How to Inject Array having Dependent Object using Spring dependency injection by constructor?

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Introduction

In Spring Framework, constructor-based dependency injection is widely used to pass mandatory dependencies to a bean at the time of object initialization. In enterprise applications, you often deal with arrays of custom complex objects rather than just simple primitive types.

In this tutorial, you will learn how to configure Spring XML to inject an Array of Dependent Objects into another class through its constructor.

1. Create the Dependent Class (Fruit)

First, let's create a Fruit class which acts as the dependent model object. It contains basic attributes and a constructor:

public class Fruit {
    private String name;
    private String color;

    public Fruit(String name, String color) {
        this.name = name;
        this.color = color;
    }

    @Override
    public String toString() {
        return "Fruit [name=" + name + ", color=" + color + "]";
    }
}
  

2. Create the Target Class (FruitShop)

Next, create the FruitShop class containing an array of Fruit objects, which will be initialized through its constructor:

import java.util.Arrays;

public class FruitShop {
    private String shopName;
    private Fruit[] fruits;

    public FruitShop(String shopName, Fruit[] fruits) {
        this.shopName = shopName;
        this.fruits = fruits;
    }

    public void displayFruitShopInfo() {
        System.out.println("Shop Name: " + shopName);
        System.out.println("Fruits Array: " + Arrays.toString(fruits));
    }
}
  

3. Configure Spring XML with <array> and <ref>

In your applicationContext.xml, declare the Fruit beans first. Then, use <constructor-arg> with the <array> tag and reference the dependent beans using <ref bean="..." />:

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans 
       http://www.springframework.org/schema/beans/spring-beans.xsd">

    <!-- Dependent Beans -->
    <bean id="fruit1" class="Fruit">
        <constructor-arg value="Apple" />
        <constructor-arg value="Red" />
    </bean>

    <bean id="fruit2" class="Fruit">
        <constructor-arg value="Banana" />
        <constructor-arg value="Yellow" />
    </bean>

    <!-- Target Bean with Array Injection -->
    <bean id="fruitShop" class="FruitShop">
        <constructor-arg value="City Fresh Fruits" />
        <constructor-arg>
            <array value-type="Fruit">
                <ref bean="fruit1" />
                <ref bean="fruit2" />
            </array>
        </constructor-arg>
    </bean>

</beans>
  

4. Test the Implementation

Load the Spring IoC container and run the application to verify that the array with dependent objects is correctly initialized:

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MainApp {
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
        FruitShop shop = (FruitShop) context.getBean("fruitShop");
        shop.displayFruitShopInfo();
    }
}
  

Watch More Spring Tutorials

• How to Inject Array of String using Spring dependency injection by constructor?
• How to Inject List having Dependent Object using Spring dependency injection by constructor?
• How to Inject Dependent Object using Spring dependency injection by constructor?

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How to Inject Array having Dependent Object using Spring dependency injection by constructor?

How to Inject Array having Dependent Object using Spring dependency injection by constructor?

How to Inject Array having Dependent Object using Spring dependency injection by constructor?

How to Inject Array having Dependent Object using Spring dependency injection by constructor?