MySQL, Java, and JDBC

CSE 3330Southern Methodist University

Question

• When’s the last time you pulled up Amazon.com and typed in an SQL Query directly?

• How about with Access.SMU? Issued any SQL Queries directly recently?

Accessing MySQL

• We need a way to access from a programming languages

• Various ways to do this in different languages• Java uses the JDBC API– JDBC = Java Database Connectivity– Allows standardized access to relational databases

from Java

Overview

Java-based Application

MySQL Connector/J

MySQL DBMS

JDBC

• JDBC standardizes:– Initiating a connection to a RDBMS– Creating a SQL statement for later execution– Executing a SQL statement against the RDBMS– Retrieving the result of a query (if applicable)

• MySQL’s Connector/J– Type 4 JDBC Driver– All Java/Native protocol driver

JDBC

• Some Important JDBC API classes:– Driver Manager– Connection– Statement– ResultSet– SQLException

In your IDE

• Create a new Project called JDBCTest• Add MySql JDBC Driver to your “libraries” that

are used in compiling– In Netbeans, go to project properties, choose

libraries on left, and select the aforementioned driver

• Create an empty Java source file– import java.sql.*;– add a main method to the file.

public static void main (String [] args) { try {Class.forName("com.mysql.jdbc.Driver"); Connection conn = DriverManager.getConnection( "jdbc:mysql://localhost/cse3330a?”+

“user=root&password=aSecret123" );

Statement stmt = conn.createStatement();ResultSetrs = stmt.executeQuery("SELECT * FROM classes");

while (rs.next()){System.out.println(rs.getString("prof"));}rs.close();stmt.close();conn.close(); } catch (Exception e) {System.out.println(e.getMessage()); }

Overview

DOES NOT WORK;Get Main.java exampleFrom http:lyle.smu.edu/~rkotamarti/Main.java

Step 1) Load the MySQL JDBC Driver

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

Step 2) Create a Connection

Connection conn =DriverManager.getConnection("jdbc:mysql://localhost/cse3330a?”+

“user=root&password=aSecret123”);

Server

Database

Username Password

Step 3) Create Statement and Execute SQL Query

Statement stmt = conn.createStatement();

ResultSetrs = stmt.executeQuery("SELECT * FROM

classes");

Step 4) Iterate over Results

• Imagine result set is a “table” or grid with each column having a name

while (rs.next()){System.out.println(rs.getString("prof"));}

Step 5) Clean Up

rs.close();stmt.close();conn.close();

Note – Reverse Order

In-Class Exercise

• Write a program that will:– Allow the user to enter their student id– Show a list of classes to the user (SELECT)– Allow the user to “register” for a class (INSERT)

• Log in to MySQL directly to make sure the insert took place.

• Don’t worry about details like double registering or overlapping times (esp. since we’re not storing times)