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readme.md

Spring In Depth

  • Step 1 - Setting up a Spring Project using htttp://start.spring.io
  • Step 2 - Understanding Tight Coupling using the Binary Search Algorithm Example
  • Step 3 - Making the Binary Search Algorithm Example Loosely Coupled
  • Step 4 - Using Spring to Manage Dependencies - @Component, @Autowired
  • Step 5 - What is happening in the background?
  • Step 6 - Dynamic auto wiring and Troubleshooting - @Primary
  • Step 7 - Constructor and Setter Injection
  • Step 8 - Spring Modules
  • Step 9 - Spring Projects
  • Step 10 - Why is Spring Popular?
  • Step 11 - Dependency Injection - A few more examples
  • Step 12 - Autowiring in Depth - by Name and @Primary
  • Step 13 - Autowiring in Depth - @Qualifier annotation
  • Step 14 - Scope of a Bean - Prototype and Singleton
  • Step 15 - Complex scenarios with Scope of a Spring Bean - Mix of Prototype and Singleton
  • Step 15B - Difference Between Spring Singleton and GOF Singleton
  • Step 16 - Using Component Scan to scan for beans
  • Step 17 - Lifecycle of a Bean - @PostConstruct and @PreDestroy
  • Step 18 - Container and Dependency Injection (CDI) - @Named, @Inject
  • Step 19 - Removing Spring Boot in Basic Application
  • Step 20 - Fixing minor stuff - Add Logback and Close Application Context
  • Step 21 - Defining Spring Application Context using XML - Part 1
  • Step 22 - Defining Spring Application Context using XML - Part 2
  • Step 23 - Mixing XML Context with Component Scan for Beans defined with Annotations
  • Step 24 - IOC Container vs Application Context vs Bean Factory
  • Step 25 - @Component vs @Service vs @Repository vs @Controller
  • Step 26 - Read values from external properties file
  • Step 27 - Spring Unit Testing with a Java Context
  • Step 28 - Spring Unit Testing with an XML Context
  • Step 29 - Spring Unit Testing with Mockito

Notes

[componentDAO, scopedTarget.componentJdbcConnection, 
componentJdbcConnection, springIn5StepsBasicApplication, 
springIn5StepsCdiApplication, 
springIn5StepsComponentScanApplication, springIn5StepsScopeApplication, 
binarySearchImpl, bubbleSortAlgorithm, quickSortAlgorithm, 
someCdiBusiness, someCdiDao, scopedTarget.jdbcConnection, 
jdbcConnection, personDAO, org.springframework.context.annotation.internalConfigurationAnnotationProcessor, org.springframework.context.annotation.internalAutowiredAnnotationProcessor, org.springframework.context.annotation.internalRequiredAnnotationProcessor, org.springframework.context.annotation.internalCommonAnnotationProcessor, org.springframework.context.event.internalEventListenerProcessor, org.springframework.context.event.internalEventListenerFactory, 
xmlJdbcConnection, xmlPersonDAO]

Complete Code Example

/pom.xml

<?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>com.in28minutes.spring.basics</groupId>
	<artifactId>spring-in-5-steps</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>jar</packaging>

	<name>spring-in-5-steps</name>
	<description>Demo project for Spring Boot</description>

	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.0.0.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</groupId>
			<artifactId>spring-core</artifactId>
		</dependency>

		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-context</artifactId>
		</dependency>

		<dependency>
			<groupId>org.slf4j</groupId>
			<artifactId>slf4j-api</artifactId>
		</dependency>

		<dependency>
			<groupId>ch.qos.logback</groupId>
			<artifactId>logback-classic</artifactId>
		</dependency>

		<dependency>
			<groupId>javax.inject</groupId>
			<artifactId>javax.inject</artifactId>
			<version>1</version>
		</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>

	<repositories>
		<repository>
			<id>spring-snapshots</id>
			<name>Spring Snapshots</name>
			<url>https://repo.spring.io/snapshot</url>
			<snapshots>
				<enabled>true</enabled>
			</snapshots>
		</repository>
		<repository>
			<id>spring-milestones</id>
			<name>Spring Milestones</name>
			<url>https://repo.spring.io/milestone</url>
			<snapshots>
				<enabled>false</enabled>
			</snapshots>
		</repository>
	</repositories>

	<pluginRepositories>
		<pluginRepository>
			<id>spring-snapshots</id>
			<name>Spring Snapshots</name>
			<url>https://repo.spring.io/snapshot</url>
			<snapshots>
				<enabled>true</enabled>
			</snapshots>
		</pluginRepository>
		<pluginRepository>
			<id>spring-milestones</id>
			<name>Spring Milestones</name>
			<url>https://repo.spring.io/milestone</url>
			<snapshots>
				<enabled>false</enabled>
			</snapshots>
		</pluginRepository>
	</pluginRepositories>


