Use Java Server Pages(JSP) to develop web based applications in simple and easy steps.
Start from the beginning, learning the fundamentals of JSP, Directives, and Standard Actions
Next, explore Java Standard Tag Library, Expression Language, Using Custom Tags, and Projects.
Finally, tackle Project Development using the above topics (Check LearnToday Project https://github.com/ZUBOGU/LearnToday).
Java Server Pages is a technology that helps software developers to create platform independent dynamic web applications rapidly based on HTML or XML document types.
limitations of servlets:
Requires strong knowledge of Java
Writing HTML code will be difficult
Need to recompile & redeploy
Advantage of Using JSP:
Not mandatory to have a strong programming knowledge.
Writing the HTML code in JSP program is easy and it is similar to HTML.
Modifications done to the JSP is recognized automatically and immediate.
JSP programs are by default thread safe.
JSP programs can use standard tags, we can create our own custom tags using tag extension API.
Easy to learn, implement, and to maintain JSP pages.
Pros:
Development will be easy and faster
Cons:
Not suitable for large-scale application development
No Separation of Concerns
Maintenance will be problem
Model: hold business logic and the state, retrieving and update the data. Talks to the DB.
View: presentation.
Controller: tell the model to update itself and make the model state available for the view.
JSP - controller and view. Java Components - model.
Servlet - Controller. JSP - View. Java Beans - model.
Pros:
Navigation Control Centralized
Follows Industry Standard
Easy to Maintain
Better Separation Of Concern
Parallel Development
Cons :
Need to Recompile the Servlet Class
JSP expressions are used to compute an expression and the result of that is included in HTML page that's returned to the browser.
<p> current date and time
<%=
new java,util.Date()
%>
<p>
This is a out.write() in _jspService(...) java class.
Syntax: to define the declaration tag
<%!%>
<%! int id = 10; %>
This is a declaration(method or variable) in demo_jsp.java class.
Scripting Element which allows us to add any variable declaration and any computed logic with in the JSP page. It cannot have any method.
Syntax
<%
// Java Code Block1
%>
This is a variable or computed logic inside _jspService(...) method of demo_jsp.java class.
The directives of JSP are used to provide some meaningful information about the current JSP page to the JSP Container which will be required during the Translation phase.
Syntax: Define a page directive
<%@ page attribute="value" attribute="value" ... %>
Can use multiple page directives. Cannot specify same attribute more than once(exclude import).
language="scripting language"
extends="className"
import="importList"
session="true|false"
buffer="none="none|sizekb"
autoFlush="true|false"
info="info_text"
contenetType="ctinfo"
errorPage="error_url"
isErrorpage="true|false"
<%@ page language="java" %>
<%@ page import="java.sql.*, java,util.*" %>
<%@ page import=“java.sql.*”,import=“java.util.*”%>
<%@ page info="this is home page" %>
<%@ page extend="this is home page" %>
<%@ page contentType="text/html" %>
<%@ page isELIgnored="true" %> // expression language
<%@ page isThreadSafe="true" %>
<%@ page pageEncoding="UTF-8" %>
<%@ page session="false" %>
<%@ page buffer="10kb" %>
<%@ page autoFlush="true|false" %>
will specify the JSP Container to read the specified file and merges its contents into the JSP source code currently being parsed at the Translation phase Include Directive
<%@ include file="filename"%>
<%@ include file="header.jsp"%>
Set of custom tags
Identifies the location of the library
Identifying the custom tags
Syntax: To Define the taglib directive
<%@ taglib uri="uriofTagLibrary" prefix="prefixOfTag"/%>
<%jsp:directive.tagliburi="uri" prefix="prefixOfTag"/%>
Request Object Methods
setAttribute
getAttribute
getCookies()
getHeaderNames()
getHeader(string name)
getMethod()
getParameter(string name)
getQueryString(string name)
getLocale()
setIntHeader(String name,Intvalue)
response.setHeader("Refresh",5)
setContentType(String type)
response.setContentType("text/html")
sendRedirect(String location)
response.sendRedirect("sucess.jsp")
addCookie(Cookie cookie)
response.addCookie(userCookie)
In Servlets
Prinitwriterout =response.getWriter();
In JSP
Out [BuiltinObject]
jspWriterout=pagecontext.getout()
Throws IOException
Out Built-in Object Methods
print
printIn
flush
Syntax to display the current date and time
out.print("Today is:"+java.util.Calendar.getInsatance().getTime());
Important Methods to PageContext
setAttribute
getAttribute
findAttribute
removeAttribute
<%Float no1=newFloat(62.5)%>
<%pageContext.setAttribute("no1“,no1);%>
<%pageContext.getAttribute("no1“,no1)%>
<%Float no2=newFloat(84.3)%>
<%pageContext.setAttribute
("no2“,no2,PageContext.”SESSION_SCOPE");%>
<%pageContext.getAttribute
("no2“,PageContext.”SESSION_SCOPE");%>
Session Builtin Object
setAttribute( String name,Objectvalue)
getAttribute(String name)
removeAttribute(String name)
Syntax To set the session
<%pageContext.setAttribute
("no",value,PageContext.SESSION_SCOPE); %>
<%session.setAttribute("no",value)%>
javax.servlet.ServletContextapplication=pageContext.getServeltContext()
Syntax
application.setAttribute(String name,Object value) // To Set
application.getAttribute(String name) // To Read
Config build in object is used for getting configuration information for a particular JSP page. Config Implicit Object
getInitParameter(String name)
getInitParameterNames()
getServletContext()
getServletName()
Try-Catch Block
isErrorPage and ErrorPageattribute
<error-page> tag
Syntax To Declare an Error Page for All Type of Exception
<error-page>
<exception-type>java.lang.Throwable</exception-type>
<location>/error.jsp</location>
</error-page>
Syntax To Declare an Error Page for More Detailed Exception
<error-page>
<exception-type>java.lang.ArithmeticException
</exception-type>
<location>/error.jsp</ location>
</error-page> </error-page>
Syntax To Declare an Error Page for Based on HTTP Error Status Codes
<error-page>
<error-code>404</error-code>
<location>/error.jsp</location>
</error-page>
JSP Standard Actions
<jsp:include> <jsp:forward> <jsp:param> <jsp:useBean> <jsp:setProperty> <jsp:getProperty> <jsp:plugins> <jsp:fallback> <jsp:attribute> <jsp:body> <jsp:invoke> <jsp:element> <jsp:text>
Syntax
<jsp:include page="url flush=“true| false"/>
What is the difference between include action and include directive?
Include directive (<%@include%>)
Copies the code from one page to another page
Copies the code during the translation time
Generates only one Servlet
Static Binding
Include action (jsp:include)
Copies the results from one page to another page
Copies the output during the runtime
Generates two Servlets Performs
Dynamic Binding
<jsp:forward=getRequestDispatcher().forward()
JSP page must be buffered to use a <jsp:forward > tag
Syntax
<jsp:forward page="url"/>
Compare <jsp:forward>
Direct communication between source and destination pages
Uses same request and response object
Source and destination pages should belong to same application
Sendredirect
Indirect communication between source and destination page
Uses separate request and response object
Can be in one same application / different application / same server / different server
Sytax
<jsp:param name="..." value="..."/>
Used as a sub-tag for include,forward or plugin action
UseBean action is a way for declaring and initializing the actual java bean component object.
What is JavaBean?
Class must be public. Have 0 argumnet constructor. variable declared inside are called as bean properties. All the bean propertieshsould bedeclared private. Bean property must be specift a setter and getter methods and public. Class must implement serializable interface.
Sample Java Class
package com.learntoday.model;
import java.io.Serializable;
@SuppressWarnings("serial")
public class Name implements Serializable {
private String firstName;
private String lastName;
public Name(){ }
public void setFirstName(String fname){
this.firstName = fname;
}
public String getFirstName(){
return this.firstName;
}
public void setLastName(String lname){
this.lastName = lname;
}
public String getLastName(){
return this.lastName;
}
}
Syntax:
<jsp:useBean attributes/>
Attributes:
id
class
scope
page
request
session
application
type
beanName
Syntax:
<jsp:setProperty name= "..." property="propertyName|*" value="..."param="..."/>
setProperty
<jsp:useBean id="nameBean" class="com.model.Name" scope="session">
<jsp:setProperty name="nameBean“ property="firstName“ params="firstName"/>
<jsp:setProperty name="nameBean“ property="lastName“ params="lastName"/> </jsp:useBean>
If the params and properties name match
<jsp:useBean id="nameBean" class="com.psdemos.model.Name" scope="session">
<jsp:useBean id="nameBean“ property="*"/> </jsp:useBean>
Syntax:
<jsp:getProperty name="..." property="..."/>
In another JSP page, Without scope session, inside useBean and outside useBean's getProperty is returning null.
