Basic part - basic project analysis

• SpringBoot advantage

  Start relying on （ Simplify dependencies ）
  Automatic configuration （ Simplify project related configuration ）
  Auxiliary function （ Built in server , …）

parent

• spring-boot-dependencies-2.6.1.pom Many versions and coordinate relationships are defined in
• Alibaba cloud creates a version that directly references spring-boot-dependencies（ Inheritance can only be used once ）
• Avoid version conflicts when multiple dependencies use the same technology

<parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.6.1</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

Can only write GA Do not write V

• Join again after encountering errors V Version information , But to Beware of version conflicts

starter

• One starter Provides various dependencies required by a technology , achieve The purpose of reducing dependency configuration
• Purpose of simplified configuration

<dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

Boot class

• The bootstrap class is Boot The entrance to the execution of the works , function main Method to start the project
• SpringBoot Initialize after the project runs Spring Containers , Scan the package where the boot class is loaded Bean

@SpringBootApplication
public class Springboot0101QuickstartApplication {
    

    public static void main(String[] args) {
    
        ConfigurableApplicationContext run = SpringApplication.run(Springboot0101QuickstartApplication.class, args);
        BookController bean = run.getBean(BookController.class);
        System.out.println("book--==>"+ bean);
        User bean1 = run.getBean(User.class);
        System.out.println("User--==>"+ bean1);
    }
}

Embedded tomcat

• SpringBoot Built in one tomcat The server
• It can be downloaded from starter-web Exclude and replace with other servers , For example, in the following case jetty

• Common built-in servers

  apache Produce , More fans , It's widely used , Several heavier components are loaded
  jetty More lightweight , Load performance is far less than tomcat
  undertow Load performance barely outperforms tomcat

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
    <exclusions>
        <exclusion>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
        </exclusion>
    </exclusions>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-jetty</artifactId>
</dependency>