How to identify html escape characters through code

Occasionally, you will see characters such as ' in the data. When the browser encounters these escape characters, it will escape them back. But how to identify them through codes? Let's discuss html escape characters with you. Friends who like it You can understand

Occasionally you will see characters such as ' in the data. The characteristics are as follows

Starts with , is a string of numbers in the middle, and ends with;
It starts with &, a string of characters in the middle, and ends with;

For example, the most common   or the equivalent  

When the browser encounters these escape characters, it will be escaped back, but how to identify it by code? org.apache.commons.lang.StringEscapeUtils.unescapeHtml provides a good explanation

When encountering the first situation above, the middle is a number, directly convert the number (unicode) to char
Encounter In the second case, there are characters in the middle, so we can only check the mapping table. Find the number corresponding to the character from the mapping table and convert it to char. It will be clear at a glance by looking at the code.

Look at how HTML40 defines it

The code is as follows:

static { 
HTML40 = new Entities(); 
fillWithHtml40Entities(HTML40); 
} 
static void fillWithHtml40Entities(Entities entities) { 
entities.addEntities(BASIC_ARRAY); 
entities.addEntities(ISO8859_1_ARRAY); 
entities.addEntities(HTML40_ARRAY); 
}

Look at what BASIC_ARRAY, ISO8859_1_ARRAY and HTML40_ARRAY are respectively

BASIC_ARRAY

The code is as follows:

private static final String[][] BASIC_ARRAY = {{"quot", "34"}, // " - double-quote 
{"amp", "38"}, // & - ampersand 
{"lt", "60"}, // < - less-than 
{"gt", "62"}, // > - greater-than 
};

ISO8859_1_ARRAY

The code is as follows:

