Dependency Injection in Spring Example

Dependency Injection in Spring Example
Here is the code for Dependency Injection in Spring. This code is tested using NetBeans 8.0.2.

Dependency Injection:
Dependency Injection is a process where the Object define its Dependencies, that is with the Objects they work with.

Tightly Coupled vs Loosely Coupled
Tightly Coupled: 
In tightly coupled objects interdependent on each other, So when a change is one Object requires changes to number of other objects.

Loosely Coupled:
In Loosely coupled, Reduces the inter-dependencies of the Objects, that is, Change made in one object does not require to make changes in other objects.

Types of Dependency Injection:
There are two ways in Dependency Injection,

• Setter Injection
• Constructor Injection

Create Project:
File –>New Project –>Java –>Web Application
Give a name to Web Application and click Next–>Next–>
Choose the Framework Spring and click Finish

Required Folders:
Right click the Source Packages and Create 2 Java Packages and name them as
1) Dao
2) SimpleValues

Inside Dao create a Java Class and name it as Studentdao.java
Inside SimpleValues create java class and name it as Student.java

Directory Structure

Student.java

public class Student {
    String sname;
    String marks;
    int number;
    
    public Student(int number) // Constructor Injection
    {
        this.number=number;
    }
    
    public void sid()
    {
        System.out.println("ID number is: "+number);
    }
    
    public int getNumber() { //Setter Injection
        return number;
    }

    public void setNumber(int number) {
        this.number = number;
    }

    public String getSname() {
        return sname;
    }

    public void setSname(String sname) {
        this.sname = sname;
    }

    public String getMarks() {
        return marks;
    }

    public void setMarks(String marks) {
        this.marks = marks;
    }
    
    public void display()
    {
        System.out.println(sname+" scored marks of "+marks+" in Computer Science");
    }
   
}

applicationContext.xml

<beans>
  <bean id="Alpha" class="SimpleValues.Student">
        <property name="sname" value="Alpha"></property>
        <property name="marks" value="92"></property>
        <constructor-arg value="132"/>
    </bean>
    
    <bean id="Beta" class="SimpleValues.Student">
        <property name="sname" value="Beta"></property>
        <property name="marks" value="96"></property>
        <constructor-arg value="212"/>
    </bean>
</beans>

Studentdao.java

public class StudentDao {
    public static void main(String args[])
    {
        ApplicationContext ac=new ClassPathXmlApplicationContext("applicationContext.xml");
        Student student1=(Student)ac.getBean("Alpha");
        Student student2=(Student)ac.getBean("Beta");
        
        student1.display();
        student1.sid();
        
        student2.display();
        student2.sid();    
    }
}

Output: