mybatis SqlSessionFactory工厂模式

一、工厂方法模式实现sqlsession

（从别人博客复制的图）

 1.Sqlsession接口

在sqlsession接口中包含了所有可能执行的sql语句。而Defaultsqlsession是他的实现类，实现了其中的方法。

public interface SqlSession extends Closeable {

  /**
   * Retrieve a single row mapped from the statement key
   * @param <T> the returned object type
   * @param statement
   * @return Mapped object
   */
  <T> T selectOne(String statement);
/**
   * Retrieve a list of mapped objects from the statement key and parameter.
   * @param <E> the returned list element type
   * @param statement Unique identifier matching the statement to use.
   * @return List of mapped object
   */
  <E> List<E> selectList(String statement);

2.DefaultSqlSession

public class DefaultSqlSession implements SqlSession {

  private Configuration configuration;
  private Executor executor;

  private boolean dirty;

 public <E> List<E> selectList(String statement, Object parameter, RowBounds rowBounds) {
    try {
      MappedStatement ms = configuration.getMappedStatement(statement);
      List<E> result = executor.query(ms, wrapCollection(parameter), rowBounds, Executor.NO_RESULT_HANDLER);
      return result;
    } catch (Exception e) {
      throw ExceptionFactory.wrapException("Error querying database.  Cause: " + e, e);
    } finally {
      ErrorContext.instance().reset();
    }
  }

3.SqlSessionFactory接口

sqlsessionfactory类中有opsession方法，用来创建sqlsession。

4、DefaultSqlSessionFactory类实现了SqlSessionFactory