春天启动 @SpringBootApplication 注释
Spring Boot @SpringBootApplication 注释用来标记一个声明一个或多个 @Bean 方法的配置类,并引发 auto-configuration 和组件扫描。
春天游艇应用程序类
Spring Boot‘SpringApplication’类用于从Java的主要方法启动和启动一个Spring应用程序。这个类会自动从类路径创建ApplicationContext,扫描配置类并启动应用程序。
SpringBoot 应用程序和 SpringApplication 示例
在 Spring RestController上的最后一本教程中,我们创建了一个 Spring RESTful 网页服务,并在 Tomcat 上部署了它,我们不得不创建 web.xml 和 Spring 背景文件,我们还不得不手动添加 Spring MVC 依赖并管理它们的版本,在这里我们将更改项目以运行作为一个 Spring Boot 应用程序并摆脱配置文件,这将有助于快速测试我们的应用程序逻辑,因为我们不必手动构建和部署项目到外部 Tomcat 服务器。
您应该从我们的 GitHub 存储库查看现有项目,在以下部分,我们将对项目文件做出必要的更改。
Below image shows our final project structure. 
添加 Spring Boot Maven 依赖
第一步是清理pom.xml文件并将其配置为Spring Boot。由于它是REST网络服务,我们只需要spring-boot-starter-web依赖性。然而,我们将不得不保持JAXB依赖性,因为我们在Java 10上运行,我们也希望支持XML请求和响应。我们还需要添加spring-boot-maven-plugin插件,这个插件允许我们运行我们的简单的Java应用程序作为春季启动应用程序。
1<project xmlns="https://maven.apache.org/POM/4.0.0"
2 xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance"
3 xsi:schemaLocation="https://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
4 <modelVersion>4.0.0</modelVersion>
5 <groupId>Spring-RestController</groupId>
6 <artifactId>Spring-RestController</artifactId>
7 <version>0.0.1-SNAPSHOT</version>
8 <packaging>war</packaging>
9
10 <parent>
11 <groupId>org.springframework.boot</groupId>
12 <artifactId>spring-boot-starter-parent</artifactId>
13 <version>2.0.2.RELEASE</version>
14 <relativePath /> <!-- lookup parent from repository -->
15 </parent>
16 <properties>
17 <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
18 <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
19 <java.version>10</java.version>
20 </properties>
21 <dependencies>
22 <dependency>
23 <groupId>org.springframework.boot</groupId>
24 <artifactId>spring-boot-starter-web</artifactId>
25 </dependency>
26
27 <!-- JAXB for XML Response needed to explicitly define from Java 9 onwards -->
28
29 <dependency>
30 <groupId>javax.xml.bind</groupId>
31 <artifactId>jaxb-api</artifactId>
32 </dependency>
33 <dependency>
34 <groupId>org.glassfish.jaxb</groupId>
35 <artifactId>jaxb-runtime</artifactId>
36 <version>2.3.0</version>
37 <scope>runtime</scope>
38 </dependency>
39 <dependency>
40 <groupId>javax.activation</groupId>
41 <artifactId>javax.activation-api</artifactId>
42 <version>1.2.0</version>
43 </dependency>
44 </dependencies>
45
46 <build>
47 <!-- added to remove Version from WAR file -->
48 <finalName>${project.artifactId}</finalName>
49 <plugins>
50 <plugin>
51 <groupId>org.springframework.boot</groupId>
52 <artifactId>spring-boot-maven-plugin</artifactId>
53 </plugin>
54 </plugins>
55 </build>
56</project>
我们可以删除 WebContent 目录或将其留下,它不会被我们的 Spring Boot 应用程序使用。
春天应用程序班级
现在我们必须用主方法创建一个 java 类,用@SpringBootApplication的注释来标记它,然后调用SpringApplication.run()的方法。
1package com.journaldev.spring;
2
3import org.springframework.boot.SpringApplication;
4import org.springframework.boot.autoconfigure.SpringBootApplication;
5
6@SpringBootApplication
7public class SpringBootRestApplication {
8
9 public static void main(String[] args) {
10 SpringApplication.run(SpringBootRestApplication.class, args);
11 }
12}
只需运行类作为Java应用程序,它将产生接下来的输出。我已经删除了一些我们在这里不关心的日志。
12018-06-18 14:33:51.276 INFO 3830 --- [ main] c.j.spring.SpringBootRestApplication : Starting SpringBootRestApplication on pankaj with PID 3830 (/Users/pankaj/Documents/eclipse-jee-workspace/Spring-RestController/target/classes started by pankaj in /Users/pankaj/Documents/eclipse-jee-workspace/Spring-RestController)
