JDBC Exception Handling (SQLException)

Exception handling allows you to handle abnormal situations in a controlled manner, such as errors defined by the program.

When an abnormal situation occurs, an exception will be triggered. The word 'throw' means that the current program execution stops and the control is redirected to the nearest applicable catch clause. If there is no applicable catch clause, the execution of the program ends.

JDBC exception handling is very similar to Java exception handling, but for JDBC, the most common exceptions you need to handle are java.sql.SQLException.

SQLException methods

SQLException can occur in both drivers and databases. When such an exception occurs, an SQLException object of type is passed to the catch clause.

The SQLException object passed in has the following methods available for retrieving other information about the exception-

By utilizing the information provided by the Exception object, you can catch exceptions and continue executing the program appropriately. This is the general form of the try block-

try {
　　　//　Your exception code between these braces！！！
}
catch(Exception ex) {
　　　//　Your exception handling code between these two　
　　　//　Braces, similar to the exception clause　
　　　//　In PL　/　in the SQL block.
}
finally {
　　　//　The code you must always execute between these two　
　　　//Braces. Just like closing the database connection.
}

Online examples

Study the following example code to understandtry....catch...finallyUsage of the block.

//Step1.Import the required software packages
import java.sql.*;
public class JDBCExample {
　　　//　JDBC driver program 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;
　　　try{
　　　　　　//Step2Register JDBC driver
　　　　　　Class.forName("com.mysql.jdbc.Driver");
　　　　　　//Step3Establish connection
　　　　　　System.out.println("Connecting to database...");
　　　　　　conn = DriverManager.getConnection(DB_URL, USER, PASS);
　　　　　　//Step4Execute query
　　　　　　System.out.println("Creating statement...");
　　　　　　Statement stmt = conn.createStatement();
　　　　　　String sql;
　　　　　　sql = "SELECT id, first, last, age FROM Employees";
　　　　　　ResultSet rs = stmt.executeQuery(sql);
　　　　　　//Step5Extract data from the result set
　　　　　　while(rs.next()){
　　　　　　　　　//Search by column name
　　　　　　　　　int id = rs.getInt("id");
　　　　　　　　　int age = rs.getInt("age");
　　　　　　　　　String first = rs.getString("first");
　　　　　　　　　String last = rs.getString("last");
　　　　　　　　　//Display value
　　　　　　　　　System.out.print("ID: ",　+　id;
　　　　　　　　　System.out.print(", Age: ",　+　age;
　　　　　　　　　System.out.print(", First: ",　+　first);
　　　　　　　　　System.out.println(", Last: ",　+　last);
　　　　　　}
　　　　　　//Step6Clean up environment
　　　　　　rs.close();
　　　　　　stmt.close();
　　　　　　conn.close();
　　　catch(SQLException se){
　　　　　　//Handling JDBC error
　　　　　　se.printStackTrace();
　　　Handling Class.forName error
　　　　　　//e.printStackTrace();
　　　　　　finally{
　　　}
　　　　　　//Finally block to prevent resource from being blocked
　　　　　　try{
　　　　　　　　　if(conn!=null)
　　　　　　　　　　　　conn.close();
　　　　　　catch(SQLException se){
　　　　　　　　　se.printStackTrace();
　　　　　　}
　　　}//End try
　　　System.out.println("Goodbye!");
}//End main
}//End JDBCExample

Now, let's compile the above example as follows:

C:\>javac JDBCExample.java
C:\>

RuntimeJDBCExampleIf there is no problem, it will produce the following result, otherwise it will catch the corresponding error and display the error message-

C:\>java JDBCExample
Connecting to database...
Creating statement...
ID:　10, Age:　18, First: Zara, Last: Ali
ID:　101, Age:　25, First: Mahnaz, Last: Fatma
ID:　102, Age:　3, First: Zaid, Last: Khan
ID:　103, Age:　28, First: Sumit, Last: Mittal
C:\>

Try the above example by passing an incorrect database name or an incorrect username or password, and then check the result.