Java

Spring Autowire beans that have the same type

With spring annotation @Autowired annotation, we can bind the bean automatically by type.

If there are several beans with the same type, how to decide which one to autowire?

Spring Beans scope: Singleton and Prototype

Singleton

By default, the bean is in singleton pattern. That is, in the spring application context, there will be only instance.

Prototype

Consider builder when facing with many constructor -Effective Java Notes

When to use? we have many parameters in a class.

Some other methods(not good options)

3 Methods to Create Singleton with Java — Effective Java Notes

I only know one singleton creation method before, the factory method. The book list three methods and suggusts that the third method-Enum method is the best one. What a supurise :)

5 Rules for overriding equal method — Effective Java Notes

When we create a new class, most time we need to override the equal method. The book lists 5 rules.

1. Reflexive: x.equals(x) == true , an object must equal to itself.

Overriding hashCode method — Effective Java Notes

When overriding the equalmethod, always override the hashCode()method, or the HashSet, HashMap... methods would fail.

• If two objects equal, then their hashCode must equal.
• If two objects not…