server-side Web development with JAVA servlet and JSP

Following Topics/Concepts have been covered in this project:

Lesson 2: Background

Web Containers:

Software to generate request and responses
Listening and responding
- Receives request via a url
- parse URL
- Retrieve response page
- Run code within the response page to dynamically generate html version of response
- Send response to client
WCS runs on a web server listening for web URL via particular port

IDE

Tools for editing/compiling code, running/debugging
Integrated database
NB includes Glassfish/Tomcat
Can run both client and server
Run the page in IDE
IDE starts the browser, loading the page
Request sent to the port in the computer using localhost
Run web containers
IDE sends response to browser
client/server development

NetBeans/JDK

JAVA EE contains Tomcat and Glassfish
JDK 8.2/NetBeans 8.2

Model View Control Paradigm:

Model View Control (MVC) Architecture use to design most large scale websites A request is sent to a component that acts as a control, which then determines what types of views/web-pages to generate. Oftentimes, control and views interact with another component called Model, which in turn sometimes incorporate database This generates the final response Used by most frameworks eg. Grails

Control:

Implementing control logic to determine what happens next, Categorizing the request information Databases, legal/illegal Once the control categorizes the request, it determines which views to send Control is written with java servlets View Represents the user interface One view for each page Dynamically generated Implemented as Java server pages Model Implement as Business logics Supports the organizational logic Use separate software classes to store and manipulate the data or the information Often Interacts with the database Used by control to determine which views to respond Implementation in Java based System Loan Calculator

Loan Calculator Example

Requirements
Enter info
Validation
Use info to compute payment
display

What are the views, model components of the Loan Calculator example?

HTML FORM TAGS

The form tag:

Defines values for element, url, and method

<formaction =””method=””>
…
</form>

GET vs. POST methods:

GET:
- Default method
- Appends form data at the end of URL
- Faster
- No limit to the form data passed
- Allows bookmarking of pages
POST:
- Must specify in FORM
- Form data is not visible
- Isn’t the fastest method
- Data passed is limited to 4K
- Prevents bookmarking

Input Tags

<inputtype=””name=””value=””/>

type
- text
checkbox (default not checked)
- checked = “true”
radio
- value = what is sent to server
- selected = “true”

<inputtype=”radio”name=”courseprefix”value=”CSIS”checked=”true”/>CSIS
<inputtype=”radio”name=”courseprefix”value=”CSCI”/>CSCI
<inputtype=”radio”name=”courseprefix”value=”INFO”/>INFO

Select/Option Tag
- Use to create the dropdown menu

<Selectname=”coursehours”><optionvalue=”1”>1</option><optionvalue=”2”selected=”true>2</option> //default selected
</select>

Submit Button
- Value attribute displays the label displayed in the button

<inputtype=”submit”value=”SUBMIT”/>

Form Submission
- Values of all the element in the form are submitted in the format of [element name = element value]. This can be checked on link when using the GET method
FORM elements and Requests
- Data is appended at the end of URL in GET method
Submitted values by Element
- txt: value entered by the user; NULL if nothing is entered
- radio: value of the element selected by the user
- select/option: name of the select option and value of the option is used
  - Eg. coursehours=4
checkbox:
- “on” if checked/nothing if not checked

Lesson 3. JAVA Server Pages

Intro to Java Server Pages:

JSP Syntax:

 <% … %>
<%= someJavaexpression%>

Example: Two plus two is <%= 2+2%>.

