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Editor to share with you how html escape characters through code recognition, I believe that most people do not know much about it, so share this article for your reference, I hope you can learn a lot after reading this article, let's go to know it!

Occasionally see characters such as & # 39; in the data, with the following characteristics

Begins with & # and ends with a string of numbers ending with;

Begins with & and ends with a string of characters that ends with

Such as the most common or equivalent

When the browser encounters these escape characters, it will escape back, but how can it be identified by the code? Org.apache.commons.lang.StringEscapeUtils.unescapeHtml provides a good explanation.

In the first case above, the number is in the middle, and the number (unicode) is converted directly into char.

In the second case, there are characters in the middle, so we can only look up the mapping table. Find the number corresponding to the characters in the mapping table and convert it to char. Look at the code at a glance.

See how HTML40 defines it.

Static {

HTML40 = new Entities ()

FillWithHtml40Entities (HTML40)

}

Static void fillWithHtml40Entities (Entities entities) {

Entities.addEntities (BASIC_ARRAY)

Entities.addEntities (ISO8859_1_ARRAY)

Entities.addEntities (HTML40_ARRAY)

}

Let's see what BASIC_ARRAY, ISO8859_1_ARRAY and HTML40_ARRAY are, respectively.

BASIC_ARRAY

Private static final String [] [] BASIC_ARRAY = {{"quot", "34"}, / / "- double-quote

{"amp", "38"}, / / &-ampersand

{"lt", "60"}, / /

< - less-than {"gt", "62"}, // >

-greater-than

}

ISO8859_1_ARRAY

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"}, / / reg-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"}, / / engineer-lowercase o, acute accent

{"ocirc", "244"}, / / engineer-lowercase o, circumflex accent

{"otilde", "245"}, / / lowercase o, tilde

{"ouml", "246"}, / / lowercase o, umlaut

{"divide", "247"}, / / division 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

Static final String [] HTML40_ARRAY = {

/ /

{"fnof", "402"}, / / latin small f with hook = function= florin, Ubun0192 ISOtech-- >

/ /

{"Alpha", "913"}, / / greek capital letter alpha, Ubun0391-- >

{"Beta", "914"}, / / greek capital letter beta, Ubun0392-- >

{"Gamma", "915"}, / / greek capital letter gamma,U+0393 ISOgrk3-- >

{"Delta", "916"}, / / greek capital letter delta,U+0394 ISOgrk3-- >

{"Epsilon", "917"}, / / greek capital letter epsilon, Ubun0395-- >

{"Zeta", "918"}, / / greek capital letter zeta, Ubun0396-- >

{"Eta", "919"}, / / greek capital letter eta, Ubun0397-- >

{"Theta", "920"}, / / greek capital letter theta,U+0398 ISOgrk3-- >

{"Iota", "921"}, / / greek capital letter iota, Ubun0399-- >

{"Kappa", "922"}, / / greek capital letter kappa, Ubun039A-- >

{"Lambda", "923"}, / / greek capital letter lambda,U+039B ISOgrk3-- >

{"Mu", "924"}, / / greek capital letter mu, Ubun039C-- >

{"Nu", "925"}, / / greek capital letter nu, Utility 039D-- >

{"Xi", "926"}, / / greek capital letter xi, Utility 039E ISOgrk3-- >

{"Omicron", "927"}, / / greek capital letter omicron, Ubun039F-- >

{"Pi", "928"}, / / greek capital letter pi, U+03A0 ISOgrk3-- >

{"Rho", "929"}, / / greek capital letter rho, U+03A1-- >

/ /

{"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-- >

/ /

{"bull", "8226"}, / / bullet = black small circle,U+2022 ISOpub-- >

/ /

{"hellip", "8230"}, / / horizontal ellipsis = three dot leader,U+2026 ISOpub-- >

{"prime", "8242"}, / / prime = minutes = feet, Utility 2032 ISOtech-- >

{"Prime", "8243"}, / / double prime = seconds = inches,U+2033 ISOtech-- >

{"oline", "8254"}, / / overline = spacing overscore,U+203E NEW-- >

{"frasl", "8260"}, / / fraction slash, Utility 2044 NEW-- >

/ /

{"weierp", "8472"}, / / script capital P = power set= Weierstrass p, ISOamso 2118-- >

