Dependency injection through constructor

// Employee.java

// EmployeeClient.java

//applicationContext.xml

// Student.java

//StudentClient.java

//studentbean.xml

                                                                    Project Hierarchy:-

// Employee.java

package govind;

public class Employee {

int empId;

String empName;

String empAddress;

float empSalary;

public Employee()

{

            System.out.println("Default Constructor");

}

public Employee(int empId) {

            super();

            this.empId = empId;

}

public Employee(String empName) {

            super();

            this.empName = empName;

}

public Employee(float empSalary) {

            super();

            this.empSalary = empSalary;

}

public Employee(int empId, String empName, String empAddress, float empSalary) {

            super();

            this.empId = empId;

            this.empName = empName;

            this.empAddress = empAddress;

            this.empSalary = empSalary;

}

public void displayData()

{

            System.out.println("Empid="+empId+"EmpName="+empName+"EmpAddress="+empAddress+"EmpSalary="+empSalary);

}

}

//applicationContext.xml

<?xml version="1.0" encoding="UTF-8"?>

<beans 

    xmlns="http://www.springframework.org/schema/beans" 

    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 

    xmlns:p="http://www.springframework.org/schema/p" 

    xsi:schemaLocation="http://www.springframework.org/schema/beans 

                http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">

               

          

  <bean id="empbean" class="govind.Employee">

   <!-- case 1 calling int arg constructor -->

 <!--  <constructor-arg value="1001" type="int"></constructor-arg> -->

 

     <!-- case 2 calling float arg constructor-->

   <!--  <constructor-arg value="10000.00" type="float"></constructor-arg> -->  

   <!-- case 3 calling String arg constructor-->

   <!-- <constructor-arg value="GovindBallabhKhan" type="java.lang.String"></constructor-arg>  -->

     <!-- case 4 calling parameterized constructor -->

   <constructor-arg value="1001"  type="int"></constructor-arg>

                <constructor-arg value="GovindBallabhKhan" ></constructor-arg>

        <constructor-arg value="Madhubani-Bihar" ></constructor-arg>

         <constructor-arg value="35000.00" type="float" ></constructor-arg>

      

       <!-- case 5 type not defined then string type arg call-->

       <!--   <constructor-arg value="1001" ></constructor-arg>-->

      

 

  </bean>              

 </beans>

//EmployeeClient.java

package govind;

import org.springframework.context.ApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class EmployeeClient {

               

                public static void main(String[] args) {

                                ApplicationContext ac=new ClassPathXmlApplicationContext("applicationContext.xml");

                                Employee e = (Employee)ac.getBean("empbean");

                                e.displayData();

                }

}

o/p view:----calling parametrized constructor

Empid=1001EmpName=GovindBallabhKhanEmpAddress=Madhubani-BiharEmpSalary=35000.0

=====================================================================

// Student.java

package govind;

public class Student {

           

            int sid;

            String sname;

            float percentage;

            public Student(int sid, String sname,float percentage) {

           

                        super();

                        System.out.println("3 arg constructor");

                        this.sid = sid;

                        this.sname = sname;

                        this.percentage=percentage;

            }

           

            public Student( String sname,int sid) {

                        super();

                        System.out.println("2 arg constructor");

                        this.sname = sname;

                        this.sid = sid;

                       

            }

           

            public void displayData()

            {

                        System.out.println("Student Name="+sname+" "+"Student Id="+sid+" Student Percentage="+percentage);

            }

           

           

}

//studentbean.xml

<?xml version="1.0" encoding="UTF-8"?>

<beans 

    xmlns="http://www.springframework.org/schema/beans" 

    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 

    xmlns:p="http://www.springframework.org/schema/p" 

    xsi:schemaLocation="http://www.springframework.org/schema/beans 

                http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">

               

          

  <bean id="stubean1" class="govind.Student">

  <constructor-arg value="Govind Ballabh Khan" type="java.lang.String"></constructor-arg>

   <constructor-arg value="1001" type="int"></constructor-arg>

  </bean> 

<bean id="stubean2" class="govind.Student">

  <constructor-arg value="1001" type="int"></constructor-arg>

  <constructor-arg value="Govind Ballabh Khan" type="java.lang.String"></constructor-arg>

    <constructor-arg value="76.7" type="float"></constructor-arg>

  </bean>

</beans>

// StudentClient.java

package govind;

import org.springframework.context.ApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class StudentClient {

            public static void main(String[] args) {

                        ApplicationContext ac=new ClassPathXmlApplicationContext("studentbean.xml");

                        Student s1 = (Student)ac.getBean("stubean1");

                        s1.displayData();

                        Student s2 = (Student)ac.getBean("stubean2");

                        s2.displayData();

                       

            }

            }

o/p  view :-----

2 arg constructor

3 arg constructor

Student Name=Govind Ballabh Khan Student Id=1001 Student Percentage=0.0

Student Name=Govind Ballabh Khan Student Id=1001 Student Percentage=76.7