42 * A DnsContextFactory serves as the initial context factory for DNS.
43 *
44 * <p> When an initial context is being created, the environment
45 * property "java.naming.provider.url" should contain a DNS pseudo-URL
46 * (see DnsUrl) or a space-separated list of them. Multiple URLs must
47 * all have the same domain value.
48 * If the property is not set, the default "dns:" is used.
49 *
50 * @author Scott Seligman
51 */
52
53
54 public class DnsContextFactory implements InitialContextFactory {
55
56 private static final String DEFAULT_URL = "dns:";
57 private static final int DEFAULT_PORT = 53;
58
59
60 public Context getInitialContext(Hashtable<?,?> env) throws NamingException {
61 if (env == null) {
62 env = new Hashtable(5);
63 }
64 return urlToContext(getInitCtxUrl(env), env);
65 }
66
67 public static DnsContext getContext(String domain,
68 String[] servers, Hashtable<?,?> env)
69 throws NamingException {
70 return new DnsContext(domain, servers, env);
71 }
72
73 /*
74 * "urls" are used to determine the servers, but any domain
75 * components are overridden by "domain".
76 */
77 public static DnsContext getContext(String domain,
78 DnsUrl[] urls, Hashtable env)
79 throws NamingException {
80
81 String[] servers = serversForUrls(urls);
82 DnsContext ctx = getContext(domain, servers, env);
83 if (platformServersUsed(urls)) {
84 ctx.setProviderUrl(constructProviderUrl(domain, servers));
85 }
86 return ctx;
87 }
88
89 /*
90 * Public for use by product test suite.
91 */
92 public static boolean platformServersAvailable() {
93 return !filterNameServers(
94 ResolverConfiguration.open().nameservers(), true
95 ).isEmpty();
96 }
97
98 private static Context urlToContext(String url, Hashtable env)
99 throws NamingException {
100
101 DnsUrl[] urls;
102 try {
103 urls = DnsUrl.fromList(url);
104 } catch (MalformedURLException e) {
105 throw new ConfigurationException(e.getMessage());
106 }
107 if (urls.length == 0) {
108 throw new ConfigurationException(
109 "Invalid DNS pseudo-URL(s): " + url);
110 }
111 String domain = urls[0].getDomain();
112
113 // If multiple urls, all must have the same domain.
114 for (int i = 1; i < urls.length; i++) {
115 if (!domain.equalsIgnoreCase(urls[i].getDomain())) {
116 throw new ConfigurationException(
117 "Conflicting domains: " + url);
118 }
195 path = "/" + UrlUtil.encode(domain, "ISO-8859-1");
196 } catch (java.io.UnsupportedEncodingException e) {
197 // assert false : "ISO-Latin-1 charset unavailable";
198 }
199 }
200
201 StringBuffer buf = new StringBuffer();
202 for (int i = 0; i < servers.length; i++) {
203 if (i > 0) {
204 buf.append(' ');
205 }
206 buf.append("dns://").append(servers[i]).append(path);
207 }
208 return buf.toString();
209 }
210
211 /*
212 * Reads environment to find URL(s) of initial context.
213 * Default URL is "dns:".
214 */
215 private static String getInitCtxUrl(Hashtable env) {
216 String url = (String) env.get(Context.PROVIDER_URL);
217 return ((url != null) ? url : DEFAULT_URL);
218 }
219
220 /**
221 * Removes any DNS server that's not permitted to access
222 * @param input the input server[:port] list, must not be null
223 * @param oneIsEnough return output once there exists one ok
224 * @return the filtered list, all non-permitted input removed
225 */
226 private static List filterNameServers(List input, boolean oneIsEnough) {
227 SecurityManager security = System.getSecurityManager();
228 if (security == null || input == null || input.isEmpty()) {
229 return input;
230 } else {
231 List output = new ArrayList();
232 for (Object o: input) {
233 if (o instanceof String) {
234 String platformServer = (String)o;
235 int colon = platformServer.indexOf(':',
236 platformServer.indexOf(']') + 1);
237
238 int p = (colon < 0)
239 ? DEFAULT_PORT
240 : Integer.parseInt(
241 platformServer.substring(colon + 1));
242 String s = (colon < 0)
243 ? platformServer
244 : platformServer.substring(0, colon);
245 try {
246 security.checkConnect(s, p);
247 output.add(platformServer);
248 if (oneIsEnough) {
249 return output;
250 }
251 } catch (SecurityException se) {
252 continue;
253 }
254 }
255 }
256 return output;
257 }
258 }
259 }
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42 * A DnsContextFactory serves as the initial context factory for DNS.
