Hadoop为每个映射器使用一个实例(Hadoop use one instance for each mapper)

 我正在使用Hadoop的map reduce来解析xml文件。 所以我有一个名为Parser的类，它可以有一个方法parse()来解析xml文件。 所以我应该在Mapper的map()函数中使用它。 
 
 但是，这意味着每次当我想调用Parser ，我都需要创建一个Parser实例。 但是对于每个地图作业，此实例应该相同。 所以我想知道我是否可以只将这个Parser实例化一次？ 
 
 还有另外一个附加问题，为什么Mapper类总是静态的？ 

I'm using Hadoop 's map reduce to parse xml files. So I have a class called Parser that can have a method parse() to parse the xml files. And So I should use it in the Mapper's map() function. 
 
However it means that every time, when I want to call a Parser, I need to create a Parser instance. But this instance should be the same for each map job. So I'm wondering if I can just instantize this Parser just once?
 
And just another add-on question, why the Mapper class is always static?

原文：https://stackoverflow.com/questions/37547118