Как получить Google PageRank (PR) на Java
В этом примере мы покажем вам, как получить Google PageRank (PR) на Java. Чтобы запросить PageRank для «example.com», вам просто нужно отправить следующий HTTP-запрос:
http://toolbarqueries.google.com/tbr?client=navclient-auto&hl=en&ch=6236440745 &ie=UTF-8&oe=UTF-8&features=Rank&q=info:example.com
P.S Above URL is used by Google toolbar plugin.
Сложная часть заключается в следующем значении хэширования:
ch=6236440745
Google использует алгоритм хеширования Боба Дженкинса [1] [2] для хеширования URL-адреса и создания значения выше «ch».
1. PageRank (PR) + пример Java
Получите Google PR для веб-сайта example.com.
GoogleSeoHelper.java
package com.example; import java.io.BufferedReader; import java.io.InputStreamReader; import java.net.URL; import java.net.URLConnection; import com.example.hash.JenkinsHash; public class GoogleSeoHelper { public static void main(String[] args) { GoogleSeoHelper obj = new GoogleSeoHelper(); System.out.println(obj.getPR("example.com")); } public int getPR(String domain) { String result = ""; JenkinsHash jenkinsHash = new JenkinsHash(); long hash = jenkinsHash.hash(("info:" + domain).getBytes()); //Append a 6 in front of the hashing value. String url = "http://toolbarqueries.google.com/tbr?client=navclient-auto&hl=en&" + "ch=6" + hash + "&ie=UTF-8&oe=UTF-8&features=Rank&q=info:" + domain; System.out.println("Sending request to : " + url); try { URLConnection conn = new URL(url).openConnection(); BufferedReader br = new BufferedReader(new InputStreamReader( conn.getInputStream())); String input; while ((input = br.readLine()) != null) { // What Google returned? Example : Rank_1:1:9, PR = 9 System.out.println(input); result = input.substring(input.lastIndexOf(":") + 1); } } catch (Exception e) { System.out.println(e.getMessage()); } if ("".equals(result)) { return 0; } else { return Integer.valueOf(result); } } }
Вывод - URL «example.com» имеет рейтинг страницы 5!
Sending request to : http://toolbarqueries.google.com/tbr?client=navclient-auto
&hl=en&ch=6236440745&ie=UTF-8&oe=UTF-8&features=Rank&q=info:example.com
Rank_1:1:5
5
2. Алгоритм идеального хеширования Дженкинса
Вот пример хенкинга Java-порта Jenkins.
JenkinsHash.java
package com.example.hash; /** * Hash algorithm by Bob Jenkins, 1996. * * You may use this code any way you wish, private, educational, or commercial. * It's free. See: http://burtleburtle.net/bob/hash/doobs.html * */ public class JenkinsHash { // max value to limit it to 4 bytes private static final long MAX_VALUE = 0xFFFFFFFFL; // internal variables used in the various calculations long a; long b; long c; /** * Convert a byte into a long value without making it negative. */ private long byteToLong(byte b) { long val = b & 0x7F; if ((b & 0x80) != 0) { val += 128; } return val; } /** * Do addition and turn into 4 bytes. */ private long add(long val, long add) { return (val + add) & MAX_VALUE; } /** * Do subtraction and turn into 4 bytes. */ private long subtract(long val, long subtract) { return (val - subtract) & MAX_VALUE; } /** * Left shift val by shift bits and turn in 4 bytes. */ private long xor(long val, long xor) { return (val ^ xor) & MAX_VALUE; } /** * Left shift val by shift bits. Cut down to 4 bytes. */ private long leftShift(long val, int shift) { return (val << shift) & MAX_VALUE; } /** * Convert 4 bytes from the buffer at offset into a long value. */ private long fourByteToLong(byte[] bytes, int offset) { return (byteToLong(bytes[offset + 0]) + (byteToLong(bytes[offset + 1]) << 8) + (byteToLong(bytes[offset + 2]) << 16) + (byteToLong(bytes[offset + 3]) << 24)); } /** * Mix up the values in the hash function. */ private void hashMix() { a = subtract(a, b); a = subtract(a, c); a = xor(a, c >> 13); b = subtract(b, c); b = subtract(b, a); b = xor(b, leftShift(a, 8)); c = subtract(c, a); c = subtract(c, b); c = xor(c, (b >> 13)); a = subtract(a, b); a = subtract(a, c); a = xor(a, (c >> 12)); b = subtract(b, c); b = subtract(b, a); b = xor(b, leftShift(a, 16)); c = subtract(c, a); c = subtract(c, b); c = xor(c, (b >> 5)); a = subtract(a, b); a = subtract(a, c); a = xor(a, (c >> 3)); b = subtract(b, c); b = subtract(b, a); b = xor(b, leftShift(a, 10)); c = subtract(c, a); c = subtract(c, b); c = xor(c, (b >> 15)); } /** * Hash a variable-length key into a 32-bit value. Every bit of the key * affects every bit of the return value. Every 1-bit and 2-bit delta * achieves avalanche. The best hash table sizes are powers of 2. * * @param buffer * Byte array that we are hashing on. * @param initialValue * Initial value of the hash if we are continuing from a previous * run. 0 if none. * @return Hash value for the buffer. */ public long hash(byte[] buffer, long initialValue) { int len, pos; // set up the internal state // the golden ratio; an arbitrary value a = 0x09e3779b9L; // the golden ratio; an arbitrary value b = 0x09e3779b9L; // the previous hash value //c = initialValue; c = 0x0E6359A60L; // handle most of the key pos = 0; for (len = buffer.length; len >= 12; len -= 12) { a = add(a, fourByteToLong(buffer, pos)); b = add(b, fourByteToLong(buffer, pos + 4)); c = add(c, fourByteToLong(buffer, pos + 8)); hashMix(); pos += 12; } c += buffer.length; // all the case statements fall through to the next on purpose switch (len) { case 11: c = add(c, leftShift(byteToLong(buffer[pos + 10]), 24)); case 10: c = add(c, leftShift(byteToLong(buffer[pos + 9]), 16)); case 9: c = add(c, leftShift(byteToLong(buffer[pos + 8]), 8)); // the first byte of c is reserved for the length case 8: b = add(b, leftShift(byteToLong(buffer[pos + 7]), 24)); case 7: b = add(b, leftShift(byteToLong(buffer[pos + 6]), 16)); case 6: b = add(b, leftShift(byteToLong(buffer[pos + 5]), 8)); case 5: b = add(b, byteToLong(buffer[pos + 4])); case 4: a = add(a, leftShift(byteToLong(buffer[pos + 3]), 24)); case 3: a = add(a, leftShift(byteToLong(buffer[pos + 2]), 16)); case 2: a = add(a, leftShift(byteToLong(buffer[pos + 1]), 8)); case 1: a = add(a, byteToLong(buffer[pos + 0])); // case 0: nothing left to add } hashMix(); return c; } /** * See hash(byte[] buffer, long initialValue) * * @param buffer * Byte array that we are hashing on. * @return Hash value for the buffer. */ public long hash(byte[] buffer) { return hash(buffer, 0); } }