static final String[][] ISO8859_1_ARRAY = {{"nbsp", "160"}, // non-breaking space 
{"iexcl", "161"}, // inverted exclamation mark 
{"cent", "162"}, // cent sign 
{"pound", "163"}, // pound sign 
{"curren", "164"}, // currency sign 
{"yen", "165"}, // yen sign = yuan sign 
{"brvbar", "166"}, // broken bar = broken vertical bar 
{"sect", "167"}, // section sign 
{"uml", "168"}, // diaeresis = spacing diaeresis 
{"copy", "169"}, // � - copyright sign 
{"ordf", "170"}, // feminine ordinal indicator 
{"laquo", "171"}, // left-pointing double angle quotation mark = left pointing guillemet 
{"not", "172"}, // not sign 
{"shy", "173"}, // soft hyphen = discretionary hyphen 
{"reg", "174"}, // � - registered trademark sign 
{"macr", "175"}, // macron = spacing macron = overline = APL overbar 
{"deg", "176"}, // degree sign 
{"plusmn", "177"}, // plus-minus sign = plus-or-minus sign 
{"sup2", "178"}, // superscript two = superscript digit two = squared 
{"sup3", "179"}, // superscript three = superscript digit three = cubed 
{"acute", "180"}, // acute accent = spacing acute 
{"micro", "181"}, // micro sign 
{"para", "182"}, // pilcrow sign = paragraph sign 
{"middot", "183"}, // middle dot = Georgian comma = Greek middle dot 
{"cedil", "184"}, // cedilla = spacing cedilla 
{"sup1", "185"}, // superscript one = superscript digit one 
{"ordm", "186"}, // masculine ordinal indicator 
{"raquo", "187"}, // right-pointing double angle quotation mark = right pointing guillemet 
{"frac14", "188"}, // vulgar fraction one quarter = fraction one quarter 
{"frac12", "189"}, // vulgar fraction one half = fraction one half 
{"frac34", "190"}, // vulgar fraction three quarters = fraction three quarters 
{"iquest", "191"}, // inverted question mark = turned question mark 
{"Agrave", "192"}, // � - uppercase A, grave accent 
{"Aacute", "193"}, // � - uppercase A, acute accent 
{"Acirc", "194"}, // � - uppercase A, circumflex accent 
{"Atilde", "195"}, // � - uppercase A, tilde 
{"Auml", "196"}, // � - uppercase A, umlaut 
{"Aring", "197"}, // � - uppercase A, ring 
{"AElig", "198"}, // � - uppercase AE 
{"Ccedil", "199"}, // � - uppercase C, cedilla 
{"Egrave", "200"}, // � - uppercase E, grave accent 
{"Eacute", "201"}, // � - uppercase E, acute accent 
{"Ecirc", "202"}, // � - uppercase E, circumflex accent 
{"Euml", "203"}, // � - uppercase E, umlaut 
{"Igrave", "204"}, // � - uppercase I, grave accent 
{"Iacute", "205"}, // � - uppercase I, acute accent 
{"Icirc", "206"}, // � - uppercase I, circumflex accent 
{"Iuml", "207"}, // � - uppercase I, umlaut 
{"ETH", "208"}, // � - uppercase Eth, Icelandic 
{"Ntilde", "209"}, // � - uppercase N, tilde 
{"Ograve", "210"}, // � - uppercase O, grave accent 
{"Oacute", "211"}, // � - uppercase O, acute accent 
{"Ocirc", "212"}, // � - uppercase O, circumflex accent 
{"Otilde", "213"}, // � - uppercase O, tilde 
{"Ouml", "214"}, // � - uppercase O, umlaut 
{"times", "215"}, // multiplication sign 
{"Oslash", "216"}, // � - uppercase O, slash 
{"Ugrave", "217"}, // � - uppercase U, grave accent 
{"Uacute", "218"}, // � - uppercase U, acute accent 
{"Ucirc", "219"}, // � - uppercase U, circumflex accent 
{"Uuml", "220"}, // � - uppercase U, umlaut 
{"Yacute", "221"}, // � - uppercase Y, acute accent 
{"THORN", "222"}, // � - uppercase THORN, Icelandic 
{"szlig", "223"}, // � - lowercase sharps, German 
{"agrave", "224"}, // � - lowercase a, grave accent 
{"aacute", "225"}, // � - lowercase a, acute accent 
{"acirc", "226"}, // � - lowercase a, circumflex accent 
{"atilde", "227"}, // � - lowercase a, tilde 
{"auml", "228"}, // � - lowercase a, umlaut 
{"aring", "229"}, // � - lowercase a, ring 
{"aelig", "230"}, // � - lowercase ae 
{"ccedil", "231"}, // � - lowercase c, cedilla 
{"egrave", "232"}, // � - lowercase e, grave accent 
{"eacute", "233"}, // � - lowercase e, acute accent 
{"ecirc", "234"}, // � - lowercase e, circumflex accent 
{"euml", "235"}, // � - lowercase e, umlaut 
{"igrave", "236"}, // � - lowercase i, grave accent 
{"iacute", "237"}, // � - lowercase i, acute accent 
{"icirc", "238"}, // � - lowercase i, circumflex accent 
{"iuml", "239"}, // � - lowercase i, umlaut 
{"eth", "240"}, // � - lowercase eth, Icelandic 
{"ntilde", "241"}, // � - lowercase n, tilde 
{"ograve", "242"}, // � - lowercase o, grave accent 
{"oacute", "243"}, // � - lowercase o, acute accent 
{"ocirc", "244"}, // � - lowercase o, circumflex accent 
{"otilde", "245"}, // � - lowercase o, tilde 
{"ouml", "246"}, // � - lowercase o, umlaut 
{"pide", "247"}, // pision sign 
{"oslash", "248"}, // � - lowercase o, slash 
{"ugrave", "249"}, // � - lowercase u, grave accent 
{"uacute", "250"}, // � - lowercase u, acute accent 
{"ucirc", "251"}, // � - lowercase u, circumflex accent 
{"uuml", "252"}, // � - lowercase u, umlaut 
{"yacute", "253"}, // � - lowercase y, acute accent 
{"thorn", "254"}, // � - lowercase thorn, Icelandic 
{"yuml", "255"}, // � - lowercase y, umlaut 
};

