最近在日誌數據清洗時遇到中文亂碼,如果只要有非中文字符就將該字符串過濾掉,這種方法雖簡單但並不可取,因為比如像Xperia™主題、天天四川麻將Ⅱ這樣的字符串也會被過濾掉。
1. Unicode編碼
Unicode編碼是一種涵蓋了世界上所有語言、標點等字符的編碼方式,簡單一點說,就是一種通用的世界碼;其編碼範圍:U+0000 .. U+10FFFF。按Unicode硬編碼的區間進行劃分,Unicode編碼被分成若干個block ( Unicode block);每一個Unicode編碼專屬於唯一的Unicode block,Unicode block之間互不重疊。從碼字的本身的屬性出發,Unicode編碼被分成了若干script ( Unicode>
- CJK Radicals Supplement
- Kangxi Radicals
- CJK Symbols and Punctuation中的15個字符
- CJK Unified Ideographs Extension A
- CJK Unified Ideographs
- CJK Compatibility Ideographs
- CJK Unified Ideographs Extension B
- CJK Unified Ideographs Extension C
- CJK Unified Ideographs Extension D
- CJK Unified Ideographs Extension E
- CJK Compatibility Ideographs Supplement
其中,常見的中文字符在CJK Unified Ideographs block;此外,考慮繁體字及不常見字等,CJK還有A、B、C、D、E五個extension。Basic Latin block完整地包含了ASCII碼的控制字符、標點字符與英文字母字符。
2. Java的字符編碼
JDK完整實現Unicode的block與script:
<code>Char c = '☎'
Character.UnicodeBlock ub = Character.UnicodeBlock.of(c)
Character.UnicodeScript uc = Character.UnicodeScript.of(c);/<code>
Java中的字符char內置的編碼方式是UTF-16,當char強轉成int類型時,其返回值是unicode編碼值,只有當getbyte時才返回的是utf-8編碼的byte:
<code>String s = "\\\\u00a0";
String.format("\\\\\\u%04x", (int) s.charAt(0)) // --> \\\\u00a0
import org.apache.commons.codec.binary.Hex;
Hex.encodeHex(s.getBytes()) // --> c2a0/<code>
UTF-8是Unicode字符的變長前綴編碼的一種實現,二者之間的對應關係在這裡.現在我們回到開篇過濾中文亂碼的問題,有一個基本解決思路:
- 去掉各種標點字符、控制字符,
- 計算剩下字符中非中文字符所佔的比例,如果超過閾值,則認為該字符串為亂碼串
完整代碼如下:
<code>public class ChineseUtill {
private static boolean isChinese(char c) {
Character.UnicodeScript sc = Character.UnicodeScript.of(c);
if (sc == Character.UnicodeScript.HAN) {
return true;
}
return false;
}
public static boolean isPunctuation(char c) {
Character.UnicodeBlock ub = Character.UnicodeBlock.of(c);
if ( // punctuation, spacing, and formatting characters
ub == Character.UnicodeBlock.GENERAL_PUNCTUATION
// symbols and punctuation in the unified Chinese, Japanese and Korean/> || ub == Character.UnicodeBlock.CJK_SYMBOLS_AND_PUNCTUATION
// fullwidth character or a halfwidth character
|| ub == Character.UnicodeBlock.HALFWIDTH_AND_FULLWIDTH_FORMS
// vertical glyph variants for east Asian compatibility
|| ub == Character.UnicodeBlock.CJK_COMPATIBILITY_FORMS
// vertical punctuation for compatibility characters with the Chinese Standard GB 18030
|| ub == Character.UnicodeBlock.VERTICAL_FORMS
// ascii
|| ub == Character.UnicodeBlock.BASIC_LATIN
) {
return true;
} else {
return false;
}
}
private static Boolean isUserDefined(char c) {
Character.UnicodeBlock ub = Character.UnicodeBlock.of(c);
if (ub == Character.UnicodeBlock.NUMBER_FORMS
|| ub == Character.UnicodeBlock.ENCLOSED_ALPHANUMERICS
|| ub == Character.UnicodeBlock.LETTERLIKE_SYMBOLS
|| c == '\\\\ufeff'
|| c == '\\\\u00a0'
)
return true;
return false;
}
public static Boolean isMessy(String str) {
float chlength = 0;
float count = 0;
for(int i = 0; i < str.length(); i++) {
char c = str.charAt(i);
if(isPunctuation(c) || isUserDefined(c))
continue;
else {
if(!isChinese(c)) {
count = count + 1;
}
chlength ++;
}
}
float result = count / chlength;
if(result > 0.3)
return true;
return false;
}
}
/<code>
為了得到更為完整的可接受的字符表,定義isUserDefined方法(具體字符表與日誌中的字符有關係);加上了Number Forms、Enclosed Alphanumerics、Letterlike Symbols這三個block,以及\\\\u00a0(Non-breaking space)字符與\\\\ufeff(ZERO WIDTH NO-BREAK SPACE)字符。
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