22018-06-18 14:33:51.280 INFO 3830 --- [ main] c.j.spring.SpringBootRestApplication : No active profile set, falling back to default profiles: default
32018-06-18 14:33:51.332 INFO 3830 --- [ main] ConfigServletWebServerApplicationContext : Refreshing org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext@38467116: startup date [Mon Jun 18 14:33:51 IST 2018]; root of context hierarchy
42018-06-18 14:33:52.311 INFO 3830 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat initialized with port(s): 8080 (http)
52018-06-18 14:33:52.344 INFO 3830 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat]
62018-06-18 14:33:52.344 INFO 3830 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet Engine: Apache Tomcat/8.5.31
72018-06-18 14:33:52.453 INFO 3830 --- [ost-startStop-1] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext
82018-06-18 14:33:52.453 INFO 3830 --- [ost-startStop-1] o.s.web.context.ContextLoader : Root WebApplicationContext: initialization completed in 1127 ms
92018-06-18 14:33:52.564 INFO 3830 --- [ost-startStop-1] o.s.b.w.servlet.ServletRegistrationBean : Servlet dispatcherServlet mapped to [/]
102018-06-18 14:33:52.927 INFO 3830 --- [ main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/rest/employee/get/{id}],methods=[GET]}" onto public com.journaldev.spring.model.Employee com.journaldev.spring.controller.EmployeeRestController.getEmployeeByID(int)
112018-06-18 14:33:52.928 INFO 3830 --- [ main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/rest/employee/getAll],methods=[GET]}" onto public java.util.List<com.journaldev.spring.model.Employee> com.journaldev.spring.controller.EmployeeRestController.getAllEmployees()
122018-06-18 14:33:52.929 INFO 3830 --- [ main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/rest/employee/create],methods=[POST]}" onto public com.journaldev.spring.model.Employee com.journaldev.spring.controller.EmployeeRestController.createEmployee(com.journaldev.spring.model.Employee)
132018-06-18 14:33:52.929 INFO 3830 --- [ main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/rest/employee/search/{name}],methods=[GET]}" onto public com.journaldev.spring.model.Employee com.journaldev.spring.controller.EmployeeRestController.getEmployeeByName(java.lang.String)
142018-06-18 14:33:52.929 INFO 3830 --- [ main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/rest/employee/delete/{id}],methods=[DELETE]}" onto public com.journaldev.spring.model.Employee com.journaldev.spring.controller.EmployeeRestController.deleteEmployeeByID(int)
152018-06-18 14:33:53.079 INFO 3830 --- [ main] o.s.j.e.a.AnnotationMBeanExporter : Registering beans for JMX exposure on startup
162018-06-18 14:33:53.118 INFO 3830 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path ''
172018-06-18 14:33:53.124 INFO 3830 --- [ main] c.j.spring.SpringBootRestApplication : Started SpringBootRestApplication in 2.204 seconds (JVM running for 2.633)
我们可以从日志中推断一些重要的点:
Spring Boot Application Process ID是3830
2. Spring Boot Application正在在端口8080上启动Tomcat
3.我们的应用程序背景路径是``。这意味着在召唤我们的API时,我们不需要提供服务链接
4.日志器打印了所有已配置的API,参见消息Mapped {[/rest/employee/get/{id}],methods=[GET]}`等。
Below image shows an example invocation of the APIs exposed by our Spring Boot Application. 
