spring boot实战(第一篇)第一个案例

Posted 2020-10-11 求知若渴 虚心若愚

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目录(?)[+]

 

spring boot实战(第一篇)第一个案例

前言

写在前面的话

一直想将spring boot相关内容写成一个系列的博客，今天终于有时间开始了第一篇文章
以后有时间就会继续写下去。

spring boot 博客内容规划

• spring boot 基本用法
• 自动配置
• 技术集成
• 性能监控
• 源码解析

spring boot 功能强大，后面会细细道来。

第一个案例

工程的构建

构建spring boot工程一般采用两种方式 gradle 、maven;相对于maven的pom配置gradle 更加简单，有兴趣的同学可以去学习下gradle，这里采用maven。

创建一个maven工程，对应的pom.xml文件：

 1    <parent>
 2         <groupId>org.springframework.boot</groupId>
 3         <artifactId>spring-boot-starter-parent</artifactId>
 4         <version>1.2.4.RELEASE</version>
 5     </parent>
 6 
 7     <properties>
 8         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
 9     </properties>
10 
11     <dependencies>
12 
13         <dependency>
14             <groupId>org.springframework.boot</groupId>
15             <artifactId>spring-boot-starter-web</artifactId>
16         </dependency>
17     </dependencies>
18 
19     <build>
20         <plugins>
21             <plugin>
22                 <groupId>org.springframework.boot</groupId>
23                 <artifactId>spring-boot-maven-plugin</artifactId>
24             </plugin>
25         </plugins>
26     </build>

 

版本采用1.2.4,非官网最新版，但属于稳定版本

创建 Application.java

 1 package com.lkl.springboot;
 2 
 3 import org.springframework.boot.SpringApplication;
 4 import org.springframework.boot.autoconfigure.SpringBootApplication;
 5 
 6 @SpringBootApplication
 7 public class Application {
 8     public static void main(String[] args) {
 9         SpringApplication.run(Application.class, args);
10     }
11 }

 

运行main方法

  .   ____          _            __ _ _
 /\\ / ___‘_ __ _ _(_)_ __  __ _ \ \ \ ( ( )\___ | ‘_ | ‘_| | ‘_ \/ _` | \ \ \  \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  ‘  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v1.2.4.RELEASE)

