mybatis配置加载入口-SqlSessionFactoryBuilder

骑猪看日落 2022-10-23 15:26 81阅读 0赞

### SqlSessionFactoryBuilder ###

*  作用
 *  使用
 *  源码

# 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  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM5NjU0ODQx_size_16_color_FFFFFF_t_70]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 。

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM5NjU0ODQx_size_16_color_FFFFFF_t_70]: /images/20221023/4f43e7d41c8f4231b1f816b5c1c49ab3.png