Java dynamic replacement for DNS in inetaddress simple analysis 2

2. Import Java.io.BufferedReader;
4. Import java.io.IOException;
6. Import Java.io.InputStream;
8. Import Java.io.InputStreamReader;
10. Import Java.lang.reflect.Field;
12. Import Java.lang.reflect.Method;
14. Import java.net.HttpURLConnection;
16. Import java.net.InetAddress;
18. Import java.net.MalformedURLException;
20. Import Java.net.URL;
22. Import java.net.UnknownHostException;
24. Import Java.util.HashMap;
26. Import java.util.List;
28. Import Java.util.Map;
30. Import Sun.net.spi.nameservice.NameService;
32. public class Javadnscachetest {
34. /**
36. * Tested, two ways can be in Windows environment, Linux environment to be tested
38. *
40. * @param args
42. * @throws Exception
44. */
46. public static void Main (string[] args) throws Exception {
48. /* 1. Dynamic Replacement Addresscache */
50. Changednswithaddresscache ();
52. /* 1. Dynamic Agent Nameservice */
54. Changednswithnameservice ();
56. }
58. public static void Changednswithnameservice () throws Exception {
60. /* 1. Get reflexive class */
62. class<?> addressclass = Inetaddress.class;
64. /* 2. Get addresscache field */
66. try {
68. Field Nameservicefield = Addressclass.getdeclaredfield ("Nameservice");//For JRockit or IBM JDK
70. Nameservicefield.setaccessible (TRUE);
72. Sun.net.spi.nameservice.NameService Nameservice = (nameservice) nameservicefield.get (null);
74. Nameservicefield.set (NULL, New Nameserviceproxy (Nameservice));
76. Nameservicefield.setaccessible (FALSE);
78. } catch (Nosuchfieldexception e) {
80. Field Nameservicesfield = Addressclass.getdeclaredfield ("nameservices");//For OPENJDK
82. Nameservicesfield.setaccessible (TRUE);
84. List<sun.net.spi.nameservice.nameservice> nameservices = (list<sun.net.spi.nameservice.nameservice>) Nameservicesfield.get (NULL);
86. if (nameservices! = null && nameservices.size () > 0) {
88. /* Replace as proxy instance */
90. Nameservices.set (0, New Nameserviceproxy (Nameservices.get (0)));
92. } else {
94. Could it be empty? Pending test
96. }
98. Nameservicesfield.setaccessible (FALSE);
100. }
102. Gethttpconent ("www.baidu.com");
104. }
106. public static void Changednswithcddresscache () throws Exception {
108. /* 1. Get reflexive class */
110. class<?> addressclass = Inetaddress.class;
112. /* 2. Get addresscache field */
114. Field Addresscachefield = Addressclass.getdeclaredfield ("Addresscache");
116. /* 3. Get Addresscache */
118. Addresscachefield.setaccessible (TRUE);
120. Object Addresscache = Addresscachefield.get (null);
122. Addresscachefield.setaccessible (FALSE);
124. /* 4. Get the Reflection class for Addresscache */
126. class<?> Addresscacheclass = Addresscache.getclass ();
128. /* 5. Get the Put method for Addresscache */
130. Method Putmethod = Addresscacheclass.getdeclaredmethod ("Put", String.class, Inetaddress[].class);
132. /* 5. Modify Addresscache Change wwww.baidu.com to specify any IP */
134. Putmethod.setaccessible (TRUE);
136. Putmethod.invoke (Addresscache, "www.baidu.com", new inetaddress[] {inetaddress.getbyaddress (new byte[] {, (byte) 239, (Byte) 210, 26});
138. Putmethod.setaccessible (FALSE);
140. /* 6. Test to see if it is connected */
142. Gethttpconent ("www.baidu.com");
144. }
146. private static void Gethttpconent (String host) throws Malformedurlexception, IOException {
148. HttpURLConnection conn = (httpurlconnection) New URL ("http:/" + host). OpenConnection ();
150. try {
152. Conn.setconnecttimeout (3000);//Reduce connection time for easy testing
154. Conn.setdefaultusecaches (FALSE);
156. Conn.setdoinput (TRUE);
158. Conn.setrequestmethod ("GET");
160. Conn.connect ();
162. int code = Conn.getresponsecode ();
164. System.out.format ("rest[%d]\n", code);
166. InputStream in = null;
168. in = Conn.geterrorstream ();//If not 2xx, the output is obtained by Errorstream.
170. if (in = = null) {
172. in = Conn.getinputstream ();
174. }
176. if (in = null) {
178. BufferedReader reader = new BufferedReader (new InputStreamReader (in));
180. for (String line = null; (line = Reader.readline ()) = null;) {
182. System.out.println (line);
184. }
186. }
188. } finally {
190. IF (conn! = null) {
192. Conn.disconnect ();
194. }
196. }
198. }
200. @SuppressWarnings ("restriction")
202. public static class Nameserviceproxy implements Sun.net.spi.nameservice.NameService {
204. Final Sun.net.spi.nameservice.NameService Nameservice;
206. Final map<string, inetaddress[]> mapping = new hashmap<string, inetaddress[]> ();
208. {
210. try {
212. Mapping.put ("www.baidu.com", new inetaddress[] {inetaddress.getbyaddress (new byte[] {, (byte) 239, (byte) 210, 26}) });
214. } catch (Unknownhostexception e) {
216. E.printstacktrace ();
218. }
220. }//Instance Initialization table
222. Public Nameserviceproxy (Sun.net.spi.nameservice.NameService nameservice) {
224. This.nameservice = Nameservice;
226. }
228. @Override
230. Public String gethostbyaddr (byte[] addr) throws Unknownhostexception {
232. return this.nameService.getHostByAddr (addr);
234. }
236. @Override
238. Public inetaddress[] LOOKUPALLHOSTADDR (String host) throws Unknownhostexception {
240. if (Mapping.containskey (host)) {
242. return Mapping.get (host);
244. } else {
246. return This.nameService.lookupAllHostAddr (host);
248. }
250. }
252. }
254. }

Java dynamic replacement for DNS in inetaddress simple analysis 2