代码构建

public interface UserMapper {
    @Select("select * from user where id = 1")
    User getUser(Integer id);
}


public static void main(String[] args) throws SQLException {
        // 1. datasource配置 
        MysqlDataSource dataSource = new MysqlDataSource();
        dataSource.setURL("jdbc:mysql://localhost:3306/test");
        dataSource.setUser("root");
        dataSource.setPassword("xxnydyxf");
        dataSource.setCharacterEncoding("UTF-8");
        dataSource.setServerTimezone("UTC");
        // 2. 事物
        TransactionFactory transactionFactory = new JdbcTransactionFactory();
        Environment environment = new Environment("development", transactionFactory, dataSource);
        Configuration configuration = new Configuration(environment);
    	// 3. 注册Mapper
        configuration.addMapper(UserMapper.class);
    	// 4. 构建 SqlSessionFactory
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(configuration);

		// 5. 使用
        SqlSession session = sqlSessionFactory.openSession();
        UserMapper userMapper = session.getMapper(UserMapper.class);
        User user = userMapper.getUser(1);
        System.out.println(user.getAge());
    }

// 分析

1.Datasource配置

3. 注册

// 注册Mapp类
configuration.addMapper(UserMapper.class);
/**
 * 配置信息
 */
public class org.apache.ibatis.session.Configuration{
    //...
    public <T> void addMapper(Class<T> type) {
    	mapperRegistry.addMapper(type);
  	}
    
    //...
}

public class org.apache.ibatis.binding.MapperRegistry{
    //...
    
    //
    public <T> void addMapper(Class<T> type) {
    if (type.isInterface()) {// 如果是接口
      if (hasMapper(type)) {// 判断是否已经存在
        throw new BindingException("Type " + type + " is already known to the MapperRegistry.");
      }
      boolean loadCompleted = false;
      try {
        // 缓存 此时指示暂时保存，并不生成代理
        knownMappers.put(type, new MapperProxyFactory<>(type));
        // It's important that the type is added before the parser is run
        // otherwise the binding may automatically be attempted by the
        // mapper parser. If the type is already known, it won't try.
        MapperAnnotationBuilder parser = new MapperAnnotationBuilder(config, type);
        parser.parse();
        loadCompleted = true;
      } finally {
        if (!loadCompleted) {
          knownMappers.remove(type);
        }
      }
    }
  }
    //...
}

4. 构建SqlSessionFactory

SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(configuration);

// new 一个 DefaultSqlSessionFactory
public class SqlSessionFactoryBuilder {
    public SqlSessionFactory build(Configuration config) {
        return new DefaultSqlSessionFactory(config);
      }
}
// 没啥好说的
public class DefaultSqlSessionFactory implements SqlSessionFactory {

  private final Configuration configuration;

  public DefaultSqlSessionFactory(Configuration configuration) {
    this.configuration = configuration;
  }
}