SqlSessionTemplate

SqlSessionTemplate is the heart of MyBatis-Spring. It implements SqlSession and is meant to be a drop-in replacement for any existing use of SqlSession in your code. SqlSessionTemplate is thread safe and can be shared by multiple DAOs or mappers.

When calling SQL methods, including any method from Mappers returned by getMapper(), SqlSessionTemplate will ensure that the SqlSession used is the one associated with the current Spring transaction. In addition, it manages the session life-cycle, including closing, committing or rolling back the session as necessary. It will also translate MyBatis exceptions into Spring DataAccessExceptions.

SqlSessionTemplate should always be used instead of default MyBatis implementation DefaultSqlSession because the template can participate in Spring transactions and is thread safe for use by multiple injected mapper classes. Switching between the two classes in the same application can cause data integrity issues.

A SqlSessionTemplate can be constructed using an SqlSessionFactory as a constructor argument.

<bean id="sqlSession" class="org.mybatis.spring.SqlSessionTemplate">
  <constructor-arg index="0" ref="sqlSessionFactory" />
</bean>

This bean can now be injected directly in your DAO beans. You need a SqlSession property in your bean like the following

public class UserDaoImpl implements UserDao {

  private SqlSession sqlSession;

  public void setSqlSession(SqlSession sqlSession) {
    this.sqlSession = sqlSession;
  }

  public User getUser(String userId) {
    return (User) sqlSession.selectOne("org.mybatis.spring.sample.mapper.UserMapper.getUser", userId);
  }
}

And inject the SqlSessionTemplate as follows

<bean id="userDao" class="org.mybatis.spring.sample.dao.UserDaoImpl">
  <property name="sqlSession" ref="sqlSession" />
</bean>

SqlSessionTemplate has also a constructor that takes an ExecutorType as an argument. This allows you to construct, for example, a batch SqlSession by using the following in Spring's configuration xml:

<bean id="sqlSession" class="org.mybatis.spring.SqlSessionTemplate">
  <constructor-arg index="0" ref="sqlSessionFactory" />
  <constructor-arg index="1" value="BATCH" />
</bean>

Now all your statements will be batched so the following could be coded in a DAO

public void insertUsers(User[] users) {
   for (User user : users) {
     sqlSession.insert("org.mybatis.spring.sample.mapper.UserMapper.insertUser", user);
   }
 }

Note that this configuration style only needs to be used if the desired execution method differs from the default set for the SqlSessionFactory.

The caveat to this form is that there cannot be an existing transaction running with a different ExecutorType when this method is called. Either ensure that calls to SqlSessionTemplates with different executor types run in a separate transaction (e.g. with PROPAGATION_REQUIRES_NEW) or completely outside of a transaction.

SqlSessionDaoSupport

SqlSessionDaoSupport is an abstract support class that provides you with a SqlSession. Calling getSqlSession() you will get a SqlSessionTemplate which can then be used to execute SQL methods, like the following:

public class UserDaoImpl extends SqlSessionDaoSupport implements UserDao {
  public User getUser(String userId) {
    return (User) getSqlSession().selectOne("org.mybatis.spring.sample.mapper.UserMapper.getUser", userId);
  }
}

Usually MapperFactoryBean is preferred to this class, since it requires no extra code. But, this class is useful if you need to do other non-MyBatis work in your DAO and concrete classes are required.

SqlSessionDaoSupport requires either an sqlSessionFactory or an sqlSessionTemplate property to be set. If both properties are set, the sqlSessionFactory is ignored.

Assuming a class UserDaoImpl that subclasses SqlSessionDaoSupport, it can be configured in Spring like the following:

<bean id="userMapper" class="org.mybatis.spring.sample.mapper.UserDaoImpl">
  <property name="sqlSessionFactory" ref="sqlSessionFactory" />
</bean>