Scriplets:

- ```<% ----- %>```

Executes Java code without generating html
Extract values of form elements
store/access values in databases

<html><body><% int sum = 2+2;%><p>
Two plus two is <%= sum%>.
</p></body></html>

Dynamica Example:

<%
Date now = new Date();
String nowString = now.toString();
%><p>The current date and time is <%=nowString%>.</p>

Importing Classes:

<%@Pageimport=”java.util.Date”
%>

Documentation:

Comments:

JSP:
```
 // comment
/* comment */
```
HTML:
```
 
```

The Request Object:

Advanced Request Handling:

Lesson 3. JAVA Server Pages

Introduction to Servlets
Servlet Class Structure
- Key Methods:
- void doGet(, )

Lesson 4. Entity Classes and JSTL

Entity Classes

Java Classes or Java Beans

NetBeans - Create Class (include in the package) With properties or attributes or member variables that can be gettable/settable These properties should not be named after SQL reserved words if using the SQL database Each member should have getter and setter method

publicdoublegetPrinciple () {
returnprinciple;
}
publicdoublesetPrinciple (doubleapr) {
this.apr = apr
}

Constructors

can be automatically inserted using alt+insert.

Servlet example (Loan.java)

// get parameters values and covert to numbersdoubleamount = Double.parseDouble(request.getParameter("principal"));
doublerate = Double.parseDouble(request.getParameter("apr"));
intmonths = Integer.parseInteger(request.getParameter("months"));
// construct the new loan object from the paramters and add to RequestLoanloan = newLoan(amount, rate, months);
request.setAttribute("loan", loan);
// Forward to next pagegetServletContext().
getRequestDispatcher(nextPage).
forward(request, response);

Expression Language - EL

A way of manipulating entity objects within server pages
- separate user interface design from Coding
  - Server Pages (.jsp) - User Interface: getAttribute(attributename)
  - Servlets/Model Classes (.java) - Model-based Domain ${attributename}
Provides direct access to attribute in JSP without having to use get method

Syntax:

${attributename}

${objectname.variablename}

must have a getter method getVariablename in the Entity class
and a model object objectname constructed by the Servlet added to the request see example below:

Servlet:

doubleamount = Double.parseDouble(request.getParameter("principal"));
doublerate = Double.parseDouble(request.getParameter("apr"));
intmonths = Integer.parseInteger(request.getParameter("months"));
// construct the new loan object from the paramters and add to RequestLoanloan = newLoan(amount, rate, months);
request.setAttribute("loan", loan);

Server Page:

<tableboarder="1"><tr><td>Loan Amount</td><td>${loan.principal}</td><!-- invokes loan.getPrincipal() --></tr><tr><td>Annual Percentage Rate</td><td>${loan.apr}</td></tr>

EL is mostly used to display the values computed in the Entity class

JSTL - JSP Tag Library

- Simplifying Coding in JSPs
- JSTL conditional TAGS
- EL Conditions
- Simple if statements
- multiple options conditional statements
- JSTL iteration tags

Goal - replace complex java servlets code with tags
Mostly used for conditions and iteration
Syntax: <c:tagname attributes ...

Must be imported at the start of JSP:

<%@taglibprefix="c"uri="http://java.sun.com/jsp/jstl/core" %>

EL Conditions

JSTL conditional statements are based on relational operations
Format: ${condition}
- Conditions usually involves EL attributes
- Relational Operators have both Java and letter syntax *****
- to check an empty string for var x:empty x

Conditional Tags

simple if:

You will pay $ ${loan.payment} each month for ${loan.months} month<c:iftest="${loan.months != 1}">s</c:if>.

Multiple Selection:

<c:choose><c:whentest="${loan.months} == 1">
month
</c:when><c:otherwise>
months
</c:otherwise></c:choose>

Iteration Tag:

Servlet:

String[] stoogeArray = newString[] {"Larry", "Curley", "Moe", "Shemp"};
request.setAttribute("stooges", stoogeArray);

Server Page:

<c:forEachvar="stooge" items="${stooges}">
${stooge}<br/></c:forEach>

Lession 6. Session Handeling

Intro to Session Handling

Semester Project

class Racket: String brandName String famName String famDescription Family [] Rackets class Version extends Racket: String ID String version double price String description String headSize double weight double swingWeight double balance String stringPattern String picture double rating String[] players // constructor // getters // setters

Lesson 7. User Interface Design

Modular and Uniform User Interface Design

the idea that the pages on same site should have "same look and feel"
can be achieved by using "template"
template defines the content universal to sections of pages
by using separate files for different section of the page that are shared across the site
such as Logo.html, Navbar.html, Footer.jsp, Header.jsp etc.
These are called "Static elements" because they do not change over user session
Syntax: <%@ include file ="/relative file url" %>

<header><%@ include file="/Logo.html" %></hader><nav><%@ include file="/Navbar.html"></nav>

Sometime we have to incorporate dynamic values in these static elements
Syntax: <c: import url="relative url" />

<!--File: Footer.jsp--><c:choose><c:whentest="${empty username}"><formaction='setName'>
