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 Spring > Core > Constructor Injection

Constructor Injection 

Spring Inversion of Control (IoC) also known as Dependency Injection (DI) is a process by which objects define their dependencies with collaborating objects. Constructor-based dependency injection allows us to inject dependencies through constructor arguments. Spring container instantiates the bean by invoking the constructor with user provided dependencies.

File Name  :  
/SpringCore001/conf/cons/con_inj.xml 

File Name  :  
com/bethecoder/tutorials/spring3/basic/Employee.java 
   
package com.bethecoder.tutorials.spring3.basic;

public class Employee {
  
  private int id;
  private String name;
  private double salary;
  
  public Employee() {
    super();
    this.id = -1;
    this.name = "Unknown";
    this.salary = 0;
  }
  
  public Employee(int id, String name) {
    super();
    this.id = id;
    this.name = name;
    this.salary = 20000;
  }
  
  public Employee(int id, String name, double salary) {
    super();
    this.id = id;
    this.name = name;
    this.salary = salary;
  }

  public int getId() {
    return id;
  }
  
  public void setId(int id) {
    this.id = id;
  }
  
  public String getName() {
    return name;
  }
  
  public void setName(String name) {
    this.name = name;
  }
  
  public double getSalary() {
    return salary;
  }
  
  public void setSalary(double salary) {
    this.salary = salary;
  }
  
  public String toString() {
    return "Employee[" + id + ", " + name + ", " + salary + "]";
  }
  
}
   

File Name  :  
com/bethecoder/tutorials/spring3/tests/cons/ConstructorInjection.java 
Author  :  Sudhakar KV
Email  :  [email protected]
   
package com.bethecoder.tutorials.spring3.tests.cons;

import org.springframework.beans.factory.xml.XmlBeanFactory;
import org.springframework.core.io.ClassPathResource;

import com.bethecoder.tutorials.spring3.basic.Employee;

public class ConstructorInjection {

  /**
   * @param args
   */
  public static void main(String[] args) {
    XmlBeanFactory factory = new XmlBeanFactory(
                new ClassPathResource("con_inj.xml"));

    Employee emp1 = (Employee) factory.getBean("emp1");
    System.out.println(emp1);

    Employee emp2 = (Employee) factory.getBean("emp2");
    System.out.println(emp2);
    
    Employee emp3 = (Employee) factory.getBean("emp3");
    System.out.println(emp3);
  }

}
   

It gives the following output, 
Employee[-1, Unknown, 0.0]
Employee[1, ABC, 20000.0]
Employee[2, XYZ, 80000.0]



 
  


  
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