With scope session, inside useBean is returning null and outside useBean getProperty is returning value.
Syntax:
<jsp:plugin type="bean | applet " code="..."codebase="...">
<jsp:params>
<jsp:param name="..." value="...">
</jsp:params>
</jsp:plugin>
<jsp:fallback>
used to provide some meaning information to the client's browser if the requested plugin cannot be started Optional attributes type,align,height,width,name,title
Syntax
<jsp:element> without a body
<jsp:element name="elementName"/>
<jsp:element> with a body
<jsp:element name="elementName">
<jsp:attribute>...</jsp:attribute>
<jsp:body>...</jsp:body>
</jsp:element>
Expression Language Fundamentals
Introduced from JSP 2.0
Accessing data from a JavaBean,Request,Response,Session,Applic ation
*, +, - , () , [ ] and < or It, > or gt , ! or not
Null Friendly Language
Syntax:
$ { expression }
EL Advantages
More information using simple expression
Easy to access or modify Bean Properties
Access Nested Property
Collection Elements
Provides Math and Conditional Operators
Supports Automatic Type Conversions
Syntax: Deployment Descriptor Element
<jsp:config>
<el-ignored> true | false </el-ignored>
</ jsp:config>
Syntax: With in Page directive
<%@page isELIgnored="true | false" %>
Arithmetic Operators Logical Operators Relational Operators Reserved words such as true,false,null,empty
EL-Implicit Objects
pageContext Object
- ${ pageContext.request.queryString}
header object
- $[header["user-agent"]
headerValue
scope object
pageScope
reuestScope
sessionScope
applicationScope
param
paramValues
initParam
cookie
Syntax To access the Java Bean property
${course.courseName} ${reuestScope.course.courseName}
Access Nested Property
$(requestScope.person.car.carName)
JSTL Features
Loop
Condition Execution
Database Access
Internationalization
XML Processing
Core Tags
Formatting Tags
Database Tags
Functions Tags
XML Tags
Syntax JSTL Core tags
<%@taglib prefix="c“ uri="http://java.sun.com/jsp/jstl/core" %>
<c:out> <c:set> <c:remove> <c:catch> <c:if> <c:choose> <c:when> <c:otherwise> <c:import> <c:foreach> <c:forTokens> <c:param> <c:redirect> <c:url>
Syntax To use the JSTL Formatting tags
<%@taglib prefix="fmt" uri=" http://java.sun.com/jsp/jstl/fmt " %>
<fmt:formatNumber> <fmt:parseNumber> <fmt:formatDate> <fmt:parseDate> <fmt:bundle> <fmt:setLocale>
<fmt:setBundle> <fmt:timeZone> <fmt:setTimeZone> <fmt:message> <fmt:requestEncoding>
Syntax To include the JSTL SQL tag library
<%@ taglib prefix="sql" uri ="http://java.sun.com/jsp/jstl/sql" %>
<sql:setDataSource> <sql:query> <sql:update> <sql:param> <sql:dateParam> <sql:transaction>
Syntax To include the JSTL Function tag library
<%@ taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/function" %>
fn:contains fn:containsIgnoreCase fn:endsWith fn:idexOf fn:join fn:length
fn:split fn:stratsWith fn:substring fn:toUpperCase fn:toLowerCase fn:trim
Types of Tag Handlers: Simple Tag Handlers and Classic Tag Handlers.
Create a Custom Tag
Create a Tag Handler Class
Create a Tag Library Descriptor (tld file)
Create A JSP page
Tag with Body Tag with Attributes