浅析Mybatis的SqlSource 顶

private final SqlNode rootSqlNode; //记录待解析的SqlNode的根节点，在构造函数中引入

@Override
public BoundSql getBoundSql(Object parameterObject) {
  //创建DynamicContext对象，parameterObject为用户传入的实参
  DynamicContext context = new DynamicContext(configuration, parameterObject);
  //从根节点开始，解析根节点下的所有子节点得到的SQL片段追加到context中，最终通过context.getSql()得到完整的SQL语句，这是组合模式最大的好处
  rootSqlNode.apply(context);
  //创建SqlSourceBuilder对象，解析参数属性，将SQL语句中的"#{}"解析成"?"占位符
  SqlSourceBuilder sqlSourceParser = new SqlSourceBuilder(configuration);
  Class<?> parameterType = parameterObject == null ? Object.class : parameterObject.getClass();
  SqlSource sqlSource = sqlSourceParser.parse(context.getSql(), parameterType, context.getBindings());
  //创建BoundSql对象，并将DynamicContext.bindings中参数信息复制到其additionalParameters集合中保存
  BoundSql boundSql = sqlSource.getBoundSql(parameterObject);
  for (Map.Entry<String, Object> entry : context.getBindings().entrySet()) {
    boundSql.setAdditionalParameter(entry.getKey(), entry.getValue());
  }
  return boundSql;
}

public class RawSqlSource implements SqlSource {

  private final SqlSource sqlSource; //StaticSqlSource对象

  public RawSqlSource(Configuration configuration, SqlNode rootSqlNode, Class<?> parameterType) {
    //调用getSql方法，完成SQL语句的拼装和初步解析，与DynamicSqlSource中相同
    this(configuration, getSql(configuration, rootSqlNode), parameterType);
  }

  public RawSqlSource(Configuration configuration, String sql, Class<?> parameterType) {
    //通过SqlSourceBuilder完成占位符的解析和替换操作
    SqlSourceBuilder sqlSourceParser = new SqlSourceBuilder(configuration);
    Class<?> clazz = parameterType == null ? Object.class : parameterType;
    //返回StaticSqlSource
    sqlSource = sqlSourceParser.parse(sql, clazz, new HashMap<String, Object>());
  }

  private static String getSql(Configuration configuration, SqlNode rootSqlNode) {
    DynamicContext context = new DynamicContext(configuration, null);
    rootSqlNode.apply(context);
    return context.getSql();
  }

  @Override
  public BoundSql getBoundSql(Object parameterObject) {
    return sqlSource.getBoundSql(parameterObject);
  }

}