《Spring Boot极简教程》第3章 一键启动应用程序本章源代码

第3章 一键启动应用程序

3.1 SpringBoot版的Restful Hello,World

3.1.1 Spring Boot CLI groovy版Hello World

首先安装Spring Boot CLI,参考文档:http://docs.spring.io/spring-boot/docs/current-SNAPSHOT/reference/htmlsingle/#getting-started-installing-the-cli

在命令行验证spring环境安装成功:

$ spring --version
Spring CLI v1.3.6.RELEASE

随便打开编辑器,敲入如下代码:

 @Controller
 class HelloController{
      @RequestMapping("/hello")
      @ResponseBody
      String hello(){
          return "Hello World!"
      }
 }

然后在命令行执行:

$ spring run HelloController.groovy

你将看到如下输出日志:

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v1.3.6.RELEASE)

2017-04-04 21:37:29.685  INFO 87317 --- [       runner-0] o.s.boot.SpringApplication               : Starting application on jacks-MacBook-Air.local with PID 87317 (/Users/jack/.m2/repository/org/springframework/boot/spring-boot/1.3.6.RELEASE/spring-boot-1.3.6.RELEASE.jar started by jack in /Users/jack/book)
2017-04-04 21:37:29.699  INFO 87317 --- [       runner-0] o.s.boot.SpringApplication               : No active profile set, falling back to default profiles: default
2017-04-04 21:37:30.367  INFO 87317 --- [       runner-0] ationConfigEmbeddedWebApplicationContext : Refreshing org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@30cc0018: startup date [Tue Apr 04 21:37:30 CST 2017]; root of context hierarchy
2017-04-04 21:37:33.757  INFO 87317 --- [       runner-0] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat initialized with port(s): 8080 (http)
2017-04-04 21:37:33.790  INFO 87317 --- [       runner-0] o.apache.catalina.core.StandardService   : Starting service Tomcat
2017-04-04 21:37:33.793  INFO 87317 --- [       runner-0] org.apache.catalina.core.StandardEngine  : Starting Servlet Engine: Apache Tomcat/8.0.36
2017-04-04 21:37:33.986  INFO 87317 --- [ost-startStop-1] org.apache.catalina.loader.WebappLoader  : Unknown loader org.springframework.boot.cli.compiler.ExtendedGroovyClassLoader$DefaultScopeParentClassLoader@67cc18dd class org.springframework.boot.cli.compiler.ExtendedGroovyClassLoader$DefaultScopeParentClassLoader
2017-04-04 21:37:34.037  INFO 87317 --- [ost-startStop-1] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2017-04-04 21:37:34.038  INFO 87317 --- [ost-startStop-1] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 3673 ms
2017-04-04 21:37:34.538  INFO 87317 --- [ost-startStop-1] o.s.b.c.e.ServletRegistrationBean        : Mapping servlet: 'dispatcherServlet' to [/]
2017-04-04 21:37:34.552  INFO 87317 --- [ost-startStop-1] o.s.b.c.embedded.FilterRegistrationBean  : Mapping filter: 'characterEncodingFilter' to: [/*]
2017-04-04 21:37:34.553  INFO 87317 --- [ost-startStop-1] o.s.b.c.embedded.FilterRegistrationBean  : Mapping filter: 'hiddenHttpMethodFilter' to: [/*]
2017-04-04 21:37:34.553  INFO 87317 --- [ost-startStop-1] o.s.b.c.embedded.FilterRegistrationBean  : Mapping filter: 'httpPutFormContentFilter' to: [/*]
2017-04-04 21:37:34.553  INFO 87317 --- [ost-startStop-1] o.s.b.c.embedded.FilterRegistrationBean  : Mapping filter: 'requestContextFilter' to: [/*]
2017-04-04 21:37:35.309  INFO 87317 --- [       runner-0] s.w.s.m.m.a.RequestMappingHandlerAdapter : Looking for @ControllerAdvice: org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@30cc0018: startup date [Tue Apr 04 21:37:30 CST 2017]; root of context hierarchy
2017-04-04 21:37:35.482  INFO 87317 --- [       runner-0] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/hello]}" onto public java.lang.String HelloController.hello()
2017-04-04 21:37:35.485  INFO 87317 --- [       runner-0] 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.BasicErrorController.error(javax.servlet.http.HttpServletRequest)
2017-04-04 21:37:35.486  INFO 87317 --- [       runner-0] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/error],produces=[text/html]}" onto public org.springframework.web.servlet.ModelAndView org.springframework.boot.autoconfigure.web.BasicErrorController.errorHtml(javax.servlet.http.HttpServletRequest,javax.servlet.http.HttpServletResponse)
2017-04-04 21:37:35.523  INFO 87317 --- [       runner-0] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/webjars/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2017-04-04 21:37:35.524  INFO 87317 --- [       runner-0] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2017-04-04 21:37:35.606  INFO 87317 --- [       runner-0] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/**/favicon.ico] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2017-04-04 21:37:36.225  INFO 87317 --- [       runner-0] o.s.j.e.a.AnnotationMBeanExporter        : Registering beans for JMX exposure on startup
2017-04-04 21:37:36.397  INFO 87317 --- [       runner-0] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat started on port(s): 8080 (http)
2017-04-04 21:37:36.403  INFO 87317 --- [       runner-0] o.s.boot.SpringApplication               : Started application in 8.263 seconds (JVM running for 12.897)