Name: <inputtype="text" name='username'><inputtype="submit" value="GO"/></form></c:when><c:otherwise><c:outvalue="Hello ${username}"/></c:otherwise></c:choose>

<!-- code to include Footer.jsp--><footer><c:importurl="/Footer.jsp" /></footer>

Note that there is different syntax for static and dynamic resources
Using template.jsp for all pages:

<!-- FILE: template.jsp--><html><head><linkrel="stylesheet" type="text/css" href="template.css"></head><body><header><%@ include file="/Logo.html" %></header><nav><%@ include file="/Navbar.html"%></nav><article>
INSERT PAGE CONTENT HERE!
</article><footer><c:importurl="/Footer.jsp" /></footer></body></html>

Lesson 8. Entity Class Design and Shopping Carts

Displaying list of Entity objects

Displaying a list of items

In MVC architecture

LIST as well should be an entity object
- usually Array or an dynamic ArrayList
- With getter that returns the list
the list then can be accessed in the server pages
- can be looped using JSTL
take a look at the following two classes

publicclassCourse {
privateStringcourseprefix = "";
privateStringcoursenumber = "";
privateStringcoursename = "";
privateintminhours = 0;
privateintmaxhours = 0;
privatebooleanproject = false;
publicCourse(Stringcourseprefix, Stringcoursenumber, Stringcoursename, intminhours, intmaxhours, booleanproject) {
this.courseprefix = courseprefix;
this.coursenumber = coursenumber;
this.coursename = coursename;
...
}
}
publicclassCourseArray {
Courses [] courses;
publicCourseArray () {
courses = newCourse[3];
... // put three made-up course objects in the array
}
publicCourse [] getCourses() {
returncourses;
}
}

**Setting Up the ArrayList **
- the ArrayList object is created and added to the session as attribute in the servlet

Preloading Entity Objects

how to automatically create session objects if they don't exist
session objects are created in servlets, it's our job to make sure that this servlet is get called when the user first enters the site

HttpSessionsession = request.getSession();
if (session.getAttribte("coursearray") == null) {
CourseArraycourses = newCourseArray();
session.setAttribute("coursearray", courses)
}

user enters the site -- index.html
- home page redirects to the servlet
- checks the session to see if an object exists
- if the object doesn't exist then an object is created in the session
- user is redirected back to home page
- note that this is all back-end process
We can use the redirect JSTL tag for redirection
This is best practiced in the conditional if tag to check if the object already exists in the session.
```
<c:iftest="${empty coursearray}"><c:redirecturl="GetCourseArrayServlet"/></c:if>
```
Here, we simply first check to see if coursearray object already exist, if not then we redirect to GetCourseArrayServlet servlet to create a new session object

Selecting from Lists

We use type="hidden" form element to pass form data that the user doesn't set directly, eg. passing data when selecting the button.

<input type="hidden" value="somevalue"/>

<c:forEachvar="courses" items="${coursearray.courses}"><tr><td>${course.courseprefix} ${course.coursenumber}</td><td><formaction="GetCourseServlet"><inputtype="submit" value="Details"/><!--this can be seen in the table--><inputtype="Hidden" name="prefix" value="${course.courseprefix}"/><!--this can not be seen in the table--><inputtype="hidden" name="number" value="$course.coursenumber"/></form></td></tr></c:forEach>

The efficient method for hidden tag is using the link
Instead of buttons, we can append the data in the link

Here, when selecting the link we append course prefix and number to the request url

<c:forEachvar="course" items="${coursearray.courses}"><li><ahref='GetCourseServlet?prefix=${course.courseprefix}&number=${course.coursenumber}'>
${course.courseprefix} ${course.coursenumber}
</a></li></c:forEach>

Dynamic Lists and Shopping Carts

ArrayList class

import java.util.*;
ArrayList<type> a = new ArrayList();
public void set(index, object);
public Object get(index);
public int size();
// OutOfBounceException
public void add(object);
public void add(index, object); // shifts to right
public object remove(index);
public object remove(object);

Displaying Shopping Carts

Inout Validation and Error Pages

Validation Concepts

Error
- detection
- correction
- prevention

Validation and the MVC Architecture

Displaying Error Messages

Create a ErrorList model class

it should have all the scenarios of error validation set to false
create getter and setters for each scenarios

// A model class to handle all the ErrorspublicclassRacketErrorList {
privatebooleanNameMissing = false;
privatebooleanpriceNotNumeric = false;
privatebooleanpriceNegative = false;
...
// getters// setters
}

Create a Error validation model class (eg. RacketValidation) that contains static methods to handle the errors

// methods to handle the errorspublicclassRacketValidation {
publicstaticbooleanvalidateName(Stringname, RacketErrorListerrors){
// validation code
...
}
}

Now, on the servlet, create a new error object and pass it to each validation method

RacketErrorListerrors = newRacketErrorList();
booleanisNameValid = RacketValidation.validateName(name, errors);

Finally, pass the errors object to JSP
```
