在Eclipse中将源代码链接到.jars(Linking source to .jars in Eclipse)

 你问了两个单独的问题（至少在Tomcat 7中，你问了两个单独的问题）。 
 
 Log4j2是Web应用感知的，所以它可以在每个Web应用程序中进行不同的配置。 
 
 虽然每个Web应用程序不能具有不同的系统属性（因为就其本质而言，系统意味着全局），但每个Web应用程序可以具有不同的程序员可访问属性，而不是系统属性。 
 
 将Tomcat 7配置为符合Servlet 3.0规范，您可以创建自己的ServletContainerInitializer，在所有其他初始化器之前将初始化器配置为首先初始化，然后在该初始化器中，您可以从文件，数据库或任何其他设备中读取设置否则将它们“停放”在ServletContext的属性集合中。 通常，初始化程序会检查它正在运行的系统，并根据它发现的内容设置属性。 从文件中读取它们毫无意义，因为您可以将它们放在web.xml中。 然后，您的Web应用程序中的代码可以将设置从Web应用程序的ServletContext属性集合的唯一实例中提取出来。 这允许每个Web应用程序或同一Web应用程序的每个实例进行唯一配置。 

You're asking two separate questions (well, at least as of Tomcat 7 you are asking two separate questions).
 
Log4j2 is web app aware, so it can be configured differently in each web app.
 
And while you can't have different system properties for each web app (because by its very nature, system means global), you can have different programmer accessible properties per web app, just not system properties.
 
With Tomcat 7 configured to conform to the Servlet 3.0 specification, you can create your own ServletContainerInitializer, configure that initializer to be initialized first, before all other initializers, and then, within that initializer you can read settings out of a file, DB or anything else and "park" them in the ServletContext's attributes collection. Typically, your initializer would inspect the system it's running on and set the attributes based on what it discovers. There's little point in reading them from a file, since you could simply park them in web.xml. Then code in your web app can pull the settings out of the web app's unique instance of its ServletContext's attribute collection. This allows each web app, or each instance of the same web app, to be uniquely configured.