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How can we avoid possibility of circular dependency using constructor injection approach?

To avoid circular dependency using constructor injection, make sure that two classes do not depend on each other directly through their constructors. If Class A needs Class B, and Class B also needs Class A, this creates a loop that cannot be resolved.

How to avoid it:

1: Refactor your code so only one class depends on the other via constructor.

2: Use interfaces or abstractions if needed.

3: Consider using setter injection or property injection for one of the classes, instead of constructor injection.

In short:

Never let two classes require each other in their constructors. Break the cycle by changing one dependency to a different injection method.

Problem: Circular Dependency with Constructor Injection

class A {
    private B b;
    public A(B b) { this.b = b; }
}

class B {
    private A a;
    public B(A a) { this.a = a; }
}

This code will cause a circular dependency because A needs B and B needs A via constructors.

Solution: Break the Cycle Using Setter Injection

class A {
    private B b;
    public A(B b) { this.b = b; }
}

class B {
    private A a;
    public B() { }
    public void setA(A a) { this.a = a; }
}

Now, only A depends on B via constructor, and B gets A using a setter method. This avoids the circular dependency problem.

Summary:

Use constructor injection for one class and setter (or property) injection for the other to break the circular dependency.