Spring – Setter Injection with Non-String Collection

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. In Setter Dependency Injection(SDI) the dependency will be injected with the help of setters and getters methods. A bean-configuration file is used to set DI as SDI in the bean. For this, the property to be set with the SDI is declared under the <property> tag in the bean-config file.

A Collection in java is a group of individual objects. Spring framework provides us facility of Setter injection using the following Collections:

• List
• Map
• Set

Implementation

A. Company.java

A company can have multiple employees. Here the Company class has a relationship with the Employee class. The Company class will contain the instances of Employee class. Hence, the Employee object will be the dependent object. We will use a list of this dependent object to demonstrate setter injection with non-string(dependent object) collection(list).

Java

// Java Program to Illustrate Company Class

package com.geeksforgeeks.org;

// Importing required classes
import java.util.*;

// Class
class Company {

    // Class data members
    private String companyName;
    private List<Employee> employees;

    // Setter
    public void setCompanyName(String companyName)
    {
        this.companyName = companyName;
    }

    // Setter
    public void setEmployees(List<Employee> employees)
    {
        this.employees = employees;
    }

    // method
    public String getCompanyName() { return companyName; }

    public List<Employee> getEmployees()
    {
        return employees;
    }

    // Method
    public void display()
    {
        System.out.println("Company: " + companyName);
        System.out.println("Empoyees:");

        // Iterating over using for each loop
        for (Employee employee : employees) {
            System.out.println(employee.toString());
        }
    }
}

B. Employee.java

Employee class has the following properties:

• Name
• Employee ID
• Department

Java

// Java Program to Illustrate Employee Class

package com.geeksforgeeks.org;

// Class
class Employee {

    // Class data members
    private String name;
    private String employeeID;
    private String department;

    // Method
    public String getName() { return name; }

    // Setter
    public void setName(String name) { this.name = name; }

    // Getter
    public String getEmployeeID() { return employeeID; }

    // Setter
    public void setEmployeeID(String employeeID)
    {
        this.employeeID = employeeID;
    }

    // Getter
    public String getDepartment() { return department; }

    // Setter
    public void setDepartment(String department)
    {
        this.department = department;
    }

    // Method
    // Overriding toString() method of String class
    @Override public String toString()
    {
        return ("[Name: " + name
                + ", Employee Id: " + employeeID
                + ", Department: " + department + "]");
    }
}

C. applicationContext.xml

It is a configuration file that contains all the beans.

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="employee1" class="com.geeksforgeeks.org.Employee">
        <property name="name" value="John"></property>
        <property name="employeeID" value="211"></property>
        <property name="department" value="Penetration testing"></property>
    </bean>

    <bean id="employee2" class="com.geeksforgeeks.org.Employee">
        <property name="name" value="Max"></property>
        <property name="employeeID" value="212"></property>
        <property name="department" value="Ethical hacking"></property>
    </bean>

        <bean id="company" class="com.geeksforgeeks.org.Company">
        <property name="companyName" value="GeeksForGeeks"></property>
        <property name="employees">
            <list>
                 <ref bean="employee1"/>
                <ref bean="employee2"/>
             </list>
         </property>
    </bean>
</beans>

D. Main.java

This is our application(main) class which will call the display() method of the Company class

Java

// Java Program to Illustrate Application Class

package com.geeksforgeeks.org;

// Importing required classes from respective packages
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.xml.XmlBeanFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.Resource;

// Application class
public class Main {

    // Main driver method
    public static void main(String[] args)
    {
        // Creating a new class path resource
        Resource resource = new ClassPathResource(
            "applicationContext.xml");

        // Creating an object of BeanFactory class
        BeanFactory factory = new XmlBeanFactory(resource);

        // Creating an object of Company class
        Company c = (Company)factory.getBean("company");

        // Calling display() method inside main() method
        c.display();
    }
}

Output:

Company: GeeksForGeeks
Employees:
[Name: John, Employee ID: 211, Department: Penetration testing]
[Name: Sam, Employee ID: 212, Department: Ethical hacking]