spring boot實戰(第一篇)第一個案例
阿新 • • 發佈：2019-01-07
前言
寫在前面的話
一直想將spring boot相關內容寫成一個系列的部落格，今天終於有時間開始了第一篇文章
以後有時間就會繼續寫下去。
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spring boot 部落格內容規劃
- spring boot 基本用法
- 自動配置
- 技術整合
- 效能監控
- 原始碼解析
spring boot 功能強大，後面會細細道來。
第一個案例
工程的構建
構建spring boot工程一般採用兩種方式 gradle 、maven;相對於maven的pom配置gradle 更加簡單，有興趣的同學可以去學習下gradle，這裡採用maven。
建立一個maven工程，對應的pom.xml檔案：
<parent>
<groupId - 1
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版本採用1.2.4,非官網最新版，但屬於穩定版本
建立 Application.java
package com.lkl.springboot;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
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執行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)
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spring boot已經啟動，內嵌tomcat容器，監聽為8080埠
就是這麼簡單，一個spring boot 的程式就建立了。
@SpringBootApplication 註解
SpringBootApplication註解原始碼如下：
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@Configuration
@EnableAutoConfiguration
@ComponentScan
public @interface SpringBootApplication {
/**
* Exclude specific auto-configuration classes such that they will never be applied.
* @return the classes to exclude
*/
Class<?>[] exclude() default {};
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@Configuration: 表示Application作為sprig配置檔案存在@EnableAutoConfiguration: 啟動spring boot內建的自動配置@ComponentScan: 掃描bean，路徑為Application類所在package以及package下的子路徑，這裡為com.lkl.springboot，在spring boot中bean都放置在該路徑已經子路徑下。
構建REST工程
上面的操作連個HelloWorld都沒有出來，遠遠滿不足我們的需求。
建立一個package：com.lkl.springboot.controller 儲存controller
構建 HelloWorldController.java
package com.lkl.springboot.controller;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.RestController;
@RestController
@RequestMapping("/springboot")
public class HelloWorldController {
@RequestMapping(value = "/{name}", method = RequestMethod.GET)
public String sayWorld(@PathVariable("name") String name) {
return "Hello " + name;
}
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得到結果： Hello Liaokailin
方法中涉及的註解就不解釋了，比較簡單～