Change the system class loader at runtime

Question

Main class

public class Main {
    public static void main(String[] args) {
        // Class load
        A a = new A();
        a.msg();
    }
}

A class

public class A {
    public void msg() {
      System.out.println("msg");
    }
}

I have written code in the main class that calls a msg() method of class A

After I created the jar file, I pull out A.class.

Then the path will have a jar file with missing A.class, and A.class.

A a = new A();
a.msg();

How do I dynamically load and run A.class without making any changes to the above code?

Please help me..

I think the JVM will be expecting `A.class` to be in the location whence you removed it. Hence, your code will fail. Why do you want to do this? — Tim Biegeleisen, Jan 01 '17 at 23:23
what's the purpose of removing/pulling the A.class after becoming JAR? — A-SM, Jan 01 '17 at 23:24
I wanted to get the bytecode of the class from the local network and load it. — Pneumono, Jan 01 '17 at 23:28

score 0 · Answer 1 · answered Jan 01 '17 at 23:27

0

A.class has to be in the classpath somewhere for the code to run. you can put it in a jar of its own, and add the second jar to the classpath. Then the class loader can find it.

answered Jan 01 '17 at 23:27

Aaron

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I want to get the bytecode of the class on the local network and load it. How do I do this? – Pneumono Jan 01 '17 at 23:38
I don't know how to dynamically load class bytecode. – Pneumono Jan 01 '17 at 23:40

score 0 · Accepted Answer · edited May 23 '17 at 12:16

0

Looks like you want to load a class dynamically. I would recommend you to create a jar and load it using URIClassLoader. There is a really good answer here:- How should I load Jars dynamically at runtime?

edited May 23 '17 at 12:16

Community

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1

answered Jan 02 '17 at 04:47

Mangat Rai Modi

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Change the system class loader at runtime

2 Answers2