Let’s dive into the concept of CRUD (Create, Read, Update, Delete) in the context of Servlets. CRUD operations are fundamental for managing data in web applications. I’ll provide you with a simple example of a user registration application using Servlets, along with the necessary code snippets.
- Create (Insert):
- In this step, we add a new user to our system.
- We’ll create an HTML form where users can input their details (name, password, email, and country).
- When the user submits the form, the data is sent to a Servlet.
- The Servlet processes the data and inserts it into the database.
index.html):
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<h1>Add New Employee</h1>
<form action="SaveServlet" method="post">
<table>
<tr><td>Name:</td><td><input type="text" name="name"/></td></tr>
<tr><td>Password:</td><td><input type="password" name="password"/></td></tr>
<tr><td>Email:</td><td><input type="email" name="email"/></td></tr>
<tr><td>Country:</td><td>
<select name="country" style="width:150px">
<option>India</option>
<option>USA</option>
<option>UK</option>
<option>Other</option>
</select>
</td></tr>
<tr><td colspan="2"><input type="submit" value="Save Employee"/></td></tr>
</table>
</form>
<br/>
<a href="ViewServlet">View employees</a>
</body>
</html>
- Read (Retrieve):
- To retrieve user data, we’ll create a Servlet called
ViewServlet. - This Servlet queries the database and displays the list of employees.
- To retrieve user data, we’ll create a Servlet called
- Update:
- When a user wants to update their details (e.g., change their email address), we’ll use the Update operation.
- We’ll create another form where users can edit their information.
- The updated data will be sent to a Servlet, which will update the corresponding record in the database.
- Delete:
- For deleting a user, we’ll create a Servlet called
DeleteServlet. - When a user clicks the “Delete” button next to their name, the corresponding record will be removed from the database.
- For deleting a user, we’ll create a Servlet called
Here’s a simplified example of the Java classes (Emp.java and EmpDao.java) that handle the CRUD operations:
// Emp.java
public class Emp {
private int id;
private String name, password, email, country;
// Getters and setters for fields (id, name, password, email, country)
}
// EmpDao.java
import java.sql.*;
public class EmpDao {
public static Connection getConnection() {
Connection con = null;
try {
Class.forName("oracle.jdbc.driver.OracleDriver");
con = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:xe", "system", "oracle");
} catch (Exception e) {
System.out.println(e);
}
return con;
}
public static int save(Emp e) {
// Insert logic
}
public static int update(Emp e) {
// Update logic
}
public static int delete(int id) {
// Delete logic
}
}
Remember to configure your database connection details (e.g., Oracle, MySQL) appropriately in your getConnection() method.
Feel free to adapt this example to your specific requirements. If you need further assistance or have any questions, feel free to ask! 😊