web technologies - forms and actions
TRANSCRIPT
CIS – 274:Internet Programming
Lab Session #2
Forms and DB
T.A. : Aren ZomorodianE-Mail: [email protected] : aren.z
OutlineI
• Forms and Actions
II• Processing Form Data
VIII
• Request and Response Objects
III• Database
IV• DB Connectivity
V• Working With DB
VII• The Login Servlet
HTML forms are used to pass data to a server.
The most important form element is the input element.
The input element is used to select user information.◦ An input element can vary in many ways, depending on the type attribute. An
input element can be of type text field, checkbox, password, radio button, submit button, and more.
Text Field: <input type="text" name="firstname" />
Password Field: <input type="password" name="pwd" />
A Great Source to Lookup on: http://www.w3schools.com/
http://www.w3schools.com/html/html_forms.asp
Forms
The required action attribute specifies where to send the form-data when a form is submitted.
The method attribute specifies how to send form-data (the form-data is sent to the page specified in the action attribute).
<form action="form_action.asp" method="get"> First name: <input type="text" name="fname" /><br /> Last name: <input type="text" name="lname" /><br /> <input type="submit" value="Submit" /></form>
Form Actions
Notes on the "get" method:◦ This method appends the form-data to the URL in name/value pairs◦ This method is useful for form submissions where a user want to bookmark the
result◦ There is a limit to how much data you can place in a URL (varies between
browsers), therefore, you cannot be sure that all of the form-data will be correctly transferred
◦ Never use the "get" method to pass sensitive information! (password or other sensitive information will be visible in the browser's address bar)
Notes on the "post" method:◦ This method sends the form-data as an HTTP post transaction◦ Form submissions with the "post" method cannot be bookmarked◦ The "post" method is more robust and secure than "get", and "post" does not have
size limitations
Get and Post Methods
ServletRequest◦ Defines an object to provide client request information to a servlet.
◦ A ServletRequest object provides data including parameter name and values,
attributes, and an input stream.
HttpServletRequest◦ Extends the ServletRequest interface to provide request information for HTTP
servlets.
◦ The servlet container creates an HttpServletRequest object and passes it as an
argument to the servlet's service methods (doGet, doPost, etc).
Request and Response Objects
Note: A servlet container is nothing but a compiled, executable program. The main
function of the container is to load, initialize and execute servlets. A Servlet container
may run stand alone i.e. without a web server or even on another host.
ServletResponse◦ Defines an object to assist a servlet in sending a response to the client.
HttpServletResponse◦ Extends the ServletResponse interface to provide HTTP-specific functionality in
sending a response. For example, it has methods to access HTTP headers and
cookies.
◦ The servlet container creates an HttpServletResponse object and passes it as an
argument to the servlet's service methods (doGet, doPost, etc).
Request and Response Objects (cont.)
The Old Example: Hello.javaimport java.io.*;import javax.servlet.*;import javax.servlet.http.*;
public class Hello extends HttpServlet {
public void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {
res.setContentType("text/html"); PrintWriter out = res.getWriter();
String name = req.getParameter("name"); out.println("<HTML>"); out.println("<HEAD><TITLE>Hello, " + name + "</TITLE></HEAD>"); out.println("<BODY>"); out.println("Hello, " + name); out.println("</BODY></HTML>"); }
public String getServletInfo() { return "A servlet that knows the name of the person to whom it's" + "saying hello"; }}
Often abbreviated DB. A collection of information organized in such a way that a computer program can quickly select desired pieces of data.
A relational database is a collection of data items organized as a set of formally-described tables from which data can be accessed or reassembled in many different ways without having to reorganize the database tables.
Database
MySQL
◦ MySQL Community Edition is a freely downloadable version of the world's most
popular open source database that is supported by an active community of open
source developers and enthusiasts.http://www.mysql.com/downloads/mysql/
You will also need a GUI tool for designing the DB ◦ MySQL Workbench provides DBAs and developers an integrated tools environment for:
Database Design & Modeling SQL Development (replacing MySQL Query Browser) Database Administration (replacing MySQL Administrator) The Community (OSS) Edition is available from:
http://dev.mysql.com/downloads/workbench/
Database (cont.)
Use the library provided to establish MySQL DB connectivity:mysql-connector-java-5.1.19-bin.jar
Initialize the DB using context listener in web.xml
Use context-param for setting up DB parameters from web.xml
Use MVC pattern to handle DB requests – e.g. DBManager class (It should be singleton)
How to use MySQL Java Connector: http://dev.mysql.com/usingmysql/java/
DB Connectivity
private DatabaseManager(String hostName, String databaseName, String userName, String password) {
super();
try {
StringBuilder builder = new StringBuilder(“jdbc:mysql://”);
builder.append(hostName) .append("/").append(databaseName).append("?").append(PARAM_USER + "=" + userName).append("&" + PARAM_PASSWORD + "=" + password);
Class.forName(“com.mysql.jdbc.Driver”).newInstance();
conn = DriverManager.getConnection(builder.toString());
System.out.println("[DatabaseManager] Connection is created.");
}
catch (SQLException ex) { // handle any errors
System.out.println("SQLException: " + ex.getMessage());
System.out.println("SQLState: " + ex.getSQLState());
System.out.println("VendorError: " + ex.getErrorCode());
}
catch (Exception ex) { ex.printStackTrace(); } }
Database Manager’s Sample Constructor
private Connection conn;
private static DatabaseManager instance = null;
private static final boolean[] LOCK_INSTANCE = new boolean[]{};
public static DatabaseManager getInstance(String hostName, String databaseName, String userName, String password) {
if (instance != null) { return instance; }
synchronized (LOCK_INSTANCE) { if (instance != null) { return instance; }
instance = new DatabaseManager(hostName, databaseName, userName, password); return instance; }
}
Database Manager’s Sample Instance
import java.sql.Statement;
public boolean isRegisteredUser(String username, String password) throws SQLException {
Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery("SELECT * " + "from users WHERE username='" + username + "' AND password='" + password + "'");
return rs.next();
/**********************************************************/ }
Working With DB – Sample Query
Folder Placement And Hierarchy All the content should be placed under tomcat’s “webapps”
directory
Assignment Write a login and registration pages, using database for keeping
accounts
AUA – CoEApr.21, Spring 2012
CIS-274: Internet ProgrammingForms and DB
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CIS 274 – Internet Programming
Lab Session #2