2015-08-25 22:53:35.484  INFO 554 --- [           main] com.lkl.springboot.Application       : Starting Application on mac.local with PID 554 (/Users/liaokailin/code/github/blog-springboot/target/classes started by lkl in /Users/liaokailin/code/github/blog-springboot)
2015-08-25 22:53:35.561  INFO 554 --- [           main] ationConfigEmbeddedWebApplicationContext : Refreshing org.springframework.boot[email protected]328908cd: startup date [Tue Aug 25 22:53:35 CST 2015]; root of context hierarchy
2015-08-25 22:53:36.395  INFO 554 --- [           main] o.s.b.f.s.DefaultListableBeanFactory     : Overriding bean definition for bean ‘beanNameViewResolver‘: replacing [Root bean: class [null]; scope=; abstract=false; lazyInit=false; autowireMode=3; dependencyCheck=0; autowireCandidate=true; primary=false; factoryBeanName=org.springframework.boot.autoconfigure.web.ErrorMvcAutoConfiguration$WhitelabelErrorViewConfiguration; factoryMethodName=beanNameViewResolver; initMethodName=null; destroyMethodName=(inferred); defined in class path resource [org/springframework/boot/autoconfigure/web/ErrorMvcAutoConfiguration$WhitelabelErrorViewConfiguration.class]] with [Root bean: class [null]; scope=; abstract=false; lazyInit=false; autowireMode=3; dependencyCheck=0; autowireCandidate=true; primary=false; factoryBeanName=org.springframework.boot.autoconfigure.web.WebMvcAutoConfiguration$WebMvcAutoConfigurationAdapter; factoryMethodName=beanNameViewResolver; initMethodName=null; destroyMethodName=(inferred); defined in class path resource [org/springframework/boot/autoconfigure/web/WebMvcAutoConfiguration$WebMvcAutoConfigurationAdapter.class]]
2015-08-25 22:53:37.404  INFO 554 --- [           main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat initialized with port(s): 8080 (http)
2015-08-25 22:53:37.796  INFO 554 --- [           main] o.apache.catalina.core.StandardService   : Starting service Tomcat
2015-08-25 22:53:37.798  INFO 554 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet Engine: Apache Tomcat/8.0.23
2015-08-25 22:53:37.955  INFO 554 --- [ost-startStop-1] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2015-08-25 22:53:37.955  INFO 554 --- [ost-startStop-1] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 2397 ms
2015-08-25 22:53:38.813  INFO 554 --- [ost-startStop-1] o.s.b.c.e.ServletRegistrationBean        : Mapping servlet: ‘dispatcherServlet‘ to [/]
2015-08-25 22:53:38.818  INFO 554 --- [ost-startStop-1] o.s.b.c.embedded.FilterRegistrationBean  : Mapping filter: ‘characterEncodingFilter‘ to: [/*]
2015-08-25 22:53:38.819  INFO 554 --- [ost-startStop-1] o.s.b.c.embedded.FilterRegistrationBean  : Mapping filter: ‘hiddenHttpMethodFilter‘ to: [/*]
2015-08-25 22:53:39.075  INFO 554 --- [           main] s.w.s.m.m.a.RequestMappingHandlerAdapter : Looking for @ControllerAdvice: org.springframework.boot[email protected]328908cd: startup date [Tue Aug 25 22:53:35 CST 2015]; root of context hierarchy
2015-08-25 22:53:39.151  INFO 554 --- [           main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/error],methods=[],params=[],headers=[],consumes=[],produces=[],custom=[]}" 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)
2015-08-25 22:53:39.151  INFO 554 --- [           main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/error],methods=[],params=[],headers=[],consumes=[],produces=[text/html],custom=[]}" onto public org.springframework.web.servlet.ModelAndView org.springframework.boot.autoconfigure.web.BasicErrorController.errorHtml(javax.servlet.http.HttpServletRequest)
2015-08-25 22:53:39.180  INFO 554 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2015-08-25 22:53:39.180  INFO 554 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/webjars/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2015-08-25 22:53:39.232  INFO 554 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/**/favicon.ico] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2015-08-25 22:53:39.326  INFO 554 --- [           main] o.s.j.e.a.AnnotationMBeanExporter        : Registering beans for JMX exposure on startup
2015-08-25 22:53:39.430  INFO 554 --- [           main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat started on port(s): 8080 (http)
2015-08-25 22:53:39.433  INFO 554 --- [           main] com.lkl.springboot.Application       : Started Application in 4.829 seconds (JVM running for 5.238)

 

spring boot已经启动，内嵌tomcat容器，监听为8080端口

就是这么简单，一个spring boot 的程序就创建了。

@SpringBootApplication 注解

SpringBootApplication注解源码如下：

 1 @Target(ElementType.TYPE)
 2 @Retention(RetentionPolicy.RUNTIME)
 3 @Documented
 4 @Inherited
 5 @Configuration
 6 @EnableAutoConfiguration
 7 @ComponentScan
 8 public @interface SpringBootApplication {
 9 
10     /**
11      * Exclude specific auto-configuration classes such that they will never be applied.
12      * @return the classes to exclude
13      */
14     Class<?>[] exclude() default {};
15 
16 }

 

@Configuration : 表示Application作为sprig配置文件存在 
@EnableAutoConfiguration: 启动spring boot内置的自动配置 
@ComponentScan : 扫描bean，路径为Application类所在package以及package下的子路径，这里为 com.lkl.springboot，在spring boot中bean都放置在该路径已经子路径下。

构建REST工程

上面的操作连个HelloWorld都没有出来，远远满不足我们的需求。

创建一个package：com.lkl.springboot.controller 保存controller

构建 HelloWorldController.java

 1  package com.lkl.springboot.controller;
 2 
 3 import org.springframework.web.bind.annotation.PathVariable;
 4 import org.springframework.web.bind.annotation.RequestMapping;
 5 import org.springframework.web.bind.annotation.RequestMethod;
 6 import org.springframework.web.bind.annotation.ResponseBody;
 7 import org.springframework.web.bind.annotation.RestController;
 8 
 9 @RestController
10 @RequestMapping("/springboot")
11 public class HelloWorldController {
12 
13     @RequestMapping(value = "/{name}", method = RequestMethod.GET)
14     public String sayWorld(@PathVariable("name") String name) {
15         return "Hello " + name;
16     }
17 }

 

再次执行 Application 然后访问http://localhost:8080/springboot/Liaokailin

得到结果： 
Hello Liaokailin

方法中涉及的注解就不解释了，比较简单～

第一个案例就到这里。

转载请注明 
http://blog.csdn.net/liaokailin/article/details/47988617

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