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Udemy Spring boot course: Section 1 QuickStart

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By Tresten Pool 8 min read

Overview

Github repo

Spring boot version

  • Using Spring boot 3
  • requires JDK 17 or higher

Standard Directory Structure

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  • if doing a web app place the webapp files in src>main>webapp
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    • By default Spring boot will load properties from: application.properties
    • things like where the port number can be configured
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Spring Framework

  • Lightweight dev with Java POJOs
  • Dependency injection to promote loose coupling

Overview

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  • the core container is the heart of spring
    • it manages how beans are created
    • it has a bean factory for creating beans
    • SpEL - Spring expression language: language in the config files to refer to other beans

Springboot Framework

What is it?

  • popular framework for building java applications
  • provides a large number of helper classes and annnotations
  • Normal Spring applications take a lot of effort just to get setup
  • Springboot is the solution to that making it easier and faster to get started with Spring development
  • minimizes the amount of manual configuration
  • performs auto-configuration based on props files and JAR classpath
  • provides an embedded HTTP server so you can get started quickly
    • Tomcat, jetty, undertow

Spring and Springboot

  • Springboot uses spring behind the scenes
  • Springboot simply makes it easier to use Spring

Spring Initializr

  • start.spring.io
  • Site to quickly create a starter spring boot project
  • select your dependencies
  • then creates a Maven / Gradle project
  • then import the project into your ide

Springboot Starters

Springboot embedded server

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  • springboot provides an embedded HTTP server so you can get started quickly
    • Tomcat, Jetty, Undertow
  • self contained unit in the .jar file. nothing else you have to install!!

Running a Springboot application

  • Since everything is self contained in the .jar file
  • We can run the springboot application with java -jar mycoolapp.jar
    • runs the app and spins up the server!
  • spring boot maven plugin option
  • You can also run the application by running mvn spring-boot:run or using the mvnw.sh file ./mvnw spring-boot:run

Enable Auto-reload for Spring project

  • You can enable auto-reloading for a spring project so you don’t have to stop and start all the time to see the changes
  • You have to run from intellij run logo, won’t work if you run from the terminal with ./mvnw spring-boot:run
  • Place the dependency in the pom.xml file
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<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-devtools</artifactId>
  <optional>true</optional> <!-- Can prevent passing devtools dependencies into other modules -->
</dependency>
  • Enable “Build Project Automatically”
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  • Enable “Allow auto-make to start even if developed application is currently running”
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Deploying Springboot applications

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  • Springboot apps can also be deployed in the traditional way with WAR files
  • Deploy WAR file to an external server: Tomcat, JBoss, WebSpher
  • Do not use the src/main/webapp directory if app is packaged as a WAR
    • Although standard convention by maven, it works only with WAR packaging
    • it is silently ignored by most build tools if you generate a JAR

Does Springboot replace Spring MVC, Spring Core, Spring AOP, Spring REST, Spring….

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  • No Springboot does not replace but rather uses them behind the scenes abstracting the manual config away from the user

Does Springboot run faster than regular Spring code?

  • No, it uses the same code of the Spring framework

Spring Projects

  • Spring projects are additional Spring modules built-on top of the Spring Framework
    • Spring Cloud, Spring Data, Spring Batch, Spring Security .. .
  • spring projects site

Springboot Actuator

  • Exposes endpoints to monitor and manage springboot application
  • dev-ops functionality out of the box
  • Just add the following dependency to your pom.xml file and REST endpoints are automatically added to your application
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<dependency>
  <version>3.1.3</version>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-actuator</artifactId>
</dependency>

To get access to the /actuator/info we need to add the following lines to the application.properties file

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# Enabling the /health & /info endpoints only
#management.endpoints.web.exposure.include=health,info

# Expose all endpoints with the wildcard
management.endpoints.web.exposure.include=*

# Customizing the /actuator/info endpoint
management.info.env.enabled=true # tells the plugin to read the variables below to display on the /info route
info.app.name=Hello world App
info.app.description=Demo Spring Boot app
info.app.version=1.0
EndpointDescription
/actuator/healthHealth of the application
/actuator/infoinformation of the application
/actuator/auditeventsAudit events for your app
/actuator/beanslist of all of the beans registered in the Spring application context
/actuator/mappingslist of all @Requestmapping paths