一个极简的Restful Hello World就搞定了。浏览器访问:http://localhost:8080/hello(或者curl http://localhost:8080/hello

你会看到输出:

Hello World!

3.1.2 常规的Java版的Hello World

1.命令行输入:

$ spring init -dweb --build gradle
Using service at https://start.spring.io

Content saved to 'demo.zip'

2.解压zip,导入idea中

你将看到如下一个Demo Application

.
├── build.gradle
├── gradle
│   └── wrapper
│       ├── gradle-wrapper.jar
│       └── gradle-wrapper.properties
├── gradlew
├── gradlew.bat
└── src
    ├── main
    │   ├── java
    │   │   └── com
    │   │       └── example
    │   │           └── DemoApplication.java
    │   └── resources
    │       ├── application.properties
    │       ├── static
    │       └── templates
    └── test
        └── java
            └── com
                └── example
                    └── DemoApplicationTests.java

14 directories, 8 files

其中DemoApplication.java代码如下:

package com.example;

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

@SpringBootApplication
public class DemoApplication {

    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }
}

build.gradle配置文件如下:

buildscript {
    ext {
        springBootVersion = '1.5.2.RELEASE'
    }
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")
    }
}

apply plugin: 'java'
apply plugin: 'eclipse'
apply plugin: 'org.springframework.boot'

version = '0.0.1-SNAPSHOT'
sourceCompatibility = 1.8

repositories {
    mavenCentral()
}


dependencies {
    compile('org.springframework.boot:spring-boot-starter-web')
    testCompile('org.springframework.boot:spring-boot-starter-test')
}

OK,我们直接Run

Run

同样的,你讲看到如下日志:

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v1.5.2.RELEASE)

