Spring Boot 2 XML Based Configuration Example - RameshMF/spring-boot-developers-guide GitHub Wiki

In this article, we will quickly discuss how to develop a simple Spring boot 2 application using XML based Spring configuration.

In this example, we don't use either Annotation-based configuration or Java-based configuration, we only use XML based configuration to create and configure beans.

Spring provides a @ImportResource annotation is used to load beans from an applicationContext.xml file into an Application Context.

@ImportResource({"classpath*:applicationContext.xml"})

2. Tools and Technologies Used

  • Spring Boot - 2.0.4.RELEASE
  • JDK - 1.8 or later
  • Spring Framework - 5.0.8 RELEASE
  • Maven - 3.2+
  • IDE - Eclipse or Spring Tool Suite (STS)

Create and Import Spring Boot application

Let's quickly create a Spring Boot application using Spring Initializr at http://start.spring.io/, which is an online Spring Boot application generator.

package structure diagram

The pom.xml File

<?xml version="1.0" encoding="UTF-8"?>
<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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>

	<groupId>net.guides.springboot2</groupId>
	<artifactId>springboot2-annotation-config</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>jar</packaging>

	<name>springboot2-annotation-config</name>
	<description>Demo project for Spring Boot</description>

	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.0.4.RELEASE</version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>

	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
		<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
		<java.version>1.8</java.version>
	</properties>

	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>

		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
			<scope>test</scope>
		</dependency>
	</dependencies>

	<build>
		<plugins>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
			</plugin>
		</plugins>
	</build>
</project>

Create few Services

MessageService.java

public interface MessageService {
	public void sendMsg(String message);
}

EmailService.java

import org.springframework.stereotype.Service;

@Service("EmailService")
public class EmailService implements MessageService{

	public void sendMsg(String message) {
		System.out.println(message);
	}

}

SMSService.java

import org.springframework.stereotype.Service;

public class SMSService implements MessageService{

	public void sendMsg(String message) {
		System.out.println(message);
	}

}

TwitterService.java

import org.springframework.stereotype.Service;

public class TwitterService implements MessageService{

	public void sendMsg(String message) {
		System.out.println(message);
	}

}

UserService.java

public interface UserService {
	public void processMsg(String message);
}

UserServiceImpl.java

package net.guides.springboot2.springboot2annotationconfig.service;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Service;

public class UserServiceImpl implements UserService {

	private MessageService messageService;

	public void setMessageService(MessageService messageService) {
		this.messageService = messageService;
	}

	public void processMsg(String message) {
		messageService.sendMsg(message);
	}
}

The applicationContext.xml File

Let's create and configure Spring beans in applicationContext.xml file.

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

	<!-- <context:component-scan base-package="com.in28minutes.spring.basics"/> -->

	<bean id="emailService"
		class="net.guides.springboot2.springboot2xmlconfig.service.EmailService" />
	<bean id="sMSService"
		class="net.guides.springboot2.springboot2xmlconfig.service.SMSService" />
	<bean id="twitterService"
		class="net.guides.springboot2.springboot2xmlconfig.service.TwitterService" />
	<bean id="messageProcessor"
		class="net.guides.springboot2.springboot2xmlconfig.service.MessageProcessorImpl">
		<property name="messageService" ref="twitterService"></property>
	</bean>

</beans>

Running Application

This spring boot application has an entry point Java class called SpringBootCrudRestApplication.java with the public static void main(String[] args) method, which you can run to start the application.

Note that we have used @ImportResource annotation is used to load beans from an applicationContext.xml file into an Application Context.

@ImportResource({"classpath*:applicationContext.xml"})
package net.guides.springboot2.springboot2xmlconfig;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.ImportResource;

import net.guides.springboot2.springboot2xmlconfig.service.MessageProcessor;

@SpringBootApplication
@ImportResource({"classpath*:applicationContext.xml"})
public class Springboot2XmlConfigApplication {

	public static void main(String[] args) {
		ApplicationContext applicationContext = SpringApplication.run(Springboot2XmlConfigApplication.class, args);

		MessageProcessor userService = applicationContext.getBean(MessageProcessor.class);
		userService.processMsg("twitter message sending ");
	}
}

Output

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