request.setAttribute("errors", errors);
```

Now, this errors object can be used in JSP to check all the scenarios of validation defined in the ErrorList model class.

 price: <inputtype="text" name="name" value="${param.price}"/><c:iftest="${errors.priceNotNumeric}">
Racket price must be a positive number.
</c:if><c:iftest="${errors.weightNegative}">
Weight should not be negative.
</c:if>

- Validating Required Fields
- Validating Numeric Fields

Validation Using Regular Expression

characters must match exactly
- a only matches a
. matches any single character eg. a, Z, 7 etc.
specialized characters can be escaped using backslah
- \. is a period
[] includes matches that are allowed
- [aeiou] matches any vowel
^ lists the characters that are not allowed
- [^aeiou] matches only non-vowel
- ranges of characters
- [a-z] allows all lowercase character
can combine multiple ranges
- [a-f2-6] matches any character btween a to f and any number between 2 to 6
\d : any digits 0-9
\w : "word" character a-z, A-Z, 0-9
\s : space character , tab, return
\D : non-digit
\W : non-"word" character
\s : non-"space" character
If P and Q are regular expression:
- PQ : Regex P and Q must occur in sequence
  - eg. 1a matches \d\w
- P|Q : regex P OR Q
  - eg. A or 1 matches \d|\w
- () used to group expressions
  - eg. (\d\d|\s) matches either 2 digits in a row or a space
P* : P can occur any number of time including 0
P+ : P mist occur at least once
P{i} : P must occur exactly i times
P{i, j} : P must occur between i and j times
Examples
- Credit card number: \d{15,16}
- Phone Number: \d{3} - \d{3}-\d{4}
- Email: \w+@\w+(\.\w+)+

Echoing Fields Values

<inputtype="text" name="name" value="${param.name}"/>

Database Manipulation

Intro to server-side database

Database Servers

Intro to JDBC

JDBC Queries

publicclassRacketList {
publicstaticvoidloadRacket () {
Connectionconnection = null;
Statementstatement = null;
ResultSetresults = null;
try {
// load the database driverClass.forName("org.apache.derby.jdbc.ClientDriver").newInstance();
// connect to the database using the driverconnection = DriverManager.getConnection("jdbc:derby://localhost:1527/DBname", "app", "app");
}
catch (SQLExceptionex) {
System.out.println("Connection failed");
}
catch (Exceptionex) {
System.out.println("No Driver!")
}
try {
// create a statement from the connectionstatement = connection.createStatement();
// get all the records from the database results = statement.executeQuery( "select * from RacketList" );
while ( results.next() ) {
Stringname = results.getString("name");
Doubleprice = results.getDouble("price");
Intsize = results.getInt("size");
...
Racketr = newRacket(name, price, size, ... );
rackets.add(r);
}
}
catch (SQLExceptionex) {
}
}
}

Parameterized SQL and Prepared Statements

publicclassRacketList {
publicstaticvoidsaveCourse ( Stringname, Doubleprice, Intsize ) {
Connectionconnection = null;
PreparedStatementstatement = null;
ResultSetresults = null;
try {
// load the database driverClass.forName("org.apache.derby.jdbc.ClientDriver").newInstance();
// connect to the database using the driverconnection = DriverManager.getConnection("jdbc:derby://localhost:1527/DBname", "app", "app");
}
catch (SQLExceptionex) {
}
catch (Exceptinoex) {
}
try {
// create a template to insert data into database// use ? in place of actual valuesStringtemplate = "insert into Rackets " + "(brand, family, version, price, ...) " + "values (?, ?, ?, ?, ...)";
// pass the template to database Serverstatement = connection.prepareStatement(template);
// replace the ? with actual valuesstatement.setString(1, brand);
statement.setString(2, number);
statement.setDobule(4, prce);
...
// execute the final sql statement on databasestatement.executeUpdate();
}
catch (SQLException) {
}
catch (Exceptino) {
}
}
}

publicclassRacketValidation {
publicvoidvalidateRacket(Stringid) {
}
}

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README.md		README.md

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server-side Web development with JAVA servlet and JSP

TOC

Lesson 2: Background

Web Containers:

IDE

NetBeans/JDK

Model View Control Paradigm:

Control:

HTML FORM TAGS

The form tag:

GET vs. POST methods:

Input Tags

Lesson 3. JAVA Server Pages

Intro to Java Server Pages:

Scriplets:

Importing Classes:

The Request Object:

Advanced Request Handling:

Lesson 3. JAVA Server Pages

Lesson 4. Entity Classes and JSTL

Entity Classes

Constructors

Servlet example (Loan.java)

Expression Language - EL

JSTL - JSP Tag Library

EL Conditions

Conditional Tags

Lession 6. Session Handeling

Intro to Session Handling

Lesson 7. User Interface Design

Modular and Uniform User Interface Design

Lesson 8. Entity Class Design and Shopping Carts

Displaying list of Entity objects

Preloading Entity Objects

Selecting from Lists

Dynamic Lists and Shopping Carts

Displaying Shopping Carts

Inout Validation and Error Pages

Validation Concepts

Validation and the MVC Architecture

Displaying Error Messages

Validation Using Regular Expression

Echoing Fields Values

Database Manipulation

Intro to server-side database

Database Servers

Intro to JDBC

JDBC Queries

Parameterized SQL and Prepared Statements

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