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JDBC - Sample, Example Code


This section gives a case of how to make a basic JDBC application. This will tell you the best way to open a database association, execute a SQL question, and show the results.

All the means referenced in this layout model, would be clarified in ensuing parts of this tutorial.

Creating JDBC Application

There are following six stages associated with building a JDBC application −

  • Import the packages: Requires that you incorporate the bundles containing the JDBC classes required for database programming. Frequently, utilizing import java.sql.* will suffice.

  • Register the JDBC driver: Requires that you instate a driver so you can open a correspondence channel with the database.

  • Open a connection: Requires utilizing the DriverManager.getConnection() technique to make a Connection object, which speaks to a physical association with the database.

  • Execute a query: Requires utilizing an object of sort Statement for building and presenting a SQL proclamation to the database.

  • Extract information from result set: Requires that you utilize the proper ResultSet.getXXX() strategy to recover the information from the outcome set.

  • Clean up the environment: Requires expressly shutting all database assets as opposed to depending on the JVM's trash collection.

Sample Code

This test precedent can fill in as a template when you have to make your very own JDBC application in the future.

This test code has been composed dependent on nature and database setup done in the past chapter.

Copy and glue the accompanying precedent in FirstExample.java, arrange and keep running as pursues −

//STEP 1. Import required packages 

import java.sql.*; 

public class FirstExample { 

//JDBC driver name and database URL 

static final String JDBC_DRIVER = "com.mysql.jdbc.Driver"; 

static final String DB_URL = "jdbc:mysql://localhost/EMP"; 

//Database credentials 

static final String USER = "username"; 

static final String PASS = "password";


public static void main(String[] args) { 

Connection conn = null; 

Statement stmt = null; 

try{ 

//STEP 2: Register JDBC driver 

Class.forName("com.mysql.jdbc.Driver"); 

//STEP 3: Open a connection 

System.out.println("Connecting to database..."); 

conn = DriverManager.getConnection(DB_URL,USER,PASS); 

//STEP 4: Execute a query 

System.out.println("Creating statement..."); 

stmt = conn.createStatement(); 

String sql; 

sql = "SELECT id, first, last, age FROM Employees"; 

ResultSet rs = stmt.executeQuery(sql); 

//STEP 5: Extract information from result set 

while(rs.next()){ 

//Retrieve by segment name 

int id = rs.getInt("id"); 

int age = rs.getInt("age"); 

String first = rs.getString("first"); 

String last = rs.getString("last");

//Display values 

System.out.print("ID: " + id); 

System.out.print(", Age: " + age); 

System.out.print(", First: " + first); 

System.out.println(", Last: " + last); 

} 

//STEP 6: Clean-up environment 

rs.close(); 

stmt.close(); 

conn.close(); 

}catch(SQLException se){ 

//Handle mistakes for JDBC 

se.printStackTrace(); 

}catch(Exception e){ 

//Handle mistakes for Class.forName 

e.printStackTrace(); 

}finally{ 

//at long last square used to close resources 

try{ 

if(stmt!=null) 

stmt.close();
    
    
    }catch(SQLException se2){ 

}//nothing we can do 

try{ 

if(conn!=null) 

conn.close(); 

}catch(SQLException se){ 

se.printStackTrace(); 

}//end at long last try 

}//end try 

System.out.println("Goodbye!"); 

}//end main 

}//end FirstExample

Now let us assemble the above model as pursues −

C:\>javac FirstExample.java 

C:\>

When you run FirstExample, it creates the accompanying outcome −

C:\>java FirstExample 

Connecting to database... 

Creating statement... 

ID: 100, Age: 18, First: Zara, Last: Ali 

ID: 101, Age: 25, First: Mahnaz, Last: Fatma 

ID: 102, Age: 30, First: Zaid, Last: Khan 

ID: 103, Age: 28, First: Sumit, Last: Mittal 

C:\>






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