springboot入门--pom文件解读

spring-boot-starter-parent

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.0.0.RELEASE</version>
</parent>

spring-boot-dependencies

 <parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-dependencies</artifactId>
    <version>2.0.0.RELEASE</version>
    <relativePath>../../spring-boot-dependencies</relativePath>
  </parent>

• spring-boot-dependencies主要管理springboot应用依赖版本

导入的spring-boot-starter-web依赖

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

spring-boot-starter-web依赖导入（web容器使用的jar）

<dependencies>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter</artifactId>
      <version>2.0.0.RELEASE</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-json</artifactId>
      <version>2.0.0.RELEASE</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-tomcat</artifactId>
      <version>2.0.0.RELEASE</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>org.hibernate.validator</groupId>
      <artifactId>hibernate-validator</artifactId>
      <version>6.0.7.Final</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-web</artifactId>
      <version>5.0.4.RELEASE</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-webmvc</artifactId>
      <version>5.0.4.RELEASE</version>
      <scope>compile</scope>
    </dependency>
  </dependencies>

starter（启动器）

spring-boot-starter-xxx 对应的启动器，web开发就使用web启动器，jms就使用jms springboot提供的启动器

程序入口类

import org.springframework.boot.*;
import org.springframework.boot.autoconfigure.*;
import org.springframework.web.bind.annotation.*;

@SpringBootApplication
public class Example {

    public static void main(String[] args) throws Exception {
        SpringApplication.run(Example.class, args);
    }

}

@SpringBootApplication

springboot主配置类

package org.springframework.boot.autoconfigure;

import java.lang.annotation.*;
import org.springframework.boot.*;
import org.springframework.context.*;
import org.springframework.core.annotation.AliasFor;

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@SpringBootConfiguration
@EnableAutoConfiguration
@ComponentScan(excludeFilters = {
        @Filter(type = FilterType.CUSTOM, classes = TypeExcludeFilter.class),
        @Filter(type = FilterType.CUSTOM, classes = AutoConfigurationExcludeFilter.class) })
public @interface SpringBootApplication {

@SpringBootConfiguration

spring boot的配置类，内部使用spirng的@Configuration

package org.springframework.boot;

import java.lang.annotation.*;
import org.springframework.context.annotation.Configuration;

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Configuration
public @interface SpringBootConfiguration {
}

@EnableAutoConfiguration

开启自动配置功能，@EnableAutoConfiguration告诉springboot开启自动配置

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@AutoConfigurationPackage
@Import(AutoConfigurationImportSelector.class)
public @interface EnableAutoConfiguration {
    
}

@AutoConfigurationPackage

自动配置包，使用 @Import(AutoConfigurationPackages.Registrar.class)给容器导入组件

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@Import(AutoConfigurationPackages.Registrar.class)
public @interface AutoConfigurationPackage {

}

AutoConfigurationPackages.Registrar.class

static class Registrar implements ImportBeanDefinitionRegistrar, DeterminableImports {

        @Override
        public void registerBeanDefinitions(AnnotationMetadata metadata,
                BeanDefinitionRegistry registry) {
            //根据使用@SpringBootApplication注解的类为根路径
            register(registry, new PackageImport(metadata).getPackageName());
        }

        @Override
        public Set<Object> determineImports(AnnotationMetadata metadata) {
            return Collections.singleton(new PackageImport(metadata));
        }

    }