HTML40_ARRAY

The code is as follows:

static final String[][] HTML40_ARRAY = { 
// <!-- Latin Extended-B --> 
{"fnof", "402"}, // latin small f with hook = function= florin, U+0192 ISOtech --> 
// <!-- Greek --> 
{"Alpha", "913"}, // greek capital letter alpha, U+0391 --> 
{"Beta", "914"}, // greek capital letter beta, U+0392 --> 
{"Gamma", "915"}, // greek capital letter gamma,U+0393 ISOgrk3 --> 
{"Delta", "916"}, // greek capital letter delta,U+0394 ISOgrk3 --> 
{"Epsilon", "917"}, // greek capital letter epsilon, U+0395 --> 
{"Zeta", "918"}, // greek capital letter zeta, U+0396 --> 
{"Eta", "919"}, // greek capital letter eta, U+0397 --> 
{"Theta", "920"}, // greek capital letter theta,U+0398 ISOgrk3 --> 
{"Iota", "921"}, // greek capital letter iota, U+0399 --> 
{"Kappa", "922"}, // greek capital letter kappa, U+039A --> 
{"Lambda", "923"}, // greek capital letter lambda,U+039B ISOgrk3 --> 
{"Mu", "924"}, // greek capital letter mu, U+039C --> 
{"Nu", "925"}, // greek capital letter nu, U+039D --> 
{"Xi", "926"}, // greek capital letter xi, U+039E ISOgrk3 --> 
{"Omicron", "927"}, // greek capital letter omicron, U+039F --> 
{"Pi", "928"}, // greek capital letter pi, U+03A0 ISOgrk3 --> 
{"Rho", "929"}, // greek capital letter rho, U+03A1 --> 
// <!-- there is no Sigmaf, and no U+03A2 character either --> 
{"Sigma", "931"}, // greek capital letter sigma,U+03A3 ISOgrk3 --> 
{"Tau", "932"}, // greek capital letter tau, U+03A4 --> 
{"Upsilon", "933"}, // greek capital letter upsilon,U+03A5 ISOgrk3 --> 
{"Phi", "934"}, // greek capital letter phi,U+03A6 ISOgrk3 --> 
{"Chi", "935"}, // greek capital letter chi, U+03A7 --> 
{"Psi", "936"}, // greek capital letter psi,U+03A8 ISOgrk3 --> 
{"Omega", "937"}, // greek capital letter omega,U+03A9 ISOgrk3 --> 
{"alpha", "945"}, // greek small letter alpha,U+03B1 ISOgrk3 --> 
{"beta", "946"}, // greek small letter beta, U+03B2 ISOgrk3 --> 
{"gamma", "947"}, // greek small letter gamma,U+03B3 ISOgrk3 --> 
{"delta", "948"}, // greek small letter delta,U+03B4 ISOgrk3 --> 
{"epsilon", "949"}, // greek small letter epsilon,U+03B5 ISOgrk3 --> 
{"zeta", "950"}, // greek small letter zeta, U+03B6 ISOgrk3 --> 
{"eta", "951"}, // greek small letter eta, U+03B7 ISOgrk3 --> 
{"theta", "952"}, // greek small letter theta,U+03B8 ISOgrk3 --> 
{"iota", "953"}, // greek small letter iota, U+03B9 ISOgrk3 --> 
{"kappa", "954"}, // greek small letter kappa,U+03BA ISOgrk3 --> 
{"lambda", "955"}, // greek small letter lambda,U+03BB ISOgrk3 --> 
{"mu", "956"}, // greek small letter mu, U+03BC ISOgrk3 --> 
{"nu", "957"}, // greek small letter nu, U+03BD ISOgrk3 --> 
{"xi", "958"}, // greek small letter xi, U+03BE ISOgrk3 --> 
{"omicron", "959"}, // greek small letter omicron, U+03BF NEW --> 
{"pi", "960"}, // greek small letter pi, U+03C0 ISOgrk3 --> 
{"rho", "961"}, // greek small letter rho, U+03C1 ISOgrk3 --> 
{"sigmaf", "962"}, // greek small letter final sigma,U+03C2 ISOgrk3 --> 
{"sigma", "963"}, // greek small letter sigma,U+03C3 ISOgrk3 --> 
{"tau", "964"}, // greek small letter tau, U+03C4 ISOgrk3 --> 
{"upsilon", "965"}, // greek small letter upsilon,U+03C5 ISOgrk3 --> 
{"phi", "966"}, // greek small letter phi, U+03C6 ISOgrk3 --> 
