[JSP] Expression Language(EL) 的使用

前置準備

package model;
public class Bean {
 public String name = "今天禮拜四。";
 public String getName() {
  return name;
 }

 public void setName(String name) {
  this.name = name;
 }
}

一般

<%
 Date date = new Date();
 String DateStr = new SimpleDateFormat("yyyyMMdd").format(date);
 pageContext.setAttribute("DateStr",DateStr);
%>


${DateStr}

物件

<% 
 /**物件**/
 Bean bean = new Bean();
 pageContext.setAttribute("bean", bean);
%>

${bean.name}

${bean["name"]}

${bean.getName()}

Null

<%
 /**Null**/
 String myNull = null;
 bean = null;
 pageContext.setAttribute("myNull", myNull);
 pageContext.setAttribute("bean", bean);
 
%>

myNull =  ${myNull}

myNull =  ${bean}

判斷

<%
 /**判斷式**/
 String str = "AAAA";
 String str1 = "AAAA";
 String str2 = "BBBB";
 pageContext.setAttribute("str", str);
 pageContext.setAttribute("str1", str1);
 pageContext.setAttribute("str2", str2);
%>

${str == str1}

${str2 == str1}

容器的使用

<%
 /**容器的使用**/
 ArrayList list = new ArrayList();
 list.add("AAA");
 list.add("C");
 list.add("C");
 list.add("DDDD");

 Map map = new HashMap<>();
 map.put("s1", "AAAA");
 map.put("s2", "BBBB");
 
 pageContext.setAttribute("map", map);
 pageContext.setAttribute("list", list);
%>

${map["s1"]}

${list["0"]}

cookie

<%
 /**處理cookie**/
 Cookie[] cks = request.getCookies();
 Cookie ck = new Cookie("SJ","aBCD");
 response.addCookie(ck);
 
 
%>


${cookie.SJ.value}

其他參考