Spring Boot Part-1


 
What is Spring Boot? 

Spring boot makes it easy to create stand-alone , production grade spring based application that you can "just run".

..create...Spring based Applications...

What is Spring?

Application framework - built entreprise java application.

Programming and configuration model - focus on business logic and rest spring will take care. datalayer, service, controller, mvc address using annotation.

Problems with Spring
  1. Huge framework - Address all the issue but its overlapping.
  2. Multiple setup steps - connect to the db. needs lot of configuration is need
  3. Multiple configuration steps
  4. Multiple build and deploy steps - cost is involved.
Can we abstract these steps?

You can focus on business logic that is 80% and rest of the 20% configuration part. That we will configure depends on the environment .

 Enter Spring Boot
  • Opinionated - Start with your basic configuration and later you can change as per your wish. If required.
  • Convention over configuration - If it is default configuration. then there is no need to change configuration are required.
  • Stand alone - Built the jar file and run it stand alone.
  • Production ready - take the jar file and ready to deploy.
 Setting up Development Environment

Java 8 SDK
Spring STS - Supported by Spring.
Sprint Tool Suite




Java dependent jars are put it the class path and application use those files.
 
 

Create a simple project based on the arch-type and the download the dependent jars which are defined in the pom.xml from the repository 

Creating a spring Boot Project

Create a project - Multiple approch to create Boot project.

Creating a maven Java Project 

Steps

Open STS

Right click the Package Explorer. New ->   Maven Project.

Enable the Checkbox "Create a simple project (skip archetype selection)" -> Next

Group Id: (Package name) io.java.springbootquickstart

Artifact Id:(Project Name)course-api

Version: 0.0.1-SNAPSHOT

Packaging: jar

Name:Java Briains Course API
Click Finish

 

Convert Sample to Spring Boot Project in pom.xml
<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.4.2.RELEASE</version>
</parent>

Above set of tags, consider our project as child project, which inherits the parent project. That is spring boot.

spring-boot-starter-parent project provide default configuration that is 80%. If you wish to change 20% you can change as per your environment.
 
Step 2: Add the dependencies. We are create web application. Hence we need to add web dependencies.
<dependencies>
   <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
   </dependency>
</dependencies>
Once you save this file. You will find the Maven dependencies in the Package Explorer
 

 
 
Select the Project -> Maven -> Update Project. If you find any error
Add Java version.
<properties>    <java.version>1.8</java.version></properties>
 
Starting a Spring Boot application

Create a java class.
Go to src/main/java -> new -> class

 

package: io.javabrains.springbootstarter
Name: CoursseApiApp
Select the checkbox "public static void main method"
 
 
 
Step 1: Inform it spring application. Add the annotation in the class level
@SpringBootApplication 
Step 2: Add the below line in the public static method of CourseApiApp.
SpringApplication.run(classname where you have main method, arguments to main method)
 SpringApplication.run(CourseApiApp.class, args) 
Run as "Java Application"
 

 
Starting Spring Boot

SpringApplication.run(App.class, args) 

1.   Sets up default configuration (address 80% configuration)
2.   Start Spring application context
3.   performs class path scan
4.   Starts Tomcat server

Starting a Spring Boot App

1.   Spring Initializr
2.   Spring Boot CLI
3.   STS IDE

Configuration spring Boot
application.properties

Places your properties under src/main/resources
create file -> application.properties

Configure the property in properties file (if want to change the property)
server.port=3000

spring.datasource.url=jdbc:mysql://localhost/test
spring.datasource.username=dbuser
spring.datasource.password=dbpass
spring.datasource.driver-class-name=com.mysql.jdbc.Driver

http://localhost:3000

Common application properties which give your configuration to change
Adding a REST Controller

Let's add a controller
A Java Class
Marked with annotations
Has info about
What URL access triggers it
What method to run when accessed?

When we call url
localhost:8080/hello it return hi


Create a new controller class  

Package:io.javabrains.springbootstarter.hello

Name:HelloController
 
Add @RestController - Becomes to rest controller.

Add method with @RequestMapping("/hello")

public String sayHi(){
return "Hi";
}



Returning Objects From Controller

Create a TopicController class

package io.javabrains.springbootStarter.topic 

@RestController
public class TopicController{

    @RequestMapping("/topics")
    public String getAllTopics(){
        return "all topics"
    }
}


 
 
Return the response in JSON
Create a Topic class (model). create member with getter and setters, no arg constructor and constructor with parameters
 
Change the Return type of TopicController
When you use @RestController then return response of the list as JSON
 
What's happening here in Spring boot project (pom.xml)?
(If you change the version of the parent tag. which automatic download right version of their dependent in their project.
<parent><version>1.4.2</version></parent>
                        to
<parent><version>1.4.0</version></parent>
 
This will change the depend jars file should match to 1.4.0 version.
 
Bill of materials
 
 
 
What's happening here?Embedded Tomcat Server
Convenience - You no need to download the tomcat.
Servlet container config is now application config
Standalone application
Useful for microservice architecture -You no need to deploy for 10 ten time for 10 services. Even a single command you can achieve it.
 
1.   Request comes from user
2.   Request goes to appropriate controller
3.   Check for uri
4.   Check for the HTTP method (get, post, put, delete)
5.   Return the response in JSON format because of @RestController annotation.
 
Create a business service
 
Create a Topic service
@Service -> Sterotype. It is registered as service in servlet container. 
Controller -> Service-> return list -> response JSON
Run the application
 
 
Getting a  single resource
Add a method to get a single topic in the service class
 
Add a method in the controller which invokes the service single resource
 
Create a new resource using POST
Add a service method to add a element in the list
 
  Add a method in the controller which accept the post topic request
Postman
GET
http://localhost:8080/topics
send
GET
http://localhost:8080/topics/spring
send
method: POST
http://localhost:8080/topics
header:
content-type: application/json
body: raw
{
"id": "javaee",
"name": "Enterprise ",
"description": "Enterprise Java"
}
Send
Check the response in the postman
 
 

 
 

 
 



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