mybatis源码阅读学习过程(二) Configuration

public SqlSessionFactory build(InputStream inputStream, String environment, Properties properties) {
    try {
      XMLConfigBuilder parser = new XMLConfigBuilder(inputStream, environment, properties);
      //委托XMLConfigBuilder来解析xml文件，并构建Configuration，
      //根据Xnode.evalNode。这个builder里具体解析xml挺多的
      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.
      }
    }
  }

        <environment id="development">
            <transactionManager type="JDBC"></transactionManager>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/ssm?serverTimezone=GMT"/>
                <property name="username" value=""/>
                <property name="password" value=""/>
            </dataSource>
        </environment>
      environmentsElement(root.evalNode("environments"));
      //xml解析里比较重要的
      //环境解析

          //7.1事务管理器
          //根据type="JDBC"解析返回适当的TransactionFactory
          TransactionFactory txFactory = transactionManagerElement(child.evalNode("transactionManager"));
          //7.2数据源
          //根据type="POOLED"解析返回适当的DataSourceFactory
          DataSourceFactory dsFactory = dataSourceElement(child.evalNode("dataSource"));
          DataSource dataSource = dsFactory.getDataSource();
          Environment.Builder environmentBuilder = new Environment.Builder(id)
              .transactionFactory(txFactory)
              .dataSource(dataSource);
          configuration.setEnvironment(environmentBuilder.build());

返回factory的这几个方法都调用了resolveClass，根据别名解析Class,其实是去查看类型别名注册/事务管理器别名

  public void registerAlias(String alias, Class<?> value) {
    if (alias == null) {
      throw new TypeException("The parameter alias cannot be null");
    }
    String key = alias.toLowerCase(Locale.ENGLISH);
    if (TYPE_ALIASES.containsKey(key) && TYPE_ALIASES.get(key) != null && !TYPE_ALIASES.get(key).equals(value)) {
      throw new TypeException("The alias '" + alias + "' is already mapped to the value '" + TYPE_ALIASES.get(key).getName() + "'.");
    }
    TYPE_ALIASES.put(key, value);
  }

这个方法应该也是之前用过的标签所调用的，盲猜会将目标类放在TYPE_ALIASES这张表里。

最后一个build方法使用了一个Configuration作为参数,并返回DefaultSqlSessionFactory。这个default实现了SqlSessionFactory接口，

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

来源：CSDN

作者：xunhan0991

链接：https://blog.csdn.net/jx515519290/article/details/103645913

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