Spring – Injecting Objects by Setter Injection

Spring IoC (Inversion of Control) Container is the core of Spring Framework. It creates the objects, configures and assembles their dependencies, manages their entire life cycle. The Container uses Dependency Injection(DI) to manage the components that make up the application. It gets the information about the objects from a configuration file(XML) or Java Code or Java Annotations and Java POJO class. These objects are called Beans. Since the Controlling of Java objects and their lifecycle is not done by the developers, hence the name Inversion Of Control. The followings are some of the main features of Spring IoC,

• Creating Object for us,
• Managing our objects,
• Helping our application to be configurable,
• Managing dependencies

Spring Dependency Injection

Dependency Injection is the main functionality provided by Spring IOC(Inversion of Control). The Spring-Core module is responsible for injecting dependencies through either Constructor or Setter methods. The design principle of Inversion of Control emphasizes keeping the Java classes independent of each other and the container frees them from object creation and maintenance. These classes, managed by Spring, must adhere to the standard definition of Java-Bean. Dependency Injection in Spring also ensures loose coupling between the classes. There are two types of Spring Dependency Injection.

• Setter Dependency Injection (SDI)
• Constructor Dependency Injection (CDI)

To read more on Spring Dependency Injection please refer to this article: Spring Dependency Injection with Example

Setter Injection

Setter Injection is the simpler of the two Dependency Injection methods. In this, the Dependency Injection will be injected with the help of setter and/or getter methods. Now to set the Dependency Injection as Setter Injection in the bean, it is done through the bean-configuration file For this, the property to be set with the Setter Injection is declared under the tag in the bean-config file.

So in this article, let’s learn how we are going to use Spring to inject our dependencies into our object values by Setter Injection. Object is a basic unit of Object-Oriented Programming and represents real-life entities. So generally in Java, we create objects of a class using the new keyword.

Test t = new Test(); // creating object of class Test // t is the object

Implementation: Suppose we have a class named “Student” and inside the class, we want to inject the object of another class named “MathCheat”. And there is one method also present inside the class named “cheating()” something like that.

Example 1: