008.从 XML 中构建 SqlSessionFactory

1.在pom.xml文件中引入依赖

        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>

2.创建MybatisTest.java测试SessionFactory是否加载成功

package com.imooc.mybatis;

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 org.junit.Test;

import java.io.IOException;
import java.io.Reader;
import java.sql.Connection;

public class MybatisTest
{
    @Test
    public void testSqlSessionFactory() throws IOException
    {
        //利用Reader加载classpath下的mybatis-config.xml核心配置文件
        Reader reader = Resources.getResourceAsReader("mybatis-config.xml");
        //初始化SqlSessionFactory对象,同时解析mybatis-config.xml文件
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
        System.out.println("SessionFactory加载成功");
        SqlSession sqlSession = null;
        try
        {
            //创建SqlSession对象,SqlSession是JDBC的扩展类,用于与数据库交互
            sqlSession = sqlSessionFactory.openSession();
            //创建数据库连接(测试用)
            Connection connection = sqlSession.getConnection();
            System.out.println(connection);
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }
        finally
        {
            if (sqlSession != null)
            {
                //如果type="POOLED",代表使用连接池,close则是将连接回收到连接池中
                //如果type="UNPOOLED",代表直连,close则会调用Connection.close()方法关闭连接
                sqlSession.close();
            }
        }
    }
}