</project>

/src/main/java/com/in28minutes/spring/basics/componentscan/ComponentDAO.java

package com.in28minutes.spring.basics.componentscan;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Repository;

@Repository
public class ComponentDAO {

	@Autowired
	ComponentJdbcConnection jdbcConnection;

	public ComponentJdbcConnection getJdbcConnection() {
		return jdbcConnection;
	}

	public void setComponentJdbcConnection(ComponentJdbcConnection jdbcConnection) {
		this.jdbcConnection = jdbcConnection;
	}
}

/src/main/java/com/in28minutes/spring/basics/componentscan/ComponentJdbcConnection.java

package com.in28minutes.spring.basics.componentscan;

import org.springframework.beans.factory.config.ConfigurableBeanFactory;
import org.springframework.context.annotation.Scope;
import org.springframework.context.annotation.ScopedProxyMode;
import org.springframework.stereotype.Component;

@Component
@Scope(value=ConfigurableBeanFactory.SCOPE_PROTOTYPE, 
		proxyMode = ScopedProxyMode.TARGET_CLASS)
public class ComponentJdbcConnection {
	public ComponentJdbcConnection() {
		System.out.println("JDBC Connection");
	}
}

/src/main/java/com/in28minutes/spring/basics/springin5steps/basic/BinarySearchImpl.java

package com.in28minutes.spring.basics.springin5steps.basic;

import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.beans.factory.config.ConfigurableBeanFactory;
import org.springframework.context.annotation.Scope;
import org.springframework.stereotype.Component;
import org.springframework.stereotype.Service;

@Service
@Scope(ConfigurableBeanFactory.SCOPE_SINGLETON)
public class BinarySearchImpl {
	
	private Logger logger = LoggerFactory.getLogger(this.getClass()); 

	@Autowired
	@Qualifier("bubble")
	private SortAlgorithm sortAlgorithm;
	
	public int binarySearch(int[] numbers, int numberToSearchFor) {

		int[] sortedNumbers = sortAlgorithm.sort(numbers);
		System.out.println(sortAlgorithm);
		// Search the array
		return 3;
	}
	
	@PostConstruct
	public void postConstruct() {
		logger.info("postConstruct");
	}

	@PreDestroy
	public void preDestroy() {
		logger.info("preDestroy");
	}

}

/src/main/java/com/in28minutes/spring/basics/springin5steps/basic/BubbleSortAlgorithm.java

package com.in28minutes.spring.basics.springin5steps.basic;

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

@Service
@Qualifier("bubble")
public class BubbleSortAlgorithm implements SortAlgorithm {
	public int[] sort(int[] numbers) {
		// Logic for Bubble Sort
		return numbers;
	}
}

/src/main/java/com/in28minutes/spring/basics/springin5steps/basic/QuickSortAlgorithm.java

package com.in28minutes.spring.basics.springin5steps.basic;

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

@Service
@Qualifier("quick")
public class QuickSortAlgorithm implements SortAlgorithm {
	public int[] sort(int[] numbers) {
		// Logic for Quick Sort
		return numbers;
	}
}

/src/main/java/com/in28minutes/spring/basics/springin5steps/basic/SortAlgorithm.java

package com.in28minutes.spring.basics.springin5steps.basic;

public interface SortAlgorithm {
	public int[] sort(int[] numbers);
}

/src/main/java/com/in28minutes/spring/basics/springin5steps/cdi/SomeCdiBusiness.java

package com.in28minutes.spring.basics.springin5steps.cdi;

import javax.inject.Inject;
import javax.inject.Named;

@Named
public class SomeCdiBusiness {
	
	@Inject
	SomeCdiDao someCdiDao;

	public SomeCdiDao getSomeCDIDAO() {
		return someCdiDao;
	}

	public void setSomeCDIDAO(SomeCdiDao someCdiDao) {
		this.someCdiDao = someCdiDao;
	}
}

/src/main/java/com/in28minutes/spring/basics/springin5steps/cdi/SomeCdiDao.java

package com.in28minutes.spring.basics.springin5steps.cdi;

import javax.inject.Named;

@Named
public class SomeCdiDao {

}

/src/main/java/com/in28minutes/spring/basics/springin5steps/properties/SomeExternalService.java

package com.in28minutes.spring.basics.springin5steps.properties;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

