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JAVA, Technology

Spring Initializer – using Java and Maven

Spring Initializr is a web tool which is provided by Spring on official site https://start.spring.io/ We can create Spring Boot project by providing project details.

 

In the below example, we added the springboot-starter-web dependency to write REST Endpoints.

 

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After providing the Group, Artifact, Dependencies, Build Project, Platform and Version, click Generate Project button. The zip file will get downloaded and the files will be extracted. After the project is downloaded, unzip the file.

 

The maven file pom.xml will have the Web dependency we had selected above.

 

Web_dependency_img

 

Note that only the Spring boot starter parent has a version number. Spring boot starter web doesn’t have a version as it is automatically configured based on version of the parent.

 

You can find the main class file under src/java/main directories with the default package.

 

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To write a simple Hello World Rest Endpoint in the Spring Boot Application main class file itself, follow the steps shown below:

 

  • Firstly, add the @RestController annotation at the top of the class.
  • Now, write a Request URI method with @RequestMapping annotation.
  • Then, the Request URI method should return the Hello World string.

 

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Create an executable JAR by executing the below Maven command in the folder having pom.xml C:\Users\SaravananP\Downloads\demo\mvn clean install

 

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The .jar file will be created in the target folder as indicated above

 

Run the Jar file using java –jar and verify the results

 

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Application Properties

In the above examples, we have seen that Spring boot automatically configured Tomcat to run in port 8080. We can override this by specifying the port in the file src\main\resources\application.properties

 

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If we rebuild the jar and execute it, we will get an error in http://localhost:8080 and be able to see the Hello World message in http://localhost:9090

 

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JAVA, Technology

Spring Boot

Spring Boot is an open source Java-based framework used to create Micro Services. It is used to build stand-alone and production ready spring applications.

 

What is Micro Service?

Micro Service is an architecture that allows the developers to develop and deploy services independently. Each service running has its own process, and this achieves the lightweight model to support business applications.

 

Features and benefits of Spring Boot

  • Spring boot provides a flexible way to configure Java Beans, XML configurations, and Database Transactions.
  • It provides a powerful batch processing and manages REST endpoints.
  • In Spring Boot, everything is auto configured; no manual configurations are needed.
  • It offers annotation-based spring application.
  • Eases dependency management.
  • It includes Embedded Servlet Container.
  • It is highly dependent on the starter templates feature.

 

How Spring Boot works

Spring Boot automatically configures our application based on the dependencies we have added to the project by using @EnableAutoConfiguration annotation. For example, if MySQL database is on our classpath, but we have not configured any database connection, then Spring Boot auto-configures an in-memory database.

 

Spring Boot Starters

Handling dependency management is a difficult task for big projects. Spring Boot resolves this problem by providing a set of dependencies for developer’s convenience.

 

For example, if we want to create a web application with REST Endpoints, it is sufficient if we include spring-boot-starter-web dependency in our project.

 

Note that all Spring Boot starters follow the same naming pattern spring-boot-starter-*, where * indicates that it is a type of the application.

 

Example:

 

Spring Boot Starter Test dependency is used for writing Test cases. Its code is shown below:

 

 

Spring Boot Application

The entry point of the Spring Boot Application is the class containing @SpringBootApplication annotation. This class should have the main method to run the Spring Boot application. @SpringBootApplication annotation includes @EnableAutoConfiguration, @ComponentScan, and @SpringBootConfiguration annotations.

 

Spring Boot automatically scans all the components included in the project by using @ComponentScan annotation.

 

Observe the following code for a better understanding:

 

 

Spring Boot – Quick Start – using Groovy

The Spring Boot CLI is a command line tool and it allows us to run the Groovy scripts. Create a simple groovy file which contains the Rest Endpoint script.

 

Hello.groovy

 

 

The above file can be run using the command “spring run Hello.groovy”

 

spring_command_img

 

Once we run the groovy file, required dependencies will download automatically and it will start the application in Tomcat 8080 port as shown in the screenshot above. You can also see that sping ‘Mapped “{[/]}” onto public java.lang.String Example.hello()’.

 

We can go to the web browser and hit the URL http://localhost:8080/, and see the output from hello() function as shown below:

 

hello_spring_img

 

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