SpringBoot应用程序扫描BasePackages
默认情况下,SpringApplication 会扫描配置类包和其所有子包,所以如果我们的SpringBootRestApplication类在com.journaldev.spring.main包中,那么它不会扫描com.journaldev.spring.controller包,我们可以使用 SpringBootApplication 扫描BasePackages 属性来修复这种情况。
1@SpringBootApplication(scanBasePackages="com.journaldev.spring")
2public class SpringBootRestApplication {
3}
Spring Boot 自动配置豆类
由于Spring Boot提供自动配置,所以有很多豆子可以通过它进行配置,我们可以使用下面的代码片段来获取这些豆子的列表。
1ApplicationContext ctx = SpringApplication.run(SpringBootRestApplication.class, args);
2String[] beans = ctx.getBeanDefinitionNames();
3for(String s : beans) System.out.println(s);
下面是由我们的春天启动应用程序配置的豆类列表。
1org.springframework.context.annotation.internalConfigurationAnnotationProcessor
2org.springframework.context.annotation.internalAutowiredAnnotationProcessor
3org.springframework.context.annotation.internalRequiredAnnotationProcessor
4org.springframework.context.annotation.internalCommonAnnotationProcessor
5org.springframework.context.event.internalEventListenerProcessor
6org.springframework.context.event.internalEventListenerFactory
7springBootRestApplication
8org.springframework.boot.autoconfigure.internalCachingMetadataReaderFactory
9employeeRestController
10employeeRepository
11org.springframework.boot.autoconfigure.AutoConfigurationPackages
12org.springframework.boot.autoconfigure.context.PropertyPlaceholderAutoConfiguration
13org.springframework.boot.autoconfigure.condition.BeanTypeRegistry
14propertySourcesPlaceholderConfigurer
15org.springframework.boot.autoconfigure.websocket.servlet.WebSocketServletAutoConfiguration$TomcatWebSocketConfiguration
16websocketContainerCustomizer
17org.springframework.boot.autoconfigure.websocket.servlet.WebSocketServletAutoConfiguration
18org.springframework.boot.autoconfigure.web.servlet.ServletWebServerFactoryConfiguration$EmbeddedTomcat
19tomcatServletWebServerFactory
20org.springframework.boot.autoconfigure.web.servlet.ServletWebServerFactoryAutoConfiguration
21servletWebServerFactoryCustomizer
22tomcatServletWebServerFactoryCustomizer
23server-org.springframework.boot.autoconfigure.web.ServerProperties
24org.springframework.boot.context.properties.ConfigurationPropertiesBindingPostProcessor
25org.springframework.boot.context.properties.ConfigurationBeanFactoryMetadata
26webServerFactoryCustomizerBeanPostProcessor
27errorPageRegistrarBeanPostProcessor
28org.springframework.boot.autoconfigure.web.servlet.DispatcherServletAutoConfiguration$DispatcherServletConfiguration
29dispatcherServlet
30mainDispatcherServletPathProvider
31spring.mvc-org.springframework.boot.autoconfigure.web.servlet.WebMvcProperties
32org.springframework.boot.autoconfigure.web.servlet.DispatcherServletAutoConfiguration$DispatcherServletRegistrationConfiguration
33dispatcherServletRegistration
34org.springframework.boot.autoconfigure.web.servlet.DispatcherServletAutoConfiguration
35org.springframework.boot.autoconfigure.validation.ValidationAutoConfiguration
36defaultValidator
37methodValidationPostProcessor
38org.springframework.boot.autoconfigure.web.servlet.error.ErrorMvcAutoConfiguration$WhitelabelErrorViewConfiguration
39error
40beanNameViewResolver
41org.springframework.boot.autoconfigure.web.servlet.error.ErrorMvcAutoConfiguration$DefaultErrorViewResolverConfiguration
42conventionErrorViewResolver
43org.springframework.boot.autoconfigure.web.servlet.error.ErrorMvcAutoConfiguration
44errorAttributes
45basicErrorController
46errorPageCustomizer
47preserveErrorControllerTargetClassPostProcessor
48spring.resources-org.springframework.boot.autoconfigure.web.ResourceProperties
49org.springframework.boot.autoconfigure.web.servlet.WebMvcAutoConfiguration$WebMvcAutoConfigurationAdapter$FaviconConfiguration
50faviconHandlerMapping
51faviconRequestHandler
52org.springframework.boot.autoconfigure.web.servlet.WebMvcAutoConfiguration$EnableWebMvcConfiguration
53requestMappingHandlerAdapter
54requestMappingHandlerMapping
55mvcConversionService
56mvcValidator
57mvcContentNegotiationManager
58mvcPathMatcher
59mvcUrlPathHelper
60viewControllerHandlerMapping
61beanNameHandlerMapping
62resourceHandlerMapping
63mvcResourceUrlProvider
64defaultServletHandlerMapping
65mvcUriComponentsContributor
66httpRequestHandlerAdapter
67simpleControllerHandlerAdapter
