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📌 Problem

You want to integrate MyBatis with a custom DataSource (like HikariCP) and use XML-based mappers to interact with a relational database (e.g., MySQL).

Your goals:

• Connect to a database using a connection pool.
• Separate SQL statements from Java code using XML mappers.
• Maintain clean and scalable configuration.

🚀 Solution Overview

You will:

• Add required dependencies (MyBatis, MySQL, HikariCP).
• Configure the DataSource using HikariCP.
• Load MyBatis configuration via mybatis-config.xml.
• Use a mapper interface + XML file for SQL operations.
• Call the mapper in a Java application.

🧱 Step 1: Add Maven Dependencies

xml

<!-- MyBatis Core -->
<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis</artifactId>
    <version>3.5.7</version>
</dependency>

<!-- MyBatis Spring Support (Optional, for Spring users) -->
<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis-spring</artifactId>
    <version>2.0.6</version>
</dependency>

<!-- HikariCP (Connection Pool) -->
<dependency>
    <groupId>com.zaxxer</groupId>
    <artifactId>HikariCP</artifactId>
    <version>5.0.1</version>
</dependency>

<!-- MySQL Driver -->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.32</version>
</dependency>

🔧 Step 2: Configure DataSource Using HikariCP

java

import com.zaxxer.hikari.HikariConfig;
import com.zaxxer.hikari.HikariDataSource;

import javax.sql.DataSource;

public class DataSourceConfig {

    public static DataSource getDataSource() {
        HikariConfig config = new HikariConfig();
        config.setJdbcUrl("jdbc:mysql://localhost:3306/mydb");
        config.setUsername("root");
        config.setPassword("password");
        config.setDriverClassName("com.mysql.cj.jdbc.Driver");

        config.setMaximumPoolSize(10);
        config.setMinimumIdle(5);
        config.setIdleTimeout(30000);

        return new HikariDataSource(config);
    }
}

⚙️ Step 3: MyBatis Configuration File (mybatis-config.xml)

xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
  PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
  "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC" />
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mydb"/>
                <property name="username" value="root"/>
                <property name="password" value="password"/>
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <mapper resource="mybatis/mappers/UserMapper.xml"/>
    </mappers>
</configuration>

🧩 Step 4: Mapper Interface (UserMapper.java)

java

import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.annotations.Insert;

public interface UserMapper {
    
    User getUserById(int id);

    void insertUser(User user);
}

📄 Step 5: Mapper XML File (UserMapper.xml)

xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
  PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
  "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="UserMapper">

    <select id="getUserById" parameterType="int" resultType="User">
        SELECT id, name FROM users WHERE id = #{id}
    </select>

    <insert id="insertUser" parameterType="User">
        INSERT INTO users (id, name) VALUES (#{id}, #{name})
    </insert>

</mapper>

👤 Step 6: Create the User POJO

java

public class User {
    private int id;
    private String name;

    // Getters & Setters
    public int getId() { return id; }
    public void setId(int id) { this.id = id; }

    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
}

🧪 Step 7: SqlSessionFactory and Mapper Usage

java

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import java.io.InputStream;

public class MyBatisExample {

    public static void main(String[] args) {
        try {
            InputStream inputStream = Resources.getResourceAsStream("mybatis-config.xml");
            SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

            try (SqlSession session = sqlSessionFactory.openSession()) {
                UserMapper userMapper = session.getMapper(UserMapper.class);

                // Insert a new user
                User user = new User();
                user.setId(1);
                user.setName("John Doe");
                userMapper.insertUser(user);
                session.commit();

                // Retrieve the user
                User fetched = userMapper.getUserById(1);
                System.out.println("✅ User fetched: " + fetched.getName());
            }

        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

✅ Output

sql

✅ User fetched: John Doe

🧠 Key Highlights

ComponentRoleHikariCPEfficient connection poolingmybatis-config.xmlCentral MyBatis configurationMapper InterfaceMaps methods to SQL statementsMapper XMLClean separation of SQL from Java codeSqlSessionExecutes SQL and manages transactions

🛡️ Best Practices

• Store DB credentials securely (e.g., in application.properties or environment variables).
• For complex projects, consider Spring Boot + MyBatis-Spring.
• Always close SqlSession to avoid leaks (use try-with-resources).
• For read-heavy workloads, tune connection pool settings in HikariCP.