Re: WEB-INF/classes, WEB-INF/lib

[Craig R. McClanahan]

On Mon, 14 Oct 2002, Will Hartung wrote:

> Date: Mon, 14 Oct 2002 14:30:40 -0700
> From: Will Hartung <[EMAIL PROTECTED]>
> Reply-To: Tomcat Users List <[EMAIL PROTECTED]>
> To: Tomcat Users List <[EMAIL PROTECTED]>
> Subject: Re: WEB-INF/classes, WEB-INF/lib
>
>
> - Original Message -
> From: "Craig R. McClanahan" <[EMAIL PROTECTED]>
> To: "Tomcat Users List" <[EMAIL PROTECTED]>
> Sent: Monday, October 14, 2002 2:11 PM
> Subject: RE: WEB-INF/classes, WEB-INF/lib
>
>
> >
> >
> > On Mon, 14 Oct 2002, Scott Purcell wrote:
> >
> > > It works on my tomcat on NT. We use a lot of jars, but it it someties
> > > hard to uncompress and compress the jars with changes, so I just put the
> > > updated class in the classes dir and all works out well. When we go to
> > > production, I just jar them all back.
> >
> > Containers that follow the servlet spec's requirements will load classes
> > from "/WEB-INF/classes" before they look at the JAR files in
> > "/WEB-INF/lib".  [Section 9.5, last sentence before 9.5.1 starts].
>
> Do they do this on a class level, or on a package level. So, from what I see
> hear, "patching" a WEB-INF/lib JAR file with a overriding class in the
> WEB-INF/classes directory will work as anticipated?
>

It's done at a per-class (or per-resource if you've got embedded
resources) level, rather than per-package.

Incidentally, Tomcat implements the exact same algorithm for the shared
class loaders as well:

- Classes in $CATALINA_HOME/shared/classes override classes
  in JAR files under $CATALINA_HOME/shared/lib

- Classes in $CATALINA_HOME/common/classes override classes
  in JAR files under $CATALINA_HOME/common/lib.

> I never know how much caching of lookup Java is allowed to do with class
> lookups, or whether it does any at all (though I do assume it caches the
> directories/JARs when first visited, and does not look at those again, but
> perhaps that's a bad assumption).
>

The classes and resources themselves are cached only when they are loaded.
However, a related question is "can I add new classes and resources
dynamically while the app is running, and have them recognized"?  The
answer for Tomcat, if you're running unpacked, is yes - but ONLY until the
class has been loaded.  You can't use this technique to replace an already
loaded class, because Java gives us no mechanism to do that.

> Regards,
>
> Will Hartung
> ([EMAIL PROTECTED])
>

Craig


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Re: WEB-INF/classes, WEB-INF/lib

[Will Hartung]

- Original Message -
From: "Craig R. McClanahan" <[EMAIL PROTECTED]>
To: "Tomcat Users List" <[EMAIL PROTECTED]>
Sent: Monday, October 14, 2002 2:11 PM
Subject: RE: WEB-INF/classes, WEB-INF/lib


>
>
> On Mon, 14 Oct 2002, Scott Purcell wrote:
>
> > It works on my tomcat on NT. We use a lot of jars, but it it someties
> > hard to uncompress and compress the jars with changes, so I just put the
> > updated class in the classes dir and all works out well. When we go to
> > production, I just jar them all back.
>
> Containers that follow the servlet spec's requirements will load classes
> from "/WEB-INF/classes" before they look at the JAR files in
> "/WEB-INF/lib".  [Section 9.5, last sentence before 9.5.1 starts].

Do they do this on a class level, or on a package level. So, from what I see
hear, "patching" a WEB-INF/lib JAR file with a overriding class in the
WEB-INF/classes directory will work as anticipated?

I never know how much caching of lookup Java is allowed to do with class
lookups, or whether it does any at all (though I do assume it caches the
directories/JARs when first visited, and does not look at those again, but
perhaps that's a bad assumption).

Regards,

Will Hartung
([EMAIL PROTECTED])




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RE: WEB-INF/classes, WEB-INF/lib

[Craig R. McClanahan]

On Mon, 14 Oct 2002, Scott Purcell wrote:

> It works on my tomcat on NT. We use a lot of jars, but it it someties
> hard to uncompress and compress the jars with changes, so I just put the
> updated class in the classes dir and all works out well. When we go to
> production, I just jar them all back.

Containers that follow the servlet spec's requirements will load classes
from "/WEB-INF/classes" before they look at the JAR files in
"/WEB-INF/lib".  [Section 9.5, last sentence before 9.5.1 starts].

> Scott

Craig


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RE: WEB-INF/classes, WEB-INF/lib

[Scott Purcell]

It works on my tomcat on NT. We use a lot of jars, but it it someties hard to 
uncompress and compress the jars with changes, so I just put the updated class in the 
classes dir and all works out well. When we go to production, I just jar them all back.



Scott

-Original Message-
From: Frank Liu [mailto:[EMAIL PROTECTED]]
Sent: Monday, October 14, 2002 3:04 PM
To: [EMAIL PROTECTED]
Subject: WEB-INF/classes, WEB-INF/lib



Is it true that WEB-INF/classes overrides WEB-INF/lib in the classpath?
I have a binary jar file in WEB-INF/lib and need to overwrite on class
in the jar file, can you just put my class in the WEB-INF/classes and
tomcat will take care of it automatically?

Frank



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WEB-INF/classes, WEB-INF/lib

[Frank Liu]

Is it true that WEB-INF/classes overrides WEB-INF/lib in the classpath?
I have a binary jar file in WEB-INF/lib and need to overwrite on class
in the jar file, can you just put my class in the WEB-INF/classes and
tomcat will take care of it automatically?

Frank



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