{"chi", "967"}, // greek small letter chi, U+03C7 ISOgrk3 --> 
{"psi", "968"}, // greek small letter psi, U+03C8 ISOgrk3 --> 
{"omega", "969"}, // greek small letter omega,U+03C9 ISOgrk3 --> 
{"thetasym", "977"}, // greek small letter theta symbol,U+03D1 NEW --> 
{"upsih", "978"}, // greek upsilon with hook symbol,U+03D2 NEW --> 
{"piv", "982"}, // greek pi symbol, U+03D6 ISOgrk3 --> 
// <!-- General Punctuation --> 
{"bull", "8226"}, // bullet = black small circle,U+2022 ISOpub --> 
// <!-- bullet is NOT the same as bullet operator, U+2219 --> 
{"hellip", "8230"}, // horizontal ellipsis = three dot leader,U+2026 ISOpub --> 
{"prime", "8242"}, // prime = minutes = feet, U+2032 ISOtech --> 
{"Prime", "8243"}, // double prime = seconds = inches,U+2033 ISOtech --> 
{"oline", "8254"}, // overline = spacing overscore,U+203E NEW --> 
{"frasl", "8260"}, // fraction slash, U+2044 NEW --> 
// <!-- Letterlike Symbols --> 
{"weierp", "8472"}, // script capital P = power set= Weierstrass p, U+2118 ISOamso --> 
{"image", "8465"}, // blackletter capital I = imaginary part,U+2111 ISOamso --> 
{"real", "8476"}, // blackletter capital R = real part symbol,U+211C ISOamso --> 
{"trade", "8482"}, // trade mark sign, U+2122 ISOnum --> 
{"alefsym", "8501"}, // alef symbol = first transfinite cardinal,U+2135 NEW --> 
// <!-- alef symbol is NOT the same as hebrew letter alef,U+05D0 although the 
// same glyph could be used to depict both characters --> 
// <!-- Arrows --> 
{"larr", "8592"}, // leftwards arrow, U+2190 ISOnum --> 
{"uarr", "8593"}, // upwards arrow, U+2191 ISOnum--> 
{"rarr", "8594"}, // rightwards arrow, U+2192 ISOnum --> 
{"darr", "8595"}, // downwards arrow, U+2193 ISOnum --> 
{"harr", "8596"}, // left right arrow, U+2194 ISOamsa --> 
{"crarr", "8629"}, // downwards arrow with corner leftwards= carriage return, U+21B5 NEW --> 
{"lArr", "8656"}, // leftwards double arrow, U+21D0 ISOtech --> 
// <!-- ISO 10646 does not say that lArr is the same as the &#39;is implied by&#39; 
// arrow but also does not have any other character for that function. 
// So ? lArr canbe used for &#39;is implied by&#39; as ISOtech suggests --> 
{"uArr", "8657"}, // upwards double arrow, U+21D1 ISOamsa --> 
{"rArr", "8658"}, // rightwards double arrow,U+21D2 ISOtech --> 
// <!-- ISO 10646 does not say this is the &#39;implies&#39; character but does not 
// have another character with this function so ?rArr can be used for 
// &#39;implies&#39; as ISOtech suggests --> 
{"dArr", "8659"}, // downwards double arrow, U+21D3 ISOamsa --> 
{"hArr", "8660"}, // left right double arrow,U+21D4 ISOamsa --> 
// <!-- Mathematical Operators --> 
{"forall", "8704"}, // for all, U+2200 ISOtech --> 
{"part", "8706"}, // partial differential, U+2202 ISOtech --> 
{"exist", "8707"}, // there exists, U+2203 ISOtech --> 
{"empty", "8709"}, // empty set = null set = diameter,U+2205 ISOamso --> 
{"nabla", "8711"}, // nabla = backward difference,U+2207 ISOtech --> 
{"isin", "8712"}, // element of, U+2208 ISOtech --> 
{"notin", "8713"}, // not an element of, U+2209 ISOtech --> 
{"ni", "8715"}, // contains as member, U+220B ISOtech --> 
// <!-- should there be a more memorable name than &#39;ni&#39;? --> 
