Create SpringBoot project by hand-HelloWorld

Maven usage convention is better than configuration

table of Contents	use
${basedir}	Store pom.xml and all subdirectories
${basedir}/src/main/java	Java source code of the project
${basedir}/src/main/resources	Project resources, such as property files, springmvc.xml
${basedir}/src/test/java	The test class of the project, such as Junit code
${basedir}/src/test/resources	Resources for testing
${basedir}/src/main/webapp/WEB-INF	Web application file directory, web project information, such as web.xml, local pictures, jsp view page
${basedir}/target	Package output directory
${basedir}/target/classes	Compile output directory
${basedir}/target/test-classes	Test compile output directory
Test.java	Maven will only automatically run test classes that meet the naming rules
~/.m2/repository	Maven default local repository directory location

1. Create a maven project

// 创建项目根据目录
~/Desktop$ mkdir MySpringboot

// 按照上面maven的约定创建目录
~/Desktop$ mkdir -p MySpringboot/src/main/java
~/Desktop$ mkdir -p MySpringboot/src/main/resources
~/Desktop$ mkdir -p MySpringboot/src/test/java
~/Desktop$ mkdir -p MySpringboot/src/test/resources

// 在根目录下创建pom.xml文件
~/Desktop$ touch MySpringboot/pom.xml

// 创建好的maven项目目录结构
~/Desktop$ tree MySpringboot
MySpringboot
├── pom.xml
└── src
    ├── main
    │   ├── java
    │   └── resources
    └── test
        ├── java
        └── resources

7 directories, 1 file

2. Import spring boot related dependencies

Add the following configuration to pom.xml:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.wong</groupId>
    <!--与项目名称一致-->
    <artifactId>MySpringboot</artifactId>
    <version>1.0-SNAPSHOT</version>
    <properties>
        <java.version>1.8</java.version>
    </properties>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.2.5.RELEASE</version>
        <relativePath/>
    </parent>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
    </dependencies>
</project>

The spring-boot-starter-web scene starter will import the dependencies related to web development into the project. For more scene starters, please refer to: springboot scene starter

3. Write the main program: start the Spring Boot application

Create the package name com.wong (actually the directory):

~/Desktop/MySpringboot$ mkdir -p src/main/java/com/wong

Create the main program MainApplication.java in the package com.wong:

package com.wong;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
/**
* @SpringBootApplication用于标注主程序
*/
@SpringBootApplication
public class MainApplication{

        public static void main(String[] args){
        		// 启动Spring应用
                SpringApplication.run(MainApplication.class,args);
        }
}

4. Write business-related Controller

Create one more package to store the business controller:

~/Desktop/MySpringboot$ mkdir -p src/main/java/com/wong/controller

Create the controller HelloWorldController.java:

package com.wong.controller;

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

@RestController
@RequestMapping("world")
public class HelloWorldController{

        @GetMapping("hi")
        public String index(){
                return "Hello World!";
        }
}

5. Test

Run the program using the mvn spring-boot: run command:

~/Desktop/MySpringboot$ mvn spring-boot:run
[INFO] Scanning for projects...
...
  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.2.5.RELEASE)

2020-03-24 22:13:45.941  INFO 20580 --- [           main] com.wong.MainApplication                 : Starting MainApplication on kyun-HP-348-G3 with PID 20580 (/home/kyun/Desktop/MySpringboot/target/classes started by kyun in /home/kyun/Desktop/MySpringboot)
2020-03-24 22:13:45.944  INFO 20580 --- [           main] com.wong.MainApplication                 : No active profile set, falling back to default profiles: default
2020-03-24 22:13:46.662  INFO 20580 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)
2020-03-24 22:13:46.670  INFO 20580 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2020-03-24 22:13:46.671  INFO 20580 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.31]
2020-03-24 22:13:46.716  INFO 20580 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2020-03-24 22:13:46.716  INFO 20580 --- [           main] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 720 ms
2020-03-24 22:13:46.852  INFO 20580 --- [           main] o.s.s.concurrent.ThreadPoolTaskExecutor  : Initializing ExecutorService 'applicationTaskExecutor'
2020-03-24 22:13:46.967  INFO 20580 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2020-03-24 22:13:46.969  INFO 20580 --- [           main] com.wong.MainApplication                 : Started MainApplication in 1.298 seconds (JVM running for 1.604)

Enter http: // localhost: 8080 / world / hi in the browser:
　

7. Simplify deployment

You can release the war package and publish it to the Tomcat container. You can directly type the jar package, and then directly run it with the java -jar <name> .jar command.
First, add the following plug-in to pom.xml:

	<build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

Then execute the following packaging commands:

~/Desktop/MySpringboot$ mvn package spring-boot:repackage

The typed package is in the target directory:

~/Desktop/MySpringboot$ cd target
~/Desktop/MySpringboot/target$ ls
classes                 maven-status
generated-sources       MySpringboot-1.0-SNAPSHOT.jar
generated-test-sources  MySpringboot-1.0-SNAPSHOT.jar.original
maven-archiver          test-classes
~/Desktop/MySpringboot/target$ java -jar MySpringboot-1.0-SNAPSHOT.jar
...

That's all for creating a Spring Boot project.