2017-04-04 22:51:58.995  INFO 89676 --- [           main] com.example.DemoApplication              : Starting DemoApplication on jacks-MacBook-Air.local with PID 89676 (/Users/jack/book/demo/build/classes/main started by jack in /Users/jack/book/demo)
2017-04-04 22:51:58.998  INFO 89676 --- [           main] com.example.DemoApplication              : No active profile set, falling back to default profiles: default
2017-04-04 22:51:59.191  INFO 89676 --- [           main] ationConfigEmbeddedWebApplicationContext : Refreshing org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@6950e31: startup date [Tue Apr 04 22:51:59 CST 2017]; root of context hierarchy
2017-04-04 22:52:02.718  INFO 89676 --- [           main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat initialized with port(s): 8080 (http)
2017-04-04 22:52:02.750  INFO 89676 --- [           main] o.apache.catalina.core.StandardService   : Starting service Tomcat
2017-04-04 22:52:02.754  INFO 89676 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet Engine: Apache Tomcat/8.5.11
2017-04-04 22:52:02.974  INFO 89676 --- [ost-startStop-1] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2017-04-04 22:52:02.974  INFO 89676 --- [ost-startStop-1] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 3788 ms
2017-04-04 22:52:03.173  INFO 89676 --- [ost-startStop-1] o.s.b.w.servlet.ServletRegistrationBean  : Mapping servlet: 'dispatcherServlet' to [/]
2017-04-04 22:52:03.198  INFO 89676 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'characterEncodingFilter' to: [/*]
2017-04-04 22:52:03.199  INFO 89676 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'hiddenHttpMethodFilter' to: [/*]
2017-04-04 22:52:03.199  INFO 89676 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'httpPutFormContentFilter' to: [/*]
2017-04-04 22:52:03.200  INFO 89676 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'requestContextFilter' to: [/*]
2017-04-04 22:52:03.758  INFO 89676 --- [           main] s.w.s.m.m.a.RequestMappingHandlerAdapter : Looking for @ControllerAdvice: org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@6950e31: startup date [Tue Apr 04 22:51:59 CST 2017]; root of context hierarchy
2017-04-04 22:52:03.931  INFO 89676 --- [           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.BasicErrorController.error(javax.servlet.http.HttpServletRequest)
2017-04-04 22:52:03.932  INFO 89676 --- [           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.BasicErrorController.errorHtml(javax.servlet.http.HttpServletRequest,javax.servlet.http.HttpServletResponse)
2017-04-04 22:52:03.986  INFO 89676 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/webjars/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2017-04-04 22:52:03.987  INFO 89676 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2017-04-04 22:52:04.076  INFO 89676 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/**/favicon.ico] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2017-04-04 22:52:04.334  INFO 89676 --- [           main] o.s.j.e.a.AnnotationMBeanExporter        : Registering beans for JMX exposure on startup
2017-04-04 22:52:04.447  INFO 89676 --- [           main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat started on port(s): 8080 (http)
2017-04-04 22:52:04.455  INFO 89676 --- [           main] com.example.DemoApplication              : Started DemoApplication in 6.41 seconds (JVM running for 7.608)

通过日志,我们可以看到SpringBootApplication大致的启动流程。这个过程中,很大一部分工作是在做Spring应用的初始化。

Initializing Spring embedded WebApplicationContext

同时,嵌入式的servlet容器tomcat的启动,org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext是关键类。对细节感兴趣的可以直接debug一下源码。

上面的代码虽然看不出什么效果。但SpringBootApplication的基本架构流程已经基本在里面了。SpringBoot通过注解@SpringBootApplication,完成了自动配置的工作。(源码参见: org.springframework.boot.autoconfigure.SpringBootApplication)

3.写个HelloWorldController

package com.example.controller;

import java.util.Date;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

/**
 * Created by jack on 2017/4/4.
 */
@RestController
public class HelloWorldController {
    @RequestMapping("hello")
    String hello() {
        return "Hello World! " + new Date();
    }
}

直接Run DemoApplication,我们可以看到有如下的日志:

...
Mapped "{[/hello]}" onto java.lang.String com.example.controller.HelloWorldController.hello()
...

浏览器访问:http://localhost:8080/hello

我们将看到如下输出:

Hello World! Tue Apr 04 23:08:33 CST 2017

另外,如果是在命令行运行,使用SpringBoot gradle插件的执行:

$gradle bootRun

使用SpringBoot maven插件的执行:

$mvn spring-boot:run

3.2 启动Springboot的自动配置@EnableAutoConfiguration

SpringBoot AutoConfiguration的原理是通过Spring的@Conditional注解实现。@Conditional以编程的方式确定的bean的状态,来决定哪些bean是要初始化到容器中(根据外界条件注册不同Bean)。

@EnableAutoConfiguration的意思是启用Spring应用程序上下文的自动配置,通过扫描CLASSPATH里面所有的组件,然后基于条件来决定是否注册bean来使得Spring的ApplicationContext自动配置。

比如说,Spring检测jdbcTemplate是否在classpath?if true, 看看bean容器里面是否有DataSource ? if true, 配置一个JdbcTemplate的Bean到容器中。

看EnableAutoConfiguration源码:

package org.springframework.boot.autoconfigure;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import org.springframework.context.annotation.Import;

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@AutoConfigurationPackage
@Import({EnableAutoConfigurationImportSelector.class})
public @interface EnableAutoConfiguration {
    String ENABLED_OVERRIDE_PROPERTY = "spring.boot.enableautoconfiguration";

    Class<?>[] exclude() default {};

