Question

I want to verify binary compatibility between 2 JARs.

Following the suggestions in this answer I used jboss tattletale but it can find only missing classes.

How can I find if there are missing methods? Is it possible at all?

E.g.

“Depends – on” class Foo depends on Bar (like many other middle class workers)

import org.overlyusedclassnames.Bar

public class Foo{
    public void someMethod(){
         Bar tender = new Bar();
         tender.getJohnnyRedLabel();
         tender.getJohnnyBlueLabel(); //this method is new in the Bar class
    }
}

“Compile time” class

package org.overlyusedclassnames;

/** 
 * @Since 1992
 * Changes: added blue and gold Johnny Walker labels
 */

public class Bar {
    public Drink getJohnnyRedLabel(){
         return new JohnyWalkerFactory.get(RedLabel.class);
    }

    public Drink getJohnnyBlackLabel(){
         return new JohnyWalkerFactory.get(BlackLabel.class);
    }

    public Drink getJohnnyGoldLabel(){
         return new JohnyWalkerFactory.get(GoldLabel.class);
    }

    public Drink getJohnnyBlueLabel(){
         return new JohnyWalkerFactory.get(BlueLabel.class);
    }

}

Now imagine an old Bar jar is accedently replacing the compiled time bar:

“Runtime time” class

package org.overlyusedclassnames;

/** 
 * @Since 1909
 * Changes: added red and black Johnny Walker labels
 */

public class Bar {
    public Drink getJohnnyRedLabel(){
         return new JohnyWalkerFactory.get(RedLabel.class);
    }

    public Drink getJohnnyBlackLabel(){
         return new JohnyWalkerFactory.get(BlackLabel.class);
    }
}

Is there a way to identify the missing method without running it and getting a NoSuchMethodError?

---

Disclaimer: This is a major rephrasing of my own related question, which is undeletable. I chose asking a new question because the rephrasing will render the current 2 answers as quite unrelated to the topic.

Answer 1

japi-compliance-checker – backward API/ABI compatibility checker for a Java library:

japi-compliance-checker -lib NAME -old OLD.jar -new NEW.jar

sigtest – Oracle’s SigTest signature testing and API conformance tool

japitools – test for compatibility between Java APIs

japi-checker – a java API backward compatibility checker which works at binary level

revapi – API analysis and change tracking tool

or manually using javap decompiler:

javap OLD.class > OLD.txt
javap NEW.class > NEW.txt
diff -rNau OLD.txt NEW.txt > CHANGES.txt