SE 452 Lecture Notes

Week 6: Using Java Beans With JSP & Introduction to Ant

Admin Stuff [1/11]
Finish JSP Includes From Last Week [2/11]
A Little Background Regarding Reflection [3/11]
Reflection Sample Code [4/11]
JavaBeans [5/11]
Using Java Beans in JSP [6/11]
Set and Get Bean Properties [7/11]
Bean Sample Code [8/11]
Ant Build and Deploy Tool [9/11]
Intalling Ant [10/11]
build.xml [11/11]

Admin Stuff [1/11]

A couple of quizzes to hand back
3 Day Extension on homework.
- Due Saturday at 5:45
- But you have to meet the grader's new submission instructions that I emailed
- I'll e-mail my solution Saturday at 6
  - It's straight forward, but we'll go over next week w/ the JavaBeans added
- In the meantime any questions?
Extra credit
- Based on J2EE Design Patterns
- http://java.sun.com/blueprints/patterns/catalog.html
- Extra credit is to write a mini-app demonstrating the use of one of the J2EE design patterns
- Must use all original code
- You need to present it to me and be able to explain how your code implements the pattern and the value of the pattern
- You can do up to 3 patterns worth 35 points a piece
Any questions before the quiz

Finish JSP Includes From Last Week [2/11]

Intro JSP Slides
Printable Copy
This will conclued our use of the university notes, a bit too distracting to switch formats

A Little Background Regarding Reflection [3/11]

To understand JavaBeans we need to first get a handle on reflection
What does Java's reflection API allow you?
- Determine the class of an object.
- Get information about a class's modifiers, fields, methods, constructors, and superclasses.
- Find out what constants and method declarations belong to an interface.
- Create an instance of a class whose name is not known until runtime.
- Get and set the value of an object's field, even if the field name is unknown to your program until runtime.
- Invoke a method on an object, even if the method is not known until runtime.
- And more...
We just need the basics for this class
- If you're very interested you can pursue the subject further linked here

Reflection Sample Code [4/11]

java.lang.Class
- Every class has an associated java.lang.Class object
- The Class class gives us a tremendouse amount of information about a class
  - Information about classes at runtime
  - Names of fields, methods, and constructors
- Retrieving class objects
  - Class c = myObject.getClass();
  - Class c = java.lang.String.class;
  - Class c = Class.forName("java.lang.String");
- java.lang.reflect.Method
  - Used to obtain method's name, return type, parameter types, exceptions
  - Allows you to Method.invoke() the method

import java.lang.reflect.*; import java.util.Date; class SampleMethod { public static void main(String[] args) { Date d = new Date(); showMethods(d); } static void showMethods(Object o) { Class c = o.getClass(); Method[] theMethods = c.getMethods(); for (int i = 0; i < theMethods.length; i++) { String methodString = theMethods[i].getName(); System.out.println("Name: " + methodString); String returnString = theMethods[i].getReturnType().getName(); System.out.println(" Return Type: " + returnString); Class[] parameterTypes = theMethods[i].getParameterTypes(); System.out.print(" Parameter Types:"); for (int k = 0; k < parameterTypes.length; k ++) { String parameterString = parameterTypes[k].getName(); System.out.print(" " + parameterString); } System.out.println(); } } } SampleMethod.java

JavaBeans [5/11]

JavaBeans - standard component architecture for Java
- reusable
- self-contained
- customizable
- persistent
A object that conforms to a communication and configuration protocol, as prescribed by the JavaBeans specification
- JavaBeans are not EJBs(Enterprise Java Beans)
- The entire technology is very broad and beyond our scope
- For our class used to encapsulate data and business logic
We need to enforce the following requirements
1. Need a zero argument constructor
2. All fields should be private
3. All fields should have matching public accessors with specific naming conventions

Using Java Beans in JSP [6/11]

useBean JSP Action
Locates and instantiates a bean with a specified name and scope
Syntax or
id
- Attempts to locate a bean based on the the current id and scope
- If found, variable is initialized with reference to the bean, and the tag body is skipped
- If id does not exist instantiates new bean of typeSpec, and executes the tag body
scope
- The scope within which the object (bean) is available
- page
  - Default scope
  - Associated beans stored in pageContext predefined variable
- request
  - lasts for the request, very similar to page
  - Associated beans stored in request predefined variable
- application
  - Stored for entire application
  - Associated beans stored in ServletContext obtained by getServletContext()
- session
  - Session scope
  - Associated beans stored in session predefined variable
typeSpec options
- class: the class
- type: variable type

Set and Get Bean Properties [7/11]

getParameter
- property converted to toString()
setParameter
- expression can be any code, you can put scriplet code there

Bean Sample Code [8/11]

package myBeans; public class SimpleBean { private String theString = "hello, world!"; public String getTheString() { return theString; } public void setTheString(String theString) { this.theString = theString; } }
SimpleBean.java

