SqlSessionFactoryBuilder

作用

SqlSessionFactoryBuilder 的作用在于创建SqlSessionFactory，创建成功后就失去了作用，所以它只能作用于创建SqlSessionFactory方法中，它的最佳的生命周期是方法级别的

使用

public class UserTest {

  private final static SqlSessionFactory sqlSessionFactory;
  static {
    String resource = "mybatis-config.xml";
    Reader reader = null;
    try {
      reader = Resources.getResourceAsReader(resource);
    } catch (IOException e) {
      System.out.println(e.getMessage());
    }
    sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
  }

  @Test
  public void test1(){
    SqlSession sqlSession = sqlSessionFactory.openSession();
    final UserInfoMapper mapper = sqlSession.getMapper(UserInfoMapper.class);
    final UserInfo userInfo = mapper.selectByPrimaryKey(3L);
    System.out.println(userInfo.getName());
    sqlSession.close();

  }

}

源码

SqlSessionFactoryBuilder 有 9个重载的方法

mybatis配置加载入口-SqlSessionFactoryBuilder_配置文件上面例子中使用的是 build(Reader reader) 这个方法，但这个方法最终调用的还是 build(Reader reader, String environment, Properties properties) ，代码如下

public SqlSessionFactory build(Reader reader) {
    return build(reader, null, null);
  }

 public SqlSessionFactory build(Reader reader, String environment, Properties properties) {
    try {
      XMLConfigBuilder parser = new XMLConfigBuilder(reader, environment, properties);
      // 配置文件解析 获取到Configuration对象 返回SqlSessionFactory
      return build(parser.parse());
    } catch (Exception e) {
      throw ExceptionFactory.wrapException("Error building SqlSession.", e);
    } finally {
      ErrorContext.instance().reset();
      try {
        reader.close();
      } catch (IOException e) {
        // Intentionally ignore. Prefer previous error.
      }
    }
  }

不管哪个build()方法，最终调用的都是build(Configuration config) 来解析配置文件

public SqlSessionFactory build(Configuration config) {
    return new DefaultSqlSessionFactory(config);
  }

SqlSessionFactoryBuilder 的内容就这些，剩下的都交给了SqlSessionFactory 。