@Component
public class SomeExternalService {
	
	@Value("${external.service.url}")
	private String url;
	
	public String returnServiceURL(){
		return url;
	}

}

/src/main/java/com/in28minutes/spring/basics/springin5steps/scope/JdbcConnection.java

package com.in28minutes.spring.basics.springin5steps.scope;

import org.springframework.beans.factory.config.ConfigurableBeanFactory;
import org.springframework.context.annotation.Scope;
import org.springframework.context.annotation.ScopedProxyMode;
import org.springframework.stereotype.Component;

@Component
@Scope(value=ConfigurableBeanFactory.SCOPE_PROTOTYPE, 
		proxyMode = ScopedProxyMode.TARGET_CLASS)
public class JdbcConnection {
	public JdbcConnection() {
		System.out.println("JDBC Connection");
	}
}

/src/main/java/com/in28minutes/spring/basics/springin5steps/scope/PersonDAO.java

package com.in28minutes.spring.basics.springin5steps.scope;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Repository;

@Repository
public class PersonDAO {

	@Autowired
	JdbcConnection jdbcConnection;

	public JdbcConnection getJdbcConnection() {
		return jdbcConnection;
	}

	public void setJdbcConnection(JdbcConnection jdbcConnection) {
		this.jdbcConnection = jdbcConnection;
	}
}

/src/main/java/com/in28minutes/spring/basics/springin5steps/SpringIn5StepsBasicApplication.java

package com.in28minutes.spring.basics.springin5steps;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

import com.in28minutes.spring.basics.springin5steps.basic.BinarySearchImpl;

@Configuration
@ComponentScan
public class SpringIn5StepsBasicApplication {

	public static void main(String[] args) {

		try (AnnotationConfigApplicationContext applicationContext = 
				new AnnotationConfigApplicationContext(
				SpringIn5StepsBasicApplication.class)) {

			BinarySearchImpl binarySearch = 
					applicationContext.getBean(BinarySearchImpl.class);

			BinarySearchImpl binarySearch1 = 
					applicationContext.getBean(BinarySearchImpl.class);

			System.out.println(binarySearch);
			System.out.println(binarySearch1);

			int result = binarySearch.binarySearch(new int[] { 12, 4, 6 }, 3);
			System.out.println(result);
		}
	}
}

/src/main/java/com/in28minutes/spring/basics/springin5steps/SpringIn5StepsCdiApplication.java

package com.in28minutes.spring.basics.springin5steps;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

import com.in28minutes.spring.basics.springin5steps.cdi.SomeCdiBusiness;

@Configuration
@ComponentScan
public class SpringIn5StepsCdiApplication {

	private static Logger LOGGER = LoggerFactory.getLogger(SpringIn5StepsCdiApplication.class);

	public static void main(String[] args) {
		try (AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(
				SpringIn5StepsCdiApplication.class)) {
			SomeCdiBusiness business = applicationContext.getBean(SomeCdiBusiness.class);

			LOGGER.info("{} dao-{}", business, business.getSomeCDIDAO());
		}
	}
}

/src/main/java/com/in28minutes/spring/basics/springin5steps/SpringIn5StepsComponentScanApplication.java

package com.in28minutes.spring.basics.springin5steps;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

import com.in28minutes.spring.basics.componentscan.ComponentDAO;

@Configuration
@ComponentScan("com.in28minutes.spring.basics.componentscan")
public class SpringIn5StepsComponentScanApplication {

	private static Logger LOGGER = LoggerFactory.getLogger(SpringIn5StepsComponentScanApplication.class);

	public static void main(String[] args) {

		try (AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(
				SpringIn5StepsComponentScanApplication.class)) {
			ComponentDAO componentDAO = applicationContext.getBean(ComponentDAO.class);

			LOGGER.info("{}", componentDAO);
		}
	}
}

/src/main/java/com/in28minutes/spring/basics/springin5steps/SpringIn5StepsPropertiesApplication.java

package com.in28minutes.spring.basics.springin5steps;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;

import com.in28minutes.spring.basics.springin5steps.properties.SomeExternalService;

@Configuration
@ComponentScan
// 
@PropertySource("classpath:app.properties")
public class SpringIn5StepsPropertiesApplication {

	public static void main(String[] args) {

		try (AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(
				SpringIn5StepsPropertiesApplication.class)) {

			SomeExternalService service = applicationContext.getBean(SomeExternalService.class);
			System.out.println(service.returnServiceURL());
		}
	}
}

/src/main/java/com/in28minutes/spring/basics/springin5steps/SpringIn5StepsScopeApplication.java

package com.in28minutes.spring.basics.springin5steps;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

import com.in28minutes.spring.basics.springin5steps.scope.PersonDAO;

