CODEWITHSUNDEEP
javalogging
HashimR
HashimR

Reputation: 3843

logging java class variables and its value dynamically

How can I log class variables and its values dynamically?

Is there any way I can print variable names and its value dynamically by using only class object?

Like for example:

We pass Person class object and output is:

Person:: age:10, name: abc

something like that..

EDIT:

There are many classes. Any other solution other than Overriding toString() method? Can it all be dynamic. Like just passing the class object?

Upvotes: 1

Views: 2371

Answers (4)

user2209008
user2209008

Reputation:

You'll want to use something common in managed languages called reflection. Reflection allows you to know about the internals of the program at run-time.

In Java, you'll want to use the getFields() function on your class (or any other class).

@Override
public String toString() {
    for(Field field : this.getClass().getFields()) {
        System.out.println(field.getName() + ":" + field.get(this) + ",");
    }
}

This allows you to add new fields without the need for updating thetoString() functions.

Upvotes: 2

Subhrajyoti Majumder
Subhrajyoti Majumder

Reputation: 41210

Override the Person class toString method.

public String toString(){
   return "Person:: age:"+age+", name: "+name;
}

Upvotes: 0

Mena
Mena

Reputation: 48404

I believe you want to override Object.toString.

Then you can add whatever descriptive field or class name reference you want in the String returned.

Then if you want to log your class dynamically to whatever logger you use (or simply, System.out) you can add an instance statement (possibly after the constructor executed) and log the String representation of your class there.

For instance: 

public class Foo {

    private int blah;
    public Foo() {
        blah = 1;
        System.out.println(this);
    }
    @Override
    public String toString() {
        return getClass().getName().concat(": ").concat(String.valueOf(blah));
    }
}

public class Main {
    public static void main(String[] args) {
        new Foo();
    }
}

Output: 

test.Foo: 1

Upvotes: 0

Juned Ahsan
Juned Ahsan

Reputation: 68715

If you override toString method and use Person class in sysout statements, its toString will be called internally. So override the toString method to print the object as you mentioned.

Upvotes: 0

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