Springboot Actuator Security

  • You may want to add security so everyone doesn’t have access to the actuator endpoints
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<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-security</artifactId>
  <version>3.1.4</version>
</dependency>
  • After adding the plugin, spring security will prompt for a login
    • Default user –> user
    • Default password –> Generated by the console
  • There are more advanced ways to configure spring security like connecting to a db but for now we will just use the method below
  • If you want to override the defaults you can specify the credentials in the application.properties like below
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spring.security.user.name=tresten
spring.security.user.password=password123

Maven

What is Maven

  • When building your java project, you may need additional JAR files
    • ex. Spring, Hibernate, Commong Logging
  • One approach is to download the JAR files from each project web site
  • Manually add the JAR files to your build / classpath
  • Instead
  • All you do is have to tell maven what dependencies you will need
    • Maven will go out and download the JAR files for those projects for you

POM file

  • Project Object Model File
  • shopping list for maven
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Project Coordinates

  • where maven goes to look to download
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  • referred to as GAV (Group ID, Artificat ID, Version)
  • maven search

mvnw

  • mvnw allows you to run a Maven project
    • no need to have maven installed
    • if maven installed is not correct version it will automatically update it to the latest version
  • two mvn files for windows or linux/mac
    • mvnw.cmd – windows
    • mvnw.sh – linux/mac

Maven Errors

  • JDK17 does not work with mvn 3.6.0 error fix
  • I was getting warning error when attempting to run mvn package or mvn spring-boot:run saying Java_Home was not set
    • I had placed the following lines in /etc/environment as root
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JAVA_HOME="/usr/lib/jvm/jdk-17-oracle-x64"
export JAVA_HOME
  • After the modification run source /etc/environment

Maven Commands

  • Cheat sheet
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  • Creates the target/ directory with all necessary file and the .jar file
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    ./mvnw package
  • Deletes all in target/ directory and removes the directory
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    ./mvnw clean
  • Run the spring boot application with the maven spring boot plugin
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    ./mvnw spring-boot:run

Creating a demo springboot application

Steps

Spring initializer

  • go to the spring initializer site
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    • enter out the project information
    • add the dependencies on the right, (selected spring web for this demo)
  • hit generate, download the file, unzip to a directory and open up in ide

Run the app

  • Go to the main method and hit the run button
  • next you will see the following code in the terminal output
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2023-09-19T16:21:21.693-05:00  INFO 741662 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2023-09-19T16:21:21.693-05:00  INFO 741662 --- [           main] o.apache.catalina.core.StandardEngine    : Starting Servlet engine: [Apache Tomcat/10.1.12]
2023-09-19T16:21:21.792-05:00  INFO 741662 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2023-09-19T16:21:21.793-05:00  INFO 741662 --- [           main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 1020 ms
2023-09-19T16:21:22.146-05:00  INFO 741662 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2023-09-19T16:21:22.155-05:00  INFO 741662 --- [           main] c.s.d.HelloWorld.HelloWorldApplication   : Started HelloWorldApplication in 1.908 seconds (process running for 2.26)
  • However when we attempt to go to the site at localhost:8080 we get this error because we have no routes setup
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Setup / mapping

  • We will setup a mapping for the “/” endpoint
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package com.springboot.demo.HelloWorld.rest;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class FunRestController {
    // expose "/" that return "Hello world"
    @GetMapping("/")
    public String sayHello(){
        return "Hello world";
    }
}
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    • now when we navigate to localhost:8080 we get this message

Configure app to read from Application Properties file

  • By default springboot reads configuratoin from src/main/resources/application.properties
  • You can define ANY custom properties in this file
  • Your spring boot app can access properties using @Value
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coach.name=Mickey Mouse
team.name=The Mouse Club

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// inject the values
@Value("${coach.name}")
private String coachName;

@Value("${team.name}")
private String teamName;

// /teaminfo displays the values we injected from the .properties file
@GetMapping("/teaminfo")
public String teamInfo(){
    return "Team name: %s Coach name: %s".formatted(teamName, coachName);
}
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Common Springboot application properties

Categories
Core
Web
Security
Data
Actuator
Integration
DevTools
Testing
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server.port=8080
Udemy, Java, Spring, Springboot, Hibernate, JDBC
Java Programming Udemy Spring
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