Mybatis-Java API

Now that you know how to configure MyBatis and create mappings, you're ready for the good stuff. The MyBatis Java API is where you get to reap the rewards of your efforts. As you'll see, compared to JDBC, MyBatis greatly simplifies your code and keeps it clean, easy to understand and maintain. MyBatis 3 has introduced a number of significant improvements to make working with SQL Maps even better.

Directory Structure

Before we dive in to the Java API itself, it's important to understand the best practices surrounding directory structures. MyBatis is very flexible, and you can do almost anything with your files. But as with any framework, there's a preferred way.

SqlSessions

The primary Java interface for working with MyBatis is the SqlSession. Through this interface you can execute commands, get mappers and manage transactions. We'll talk more about SqlSession itself shortly, but first we have to learn how to acquire an instance of SqlSession. SqlSessions are created by a SqlSessionFactory instance. The SqlSessionFactory contains methods for creating instances of SqlSessions all different ways. The SqlSessionFactory itself is created by the SqlSessionFactoryBuilder that can create the SqlSessonFactory from XML, annotations or hand coded Java configuration.

SqlSessionFactoryBuilder

The SqlSessionFactoryBuilder has five build() methods, each which allows you to build a SqlSessionFactory from a different source.

SqlSessionFactory build(InputStream inputStream)
SqlSessionFactory build(InputStream inputStream, String environment)
SqlSessionFactory build(InputStream inputStream, Properties properties)
SqlSessionFactory build(InputStream inputStream, String env, Properties props)
SqlSessionFactory build(Configuration config)

SqlSessionFactory

SqlSessionFactory has six methods that are used to create SqlSession instances. In general, the decisions you'll be making when selecting one of these methods are:

Transaction: Do you want to use a transaction scope for the session?
Connection: Do you want MyBatis to acquire a Connection from the configured DataSource for you?
Execution: Do you want MyBatis to reuse PreparedStatements and/or batch updates、inserts and deletes?

The set of overloaded openSession() method signatures allow you to choose any combination of these options that makes sense.

SqlSession openSession()
SqlSession openSession(boolean autoCommit)
SqlSession openSession(Connection connection)
SqlSession openSession(TransactionIsolationLevel level)
SqlSession openSession(ExecutorType execType, TransactionIsolationLevel level)
SqlSession openSession(ExecutorType execType)
SqlSession openSession(ExecutorType execType, boolean autoCommit)
SqlSession openSession(ExecutorType execType, Connection connection)
Configuration getConfiguration();

SqlSession

As mentioned above, the SqlSession instance is the most powerful class in MyBatis. It is where you'll find all of the methods to execute statements, commit or rollback transactions and acquire mapper instances.