有没有办法将某些操作引导到我的所有servlet？

Question

I have a bunch of Servlets. I want all of them to instantiate a Logger, pretty much the exact same way.
Is there a proper (like a Main file) where I can bootsrap such code?
Currently what I do is created a subclass of the Servlet class, which does that in the init function and all the other Servltes inherit from it.

Answer 1

I don't know if it's a good idea what you are trying for the logger (i think you will lose some logger capacibilities), but well, if you want an unique instance of something in a servlet you should declare it and init it in the static way:

static final SomethingClear GLOBAL;
static{
    // do tons of things to init 
    GLOBAL = ClassWithStaticFunc.gimmeGlobalLoaded();
}

An why is better this way? because there's another funny -or well, may be annoying :( - way to load a static (in the senses of uniqueness and that always will be an instance in memory) variable in a servlet:

Servlets dont have nothing like 'main'. They are unique instances which live in a servlet container, are instanciated by it, and its methods (doGet, doPost, doPut, doDelete) are executed by the servlet container on demand giving them request and response objects. So, in memory, there will be allways one and only one instance of each servlet, so any variable outside doGet, doPut, doDelete and doPost will be unique in memory. This was done this way in the beginings of the java-time in order to save memory...

And this is a funny way to merge sessions... :(

If you assing something to anything outside that methods in a servlet it will be assigned to all sessions of your application, and is not obvious and is not so easy to find...

So its better to mark them as static and final because they'll be always created (you have no access to objects construction) and there will be only one instance. It's not nice, but servlets are not nice...

I once did a unique servlet whose invoke my custom 'Servlets' using reflection (one object per petition, giving the name of my 'servlet' in the web.xml as initParam and setting the servlet-name always to the same servlet that was the instanciator of mines) to solve session merges and worked great.