Spring boot 是什么 ?

简单说, spring boot 是一个构建项目的工具, 一个脚手架.

Spring boot 能干什么?

spring boot 做非常少的配置就可以构建生产级别的单体应用.

Spring boot 怎么干的?

下面让我们来用spring boot 做一个hello world.

1. 环境准备, 需要保证你的机器上已经有了如下软件

   • JDK1.8+
   • gradle4+

2. 创建项目目录, 假设这个新的项目叫apple.

   $ cd /tmp
   $ mkdir apple

3. 创建gradle配置文件,在这个目录下创建build.gradle文件.

   $ cd apple
   $ vi build.gradle

   将如下代码复制到build.gradle文件中.

   plugins {
       id 'org.springframework.boot' version '2.0.1.RELEASE'
   }
   
   apply plugin: 'java'
   apply plugin: 'io.spring.dependency-management'
   
   repositories {
       mavenCentral()
   }
   
   dependencies {
       compile 'org.springframework.boot:spring-boot-starter-web'
       testCompile 'org.springframework.boot:spring-boot-starter-test'
       testCompile 'org.springframework.boot:spring-boot-starter-webflux'
   }
   
   bootRun {
       main = 'com.thoughtworks.apple.Launcher'
   }

4. 写一个Hello world.

   • 按照如下目录结构初始化项目内容

   apple
     \-src
        \-main
          \-java
             \-com.thoughtworks.apple
                 |-controller
                 |   \-HomeController.java
                 \-Launcher.java

   • HomeController.java内容如下

   package com.thoughtworks.apple.controller;
   
   import org.springframework.web.bind.annotation.RequestMapping;
   import org.springframework.web.bind.annotation.RestController;
   
   @RestController
   public class HomeController {
       @RequestMapping("/")
       String home() {
           return "Hello World!";
       }
   }

   • Launcher.java内容如下

   package com.thoughtworks.apple;
   
   import org.springframework.boot.SpringApplication;
   import org.springframework.boot.SpringBootConfiguration;
   import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
   import org.springframework.context.annotation.ComponentScan;
   
   @SpringBootConfiguration
   @EnableAutoConfiguration
   @ComponentScan("com.thoughtworks.apple")
   public class Launcher {
       public static void main(String[] args) {
           SpringApplication.run(Launcher.class, args);
       }
   }

5. 运行

   执行命令gradle bootRun启动应用,之后会打印如下日志:

   $ gradle bootRun
   
   > Task :bootRun
   
     .   ____          _            __ _ _
    /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
   ( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
    \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
     '  |____| .__|_| |_|_| |_\__, | / / / /
    =========|_|==============|___/=/_/_/_/
    :: Spring Boot ::        (v2.0.1.RELEASE)
   
   2018-05-05 10:23:41.383  INFO 38941 --- [           main] com.thoughtworks.apple.Launcher          : Starting Launcher on CNyfqi.local with PID 38941 (/private/tmp/apple/build/classes/java/main started by yfqi in /private/tmp/apple)
   2018-05-05 10:23:41.386  INFO 38941 --- [           main] com.thoughtworks.apple.Launcher          : No active profile set, falling back to default profiles: default
   2018-05-05 10:23:41.432  INFO 38941 --- [           main] ConfigServletWebServerApplicationContext : Refreshing org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext@3b2c72c2: startup date [Sat May 05 10:23:41 CST 2018]; root of context hierarchy
   2018-05-05 10:23:42.289  INFO 38941 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)
   2018-05-05 10:23:42.313  INFO 38941 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
   2018-05-05 10:23:42.313  INFO 38941 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet Engine: Apache Tomcat/8.5.29
   2018-05-05 10:23:42.323  INFO 38941 --- [ost-startStop-1] o.a.catalina.core.AprLifecycleListener   : The APR based Apache Tomcat Native library which allows optimal performance in production environments was not found on the java.library.path: [/Users/yfqi/Library/Java/Extensions:/Library/Java/Extensions:/Network/Library/Java/Extensions:/System/Library/Java/Extensions:/usr/lib/java:.]
   2018-05-05 10:23:42.402  INFO 38941 --- [ost-startStop-1] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
   2018-05-05 10:23:42.403  INFO 38941 --- [ost-startStop-1] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 973 ms
   2018-05-05 10:23:42.522  INFO 38941 --- [ost-startStop-1] o.s.b.w.servlet.ServletRegistrationBean  : Servlet dispatcherServlet mapped to [/]
   2018-05-05 10:23:42.525  INFO 38941 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'characterEncodingFilter' to: [/*]
   2018-05-05 10:23:42.526  INFO 38941 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'hiddenHttpMethodFilter' to: [/*]
   2018-05-05 10:23:42.526  INFO 38941 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'httpPutFormContentFilter' to: [/*]
   2018-05-05 10:23:42.526  INFO 38941 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'requestContextFilter' to: [/*]
   2018-05-05 10:23:42.627  INFO 38941 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/**/favicon.ico] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
   2018-05-05 10:23:42.809  INFO 38941 --- [           main] s.w.s.m.m.a.RequestMappingHandlerAdapter : Looking for @ControllerAdvice: org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext@3b2c72c2: startup date [Sat May 05 10:23:41 CST 2018]; root of context hierarchy
   2018-05-05 10:23:42.878  INFO 38941 --- [           main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/]}" onto java.lang.String com.thoughtworks.apple.controller.HomeController.home()
   2018-05-05 10:23:42.884  INFO 38941 --- [           main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/error]}" onto public org.springframework.http.ResponseEntity<java.util.Map<java.lang.String, java.lang.Object>> org.springframework.boot.autoconfigure.web.servlet.error.BasicErrorController.error(javax.servlet.http.HttpServletRequest)
   2018-05-05 10:23:42.885  INFO 38941 --- [           main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/error],produces=[text/html]}" onto public org.springframework.web.servlet.ModelAndView org.springframework.boot.autoconfigure.web.servlet.error.BasicErrorController.errorHtml(javax.servlet.http.HttpServletRequest,javax.servlet.http.HttpServletResponse)
   2018-05-05 10:23:42.910  INFO 38941 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/webjars/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
   2018-05-05 10:23:42.910  INFO 38941 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
   2018-05-05 10:23:43.048  INFO 38941 --- [           main] o.s.j.e.a.AnnotationMBeanExporter        : Registering beans for JMX exposure on startup
   2018-05-05 10:23:43.100  INFO 38941 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
   2018-05-05 10:23:43.105  INFO 38941 --- [           main] com.thoughtworks.apple.Launcher          : Started Launcher in 2.148 seconds (JVM running for 2.523)
   2018-05-05 10:24:03.416  INFO 38941 --- [nio-8080-exec-1] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring FrameworkServlet 'dispatcherServlet'
   2018-05-05 10:24:03.416  INFO 38941 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : FrameworkServlet 'dispatcherServlet': initialization started
   2018-05-05 10:24:03.436  INFO 38941 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : FrameworkServlet 'dispatcherServlet': initialization completed in 20 ms
   <=========----> 75% EXECUTING [1m 28s]
   > :bootRun

