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readme.md

First 10 Steps in Spring

  • Step 1 : Setting up a Spring Project using htttp:https://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?

Complete Code Example

/pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http:https://maven.apache.org/POM/4.0.0" xmlns:xsi="http:https://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http:https://maven.apache.org/POM/4.0.0 http:https://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.boot</groupId>
			<artifactId>spring-boot-starter</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>

	<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/springin5steps/BinarySearchImpl.java

package com.in28minutes.spring.basics.springin5steps;

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

@Component
public class BinarySearchImpl {

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

		int[] sortedNumbers = sortAlgorithm.sort(numbers);
		System.out.println(sortAlgorithm);
		// Search the array
		return 3;
	}

}

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

package com.in28minutes.spring.basics.springin5steps;

import org.springframework.context.annotation.Primary;
import org.springframework.stereotype.Component;

@Component
@Primary
public class BubbleSortAlgorithm implements SortAlgorithm {
	public int[] sort(int[] numbers) {
		// Logic for Bubble Sort
		return numbers;
	}
}

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

package com.in28minutes.spring.basics.springin5steps;

import org.springframework.stereotype.Component;

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

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

package com.in28minutes.spring.basics.springin5steps;

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

/src/main/java/com/in28minutes/spring/basics/springin5steps/SpringIn5StepsApplication.java

package com.in28minutes.spring.basics.springin5steps;

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

@SpringBootApplication
public class SpringIn5StepsApplication {

	// What are the beans?
	// What are the dependencies of a bean?
	// Where to search for beans? => No need

	public static void main(String[] args) {

		// BinarySearchImpl binarySearch =
		// new BinarySearchImpl(new QuickSortAlgorithm());
		// Application Context
		ApplicationContext applicationContext = 
				SpringApplication.run(SpringIn5StepsApplication.class, args);
		BinarySearchImpl binarySearch = 
				applicationContext.getBean(BinarySearchImpl.class);
		int result = 
				binarySearch.binarySearch(new int[] { 12, 4, 6 }, 3);
		System.out.println(result);
	}
}

/src/main/resources/application.properties

logging.level.org.springframework = debug

/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/SpringIn5StepsApplicationTests.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 SpringIn5StepsApplicationTests {

	@Test
	public void contextLoads() {
	}

}