解决springboot application.properties server.port配置问题

springboot application.properties server.port配置的问题

近年来，springboot以其快速构建方便便捷，开箱即用，约定优于配置（Convention Over Configuration）的特性深受广大开发者喜爱。

springboot已经集成配置好了一套web开发的默认配置，开发者可以无需修改任何配置即可开始一个web工程，但是实际情况中有时候开发者还是需要修改部分默认配置项来使其更加契合自己的项目需求。

下面就其中一个小问题做个记录

在配置服务启动的端口时，springboot默认在application.properties配置文件中提供了server.port配置项来

让开发者自行配置服务启动端口号，**但是注意：**

#服务启动端口号
server.port=8889

该配置项要想生效其实是依赖于项目中内嵌的tomcat容器，如下图：

内嵌tomcat的jar包依赖包含在pom中

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

如果pom中不引人上述依赖，那么项目中不会导入内嵌tomcat的jar包，相应的application.properties配置文件中server.port配置项也将无法生效，因为该配置项实际上修改的就是内嵌tomcat的web端口号。

Spring Boot server.port配置原理

我们经常配置server.port=xxx，但其实这是一个比较复杂的过程才生效的，这次讲讲生效的过程。

1. autoConfigure

本质来源于自动配置

org.springframework.boot.autoconfigure.web.servlet.ServletWebServerFactoryConfiguration

TomcatServletWebServerFactory

为什么是这个类，核心是beanPostProcess原理

@ConfigurationProperties(prefix = "server", ignoreUnknownFields = true)
public class ServerProperties {
 
	/**
	 * Server HTTP port.
	 */
	private Integer port;

beanPostProcess

public class WebServerFactoryCustomizerBeanPostProcessor implements BeanPostProcessor, BeanFactoryAware {
 
	private ListableBeanFactory beanFactory; 
	private List<WebServerFactoryCustomizer<?>> customizers;  
	@Override
	public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
		if (bean instanceof WebServerFactory) {
			postProcessBeforeInitialization((WebServerFactory) bean);
		}
		return bean;
	} 
	
	@SuppressWarnings("unchecked")
	private void postProcessBeforeInitialization(WebServerFactory webServerFactory) {
		LambdaSafe.callbacks(WebServerFactoryCustomizer.class, getCustomizers(), webServerFactory)
				.withLogger(WebServerFactoryCustomizerBeanPostProcessor.class)
				.invoke((customizer) -> customizer.customize(webServerFactory));
	}
 
    private Collection<WebServerFactoryCustomizer<?>> getCustomizers() {
		if (this.customizers == null) {
			// Look up does not include the parent context
			this.customizers = new ArrayList<>(getWebServerFactoryCustomizerBeans());
			this.customizers.sort(AnnotationAwareOrderComparator.INSTANCE);
			this.customizers = Collections.unmodifiableList(this.customizers);
		}
		return this.customizers;
	}
 
	@SuppressWarnings({ "unchecked", "rawtypes" })
	private Collection<WebServerFactoryCustomizer<?>> getWebServerFactoryCustomizerBeans() {
		return (Collection) this.beanFactory.getBeansOfType(WebServerFactoryCustomizer.class, false, false).values();
	}

最终

beanFactory.getBeansOfType(WebServerFactoryCustomizer.class, false, false).values()

WebServerFactoryCustomizer对象.customize(webServerFactory)

@Configuration
@AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE)
@ConditionalOnClass(ServletRequest.class)
@ConditionalOnWebApplication(type = Type.SERVLET)
@EnableConfigurationProperties(ServerProperties.class)
@Import({ ServletWebServerFactoryAutoConfiguration.BeanPostProcessorsRegistrar.class,
		ServletWebServerFactoryConfiguration.EmbeddedTomcat.class,
		ServletWebServerFactoryConfiguration.EmbeddedJetty.class,
		ServletWebServerFactoryConfiguration.EmbeddedUndertow.class })
public class ServletWebServerFactoryAutoConfiguration {
 
	@Bean
	public ServletWebServerFactoryCustomizer servletWebServerFactoryCustomizer(ServerProperties serverProperties) {
		return new ServletWebServerFactoryCustomizer(serverProperties);
	}

这里就将port设置好了。