    String[] excludeName() default {};
}

可以发现,这里Import了EnableAutoConfigurationImportSelector。 Import主要是配合Configuration来使用的,用来导出更多的Configuration类,ConfigurationClassPostProcessor会读取Import的内容来实现具体的逻辑。 EnableAutoConfigurationImportSelector实现了DeferredImportSelector接口,并实现了selectImports方法,用来导出Configuration类。

String[] selectImports(AnnotationMetadata importingClassMetadata); 导出的类是通过SpringFactoriesLoader.loadFactoryNames()读取了ClassPath下面的META-INF/spring.factories文件,这个文件内容大致如下:

# Auto Configure
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
org.springframework.boot.autoconfigure.admin.SpringApplicationAdminJmxAutoConfiguration,\
org.springframework.boot.autoconfigure.aop.AopAutoConfiguration,\
......
org.springframework.boot.autoconfigure.websocket.WebSocketAutoConfiguration,\
org.springframework.boot.autoconfigure.websocket.WebSocketMessagingAutoConfiguration,\
org.springframework.boot.autoconfigure.webservices.WebServicesAutoConfiguration

其中EmbeddedServletContainerAutoConfiguration是实现web服务的主要的配置类。这个类会根据当前存在的类的信息注入必要的EmbeddedServletContainerFactory类。 spring-boot-starter-tomcat引入了tomcat的依赖,所以EmbeddedServletContainerAutoConfiguration发现存在Tomcat.class就会注入TomcatEmbeddedServletContainerFactory来内置web容器。

当然,如果你想排除一些bean的自动注入,你可以用Class<?>[] exclude() 或者String[] excludeName()。

SpringBoot在spring-boot-autoconfigure-{版本号}.jar里面提供了很多AutoConfiguration的类来负责注册各种不同的组件。这些组件几乎涵盖了Spring开发中需要的绝大部分的配置。

本章源代码

https://github.com/EasySpringBoot/HelloWorld/tree/hello_world_2017.4.4

本文参与腾讯云自媒体分享计划,欢迎正在阅读的你也加入,一起分享。

发表于

我来说两句

0 条评论
登录 后参与评论

相关文章

来自专栏一个会写诗的程序员的博客

Springboot从HellWorld开始第三章 从HellWorld开始

https://github.com/LightSwordSpringBoot/lightsword_helloworld

1303
来自专栏后端之路

tomcat 生产环境crash

最近生产系统erp不太稳定,时不时出现tomcat crash,并且log下面没有留下任何证据。 收到邮件如下 告警主机:f6_web0 告警时间:2016.1...

2107
来自专栏happyJared

Spring Boot几种启动问题的解决方案

  使用Spring Boot以来,遇到和解决过好几次不同的项目启动问题,大多数事故起于错误的配置和依赖。因此,本文用于汇总这些问题,以及提供相应的解决方案,帮...

6031
来自专栏一个会写诗的程序员的博客

第3章 Spring Boot快速开始Hello World本章源代码

首先安装Spring Boot CLI,参考文档:http://docs.spring.io/spring-boot/docs/current-SNAPSHOT...

1144
来自专栏三木的博客

基于Jenkins和Koji的代码管理及构建系统

<h1>Summary</h1> Currently, we KVM team are maintaining the code repository of t...

2447
来自专栏码匠的流水账

jib打包docker镜像实战

2111
来自专栏程序猿DD

Spring Boot 2.0 新特性(二):新增事件ApplicationStartedEvent

今天继续来聊Spring Boot 2.0的新特性。本文将具体说说2.0版本中的事件模型,尤其是新增的事件: ApplicationStartedEvent。 ...

4276
来自专栏李成熙heyli

Deploy Using Travis-CI And Github Webhook — webpack doc as an example

Overview Some friends and I have been running webpack-china for a few months. A...

2408
来自专栏cloudskyme

Could not find artifact com.sun:tools:jar:1.5.0

【maven package】,则依然报错,但报的是另外一个错误: [INFO] Scanning for projects…[INFO]           ...

3104
来自专栏算法修养

ZOJ 3927 Programming Ability Test

Programming Ability Test (PAT) aims to evaluate objectively, through unified exa...

2514

扫码关注云+社区

领取腾讯云代金券