Mybatis跟踪源码的那些事（二）

1.我们先看下程序入口

public static void main(String[] args) {
    
    try {
　　　　　//核心配置文件
        String resource = "configuration.xml";
　　　　　//将文件写入流
        InputStream inputStream = Resources.getResourceAsStream(resource);
　　　　　//我们跟进下build()
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession sqlSession = sqlSessionFactory.openSession();
        SysUserMapper mapper = sqlSession.getMapper(SysUserMapper.class);
        List<SysUser> list = mapper.getAll();
        System.out.println(list);
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    
}
   
}

SqlSessionFactoryBuilder

  public SqlSessionFactory build(InputStream inputStream, String environment, Properties properties) {
    try {
　　　　//XMLConfigBuilder  读取配置文件parse（）；
      XMLConfigBuilder parser = new XMLConfigBuilder(inputStream, environment, properties);
      return build(parser.parse());
    } catch (Exception e) {
      throw ExceptionFactory.wrapException("Error building SqlSession.", e);
    } finally {
      ErrorContext.instance().reset();
      try {
        inputStream.close();
      } catch (IOException e) {
        // Intentionally ignore. Prefer previous error.
      }
    }
  }

跟进parse()方法

  public Configuration parse() {
    if (parsed) {
      throw new BuilderException("Each XMLConfigBuilder can only be used once.");
    }
    parsed = true;
    parseConfiguration(parser.evalNode("/configuration"));
    return configuration;
  }

跟进parseConfiguration方法,解析配置，传入的参数就是我们xml配置文件的configuration根节点。解析我们的配置文件就需要分别解析其中的各个节点。

 private void parseConfiguration(XNode root) {
    try {
      propertiesElement(root.evalNode("properties")); //issue #117 read properties first
      typeAliasesElement(root.evalNode("typeAliases"));
      pluginElement(root.evalNode("plugins"));
      objectFactoryElement(root.evalNode("objectFactory"));
      objectWrapperFactoryElement(root.evalNode("objectWrapperFactory"));
      settingsElement(root.evalNode("settings"));
      environmentsElement(root.evalNode("environments")); // read it after objectFactory and objectWrapperFactory issue #631
      databaseIdProviderElement(root.evalNode("databaseIdProvider"));
      typeHandlerElement(root.evalNode("typeHandlers"));
      mapperElement(root.evalNode("mappers"));
    } catch (Exception e) {
      throw new BuilderException("Error parsing SQL Mapper Configuration. Cause: " + e, e);
    }
  }