[JAVA] Spring Boot Memorandum

I just touched Spring Boot, so I made a note of what I understood as a memorandum.

Hello World

For the time being, read Getting started Let's see.

Spring Boot makes it easy to create stand-alone, production-grade Spring-based Applications that you can run.

__ You can run a commercial-level Spring-based app standalone! Is it like __?

Things necessary

• Java (obviously)
• Maven (build tool) * Gradle is also OK.

How to move

There are several ways, but all of them are able to start the application with one touch without deploying after starting the web server + application server. __ Does this area feel like "standalone"?

Boot with Spring Boot CLI

Download the CLI and use sprint.bat in the bin folder to start the application (class file) written in Java.

spring run created class file

Just by starting with, the web server + application server will start and Hello World will appear at localhost: 8080.

boot with mvn spring-boot: run

Write the required definition in pom.xml, write a controller-like class, and start the app from Maven.

mvn spring-boot:run

It is built with, the web server + application server starts, and Hello World appears at localhost: 8080.

Launched in Executable Jar

Write the necessary definition in pom.xml, write a controller-like class, create a jar with Maven, and start the application.

mvn package
java -jar (Jar file)

Then, the web server + application server starts and Hello World appears at localhost: 8080. It seems that this Executable Jar can be used as it is as a batch file for starting and stopping services. Reference Why does Fully Executable Jar in Spring Boot work

RESTful Web API trial

Continue reading Building a RESTful Web Service.

Basic configuration

Understand the basic configuration through RESTful Web API implementation samples.

• representation
  So-called POJO is OK. Use Jackson 2 to convert to JSON The MappingJackson2HttpMessageConverter class will do it for you.
• controller
  • @RestController
    Set in class. Annotation to have a role as a controller.
  • @RequestMapping
    Set in the method. Mapping of Servlet path and method. If you do not specify a method like @RequestMapping (method = POST), mapping is common to all methods.
  • @RequestParam
    Mapping with query parameters. It is possible to specify the default value when it is not specified by defaultValue = xxx.
• application
  To run it as an executable jar, create an Applicaiton class with main ().
  • @SpringBootApplication
    Annotation for implementing @EnableAutoConfiguration, @ComponentScan and @Configuration together.
  • @EnableAutoConfiguration
    Annotation to play the role of that definition file that was <bean id =" xxx "> in Spring of Futu. Is this the joy of Spring-boot that the app works without writing a bean definition? (Reference) Understanding how Spring Boot AutoConfigure works

Run

Implement the above and start the server with mvn spring-boot: run. When you access http: // localhost: 8080 / xxxxx (where xxxxx is the resource name), The mapped method of the controller is called and JSON is returned.

What I noticed

• After creating a RESTful sample app of ↑ and mvn spring-boot: run, The response is now displayed at http: // localhost: 8080 / greeting, ʻExample.javathat was created in Getting Started has stopped working. (Hello World! Does not appear athttp: // localhost: 8080 /) ⇒ The class hierarchy was as follows. project/src/main/java/Example.java project/src/main/java/hello/Application.java I moved Example.java under the src / main / java / hello package and it worked. Is it because@ComponentScan` does not scan the hierarchy above itself? (No confidence)

from now on

Read Official guide page. I will add what I understood.