How Java handle duplicated class?

I am trying to send out email using SUN JavaMail. However, an old version of JavaMail was shipped with Oracle AppServer 10 R2. If I package the new JavaMail into the WAR file, the old JavaMail is still functional, and cause problem to my program. Is there a way to tell the AppServer to use the JavaMail in my WAR file instead of the old one shipped with the server?
Thanks very much!
Edited by: huaichen on Nov 6, 2008 2:02 PM

Hi,
does this help you? It's from an older vesion but might wor kin your case.
How do I setup OC4J to load local classes packaged in my Web Application overriding System classes or classes in the higher level?
OC4J 9.0.3 has a configurable option to load local classes first, overriding classes at a higher level. You have to include the following to directive in the orion-web.xml for your web module to ask OC4J to load local classes:
<web-app-class-loader search-local-classes-first="true" />Timo

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How java handles package/class names

I am developing a strategy for internationalizing our company's middle-ware product. While I have no problem with the GUI's, exceptions, log files etc, I have no concept of how things like classpaths and packages can be specified in an asian language.
For instance, if I have configuration information of com.abccompany.mypackage.MyClass, what will this look like to the asian user? Will they be able to change it to perhaps com.abccompany.mypackage.MyClass2 by entering localized data in Chinese or Arabic? I don't understand how this part works. On the command-line, will they type English script names? Do they run commands like so: java -cp com.abc.pkg1.jarfile.jar MyClass? Will my english filenames, packages, etc be represented in asian characters?
We have a lot of configuration information that specify java classes as String data. I am concerned about the ability to modify this data and have it work correctly in languages that do not use the ascii character set. Is this something I need to be worried about?
I appreciate any input. Thanks in advance.

You do not need to warry about configuration information of com.abccompany.mypackage.MyClass
and command-line no matter what languages used in Asia. Asian users also type in English script names or java -cp com.abc.pkg1.jarfile.jar MyClass as you do so. The only thing you need to note is
that any text strings or messages which you want to show on any panel/dialog/window/frame and so on should be store in a resource file for internationalizing.

How java extends Object class?

It is true that we cannot extend more than one class, it is true that java inherits Object class implicitly (if not explicitly) and it is also true that we can extend class X in class Y.
My question is if java does not support multiple inheritance (directly, using extends) then how does it extends Object (implicitly) and my class X (explicitly)?
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Java does support multi inheritance!Yes I know java support multiple inheritancethrough
interfaces but what I meant was you cannot inherit
multiple classes using "EXTENDS".and that is correct. Do you still have a question
regarding this?Nop, actually due to over-concentration and over-thinking on this topic while reading I lost the track and asked this question.
Thanks
Message was edited by:
Manish_India_1983

How 'java' handles classname passed to it

Hi,
After compiling the .java file, the .class is passed to 'java'
and that runs the program.
Does the 'java' work this way: when we give "java classname", 'java'
strictly would search for classname.class and proceeds thereafter,
The reason i got this doubt is when i gave a command "java
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Thanks for your time.
Kris.

When the java virtual machine looks for a class it uses a ClassLoader. What the default classloader does is:
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2) If it's an inner class, the inner class name is separated from the outer class by a $
4) adds .class to the end
5) Walks along the CLASSPATH. For every directory on the CLASSPATH it adds the string processed above and looks for a file. For every .jar file it tries to find the entry of the same string.
Note "." in a classname is used to separated package name from class, as in java.util.Map, for example. "classname.class" would look for a class called "class" in a package called "classname".
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How to handle similar classes nicely

Suppose I have a function and it should be able to do the same operation to the references. The references can be int[], byte[] or float[]. How can the function to handle this problem nicely? To make it simple, let's say the function will increase each element in the array 1. The best way I can think of is
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for (int i = 0; i < ((int[])array).length; i++)
((int[])array)++;
if (key.equals("float")){
for (int i = 0; i < ((float[])array).length; i++)
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Write overloaded methods:function(int[] array) {
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array[i]++;
function(float[] array) {
for (int i = 0; i < array.length; i++)
array[i]++;
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Confused about CLASSPATH and how java handles import statements...

Hello,
I must admit I don't get it. I read the articles about setting CLASSPATH etc. but I still wonder:
If you use an import statement, what does the compiler do? I.e. where does it look for the specified classes? I find it confusing because I see in different locations different .jar files:
C:\jdk1.3.1_03\lib\dt.jar
C:\jdk1.3.1_03\lib\htmlconvertor.jar
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Thanx for the answers, but I still wonder, everyone
here says I need to set the classpath, but I don't.Probably because your classes are already in the class path. The compiler/jvm also look for classes by themselves not just in jar files, when just a directory is supplied in the class path. And a period (".") is a valid directory.
Programs importing different classes compile with no
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Presumably you are referring to your own code - because they are in the class path.
Second, I still don't understand why the runtime needs
the .jar files. The runtime uses classes, like String, that have to come from somewhere.
This would also mean that end-users
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JRE directory to be able to run programs that import
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Because if I make some nice classes myself and import
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Additionally how the class path gets set is OS specific. Java does not deal with that. You will also have to find some way to deal with this (most likely part of the installation.)
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How Java handle duplicated class?

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