Java class dynamic loading process

Question

I am having an argument with my professor which I cant seem to find an answer to in google... My question is, when I use a method that is in another class, the JVM will try and find the class's .class file right? and the argument is this: if the .class file is not found will there be a search for the source file and if found it will be recompiled or will it throw an exception? Thanks!

UPDATE: I rephrased the question, I will be very grateful for your help!

JVM doesnt compile source code, so it will through an exception directly — Saddam Abu Ghaida
– Saddam Abu Ghaida, Commented Feb 11, 2014 at 9:29
Then whoever is responsible for it, because I know that this process does happen when you compile your project — user2466613
– user2466613, Commented Feb 11, 2014 at 9:30
@SaddamAbuGhaida Actually it can compile "things". E.g. it can contain a JIT compiler to compile bytecode to native code. But it doesn't compile source code, here you are correct. — Puce
– Puce, Commented Feb 11, 2014 at 9:30

Jorge_B · Accepted Answer · 2014-02-11 09:34:27Z

2

It is not at all the standard behavior, and will not work in a normal environment.

However, I have heard of some commercial app server distributions that were able to do that... someone told me about older weblogic versions, configured in development mode, but maybe just an urban legend :P

I guess that you could write a tuned classloader that looked for .java files in the classpath and, given it runs on a JDK with a java compiler, do what you say.

answered Feb 11, 2014 at 9:34

Jorge_B

9,8622 gold badges19 silver badges22 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Ingo Over a year ago

Yes, such a classloader would not even be too complicated. The only question is: who reads the error messages. :)

Holger · Accepted Answer · 2014-02-11 09:54:15Z

1

The standard JRE does not even include a compiler for Java source code. To compile Java source code you need a JDK or an IDE which includes its own Java compiler. If you compile your source code using javac or the IDE’s built-in compiler, these compilers will search for source files of the referenced classes and compile them if the .class file was not found or if the source file is newer than the class file. But if you, e.g. delete the class file of the referenced class afterwards and run your program, the JVM won’t search for a source file. It will throw an NoClassDefFoundError.

answered Feb 11, 2014 at 9:54

Holger

301k43 gold badges481 silver badges827 bronze badges

Comments

Shekhar Khairnar · Accepted Answer · 2014-02-11 10:07:28Z

0

JVM will not search for source file for the class whose method we are trying to invoke. JVM will throw a exception like:

    Exception in thread "main" java.lang.Error: Unresolved compilation problems: 
    Employee cannot be resolved to a type
    Employee cannot be resolved to a type
    at com.test.TestIt.main(TestIt.java:7)

Employee is the class whose method we want to call(.class file is not created for Employee)

answered Feb 11, 2014 at 10:07

Shekhar Khairnar

2,7013 gold badges29 silver badges46 bronze badges

Collectives™ on Stack Overflow

Java class dynamic loading process

3 Answers 3

1 Comment

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

1 Comment

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related