SpringBoot快速入门

代码实现

创建Maven工程

使用idea工具创建一个maven工程，该工程为普通的java工程即可

添加SpringBoot的起步依赖

<mark>SpringBoot要求，项目要继承SpringBoot的起步依赖spring-boot-starter-parent</mark>

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.0.1.RELEASE</version>
</parent>

<mark>SpringBoot要集成SpringMVC进行Controller的开发，所以项目要导入web的启动依赖</mark>

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

编写SpringBoot引导类

要通过SpringBoot提供的引导类起步SpringBoot才可以进行访问

package com.itheima;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

//声明该类是SpringBoot的引导类
@SpringBootApplication
public class MySpringBootApplication {

    public static void main(String[] args) {
    	//表示要运行SpringBoot的引导类，参数是引导类的字节码对象
        SpringApplication.run(MySpringBootApplication.class);
    }

}

编写Controller

在引导类MySpringBootApplication同级包或者子级包中创建QuickStartController

package com.itheima.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller
public class QuickStartController {
    
    @RequestMapping("/quick")
    @ResponseBody
    public String quick(){
        return "springboot 访问成功!";
    }
    
}

测试

执行SpringBoot起步类的主方法，控制台打印日志如下：

.   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \ ( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.0.1.RELEASE)

2018-05-08 14:29:59.714  INFO 5672 --- [           main] com.itheima.MySpringBootApplication      : Starting MySpringBootApplication on DESKTOP-RRUNFUH with PID 5672 (C:\Users\muzimoo\IdeaProjects\IdeaTest\springboot_quick\target\classes started by muzimoo in C:\Users\muzimoo\IdeaProjects\IdeaTest)
... ... ...
o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler] 2018-05-08 14:30:03.126 INFO 5672 --- [ main] o.s.j.e.a.AnnotationMBeanExporter : Registering beans for JMX exposure on startup 2018-05-08 14:30:03.196 INFO 5672 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path '' 2018-05-08 14:30:03.206 INFO 5672 --- [ main] com.itheima.MySpringBootApplication : Started MySpringBootApplication in 4.252 seconds (JVM running for 5.583) 

通过日志发现，Tomcat started on port(s): 8080 (http) with context path ‘’

tomcat已经起步，端口监听8080，web应用的虚拟工程名称为空

打开浏览器访问url地址为：http://localhost:8080/quick

快速入门解析

SpringBoot代码解析

• @SpringBootApplication：标注SpringBoot的启动类，该注解具备多种功能（后面详细剖析）
• SpringApplication.run(MySpringBootApplication.class) 代表运行SpringBoot的启动类，参数为SpringBoot启动类的字节码对象

SpringBoot工程热部署

我们在开发中反复修改类、页面等资源，每次修改后都是需要重新启动才生效，这样每次启动都很麻烦，浪费了大量的时间，我们可以在修改代码后不重启就能生效，在 pom.xml 中添加如下配置就可以实现这样的功能，我们称之为热部署。

<!--热部署配置-->
![<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-devtools</artifactId>
</dependency>](https://img-blog.csdnimg.cn/20200318173016206.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzMDQwNjg4,size_16,color_FFFFFF,t_70)

注意：IDEA进行SpringBoot热部署失败原因

出现这种情况，并不是热部署配置问题，其根本原因是因为Intellij IEDA默认情况下不会自动编译，需要对IDEA进行自动编译的设置，如下：

然后 Shift+Ctrl+Alt+/，选择Registry

使用idea快速创建SpringBoot项目

通过idea快速创建的SpringBoot项目的pom.xml中已经导入了我们选择的web的起步依赖的坐标

<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>

	<groupId>com.itheima</groupId>
	<artifactId>springboot_quick2</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>jar</packaging>

	<name>springboot_quick2</name>
	<description>Demo project for Spring Boot</description>

	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.0.1.RELEASE</version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>

	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
		<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
		<java.version>9</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>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
			</plugin>
		</plugins>
	</build>


</project>

可以使用快速入门的方式创建Controller进行访问，此处不再赘述