<html><title>Simple Bean JSP</title> <%@page import="myBeans.SimpleBean" %> <body> <jsp:useBean id="simpleBeanPageScope" class="myBeans.SimpleBean" /> <jsp:useBean id="simpleBeanApplicationScope" class="myBeans.SimpleBean" scope="application" /> <jsp:useBean id="simpleBeanSessionScope" class="myBeans.SimpleBean" scope="session" /> <h1>Simple Beans Initial Page</h1> <ul> <li>Initial value of simpleBeanPageScope: <b><jsp:getProperty name="simpleBeanPageScope" property="theString" /></b> <li>Using scriplets for simpleBeanPageScope: <b><%= simpleBeanPageScope.getTheString() %></b> <jsp:setProperty name="simpleBeanPageScope" property="theString" value="<%= \"page scope\" %>" /> <li>After set for simpleBeanPageScope:<b> <jsp:getProperty name="simpleBeanPageScope" property="theString" /></b> <% SimpleBean simpleBean1Copy = (SimpleBean)pageContext.getAttribute("simpleBeanPageScope"); %> <li>Copy from page context: <b><%= simpleBean1Copy.getTheString() %></b> <jsp:setProperty name="simpleBeanApplicationScope" property="theString" value="<%= \"application scope\" %>" /> <jsp:setProperty name="simpleBeanSessionScope" property="theString" value="<%= \"session scope\" %>" /> <li>After set for simpleBeanApplicationScope: <b> <jsp:getProperty name="simpleBeanApplicationScope" property="theString" /></b> <li>After set for simpleBeanSessionScope: <b> <jsp:getProperty name="simpleBeanSessionScope" property="theString" /></b> </uL> <form id="theForm" method="post" action="/jjungman/servlet/myBeans.ForwardServlet"> <input type="hidden" name="from" value="initial" /> <input type="submit" value="Go To Servlet"/> </form> </body></html>
SimpleBeanJSP.jsp

package myBeans; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.RequestDispatcher; public class ForwardServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String address = null; if(request.getParameter("from").equals("initial")) { address = "/SimpleBeanJSP2.jsp"; } else { request.getSession().invalidate(); address = "/SimpleBeanJSP3.jsp"; } RequestDispatcher rd = getServletContext().getRequestDispatcher(address); rd.forward(request, response); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } }
ForwardServlet.java

<html><title>Simple Bean JSP 2</title> <%@page import="myBeans.SimpleBean" %> <body> <jsp:useBean id="simpleBeanPageScope" class="myBeans.SimpleBean" /> <jsp:useBean id="simpleBeanApplicationScope" class="myBeans.SimpleBean" scope="application" /> <jsp:useBean id="simpleBeanSessionScope" class="myBeans.SimpleBean" scope="session" /> <h1>Simple Beans Second Page</h1> <ul> <li>Value of simpleBeanPageScope: <b><jsp:getProperty name="simpleBeanPageScope" property="theString" /></b> <li>Value of simpleBeanApplicationScope: <b><jsp:getProperty name="simpleBeanApplicationScope" property="theString" /></b> <li>Value of simpleBeanSessionScope: <b><jsp:getProperty name="simpleBeanSessionScope" property="theString" /></b> </uL> <form id="theForm" method="post" action="/jjungman/servlet/myBeans.ForwardServlet"> <input type="hidden" name="from" value="second" /> <input type="submit" value="Go To Servlet"/> </form> </body></html>
SimpleBeanJSP2.jsp

<html><title>Simple Bean JSP 3</title> <%@page import="myBeans.SimpleBean" %> <body> <jsp:useBean id="simpleBeanPageScope" class="myBeans.SimpleBean" /> <jsp:useBean id="simpleBeanApplicationScope" class="myBeans.SimpleBean" scope="application" /> <jsp:useBean id="simpleBeanSessionScope" class="myBeans.SimpleBean" scope="session" /> <h1>Simple Beans Third Page</h1> <ul> <li>Value of simpleBeanPageScope: <b><jsp:getProperty name="simpleBeanPageScope" property="theString" /></b> <li>Value of simpleBeanApplicationScope: <b><jsp:getProperty name="simpleBeanApplicationScope" property="theString" /></b> <li>Value of simpleBeanSessionScope: <b><jsp:getProperty name="simpleBeanSessionScope" property="theString" /></b> </uL> </body></html>
SimpleBeanJSP3.jsp

code running

Ant Build and Deploy Tool [9/11]

ANT (originally stood for Another Neat Tool) is a free tool under GNU Licence
Written purely in Java for Java (but can be used for anything
Available at http://jakarta.apache.org/ant/
Good user manual here http://ant.apache.org/manual/
Allows developers to automate the repeated process involved in the development of J2EE application
- Compilation
- Archiving
- Deployment
Platfor independent unlike .sh or .bat

Intalling Ant [10/11]

Assume we downloaded and extracted Ant into C:\jakarta-ant-1.5.1 on some Windows box

We would need to create an environment variable
ANT_HOME=C:\jakarta-ant-1.5.1

And then add Ant to our path variable
set PATH=%PATH%;%ANT_HOME%\bin

To verify ant is installed our shell should now recognize the command Ant

C:\anttest>Ant
Buildfile: build.xml does not exist!Build failed

C:\anttest>

`build.xml` [11/11]

build.xml
Ant's configuration file
project: 3 standard fields
- name: Represents the name of the project
- default: Name of the default target to use when no target is supplied
  - You can have multiple targets that depend on one another
- basedir: Name of the base directory from which all path calculations are done
property:
- name: property name
- value: associated value
- can later reference value by name using this grammar ${name}
mkdir:
- dir: the directory to create
javac: Specified task in this instance
- srcdir: Files to compile
- destdir: Destination of compiled byte code
- degug: Tag for logging levels
- includes: All files to except this task
THE USER MANUAL ABOVE ILLUSTRATES MANY, MANY MORE OPTIONS

Let's do a very simple example

class test1{
public static void main (String args[]){

System.out.println("This is example 1");

}

}

Download the code of this example and unzip it in c:\
files will be unzipped in anttest directory
Run the Ant utility by going to c:\anttest\example1 and issuing ant command.
You will receive the following out put

C:\anttest\example1>ant
Buildfile: build.xml

build:

[javac] Compiling 1 source file to C:\anttest\example1\build\src

BUILD SUCCESSFUL

Total time: 4 seconds

C:\anttest\example1>