How to Inject primitive value and String using Spring dependency injection by constructor?

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Introduction

In Spring Framework, Constructor Injection is one of the most reliable approaches to initialize beans because it ensures all mandatory fields—including simple types like numbers and text—are supplied when the object is instantiated.

In this guide, you will learn how to configure Spring XML to inject both primitive data types (such as int, double, or long) and String values using constructor dependency injection.

1. Create the Java Bean Class

Create a model class named Employee that contains a mix of primitive types and a String, along with a matching constructor:

public class Employee {
    private int id;
    private String name;
    private int age;
    private double salary;

    public Employee(int id, String name, int age, double salary) {
        this.id = id;
        this.name = name;
        this.age = age;
        this.salary = salary;
    }

    public void displayEmployeeInfo() {
        System.out.println("Employee ID: " + id);
        System.out.println("Employee Name: " + name);
        System.out.println("Employee Age: " + age);
        System.out.println("Employee Salary: " + salary);
    }
}
  

2. Configure Spring XML with <constructor-arg>

In your applicationContext.xml, declare the bean and define each argument using <constructor-arg>. You can specify the type and value attributes to avoid type ambiguity:

<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">

    <bean id="employeeBean" class="Employee">
        <constructor-arg type="int" value="101" />
        <constructor-arg type="java.lang.String" value="John Doe" />
        <constructor-arg type="int" value="28" />
        <constructor-arg type="double" value="65000.50" />
    </bean>

</beans>
  

3. Load Context and Run the Application

Initialize the Spring IoC container with ClassPathXmlApplicationContext, get the bean, and display the initialized values:

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");
        Employee emp = (Employee) context.getBean("employeeBean");
        emp.displayEmployeeInfo();
    }
}
  

Watch More Spring Tutorials

• How to Inject Primitive Value Using Spring dependency injection by constructor? | Spring Tutorial
• How to Inject String value using Spring dependency injection by constructor? | Spring Tutorial
• Spring Dependency Injection via Setter Method: Injecting Primitive Values and Strings

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How to Inject primitive value and String using Spring dependency injection by constructor?

How to Inject primitive value and String using Spring dependency injection by constructor?

How to Inject primitive value and String using Spring dependency injection by constructor?

How to Inject primitive value and String using Spring dependency injection by constructor?