Configuration and SqlSessionFactory

mybatis-config.xml

The central configuration file declares environments, mappers and global settings.

<?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="dev">
    <environment id="dev">
      <transactionManager type="JDBC"/>
      <dataSource type="POOLED">
        <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
        <property name="url" value="jdbc:mysql://localhost:3306/shop"/>
        <property name="username" value="root"/>
        <property name="password" value="secret"/>
      </dataSource>
    </environment>
  </environments>
  <mappers>
    <mapper resource="mapper/CustomerMapper.xml"/>
  </mappers>
</configuration>

Built With the XML Builder

String resource = "mybatis-config.xml";
InputStream input = Resources.getResourceAsStream(resource);
SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(input);

Using a Session

try (SqlSession session = factory.openSession()) {
  CustomerMapper mapper = session.getMapper(CustomerMapper.class);
  Customer c = mapper.findById(1L);
}

Always close sessions. The try-with-resources pattern guarantees it.

Key Points

• mybatis-config.xml wires environments, data sources and mappers.
• SqlSessionFactoryBuilder reads the XML once to build the factory.
• SqlSessionFactory is thread-safe and should be created once.
• Sessions are cheap but must be closed; use try-with-resources.