EL表達(dá)式從哪里取值？一般情況下，從作用域?qū)ο笾腥≈?br>

${a}

EL表達(dá)式優(yōu)先從哪個(gè)作用域?qū)ο笾腥≈担磕J(rèn)情況下從最小作用域取值

${scope}

EL表達(dá)式從指定作用域?qū)ο笾腥≈担簆ageScope、requestScope、sessionScope、applicationScope

${pageScope.scope} --- ${requestScope.scope} --- ${sessionScope.scope} --- ${applicationScope.scope}

EL表達(dá)式可以解析什么類型的數(shù)據(jù)？基本數(shù)據(jù)類型、對(duì)象類型、復(fù)合對(duì)象類型、Map、List

${list[2]} --- ${map.address} --- ${user.realname} --- ${user.addr.town}

EL也可以取請(qǐng)求參數(shù)的數(shù)據(jù)：param、paramValues

${param.name} --- ${paramValues.fav[2]}

EL表達(dá)式的[]內(nèi)也可以做EL表達(dá)式的解析

${user.realname} --- ${user["realname"]} ---? ${user[param.type]}

EL表達(dá)式可以做為空判斷：空字符串、null、空map、空l(shuí)ist這幾個(gè)值為true

${empty aaa} --- ${empty bbb} --- ${empty ccc} --- ${empty ddd} --- ${empty scope}

EL表達(dá)式可以做基本的邏輯運(yùn)算，和數(shù)學(xué)運(yùn)算

EL表達(dá)式?jīng)]有字符串拼接的概念，也沒(méi)有字符的概念

${5+4} --- ${5-4} --- ${5*4} --- ${5/4} --- ${5%4} --- ${5+"4"} ---

${5>4} --- ${5 < 4} --- ${5>=4} --- ${5 le 4} --- ${5 eq 4}

EL表達(dá)式中pageContext可以獲取pageContext作用域?qū)ο蟊旧?/h4>

${pageContext}