JavaMySQLNotes

Connecting Java project with MySQL database

Prerequisites:

• Must have XAMPP installed on your machine and MySQL server running on localhost:3306.
• Knowledge of some basic SQL syntax
• Recommended to go through the notes and/or recording of 4th class of Web Development (https://cc-mnnit.github.io/2021-22-Classes/WebDev/2021_05_01_WebClass-4/)
• Java 8 (or any other version if not building JavaFX app) and IntelliJ must be installed, of course.

Accessing your database from IntelliJ

As we know, IntelliJ is an Integrated Development Environment, so naturally, we would like to access our SQL schemas/databases from within IntelliJ itself, instead of phpMyAdmin. So let's look at how to setup IntelliJ to work with our database.

• Step 1:

Open IntelliJ. Select the Database option at the right side of the window. Then, click the '+' icon, then select MySQL.

• Step 2:

In the dialog box, first of all, if IntelliJ asks to download any drivers, download them. Then set User as 'root' and for Password, right-click and select 'Set Empty'. (This is the default setting in XAMPP, if changed by you, set accordingly)

• Step 3:

Click on 'Test Connection'. A success balloon should pop-up. Notice that it shows MariaDB instead of MySQL. This is because XAMPP uses that by default. This is not a cause of concern, as MariaDB is just a fork of MySQL and all syntax is identical. Select 'Use MariaDB'. Then press 'OK' to finalize.

• Step 4:

A console tab will open up. In there, select 'schema', then select your already created schema from the list (Here we have already made a 'test1' schema, with which we will be working). You can also create a new schema by right-clicking on '@localhost' and selecting New->Schema. Then enter a schema name, press OK.

Once you have selected your schema in your console tab, you can run various SQL commands there. A sample shot is provided:

Now try to further explore the various database features in IntelliJ.

Adding JDBC to your IntelliJ project

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JDBC (Java Database Connectivity) is a driver provided by MySQL and other databases, in order to serve as a bridge between the database server and your Java client application.

To add JDBC to your project, there are 2 possible scenarios:

For project without Maven or Gradle:

At first you need to download its JAR file. Here's the direct download link. Extract it and you will get a JAR file with name: mysql-connector-java-8.0.24.jar.

Now open up your IntelliJ project, select File->Project Structure. Select 'Libraries', then click on '+' then select Java. Finally in the new dialog, select the JAR file that you had extracted previously.

Select OK to add the library to your project. Now JDBC is successfully added to your project.

For project with Maven or Gradle:

It is very simple to add JDBC. Just add its dependency to pom.xml (for Maven) or build.gradle (for Gradle). Get them from here. For convenience's sake, we're also pasting them here:

Maven :

<!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.24</version>
</dependency>

Gradle :

// https://mvnrepository.com/artifact/mysql/mysql-connector-java
implementation group: 'mysql', name: 'mysql-connector-java', version: '8.0.24'

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Finally, some code

Following is a simple Java code which uses JDBC to connect to a MySQL database named 'test1' (implied in the URL), creates a table STUDENT, if not already present, containing columns 'name', 'regno', 'branch'. Then it inserts a row into the table, then finally, we print all the rows contained in the table. I've commented the code extensively for easy understanding.

import java.sql.*;

/**
 * @author Aritra Chatterjee
 * JDBC sample program
 */

public class DatabaseConnectivity {

    public static void main(String[] args) throws SQLException {

        String url = "jdbc:mysql://localhost:3306/test1"; //URL of database to be connected
        Connection myConn = DriverManager.getConnection(url, "root", ""); //Connect to database (Requires JDBC) [Default username:root, pw empty]
        Statement statement= myConn.createStatement(); //Create a Statement object to run SQL statements on DB

        String query0="CREATE TABLE IF NOT EXISTS STUDENT ("+  // Initial query to create table if not already present in DB
                "name VARCHAR(30) NOT NULL," +
                "regno INT(8) PRIMARY KEY," +
                "branch VARCHAR(30) NOT NULL" +
                ")";

        statement.executeUpdate(query0); //executeUpdate(statement) is used to run DDL (e.g. CREATE) or DML (e.g INSERT) commands


            String query1 = "INSERT INTO STUDENT VALUES (?, ?, ?)";
            PreparedStatement preStat = myConn.prepareStatement(query1); //PreparedStatement is a subclass of Statement that supports data substitution and can execute a statement multiple times
            preStat.setString(1, "Aritra"); //Using the setter methods to substitute values corresponding to the ?s
            preStat.setInt(2, 20184196);
            preStat.setString(3, "CSE");
            preStat.executeUpdate(); //Executing the statement using executeUpdate()


        String query2 = "SELECT * FROM STUDENT;";

        ResultSet result = statement.executeQuery(query2); //executeQuery(statement) is used to run DQL command (i.e. SELECT) and returns a ResultSet object

        while(result.next()) { //Now iterating over the ResultSet object to print the results of the query. next() returns false after all rows exhausted, else returns true
            int regno = result.getInt("regno"); //Getters extract corresponding data from column names
            String name = result.getString("name");
            String branch = result.getString("branch");
            System.out.println("Name - " + name);
            System.out.println("Branch - " + branch);
            System.out.println("Registration number - " + regno);
        }
    }
}

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Content contributor:

• Aritra Chatterjee