Getting Started With Spring Framework

Creating Project

1. Install STS (Spring Tool Suite). It is recommended IDE. If you have ever worked with Eclipse, you find it very easy to use as it is extension of Eclipse. Download STS from https://spring.io/tools/sts. Extract downloaded zip file to a folder and it creates sts-bundle folder. Inside that folder you find sts-3.8.3.RELEASE (current version as of this writing) folder, which contains STS.exe. Run STS.EXE to start STS.
2. STS looks and works very much like Eclipse. Create a new project by selecting File -> New -> Spring Legacy Project.
3. Select Simple Spring Maven as template and enter springdemo as project name.
4. STS creates a simple Java project that uses Maven. Maven takes care of downloading required dependencies. Maven is indispensible when working with frameworks like Spring as it downloads all required JAR files from Maven Central Repository for all dependencies mentioned in POM (project object model) file.
5. Modify POM.XML as follows so that we include only required dependencies and also change Java version to 1.8.

   
   <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>st.com</groupId>
   	<artifactId>springdemo</artifactId>
   	<version>1.0-SNAPSHOT</version>
   
   	<properties>
   		<!-- Generic properties -->
   		<java.version>1.8</java.version>
   		<!-- Spring -->
   		<spring-framework.version>4.3.3.RELEASE</spring-framework.version>
   	</properties>
   
   	<dependencies>
   		<!-- Spring and Transactions -->
   		<dependency>
   			<groupId>org.springframework</groupId>
   			<artifactId>spring-context</artifactId>
   			<version>${spring-framework.version}</version>
   		</dependency>
   	</dependencies>
   	
   	<build>
   		<finalName>springdemo</finalName>
   		<plugins>
   			<plugin>
   				<groupId>org.apache.maven.plugins</groupId>
   				<artifactId>maven-compiler-plugin</artifactId>
   				<version>3.3</version>
   				<configuration>
   					<source>${java.version}</source>
   					<target>${java.version}</target>
   				</configuration>
   			</plugin>
   		</plugins>
   	</build>
   	
   </project>
   
           

6. Update project with changes to POM file using ALT+F5. It will ask you for confirmation, click on OK. Alternatively you can select same option by righ click on project and selecting Maven -> Update Project option.
7. As Maven downloaded all required libraries, we are all set to write code using Spring Framework.

Implement Dependency Injection

Books.java

import java.util.List;

public interface Books {
 	   List<String> getBooks();	 
}

JavaBooks.java

import java.util.ArrayList;
import java.util.List;

public class JavaBooks implements Books {
	@Override
	public List<String> getBooks() {
		ArrayList<String> books = new ArrayList<String>();

		books.add("Java Complete Reference");
		books.add("Spring in Action");
		return books;
	}
}

Catalog.java

public class Catalog {
	private Books books;

	public void setBooks(Books books) {
		this.books = books;
	}

	public void print() {
		for (String book : books.getBooks()) {
			System.out.println(book);
		}
	}
 }

Beans.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 id="javabooks" class="JavaBooks" />
	<bean id="catalog" class="Catalog">
		<property name="books" ref="javabooks"></property>
	</bean>
</beans>

Application.Java

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

public class Application {
	public static void main(String[] args) {
		ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");

		Catalog cat = context.getBean("catalog", Catalog.class);
		cat.print();
	}
}