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Sunday, July 09, 2017

Standalone Spring Application

Having a basic spring standalone application ready always helps when you want to do a quick POC or test of new libraries or tools you plan to use. This post shows a couple of ways in which you can setup a basic Spring standalone application.

  • Spring Standalone application with ApplicationContext XML Configuration file.
  • Spring Standalone application with Annotations

Continue to full post...

For this application I will use a simple service class TestService that has a single method echo(), which returns the Upper case version of any string passed as a parameter. The TestService class will be used a component to be injected into the main application class.

Spring Standalone application with ApplicationContext XML Configuration file

In this model we have 4 files

  1. SpringStandaloneTest.java
  2. TestService.java
  3. applicationContext.xml
  4. build.gradle (will go over the gradle build in the next post)
Following are the files used for this application

SpringStandaloneTest.java
package main;

import org.springframework.context.support.ClassPathXmlApplicationContext;

import service.TestService;

public class SpringStandaloneTest {

 public static void main(String[] args) {
  ClassPathXmlApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
  SpringStandaloneTest test = ctx.getBean("springStandalone", SpringStandaloneTest.class);
  test.callService();

 }

 private TestService testService = null;

 private void callService() {
  System.out.println(testService.echo("Hello"));

 }

 public TestService getTestService() {
  return testService;
 }

 public void setTestService(TestService testService) {
  this.testService = testService;
 }

}
TestService.java
package service;

public class TestService {
 
 public String echo(String str) {
  return str.toUpperCase();
 }

}
applicationContext.xml
<?xml version="1.0" encoding="UTF-8"?>
<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 name="testService" class="service.TestService" />
 <bean name="springStandalone" class="main.SpringStandaloneTest">
  <property name="testService" ref="testService"></property>
 </bean>

</beans>

Spring Standalone application with Annotations

In this model, we will setup the standalone application with annotations instead of the applicationContext.xml file. The annotation @Component is used to define a class as a Spring component, so that Spring can detect it as a Spring bean. The @ComponentScan is used to direct Spring where to look for Components. It is similar to the directive when using Spring XML configuration. The following is the code used to implement the Standalone Spring application using annotations.

SpringStandaloneTest.java
package main;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.ComponentScan;

import service.TestService;

@ComponentScan(basePackages= {"main", "service"})
public class SpringStandaloneTest {

 public static void main(String[] args) {
  ApplicationContext context = new AnnotationConfigApplicationContext(SpringStandaloneTest.class);

  SpringStandaloneTest test = context.getBean(SpringStandaloneTest.class);
  test.callService();
  
 }

 @Autowired
 private TestService service = null;

 private void callService() {
  System.out.println(service .echo("Hello"));

  
 }

}
TestService.java
package service;

import org.springframework.stereotype.Component;

@Component
public class TestService {
 
 public String echo(String str) {
  return str.toUpperCase();
 }

}
In the next post I will describe the Gradle build setup used for this standalone application.

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