This tutorial provides examples of how to create a simple JDBC application. Demonstrate how to open a database connection, execute SQL queries, and display the results.
All the steps mentioned in this template example will be explained in the subsequent chapters of this tutorial.
Create a JDBC application:
There are six steps involved in building a JDBC application:
Importing data packets . It needs to include packages containing JDBC classes that require database programming. In most cases, just use import java.sql.*.
Register the JDBC driver . The driver needs to be initialized and a communication channel can be opened with the database.
Open the connection . You need to use the DriverManager.getConnection() method to create a Connection object, which represents the physical connection to the database.
Execute the query . You need to use the type declaration object to create and submit an SQL statement to the database.
Extract data from the result set . It is required to use the appropriate ResultSet.getXXX() method to retrieve the data from the result set.
Clean up the environment . All database resources need to be explicitly closed, which rely on JVM garbage collection.
Sample code:
This example can be used as a template when you need to build a JDBC application.
This sample code is written based on the environment and database installation in the previous chapter.
Copy the following example FirstExample.java, compile and run as follows:
The code copy is as follows:
//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 data from result set
while(rs.next()){
//Retrieve by column 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 errors for JDBC
se.printStackTrace();
}catch(Exception e){
//Handle errors for Class.forName
e.printStackTrace();
} finally{
// finally block 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 finally try
}//end try
System.out.println("Goodbye!");
}//end main
}//end FirstExample
Now let’s compile the above example as follows:
The code copy is as follows:
C:/> javac FirstExample.java
C:/>
When running FirstExample, it produces the following results:
The code copy is as follows:
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:/>