一、spring-boot程序
maven引入springboot父项目
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.4.0</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
引入springweb的启动器spring-boot-web-starter
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
整个pom文件：
<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.4.0</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.example</groupId>
<artifactId>demo</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>demo</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>1.8</java.version>
</properties>
<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>
<build>
<plugins>
<!--插件作用是将程序打包成可执行jar包-->
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
创建主程序类（程序入口，mian方法启动）
/**
* @SpringBootApplication 标注springboot主程序类
*/
@SpringBootApplication
public class DemoApplication {
public static void main(String[] args) {
SpringApplication.run(DemoApplication.class, args);
}
}
编写hello world
/**
* controller
*/
@RestController
public class HelloController {
@GetMapping(value = "hello")
public String say(){
return "hello world";
}
}
项目结构
运行主程序类访问接口
二、pom文件
工程pom里引入了parent：spring-boot-starter-parent，spring-boot-starter-parent的pom里引入parent：spring-boot-dependencies 。spring-boot-dependencies 里有starter的版本信息。
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.4.0</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-dependencies</artifactId>
<version>2.4.0</version>
</parent>
springboot启动器（starter）
spring-boot-starter-web ：springboot web启动器。
里面引入了web项目正常运行的组件。其他springboot的启动器也是一样。自动帮忙配置好正常使用的依赖。
springboot将开发中极大部分的场景封装成启动器（starter），直接项目中配置上就可以使用。
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<?xml version="1.0" encoding="UTF-8"?>
<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<!-- This module was also published with a richer model, Gradle metadata, -->
<!-- which should be used instead. Do not delete the following line which -->
<!-- is to indicate to Gradle or any Gradle module metadata file consumer -->
<!-- that they should prefer consuming it instead. -->
<!-- do_not_remove: published-with-gradle-metadata -->
<modelVersion>4.0.0</modelVersion>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
<version>2.4.0</version>
<name>spring-boot-starter-web</name>
<description>Starter for building web, including RESTful, applications using Spring MVC. Uses Tomcat as the default embedded container</description>
<url>https://spring.io/projects/spring-boot</url>
<organization>
<name>Pivotal Software, Inc.</name>
<url>https://spring.io</url>
</organization>
<licenses>
<license>
<name>Apache License, Version 2.0</name>
<url>https://www.apache.org/licenses/LICENSE-2.0</url>
</license>
</licenses>
<developers>
<developer>
<name>Pivotal</name>
<email>info@pivotal.io</email>
<organization>Pivotal Software, Inc.</organization>
<organizationUrl>https://www.spring.io</organizationUrl>
</developer>
</developers>
<scm>
<connection>scm:git:git://github.com/spring-projects/spring-boot.git</connection>
<developerConnection>scm:git:ssh://git@github.com/spring-projects/spring-boot.git</developerConnection>
<url>https://github.com/spring-projects/spring-boot</url>
</scm>
<issueManagement>
<system>GitHub</system>
<url>https://github.com/spring-projects/spring-boot/issues</url>
</issueManagement>
<!--spring-boot-starter-web所引入的依赖-->
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</artifactId>
<version>2.4.0</version>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-json</artifactId>
<version>2.4.0</version>
<scope>compile</scope>
</dependency>
<!--内置tomcat启动器（内置了tomcat）-->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-tomcat</artifactId>
<version>2.4.0</version>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-web</artifactId>
<version>5.3.1</version>
<scope>compile</scope>
</dependency>
<!--springMVC-->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>5.3.1</version>
<scope>compile</scope>
</dependency>
</dependencies>
</project>
三、springboot程序入口
/**
* @SpringBootApplication 标注springboot主程序类
*/
@SpringBootApplication
public class DemoApplication {
public static void main(String[] args) {
SpringApplication.run(DemoApplication.class, args);
}
}
注解：@SpringBootApplication
//前四个java元注解
@Target({
ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
//标注在某个类上，表示这个类是springboot的配置类
@SpringBootConfiguration
//开启自动配置功能，帮忙配置自动默认的配置
@EnableAutoConfiguration
@ComponentScan(
excludeFilters = {
@Filter(
type = FilterType.CUSTOM,
classes = {
TypeExcludeFilter.class}
), @Filter(
type = FilterType.CUSTOM,
classes = {
AutoConfigurationExcludeFilter.class}
)}
)
public @interface SpringBootApplication {
@AliasFor(
annotation = EnableAutoConfiguration.class
)
Class<?>[] exclude() default {
};
@AliasFor(
annotation = EnableAutoConfiguration.class
)
String[] excludeName() default {
};
@AliasFor(
annotation = ComponentScan.class,
attribute = "basePackages"
)
String[] scanBasePackages() default {
};
@AliasFor(
annotation = ComponentScan.class,
attribute = "basePackageClasses"
)
Class<?>[] scanBasePackageClasses() default {
};
@AliasFor(
annotation = ComponentScan.class,
attribute = "nameGenerator"
)
Class<? extends BeanNameGenerator> nameGenerator() default BeanNameGenerator.class;
@AliasFor(
annotation = Configuration.class
)
boolean proxyBeanMethods() default true;
}
@SpringBootConfiguration注解：标注在某个类上，表示这个类是springboot的配置类
@Target({
ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Configuration //spring配置注解，内部被@Component注解修饰
public @interface SpringBootConfiguration {
@AliasFor(
annotation = Configuration.class
)
boolean proxyBeanMethods() default true;
}
@EnableAutoConfiguration 注解：开启自动配置功能，帮忙配置自动默认的配置
@Target({
ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
//自动配置包,里面被@Import注解修饰，将主配置类(程序入口标注@SpringBootApplication)包下面所有子包里面
//含有spring注解的类注入到spring容器中
@AutoConfigurationPackage
//AutoConfigurationImportSelector自动导入pom里引的组件starter，数组中筛选。
@Import({
AutoConfigurationImportSelector.class})
public @interface EnableAutoConfiguration {
String ENABLED_OVERRIDE_PROPERTY = "spring.boot.enableautoconfiguration";
Class<?>[] exclude() default {
};
String[] excludeName() default {
};
}
四、spring boot配置
全局配置文件：application.(properties|yml)
两种格式配置文件application.properties、application.yml。
配置文件可以修改spring boot启动器的默认值。