{"prod", "8719"}, // n-ary product = product sign,U+220F ISOamsb --> 
// <!-- prod is NOT the same character as U+03A0 &#39;greek capital letter pi&#39; 
// though the same glyph might be used for both --> 
{"sum", "8721"}, // n-ary summation, U+2211 ISOamsb --> 
// <!-- sum is NOT the same character as U+03A3 &#39;greek capital letter sigma&#39; 
// though the same glyph might be used for both --> 
{"minus", "8722"}, // minus sign, U+2212 ISOtech --> 
{"lowast", "8727"}, // asterisk operator, U+2217 ISOtech --> 
{"radic", "8730"}, // square root = radical sign,U+221A ISOtech --> 
{"prop", "8733"}, // proportional to, U+221D ISOtech --> 
{"infin", "8734"}, // infinity, U+221E ISOtech --> 
{"ang", "8736"}, // angle, U+2220 ISOamso --> 
{"and", "8743"}, // logical and = wedge, U+2227 ISOtech --> 
{"or", "8744"}, // logical or = vee, U+2228 ISOtech --> 
{"cap", "8745"}, // intersection = cap, U+2229 ISOtech --> 
{"cup", "8746"}, // union = cup, U+222A ISOtech --> 
{"int", "8747"}, // integral, U+222B ISOtech --> 
{"there4", "8756"}, // therefore, U+2234 ISOtech --> 
{"sim", "8764"}, // tilde operator = varies with = similar to,U+223C ISOtech --> 
// <!-- tilde operator is NOT the same character as the tilde, U+007E,although 
// the same glyph might be used to represent both --> 
{"cong", "8773"}, // approximately equal to, U+2245 ISOtech --> 
{"asymp", "8776"}, // almost equal to = asymptotic to,U+2248 ISOamsr --> 
{"ne", "8800"}, // not equal to, U+2260 ISOtech --> 
{"equiv", "8801"}, // identical to, U+2261 ISOtech --> 
{"le", "8804"}, // less-than or equal to, U+2264 ISOtech --> 
{"ge", "8805"}, // greater-than or equal to,U+2265 ISOtech --> 
{"sub", "8834"}, // subset of, U+2282 ISOtech --> 
{"sup", "8835"}, // superset of, U+2283 ISOtech --> 
// <!-- note that nsup, &#39;not a superset of, U+2283&#39; is not covered by the 
// Symbol font encoding and is not included. Should it be, for symmetry? 
// It is in ISOamsn --> <!ENTITY nsub", "8836"}, 
// not a subset of, U+2284 ISOamsn --> 
{"sube", "8838"}, // subset of or equal to, U+2286 ISOtech --> 
{"supe", "8839"}, // superset of or equal to,U+2287 ISOtech --> 
{"oplus", "8853"}, // circled plus = direct sum,U+2295 ISOamsb --> 
{"otimes", "8855"}, // circled times = vector product,U+2297 ISOamsb --> 
{"perp", "8869"}, // up tack = orthogonal to = perpendicular,U+22A5 ISOtech --> 
{"sdot", "8901"}, // dot operator, U+22C5 ISOamsb --> 
// <!-- dot operator is NOT the same character as U+00B7 middle dot --> 
// <!-- Miscellaneous Technical --> 
{"lceil", "8968"}, // left ceiling = apl upstile,U+2308 ISOamsc --> 
{"rceil", "8969"}, // right ceiling, U+2309 ISOamsc --> 
{"lfloor", "8970"}, // left floor = apl downstile,U+230A ISOamsc --> 
{"rfloor", "8971"}, // right floor, U+230B ISOamsc --> 
{"lang", "9001"}, // left-pointing angle bracket = bra,U+2329 ISOtech --> 
// <!-- lang is NOT the same character as U+003C &#39;less than&#39; or U+2039 &#39;single left-pointing angle quotation 
// mark&#39; --> 
{"rang", "9002"}, // right-pointing angle bracket = ket,U+232A ISOtech --> 
// <!-- rang is NOT the same character as U+003E &#39;greater than&#39; or U+203A 
// &#39;single right-pointing angle quotation mark&#39; --> 
// <!-- Geometric Shapes --> 
