 }
143 }
144 catch (ClassNotFoundException e) { }
145 catch (InstantiationException e) { }
146 catch (IllegalAccessException e) { }
147 catch (LinkageError e) { }
148 }
149 classNames = null;
150 }
151 }
152
153 private static final int START = 0;
154 private static final int IN_NAME = 1;
155 private static final int IN_COMMENT = 2;
156
157 private static Enumeration parseConfigFile(URL url) {
158 try {
159 InputStream in = url.openStream();
160 Reader r;
161 try {
162 r = new InputStreamReader (in, "UTF-8");
163 }
164 catch (UnsupportedEncodingException e) {
165 r = new InputStreamReader (in, "UTF8");
166 }
167 r = new BufferedReader (r);
168 Vector tokens = new Vector ();
169 StringBuffer tokenBuf = new StringBuffer ();
170 int state = START;
171 for (;;) {
172 int n = r.read();
173 if (n < 0)
174 break;
175 char c = (char)n;
176 switch (c) {
177 case '\r':
178 case '\n':
179 state = START;
180 break;
181 case ' ':
182 case '\t':
183 break;
184 case '#':
185 state = IN_COMMENT;
186 break;
187 default:
188 if (state != IN_COMMENT) {
189 state = IN_NAME;
190 tokenBuf.append(c);
191 }
192 break;
193 }
194 if (tokenBuf.length() != 0 && state != IN_NAME) {
195 tokens.addElement(tokenBuf.toString());
196 tokenBuf.setLength(0);
197 }
198 }
199 if (tokenBuf.length() != 0)
200 tokens.addElement(tokenBuf.toString());
201 return tokens.elements();
202 }
203 catch (IOException e) {
204 return null;
205 }
206 }
207
208 public static void main(String [] args) throws ClassNotFoundException {
209 Service svc = new Service(Class.forName(args[0]));
210 for (Enumeration e = svc.getProviders(); e.hasMoreElements();)
211 System.out.println(e.nextElement().getClass().getName());
212 }
213 }
214 |
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