“This is the first day I participate in the August more text challenge, activity details check: August more text challenge” I am small white, pure own record master don’t waste time

SpringBoot is the use of the SPRING framework to quickly build Java EE projects can be packaged into a WAR package, run with Tomcat, can also be packaged into a JAR package with Java-jar, or directly click the run method.

Create a new project using idea as an example, select Spring Initializr and choose the default (select a startup dependency and choose a Web). It will automatically generate a XXXXApplication with annotations on it

Starting dependencies can be seen in the POM.xml file to define transition-dependent dependencies on other libraries, which together support some functionality

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>
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@springBootApplication // Added annotation public class DemoApplication {! [image.png](https://p1-juejin.byteimg.com/tos-cn-i-k3u1fbpfcp/801388fd3cd74dd2b2a50fac90ee8aca~tplv-k3u1fbpfcp-watermark .image) public static void main(String[] args) { SpringApplication.run(DemoApplication.class, args); }}Copy the code

Create a Controller package, for example

Public class demoController {@getMapping Public String Hello (){String STR = "hello,springBoot"; return str; }}Copy the code

OK, run it now when SpringBoot is up

The browser accesses localhost:8080

To explain what an annotation means :@SpringBootApplication is a composite annotation

If you press Ctrl to enter IDEA, you can see that there are many annotations and three key ones

@SpringBootConfiguration

@EnableAutoConfiguration

@ComponentScan(
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So the first one I’m going to click on and you can see itA little closer to the truth is an @Configuration. So the @SpringBootConfiguration function is to indicate that it is a Configuration class, and developers can configure beans on both sides similar to the applicationContext.xml file in Spring. The second annotation @enableAutoConfiguration can be seen from the name is automatically imported configuration of the third annotation @ComponentScan open package scan OK, end hard work not overtime rush