{"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, Utility 2122 ISOnum-- >

{"alefsym", "8501"}, / / alef symbol = first transfinite cardinal,U+2135 NEW-- >

/ /

/ /

{"larr", "8592"}, / / leftwards arrow, Utility 2190 ISOnum-- >

{"uarr", "8593"}, / / upwards arrow, Utility 2191 ISOnum-- >

{"rarr", "8594"}, / / rightwards arrow, Utility 2192 ISOnum-- >

{"darr", "8595"}, / / downwards arrow, Utility 2193 ISOnum-- >

{"harr", "8596"}, / / left right arrow, Utility 2194 ISOamsa-- >

{"crarr", "8629"}, / / downwards arrow with corner leftwards= carriage return, U+21B5 NEW-- >

{"lArr", "8656"}, / / leftwards double arrow, U+21D0 ISOtech-- >

/ /

{"uArr", "8657"}, / / upwards double arrow, U+21D1 ISOamsa-- >

{"rArr", "8658"}, / / rightwards double arrow,U+21D2 ISOtech-- >

/ /

{"dArr", "8659"}, / / downwards double arrow, U+21D3 ISOamsa-- >

{"hArr", "8660"}, / / left right double arrow,U+21D4 ISOamsa-- >

/ /

{"forall", "8704"}, / / forall, Utility 2200 ISOtech-- >

{"part", "8706"}, / / partial differential, Ubun2202 ISOtech-- >

{"exist", "8707"}, / / there exists, Utility 2203 ISOtech-- >

{"empty", "8709"}, / / empty set = null set = diameter,U+2205 ISOamso-- >

{"nabla", "8711"}, / / nabla = backward difference,U+2207 ISOtech-- >

{"isin", "8712"}, / / element of, Utility 2208 ISOtech-- >

{"notin", "8713"}, / / not an element of, Utility 2209 ISOtech-- >

{"ni", "8715"}, / / contains as member, Utility 220B ISOtech-- >

/ /

{"prod", "8719"}, / / n-ary product = product sign,U+220F ISOamsb-- >

/ /

{"sum", "8721"}, / / n-ary summation, Utility 2211 ISOamsb-- >

/ /

{"minus", "8722"}, / / minus sign, Utility 2212 ISOtech-- >

{"lowast", "8727"}, / / asterisk operator, Utility 2217 ISOtech-- >

{"radic", "8730"}, / / square root = radical sign,U+221A ISOtech-- >

{"prop", "8733"}, / / proportional to, Utility 221D ISOtech-- >

{"infin", "8734"}, / / infinity, Utility 221E ISOtech-- >

{"ang", "8736"}, / / angle, Utility 2220 ISOamso-- >

{"and", "8743"}, / / logical and = wedge, Utility 2227 ISOtech-- >

{"or", "8744"}, / / logical or = vee, Utility 2228 ISOtech-- >

{"cap", "8745"}, / / intersection = cap, Utility 2229 ISOtech-- >

{"cup", "8746"}, / / union = cup, Utility 222A ISOtech-- >

{"int", "8747"}, / / integral, Utility 222B ISOtech-- >

{"there4", "8756"}, / / therefore, Utility 2234 ISOtech-- >

{"sim", "8764"}, / / tilde operator = varies with = similar to,U+223C ISOtech-- >

/ /

{"cong", "8773"}, / / approximately equal to, Utility 2245 ISOtech-- >

{"asymp", "8776"}, / / almost equal to = asymptotic to,U+2248 ISOamsr-- >

{"ne", "8800"}, / / not equal to, Utility 2260 ISOtech-- >

{"equiv", "8801"}, / / identical to, Utility 2261 ISOtech-- >

{"le", "8804"}, / / less-than or equal to, Utility 2264 ISOtech-- >

{"ge", "8805"}, / / greater-than or equal to,U+2265 ISOtech-- >

{"sub", "8834"}, / / subset of, Ubun2282 ISOtech-- >

{"sup", "8835"}, / / superset of, Utility 2283 ISOtech-- >

/ /

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