EL

Express Language: replace the function of <%= ..... %> in JSP.

The grammar of EL: ${ EL content }:

　　　　<%= 1+1 %>  equals ${ 1+1 }

Where to get the data via EL?

　　pageContext, request, session, application the four important domain object.

The following is a JavaBean class:

class Person{
  private String name = "pp";
  private String city;

  getter/setter;
}

To get the Person class's name String in the JSP:

 <%

　　Person p = new Person();

　　pageContext.setAttribute("p",p);

%>

name: ${p.name} <%-- the "." means call the getter method fo Person class --%>
name: ${p["name"]} <%-- has the same function --%>

Get the data in List:

<%
     List<String> list = new ArrayList<String>();
     list.add("aaa");
     list.add("bbb");
     list.add("ccc");
     
     pageContext.setAttribute("list", list);
      %>
      
     List:${list[1] }

 Get the data in Map:

<%
          Map<String,String> map = new HashMap<String,String>();
          
          map.put("a", "aaa");
          map.put("b", "bbb");
          map.put("c", "ccc");
          
          pageContext.setAttribute("map", map);
       %>

       Map:${map.a }

 .