1.2. SpringBoot 优点Spring Boot makes it easy to create stand-alone, production-grade Spring based Applications that you can “just run”.
能快速的创建一个生产级别的 Spring 应用。
Create stand-alone Spring applications
Embed Tomcat, Jetty or Undertow directly (no need to deploy WAR files)
Provide opinionated ‘starter’ dependencies to simplify your build configuration
Automatically configure Spring and 3rd party libraries whenever possible
Provide production-ready features such as metrics, health checks, and externalized configuration
Absolutely no code generation and no requirement for XML configuration
修改 Maven 的 settings.xml ：
1.4.3. 创建 Hello Worldnexus-aliyun central Nexus aliyun. http://maven.aliyun.com/nexus/content/groups/public jdk-1.8 true 1.8 1.8 1.8 1.8
需求：浏览器发送 /Hello，响应 Hello Spring Boot 2
1.4.3.1. 创建 Maven 工程并且引入依赖pom.xml
1.4.3.2. 创建主程序4.0.0 cn.com.springboot.demo boot-01-helloworld 1.0-SNAPSHOT org.springframework.boot spring-boot-starter-parent 2.5.5 org.springframework.boot spring-boot-starter-web
dir：cn.com.springboot.demo.MainApp.java
package cn.com.springboot.demo;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class MainApp {
public static void main(String[] args) {
SpringApplication.run(MainApp.class, args);
}
}
1.4.3.3. 创建业务类
dir：cn.com.springboot.demo.controller.HelloController.java
package cn.com.springboot.demo.controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class HelloController {
@RequestMapping("/hello")
public String handler() {
return "Hello Spring Boot";
}
}
1.4.3.4. 测试
直接运行主程序。
. ____ _ __ _ _ /\ / ___'_ __ _ _(_)_ __ __ _ ( ( )___ | '_ | '_| | '_ / _` | \/ ___)| |_)| | | | | || (_| | ) ) ) ) ' |____| .__|_| |_|_| |___, | / / / / =========|_|==============|___/=/_/_/_/ :: Spring Boot :: (v2.5.5) 2021-09-29 00:18:47.607 INFO 8248 --- [ main] cn.com.springboot.demo.MainApp : Starting MainApp using Java 1.8.0_121 on DESKTOP-LT8H9RE with PID 8248 (F:IdeaProjectsboot-01-helloworldtargetclasses started by wwwjy in F:IdeaProjectsmy-app) 2021-09-29 00:18:47.617 INFO 8248 --- [ main] cn.com.springboot.demo.MainApp : No active profile set, falling back to default profiles: default 2021-09-29 00:18:48.255 INFO 8248 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat initialized with port(s): 8080 (http) 2021-09-29 00:18:48.265 INFO 8248 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat] 2021-09-29 00:18:48.265 INFO 8248 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet engine: [Apache Tomcat/9.0.53] 2021-09-29 00:18:48.328 INFO 8248 --- [ main] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext 2021-09-29 00:18:48.328 INFO 8248 --- [ main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 676 ms 2021-09-29 00:18:48.578 INFO 8248 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path '' 2021-09-29 00:18:48.586 INFO 8248 --- [ main] cn.com.springboot.demo.MainApp : Started MainApp in 1.252 seconds (JVM running for 1.529)1.4.3.5. 简化配置
dir：resources/application.properties
server.port=80811.4.3.6. 简化部署
生成可执行 jar ，引入以下的依赖：
...... org.springframework.boot spring-boot-maven-plugin 2.5.5
执行以下的命令：
mvn -clean mvn -package
进入 jar 所在路径，执行以下的命令：
