Spring – Setter Injection with 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 has a list of employees.

Java

// Java program to Illustrate Company Class

package com.geeksforgeeks.org;

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

// Company Class
class Company {

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

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

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

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

    // Getter
    public List<String> getEmployees() { return employees; }

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

        // Iterating over using for each loop
        for (String employee : employees) {
            System.out.println("-" + employee);
        }
    }
}

B. applicationContext.xml

We will use property element for setter injection. The name element of the property attribute will be equal to the variable name and the value element will contain the value you want to assign to that variable.

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="company" class="com.geeksforgeeks.org.Company">
        <property name="companyName" value="GeeksForGeeks"></property>
        <property name="employees">
            <list>
                 <value>"John"</value>
                <value>"Max"</value>
                <value>"Sam"</value>
             </list>
         </property>
    </bean>
</beans>

C. Main.java

Java

// Java Program to Illustrate Application Class

package com.geeksforgeeks.org;

// Importing required classes
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 (Main) 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 Employee class
        Employee e = (Employee)factory.getBean("employee");

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

Output:

Company: GeeksForGeeks
Employee list:
-John
-Max
-Sam