Unified Expression Language

The Unified Expression Language Svetlin Nakov Borislava Spasova

Contents ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

What is Unified EL? ,[object Object],[object Object],[object Object],[object Object],[object Object],${some Bean .someProperty}

History of the EL ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

JSP and JavaBeans Using JavaBeans in a JSP Page

<jsp:useBean> ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],<jsp:useBean id="name" class="package.class" scope="page | request | session | application" />

<jsp:useBean> and Scope ,[object Object],[object Object],[object Object],[object Object],[object Object]

<jsp:useBean> – Example ,[object Object],[object Object],<jsp:useBean id="user" class="beans.User" scope="session" /> beans. User user = (beans. User ) session.getAttribute(" user "); if ( user == null) { user = new beans. User (); session.setAttribute(" user ", user ); }

<jsp:setProperty> ,[object Object],[object Object],[object Object],<jsp:setProperty name="user" property="firstName" value="Nakov" /> <jsp:useBean id="user" class="beans.User" scope="page" /> <jsp:setProperty name="user" property="firstName" value="Nakov" /> </jsp:useBean>

<jsp:getProperty> ,[object Object],[object Object],[object Object],[object Object],<jsp:useBean id="user" ... /> ... User login : <jsp:getProperty name="user" property=" login " /> User home page: <jsp:getProperty name="user" property="home P age" />

The Unified Expression Language

Why Do We Need EL? ,[object Object],[object Object],[object Object],[object Object],<jsp:useBean id="some Bean " class ="somePackage.someClass " scope="request, session, or application"/> ${some Bean .someProperty} <jsp:getProperty name="some Bean " property="someProperty"/>

EL and JavaBeans – Example <% String name = "Svetlin Nakov"; pageContext.setAttribute("name", name); %> Name: ${name} <br /> <% User user = new User( "snakov", "Svetlin", "Nakov"); pageContext.setAttribute("user", user); %> User first name: ${user.firstName} <br /> User last name: ${user['lastName']} <br /> User login: ${user["login"]} <br />

Advantages of the EL ,[object Object],[object Object],[object Object],[object Object],${saleItem} ${collectionObject[indexOrKey]}

Advantages of the EL (2) ,[object Object],[object Object],[object Object],${company.companyName} ${company.president.firstName}

Advantages of the EL (3) ,[object Object],[object Object],[object Object],${param["username"]} ${cookie["dateOfLastVisit"]} ${ ( 2 + 5 ) * 3 } ${visitors. t otal C ount - 1} ${empty userBean}  true / false ${empty userBean ? "N/A" : "user found"}

Advantages of the EL (4) ,[object Object],[object Object],[object Object],[object Object],[object Object]

How Scoped Variables Are Accessed? ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],${someBean}

How Bean Properties Are Accessed? ,[object Object],[object Object],[object Object],${customer.firstName} <%@ page import="beans.Customer" %> <% Customer customer = (Customer) pageContext.findAttribute("customer"); %> <%= customer.getFirstName() %>

How Collections Are Accessed? ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],${someCollection[entryName]} ${someCollection . entryName}

Referencing Implicit O bjects ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

EL Operators ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Conditional Evaluation ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],${condition ? expression1 : expression2}

Unified Expression Language in JSP and JSF

Types of Expressions ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Immediate and Deferred Evaluation ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],${user.firstName} # {user.firstName}

The Unified Expression Language (Unified EL) ,[object Object]

Problems ,[object Object],[object Object],[object Object]

Homework ,[object Object],[object Object]

Unified Expression Language

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Editor's Notes