   之后在浏览器中访问http://localhost:8080/ 能看到如下页面说明程序运行成功了.
   

进阶

如何将gradle命令引入项目

当我们本地有多个项目, 且每个项目的gradle版本不一样时, 我们就需要把gradle命令保存在项目内, 然后每个项目用自己的gradle来构建. 下面这个命令可以直接初始化引入一个gradle命令到项目内部.

$ gradle wrapper --gradle-version 4.0

之后项目目录下会多出四个文件

drwxr-xr-x   4 yfqi  wheel   128 May  5 10:49 .gradle
drwxr-xr-x   3 yfqi  wheel    96 May  5 10:49 gradle
-rwxr-xr-x   1 yfqi  wheel  5296 May  5 10:49 gradlew
-rw-r--r--   1 yfqi  wheel  2260 May  5 10:49 gradlew.bat

以后就可以在项目根目录下执行 ./gradlew来运行gradle的tasks了.

测试Hello World

程序成功运行了, 让我们来写一个测试用例测试一下hello world.

• 测试目录结构如下

  apple
    \-src
       |-main   
       \-test
          \-java
              \-com.thoughtworks.apple.controller
                 \-HomeControllerTest.java

• HomeControllerTest.java内容如下

  package com.thoughtworks.apple.controller;
  
  import org.junit.Test;
  import org.junit.runner.RunWith;
  import org.springframework.beans.factory.annotation.Autowired;
  import org.springframework.boot.test.context.SpringBootTest;
  import org.springframework.test.context.junit4.SpringRunner;
  import org.springframework.test.web.reactive.server.WebTestClient;
  
  @RunWith(SpringRunner.class)
  @SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
  public class HomeControllerTest {
      @Autowired
      private WebTestClient webClient;
  
      @Test
      public void should_get_home() {
          this.webClient.get().uri("/").exchange()
                  .expectStatus().isOk()
                  .expectBody(String.class).isEqualTo("Hello World!");
      }
  }

• 运行测试使用命令./gradlew test能看到如下日志说明测试执行成功

  $ gradle test
  Starting a Gradle Daemon (subsequent builds will be faster)
  
  > Task :test
  2018-05-05 10:36:18.034  INFO 39291 --- [       Thread-6] ConfigServletWebServerApplicationContext : Closing org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext@918accb: startup date [Sat May 05 10:36:15 CST 2018]; root of context hierarchy
  
  
  BUILD SUCCESSFUL in 12s
  3 actionable tasks: 3 executed

打包部署

1. 执行命令./grdlew bootJar来打包spring boot项目. 命令执行成功后会在apple/build/libs下多出一个jar包apple.jar.这就打包成功了.
2. 把打包好的jar包复制到运行的服务器, 执行命令java -jar apple.jar &就可以把应用启动起来.

Spring Boot Starters

上面的例子大家会发现项目只是依赖了三个Spring Boot的Starter就完成了对所有第三方jar包的引用.Starter其实就是对第三方jar包依赖按照业务需要做了一个聚合,Spring Boot提供了大量的Starter来帮助开发人员快速开始构建项目, 降低了开发人员调包依赖的工作量.在这两个地址可以查看Spring Boot的所有的Starters.

• https://docs.spring.io/spring-boot/docs/current-SNAPSHOT/reference/htmlsingle/#using-boot-starter
• https://github.com/spring-projects/spring-boot/tree/master/spring-boot-project/spring-boot-starters

源码

文章的完整代码可以在这里找到: https://github.com/qyf404/learning-spring-boot

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