JAVA EE: How to use ClassPathXmlApplicationContext? | Spring Tutorial | Spring basics

Thursday, 24 May 2018

How to use ClassPathXmlApplicationContext? | Spring Tutorial | Spring basics | Spring Framework

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Introduction

In Spring applications, the IoC (Inversion of Control) container manages bean creation, wiring, and lifecycle. One of the most popular implementations of ApplicationContext is ClassPathXmlApplicationContext, which loads bean configuration XML files directly from your application's classpath.

In this guide, you will learn how to configure Spring XML files and bootstrap the Spring IoC container using ClassPathXmlApplicationContext in Java.

1. Create the Java Bean Class

Start by creating a standard Java POJO class (for example, HelloWorld) with a message property and a greeting method:

public class HelloWorld {
    private String message;

    public void setMessage(String message) {
        this.message = message;
    }

    public void sayHello() {
        System.out.println("Greeting Message: " + message);
    }
}

2. Define Spring XML Configuration (applicationContext.xml)

Place your configuration file in the classpath root (such as src/main/resources) and declare your bean definition:

<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="helloWorldBean" class="HelloWorld">
        <property name="message" value="Welcome to Spring Framework!" />
    </bean>

</beans>

3. Load Context Using ClassPathXmlApplicationContext

Instantiate ClassPathXmlApplicationContext by passing the name of the XML configuration file, retrieve the bean by ID, and execute the method:

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

public class App {
    public static void main(String[] args) {
        // Load the Spring XML configuration from classpath
        ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");

        // Retrieve the bean from the IoC container
        HelloWorld hello = (HelloWorld) context.getBean("helloWorldBean");

        // Call the method
        hello.sayHello();
    }
}

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pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0%20http://maven.apache.org/maven-v4_0_0.xsd">

    <modelVersion>4.0.0</modelVersion>

    <groupId>com.ram.core</groupId>

    <artifactId>SpringDemo</artifactId>

    <packaging>jar</packaging>

    <version>1.0-SNAPSHOT</version>

    <name>SpringDemo</name>

    <url>http://maven.apache.org</url>

    <properties>

        <spring.version>5.0.2.RELEASE</spring.version>

    </properties>

    <dependencies>

        <dependency>

            <groupId>junit</groupId>

            <artifactId>junit</artifactId>

            <version>3.8.1</version>

            <scope>test</scope>

        </dependency>

        <!-- Spring 5 dependencies -->

        <dependency>

            <groupId>org.springframework</groupId>

            <artifactId>spring-core</artifactId>

            <version>${spring.version}</version>

        </dependency>

        <dependency>

            <groupId>org.springframework</groupId>

            <artifactId>spring-context</artifactId>

            <version>${spring.version}</version>

        </dependency>

    </dependencies>

</project>

Employee.java

package com.ram.model;

/**

 * Spring bean

 *

 */

public class Employee

{

    private String name;

    public void setName(String name)

    {

        this.name = name;

    }

    public void employeeDetails()

    {

        System.out.println("Employee Name =  " + name);

    }

}

applicationContext.xml

<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-4.3.xsd">

    <bean id="employee" class="com.ram.model.Employee">

        <property name="name" value="Peter" />

    </bean>

</beans>

App.java

package com.ram.core;

import org.springframework.context.ApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.ram.model.Employee;

public class App

{

    public static void main(String[] args)

    {

        /*

         * Create a new ClassPathXmlApplicationContext, loading the

         * definitions from the given XML file and automatically

         * refreshing the context.

         * 

         * Parameters:

         * 

         * configLocation - resource location

         */

        ApplicationContext context = new ClassPathXmlApplicationContext(

                "applicationContext.xml");

        System.out.println("---------------------------------------");

        Employee employee = context.getBean("employee", Employee.class);

        System.out.println(

                "Got employee object from the ApplicationContext(Spring Container)");

        employee.employeeDetails();

    }

}

Output

Apr 09, 2018 8:36:57 AM org.springframework.context.support.AbstractApplicationContext prepareRefresh

INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@2096442d: startup date [Mon Apr 09 08:36:56 IST 2018]; root of context hierarchy

Apr 09, 2018 8:36:58 AM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions

INFO: Loading XML bean definitions from class path resource [applicationContext.xml]

---------------------------------------

Got employee object from the ApplicationContext(Spring Container)

Employee Name =  Peter