JDBC Exception Handling
JDBC is a Java API that allows interaction with databases. JDBC exceptions like SQLException commonly occur due to connection issues, SQL syntax errors or data type mismatches and are handled using standard Java exception handling.
Why is JDBC Exception Handling Important?
When we communicate with databases,some problems occur like:
- Invalid SQL syntax bad query
- Connection time out problem
- Wrong data types mentioned
- miss database drivers
The below code describes how we handle exceptions.
try {
//Risky code is define in that block
}
catch(Exception ex) {
//Exception handling code define hare
}
finally {
// This block always used for closing resource
}
Types of JDBC Exceptions in Java
1. SQLException: it is a Checked Exception. it is occur when we have defined wrong sql syntax like Incorrect SQL syntax, Invalid table or column name.
Incorrect SQL syntax:
Example:
SELECT * FORM person; // 'FROM' is misspelled
Error:
java.sql.SQLSyntaxErrorException: Syntax error in SQL statement
Invalid table or column names
Example:
SELECT * FROM perso; // 'person' is misspelled
Error:
java.sql.SQLSyntaxErrorException: Table 'person' doesn't exist
2. ClassNotFoundException: It is a checked exception. This occur when the JDBC driver class is not found.
Example:
Class.forName("com.mysql.cj.jdbc.Driver");
If the MySQL driver is missing from the classpath.
3. SQLTimeoutException: It is a subclass of SQLException. It occurs when a query takes too long and exceeds the configured timeout limit.
Example:
statement.setQueryTimeout(seconds)
Example: The below-described code describes how to handle Jdbc Exception.
package org.vishnu;
import java.sql.*;
import javax.sound.midi.Soundbank;
public class App {
public static void main(String[] args) throws Exception
{
// fetching data from database
String email = "gaurav@gmail.com";
// we have use try with resourse for automatically close JDBC resources
try {
// Load and ragister the driver
Class.forName("com.mysql.cj.jdbc.Driver");
try (
// create connection
Connection con
= DriverManager.getConnection(
"jdbc:mysql://localhost:3306/jdbc_db",
"root", "password");
// execute dynamic query
PreparedStatement ps = con.prepareStatement(
"select * from ragister");
// store the result
ResultSet rs = ps.executeQuery();
// process the result
) {
while (rs.next()) {
String name1 = rs.getString("name");
System.out.println("name->" + name1);
String email1 = rs.getString("email");
System.out.println("email->" + email1);
String poss = rs.getString("possword");
System.out.println("poss->" + poss);
String gen = rs.getString("gender");
System.out.println("gender->" + gen);
String city1 = rs.getString("city");
System.out.println("city->" + city1);
System.out.println(
"------------------------");
}
}
}
catch (SQLSyntaxErrorException se) {
System.err.println("Error in sql syntax: "
+ se.getMessage());
}
catch (SQLTimeoutException te) {
System.err.println("Query Time Expire: "
+ te.getMessage());
}
catch (ClassNotFoundException e) {
System.err.println("jdbc driver not found.");
}
catch (Exception e) {
System.err.println("Unexpected error: "
+ e.getMessage());
}
}
}
Output:
Explanation
- Connects to a MySQL database named jdbc_db using JDBC.
- Uses try-with-resources to automatically close JDBC resources.
- Loads the MySQL JDBC driver using Class.forName.
- Establishes a connection using DriverManager.getConnection.
- Prepares and executes a SQL query to select all records from the ragister table.
- Iterates through the ResultSet to print values of name, email, possword, gender and city.
- Catches and handles SQLSyntaxErrorException for SQL syntax issues.
- Catches and handles SQLTimeoutException if the query exceeds time limits.
- Catches and handles ClassNotFoundException if the JDBC driver is missing.
- Catches any other unexpected exceptions.
Best Way for JDBC Exception Handling
- Always close resources using try-with-resources.
- Avoid exposing DB details in production error messages.
- Use meaningful messages in catch blocks.
- Don't catch generic Exception unless necessary