{"loz", "9674"}, // lozenge, U+25CA ISOpub --> 
// <!-- Miscellaneous Symbols --> 
{"spades", "9824"}, // black spade suit, U+2660 ISOpub --> 
// <!-- black here seems to mean filled as opposed to hollow --> 
{"clubs", "9827"}, // black club suit = shamrock,U+2663 ISOpub --> 
{"hearts", "9829"}, // black heart suit = valentine,U+2665 ISOpub --> 
{"diams", "9830"}, // black diamond suit, U+2666 ISOpub --> 
// <!-- Latin Extended-A --> 
{"OElig", "338"}, // -- latin capital ligature OE,U+0152 ISOlat2 --> 
{"oelig", "339"}, // -- latin small ligature oe, U+0153 ISOlat2 --> 
// <!-- ligature is a misnomer, this is a separate character in some languages --> 
{"Scaron", "352"}, // -- latin capital letter S with caron,U+0160 ISOlat2 --> 
{"scaron", "353"}, // -- latin small letter s with caron,U+0161 ISOlat2 --> 
{"Yuml", "376"}, // -- latin capital letter Y with diaeresis,U+0178 ISOlat2 --> 
// <!-- Spacing Modifier Letters --> 
{"circ", "710"}, // -- modifier letter circumflex accent,U+02C6 ISOpub --> 
{"tilde", "732"}, // small tilde, U+02DC ISOdia --> 
// <!-- General Punctuation --> 
{"ensp", "8194"}, // en space, U+2002 ISOpub --> 
{"emsp", "8195"}, // em space, U+2003 ISOpub --> 
{"thinsp", "8201"}, // thin space, U+2009 ISOpub --> 
{"zwnj", "8204"}, // zero width non-joiner,U+200C NEW RFC 2070 --> 
{"zwj", "8205"}, // zero width joiner, U+200D NEW RFC 2070 --> 
{"lrm", "8206"}, // left-to-right mark, U+200E NEW RFC 2070 --> 
{"rlm", "8207"}, // right-to-left mark, U+200F NEW RFC 2070 --> 
{"ndash", "8211"}, // en dash, U+2013 ISOpub --> 
{"mdash", "8212"}, // em dash, U+2014 ISOpub --> 
{"lsquo", "8216"}, // left single quotation mark,U+2018 ISOnum --> 
{"rsquo", "8217"}, // right single quotation mark,U+2019 ISOnum --> 
{"sbquo", "8218"}, // single low-9 quotation mark, U+201A NEW --> 
{"ldquo", "8220"}, // left double quotation mark,U+201C ISOnum --> 
{"rdquo", "8221"}, // right double quotation mark,U+201D ISOnum --> 
{"bdquo", "8222"}, // double low-9 quotation mark, U+201E NEW --> 
{"dagger", "8224"}, // dagger, U+2020 ISOpub --> 
{"Dagger", "8225"}, // double dagger, U+2021 ISOpub --> 
{"permil", "8240"}, // per mille sign, U+2030 ISOtech --> 
{"lsaquo", "8249"}, // single left-pointing angle quotation mark,U+2039 ISO proposed --> 
// <!-- lsaquo is proposed but not yet ISO standardized --> 
{"rsaquo", "8250"}, // single right-pointing angle quotation mark,U+203A ISO proposed --> 
// <!-- rsaquo is proposed but not yet ISO standardized --> 
{"euro", "8364"}, // -- euro sign, U+20AC NEW --> 
};

Expand again

As you can see from the front, the number in the middle of the escape character is unicode, so this transfer character can be constructed casually, and is not limited to the above definition, such as the unicode in It is 20013, then construct a transfer character 中, and it will change back to center after rendering by the browser. Although it is not necessary to display a character like this, it can come in handy in some scenarios where it is inconvenient to transmit special characters.

The above is the detailed content of How to identify html escape characters through code. For more information, please follow other related articles on the PHP Chinese website!