java threadlocal singleton-这是什么? [英] java threadlocal singleton - what is it?

问题描述

用外行人的话来说，当有人说一个对象是Java中的线程局部单例时，这意味着什么?我在关于Java Server Faces的讲座中，每次都谈到FacesContext时-讲师总是提醒我们这是一个线程局部单例.

解决方案

FacesServlet 创建 ThreadLocal<FacesContext> ，并在HTTP servlet结束时将其删除与HTTP Servlet请求关联的HTTP Servlet响应.每当您在以下位置执行 FacesContext#getCurrentInstance() 您的JSF代码，您将在整个HTTP Servlet请求/响应处理过程中始终获得同一实例.

由于HTTP servlet请求是由不同的线程执行的，并且FacesContext实例作为线程局部变量附加到单个线程，所以没有两个HTTP servlet请求共享相同 FacesContext实例. /p>

In layman speak, what does it mean when somebody says an object is a threadlocal singleton in Java? I was at a lecture about Java Server Faces, and everytime the FacesContext was spoken of - the instructor always reminded us that it is a threadlocal singleton.

解决方案

There is only one unique instance of the FacesContext per thread.

The FacesServlet creates a ThreadLocal<FacesContext> on the beginning of the HTTP servlet request and removes it on the end of the HTTP servlet response associated with the HTTP servlet request. Whenever you do a FacesContext#getCurrentInstance() in your JSF code, you'll always get the one and the same instance throughout the entire HTTP servlet request/response processing.

Since HTTP servlet requests are executed by distinct threads and the FacesContext instance is attached as thread local variable to a single thread, no two HTTP servlet requests share the same FacesContext instance.

这篇关于java threadlocal singleton-这是什么?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！