43 *
44 * <p> When an initial context is being created, the environment
45 * property "java.naming.provider.url" should contain a DNS pseudo-URL
46 * (see DnsUrl) or a space-separated list of them. Multiple URLs must
47 * all have the same domain value.
48 * If the property is not set, the default "dns:" is used.
49 *
50 * @author Scott Seligman
51 */
52
53
54 public class DnsContextFactory implements InitialContextFactory {
55
56 private static final String DEFAULT_URL = "dns:";
57 private static final int DEFAULT_PORT = 53;
58
59
60 public Context getInitialContext(Hashtable<?,?> env) throws NamingException {
61 if (env == null) {
62 env = new Hashtable<>(5);
63 }
64 return urlToContext(getInitCtxUrl(env), env);
65 }
66
67 public static DnsContext getContext(String domain,
68 String[] servers, Hashtable<?,?> env)
69 throws NamingException {
70 return new DnsContext(domain, servers, env);
71 }
72
73 /*
74 * "urls" are used to determine the servers, but any domain
75 * components are overridden by "domain".
76 */
77 public static DnsContext getContext(String domain,
78 DnsUrl[] urls, Hashtable<?,?> env)
79 throws NamingException {
80
81 String[] servers = serversForUrls(urls);
82 DnsContext ctx = getContext(domain, servers, env);
83 if (platformServersUsed(urls)) {
84 ctx.setProviderUrl(constructProviderUrl(domain, servers));
85 }
86 return ctx;
87 }
88
89 /*
90 * Public for use by product test suite.
91 */
92 public static boolean platformServersAvailable() {
93 return !filterNameServers(
94 ResolverConfiguration.open().nameservers(), true
95 ).isEmpty();
96 }
97
98 private static Context urlToContext(String url, Hashtable<?,?> env)
99 throws NamingException {
100
101 DnsUrl[] urls;
102 try {
103 urls = DnsUrl.fromList(url);
104 } catch (MalformedURLException e) {
105 throw new ConfigurationException(e.getMessage());
106 }
107 if (urls.length == 0) {
108 throw new ConfigurationException(
109 "Invalid DNS pseudo-URL(s): " + url);
110 }
111 String domain = urls[0].getDomain();
112
113 // If multiple urls, all must have the same domain.
114 for (int i = 1; i < urls.length; i++) {
115 if (!domain.equalsIgnoreCase(urls[i].getDomain())) {
116 throw new ConfigurationException(
117 "Conflicting domains: " + url);
118 }
195 path = "/" + UrlUtil.encode(domain, "ISO-8859-1");
196 } catch (java.io.UnsupportedEncodingException e) {
197 // assert false : "ISO-Latin-1 charset unavailable";
198 }
199 }
200
201 StringBuffer buf = new StringBuffer();
202 for (int i = 0; i < servers.length; i++) {
203 if (i > 0) {
204 buf.append(' ');
205 }
206 buf.append("dns://").append(servers[i]).append(path);
207 }
208 return buf.toString();
209 }
210
211 /*
212 * Reads environment to find URL(s) of initial context.
213 * Default URL is "dns:".
214 */
215 private static String getInitCtxUrl(Hashtable<?,?> env) {
216 String url = (String) env.get(Context.PROVIDER_URL);
217 return ((url != null) ? url : DEFAULT_URL);
218 }
219
220 /**
221 * Removes any DNS server that's not permitted to access
222 * @param input the input server[:port] list, must not be null
223 * @param oneIsEnough return output once there exists one ok
224 * @return the filtered list, all non-permitted input removed
225 */
226 private static List<String> filterNameServers(List<String> input, boolean oneIsEnough) {
227 SecurityManager security = System.getSecurityManager();
228 if (security == null || input == null || input.isEmpty()) {
229 return input;
230 } else {
231 List<String> output = new ArrayList<>();
232 for (String platformServer: input) {
233 int colon = platformServer.indexOf(':',
234 platformServer.indexOf(']') + 1);
235
236 int p = (colon < 0)
237 ? DEFAULT_PORT
238 : Integer.parseInt(
239 platformServer.substring(colon + 1));
240 String s = (colon < 0)
241 ? platformServer
242 : platformServer.substring(0, colon);
243 try {
244 security.checkConnect(s, p);
245 output.add(platformServer);
246 if (oneIsEnough) {
247 return output;
248 }
249 } catch (SecurityException se) {
250 continue;
251 }
252 }
253 return output;
254 }
255 }
256 }
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