parent，starter，引导类

parent 依赖管理，减少依赖冲突

<parent>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-parent</artifactId>
  <version>2.6.7</version>
  <relativePath/> <!-- lookup parent from repository -->
    </parent>

starter 定义依赖

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

引导类

package com.tj;
import com.tj.controller.BookController;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;
@SpringBootApplication
public class Application {
    public static void main(String[] args) {
        ConfigurableApplicationContext ctx = SpringApplication.run(Application.class, args);
        // 获取bean
        BookController bean = ctx.getBean(BookController.class);
        System.out.println("bean = " + bean);
        // 获取bean
        User bean1 = ctx.getBean(User.class);
        System.out.println("bean1 = " + bean1);
    }
}

可以使用exclusions排除依赖

<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-web</artifactId>
  <!--排除依赖里的依赖，比如tomcat-->
  <exclusions>
    <exclusion>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-tomcat</artifactId>
    </exclusion>
  </exclusions>
</dependency>
<!--单独添加依赖，比如tomcat-->
<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-tomcat</artifactId>
</dependency>