68handlerExceptionResolver
69mvcViewResolver
70mvcHandlerMappingIntrospector
71org.springframework.boot.autoconfigure.web.servlet.WebMvcAutoConfiguration$WebMvcAutoConfigurationAdapter
72defaultViewResolver
73viewResolver
74welcomePageHandlerMapping
75requestContextFilter
76org.springframework.boot.autoconfigure.web.servlet.WebMvcAutoConfiguration
77hiddenHttpMethodFilter
78httpPutFormContentFilter
79org.springframework.boot.autoconfigure.jmx.JmxAutoConfiguration
80mbeanExporter
81objectNamingStrategy
82mbeanServer
83org.springframework.boot.autoconfigure.context.ConfigurationPropertiesAutoConfiguration
84org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration$Jackson2ObjectMapperBuilderCustomizerConfiguration
85standardJacksonObjectMapperBuilderCustomizer
86spring.jackson-org.springframework.boot.autoconfigure.jackson.JacksonProperties
87org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration$JacksonObjectMapperBuilderConfiguration
88jacksonObjectMapperBuilder
89org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration$ParameterNamesModuleConfiguration
90parameterNamesModule
91org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration$JacksonObjectMapperConfiguration
92jacksonObjectMapper
93org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration
94jsonComponentModule
95org.springframework.boot.autoconfigure.http.HttpMessageConvertersAutoConfiguration$StringHttpMessageConverterConfiguration
96stringHttpMessageConverter
97spring.http.encoding-org.springframework.boot.autoconfigure.http.HttpEncodingProperties
98org.springframework.boot.autoconfigure.http.JacksonHttpMessageConvertersConfiguration$MappingJackson2HttpMessageConverterConfiguration
99mappingJackson2HttpMessageConverter
100org.springframework.boot.autoconfigure.http.JacksonHttpMessageConvertersConfiguration
101org.springframework.boot.autoconfigure.http.HttpMessageConvertersAutoConfiguration
102messageConverters
103org.springframework.boot.autoconfigure.http.codec.CodecsAutoConfiguration$JacksonCodecConfiguration
104jacksonCodecCustomizer
105org.springframework.boot.autoconfigure.http.codec.CodecsAutoConfiguration
106org.springframework.boot.autoconfigure.info.ProjectInfoAutoConfiguration
107spring.info-org.springframework.boot.autoconfigure.info.ProjectInfoProperties
108org.springframework.boot.autoconfigure.security.reactive.ReactiveSecurityAutoConfiguration
109spring.security-org.springframework.boot.autoconfigure.security.SecurityProperties
110org.springframework.boot.autoconfigure.web.client.RestTemplateAutoConfiguration
111restTemplateBuilder
112org.springframework.boot.autoconfigure.web.embedded.EmbeddedWebServerFactoryCustomizerAutoConfiguration$TomcatWebServerFactoryCustomizerConfiguration
113tomcatWebServerFactoryCustomizer
114org.springframework.boot.autoconfigure.web.embedded.EmbeddedWebServerFactoryCustomizerAutoConfiguration
115org.springframework.boot.autoconfigure.web.servlet.HttpEncodingAutoConfiguration
116characterEncodingFilter
117localeCharsetMappingsCustomizer
118org.springframework.boot.autoconfigure.web.servlet.MultipartAutoConfiguration
119multipartConfigElement
120multipartResolver
121spring.servlet.multipart-org.springframework.boot.autoconfigure.web.servlet.MultipartProperties
我们可以通过使用 @SpringBootApplication exclude 或 excludeName 属性来激活我们的春天启动应用程序来优化。
1@SpringBootApplication(scanBasePackages = "com.journaldev.spring", exclude = {
2org.springframework.boot.autoconfigure.web.servlet.MultipartAutoConfiguration.class, org.springframework.boot.autoconfigure.jmx.JmxAutoConfiguration.class })
3public class SpringBootRestApplication {
4}
请注意,如果我们试图排除任何非自动配置类,我们会收到错误,我们的应用程序将无法启动。
1@SpringBootApplication(scanBasePackages = "com.journaldev.spring", exclude = {com.journaldev.spring.controller.EmployeeRestController.class })
2public class SpringBootRestApplication {
3}
上面的代码片段会引发以下错误:
12018-06-18 15:10:43.602 ERROR 3899 --- [main] o.s.boot.SpringApplication: Application run failed
2
3java.lang.IllegalStateException: The following classes could not be excluded because they are not auto-configuration classes:
4 - com.journaldev.spring.controller.EmployeeRestController
这就是SpringBootApplication的注释和SpringApplication的例子。
您可以从我们的 GitHub 存储库下载最终项目。