@Configuration
@ComponentScan
public class SpringIn5StepsScopeApplication {

	private static Logger LOGGER = LoggerFactory.getLogger(SpringIn5StepsScopeApplication.class);

	public static void main(String[] args) {

		try (AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(
				SpringIn5StepsScopeApplication.class)) {

			PersonDAO personDao = applicationContext.getBean(PersonDAO.class);

			PersonDAO personDao2 = applicationContext.getBean(PersonDAO.class);

			LOGGER.info("{}", personDao);
			LOGGER.info("{}", personDao.getJdbcConnection());
			LOGGER.info("{}", personDao.getJdbcConnection());

			LOGGER.info("{}", personDao2);
			LOGGER.info("{}", personDao.getJdbcConnection());
		}
	}
}

/src/main/java/com/in28minutes/spring/basics/springin5steps/SpringIn5StepsXMLContextApplication.java

package com.in28minutes.spring.basics.springin5steps;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.in28minutes.spring.basics.springin5steps.xml.XmlPersonDAO;

public class SpringIn5StepsXMLContextApplication {

	private static Logger LOGGER = LoggerFactory.getLogger(SpringIn5StepsScopeApplication.class);

	public static void main(String[] args) {

		try (ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext(
				"applicationContext.xml")) {

			LOGGER.info("Beans Loaded -> {}", (Object) applicationContext.getBeanDefinitionNames());
			// [xmlJdbcConnection, xmlPersonDAO]

			XmlPersonDAO personDao = applicationContext.getBean(XmlPersonDAO.class);

			LOGGER.info("{} {}", personDao, personDao.getXmlJdbcConnection());
		}
	}
}

/src/main/java/com/in28minutes/spring/basics/springin5steps/xml/XmlJdbcConnection.java

package com.in28minutes.spring.basics.springin5steps.xml;

public class XmlJdbcConnection {
	public XmlJdbcConnection() {
		System.out.println("JDBC Connection");
	}
}

/src/main/java/com/in28minutes/spring/basics/springin5steps/xml/XmlPersonDAO.java

package com.in28minutes.spring.basics.springin5steps.xml;

public class XmlPersonDAO {

	XmlJdbcConnection xmlJdbcConnection;

	public XmlJdbcConnection getXmlJdbcConnection() {
		return xmlJdbcConnection;
	}

	public void setXmlJdbcConnection(XmlJdbcConnection jdbcConnection) {
		this.xmlJdbcConnection = jdbcConnection;
	}
}

/src/main/resources/app.properties

external.service.url=http://someserver.dev.com/service

/src/main/resources/application.properties

#logging.level.org.springframework = debug

/src/main/resources/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"
    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="xmlJdbcConnection" 
    	class="com.in28minutes.spring.basics.springin5steps.xml.XmlJdbcConnection">
    </bean>

    <bean id="xmlPersonDAO" class="com.in28minutes.spring.basics.springin5steps.xml.XmlPersonDAO">
    		<property name="xmlJdbcConnection" ref="xmlJdbcConnection"/>
    </bean>

</beans>

/src/main/resources/log.txt

Searching directory [/in28Minutes/git/getting-started-in-5-steps/spring-in-5-steps/target/classes/com/in28minutes/spring/basics/springin5steps] for files matching pattern [/in28Minutes/git/getting-started-in-5-steps/spring-in-5-steps/target/classes/com/in28minutes/spring/basics/springin5steps/**/*.class]
Identified candidate component class: file [/in28Minutes/git/getting-started-in-5-steps/spring-in-5-steps/target/classes/com/in28minutes/spring/basics/springin5steps/BinarySearchImpl.class]
Identified candidate component class: file [/in28Minutes/git/getting-started-in-5-steps/spring-in-5-steps/target/classes/com/in28minutes/spring/basics/springin5steps/BubbleSortAlgorithm.class]

Creating instance of bean 'binarySearchImpl'
Creating instance of bean 'bubbleSortAlgorithm'
Finished creating instance of bean 'bubbleSortAlgorithm'

Constuctor - Autowiring by type from bean name 'binarySearchImpl' via constructor 
to bean named 'bubbleSortAlgorithm'
Setter -  Autowiring by type from bean name 'binarySearchImpl' to bean named 'bubbleSortAlgorithm'
No Setter or Constructor - Autowiring by type from bean name 'binarySearchImpl' to bean named 'bubbleSortAlgorithm'


Finished creating instance of bean 'binarySearchImpl'

/src/test/java/com/in28minutes/spring/basics/springin5steps/SpringIn5StepsBasicApplicationTests.java

package com.in28minutes.spring.basics.springin5steps;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;

@RunWith(SpringRunner.class)
@SpringBootTest
public class SpringIn5StepsBasicApplicationTests {

	@Test
	public void contextLoads() {
	}

}