Spring c-namespace example

By Atul Rai | Last Updated: July 25, 2018 Previous       Next

Spring c-namespace is used to inject the constructor-based dependency injection. It is similar to p-namespace as described previous tutorial. The c-namespace is XML shortcut and replacement of <constructor-arg/> subelement of <bean/> tag. It also reduces the numbers of line in the configuration file and introduced in Spring 3.1.

The following example shows two XML snippets that resolve to the same result: The first uses standard XML format and the second uses the c-namespace.

<!-- old style -->
<bean id="oldboss" class="beans.Boss">
    <constructor-arg name="name" value="Atul Rai" />
    <constructor-arg name="employee" ref="oldemp" />
</bean>
<bean id="oldemp" class="beans.Employee">
    <constructor-arg name="empName" value="Mukul" />
    <constructor-arg name="empSalary" value="1000000" />
</bean>

<!-- new style -->
<bean id="newboss" class="beans.Boss" c:name="Atul Rai" c:employee-ref="newemp" />
<bean id="newemp" class="beans.Employee" c:empName="Mukul" c:empSalary="1000000" />

Note: In case of an overloaded constructor, just pass the parameter name and Spring will find out its type.

Dependency Required

To resolve the dependency problem, add the following to your pom.xml file.

<dependencies>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context</artifactId>
        <version>5.0.2.RELEASE</version>
    </dependency>
</dependencies>

Or directly add these JARs to your project build path.

1. spring-context-5.0.2.RELEASE.jar
2. spring-aop-5.0.2.RELEASE.jar
3. spring-beans-5.0.2.RELEASE.jar
4. spring-core-5.0.2.RELEASE.jar
5. spring-expression-5.0.2.RELEASE.jar

Spring Beans

Create the bean classes and its parameterized constructor.

package org.websparrow.beans;

public class Employee {

	// Generate getters....
	private String empName;
	private int empSalary;

	public Employee(String empName, int empSalary) {
		this.empName = empName;
		this.empSalary = empSalary;
	}

	public String getEmpName() {
		return empName;
	}

	public int getEmpSalary() {
		return empSalary;
	}

}

package org.websparrow.beans;

public class Boss {

	private String name;
	private String officeLocation;
	private Employee employee;

	// Parameterized constructor
	public Boss(String name, String officeLocation, Employee employee) {
		this.name = name;
		this.officeLocation = officeLocation;
		this.employee = employee;
	}

	// business logic
	public void display() {
		System.out.println("Boss and Employee details....\n");
		System.out.println("Boss name: " + name);
		System.out.println("Office Location: " + officeLocation);
		System.out.println("Employee name: " + employee.getEmpName());
		System.out.println("Employee salary: " + employee.getEmpSalary());
	}

}

Spring Beans Configuration

Add c-namespace schema into root tag beans.

<?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:c="http://www.springframework.org/schema/c"
	xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans.xsd">

	<bean id="boss" class="org.websparrow.beans.Boss" c:name="Atul Rai" c:officeLocation="India"
		c:employee-ref="emp" />

	<bean id="emp" class="org.websparrow.beans.Employee" c:empName="Mukul" c:empSalary="1000000" />

</beans>

Run it

Load the configuration file and run it.

package org.websparrow.clients;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.websparrow.beans.Boss;

public class Client {
	public static void main(String[] args) {

		ApplicationContext context = new ClassPathXmlApplicationContext("spring.xml");
		Boss boss = (Boss) context.getBean("boss");
		boss.display();
	}
}

You will get the following result in your console log.

Boss and Employee details....

Boss name: Atul Rai
Office Location: India
Employee name: Mukul
Employee salary: 1000000