F:IdeaProjectsboot-01-helloworldtarget>java -jar boot-01-helloworld-1.0-SNAPSHOT.jar . ____ _ __ _ _ /\ / ___'_ __ _ _(_)_ __ __ _ ( ( )___ | '_ | '_| | '_ / _` | \/ ___)| |_)| | | | | || (_| | ) ) ) ) ' |____| .__|_| |_|_| |___, | / / / / =========|_|==============|___/=/_/_/_/ :: Spring Boot :: (v2.5.5) 2021-09-29 00:25:34.990 INFO 2120 --- [ main] cn.com.springboot.demo.MainApp : Starting MainApp v1.0-SNAPSHOT using Java 1.8.0_121 on DESKTOP-LT8H9RE with PID 2120 (F:IdeaProjectsboot -01-helloworldtargetboot-01-helloworld-1.0-SNAPSHOT.jar started by wwwjy in F:IdeaProjectsboot-01-helloworldtarget) 2021-09-29 00:25:34.992 INFO 2120 --- [ main] cn.com.springboot.demo.MainApp : No active profile set, falling back to default profiles: default 2021-09-29 00:25:35.823 INFO 2120 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat initialized with port(s): 8081 (http) 2021-09-29 00:25:35.833 INFO 2120 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat] 2021-09-29 00:25:35.833 INFO 2120 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet engine: [Apache Tomcat/9.0.53] 2021-09-29 00:25:35.881 INFO 2120 --- [ main] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext 2021-09-29 00:25:35.881 INFO 2120 --- [ main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 848 ms 2021-09-29 00:25:36.156 INFO 2120 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8081 (http) with context path '' 2021-09-29 00:25:36.164 INFO 2120 --- [ main] cn.com.springboot.demo.MainApp : Started MainApp in 1.504 seconds (JVM running for 1.831)1.5. SpringBoot 特点 1.5.1. 依赖管理 1.5.1.1. 父项目做依赖管理
所有的项目（这里指：用 Maven 构建的项目）的 pom.xml 文件都会引入以下的内容：
...... org.springframework.boot spring-boot-starter-parent 2.5.5
这将导致下边的所有依赖都不需要指定版本号。如引入 web 开发的依赖：
...... org.springframework.boot spring-boot-starter-web
进入 spring-boot-starter-parent 中（Ctrl + 左键），发现它还引用了父项目：
...... org.springframework.boot spring-boot-dependencies 2.5.5
进入 spring-boot-dependencies 中（Ctrl + 左键），它引入了所有的常规开发所需要的依赖。
1.5.1.2. 场景启动器...1.5.1.3. 版本仲裁... org.springframework.boot spring-boot-starter 2.5.5 compile
因为在 spring-boot-dependencies 中配置了当前 spring-boot 版本（2.5.5）所支持依赖版本。
如：
...5.16.3 2.7.7 1.9.91 2.17.0 1.9.7 3.19.0 4.0.6 4.0.3 ...3.2.0 1.10.22 2.9.2 4.11.3 1.5.1 1.15 2.8.0 3.12.0 1.6 2.9.0 ...8.0.26 ...
所以引入的依赖都不需要写版本号，这就是 spring-boot 的自动版本仲裁机制。
如果不想使用 spring-boot 自动仲裁的版本
在当前项目（开发项目中）的 pom.xml 中，指定自己的依赖即可，如：
...... 6.0.6
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1.5.2. 自动配置 1.5.2.1. 引入 spring-boot-starter-web自动配置好了以下的内容：
...1.5.2.2. 默认的包结构org.springframework.boot spring-boot-starter-tomcat 2.5.5 compile org.springframework spring-web 5.3.10 compile ... org.springframework spring-webmvc 5.3.10 compile
主程序所在的包及其子包都会被扫描到。
示例：在主程序所在包外新建 controller
主程序
package cn.com.springboot.demo;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class MainApp {
public static void main(String[] args) {
SpringApplication.run(MainApp.class, args);
}
}
WorldController
package cn.com.springboot;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class WorldController {
@RequestMapping("/world")
public String handler() {
return "Hello World.";
}
}
运行结果
1.5.2.3. 默认配置都拥有默认值
