Spring Boot内置了tomcat容器，直接运行Application就可以启动web服务器。
在tomcat中提供了三种方式：BIO、NIO、APR。
BIO
tomcat7以下的版本都是BIO，就是一个请求是一个独立的线程。不能适用高并发的场景。
NIO
在8以上的版本，默认都是NIO
APR
APR说白了就是一种异步的服务模式，个人理解就是AIO。不过底层的原理还不太了解。
在tomcat中配置，很好配置，直接修改protocol就可以了。但是在spring boot中，配置是在Java代码中写的。
下面是配置的代码：
import org.apache.catalina.core.AprLifecycleListener;
import org.springframework.boot.context.embedded.EmbeddedServletContainerFactory;
import org.springframework.boot.context.embedded.tomcat.TomcatEmbeddedServletContainerFactory;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
public class APRConfig {
// https://docs.spring.io/spring-boot/docs/1.5.6.RELEASE/reference/htmlsingle/#howto-discover-build-in-options-for-external-properties
@Bean
public EmbeddedServletContainerFactory servletContainer() {
TomcatEmbeddedServletContainerFactory tomcat = new TomcatEmbeddedServletContainerFactory();
tomcat.setProtocol("org.apache.coyote.http11.Http11AprProtocol");
tomcat.addContextLifecycleListeners(new AprLifecycleListener());
return tomcat;
}
}配置完启动，有可能会报错：
2018-06-06 16:21:44,891 [main] ERROR org.apache.catalina.core.StandardService:181 - Failed to start connector [Connector[org.apache.coyote.http11.Http11AprProtocol-8104]]
org.apache.catalina.LifecycleException: Failed to initialize component [Connector[org.apache.coyote.http11.Http11AprProtocol-8104]]
at org.apache.catalina.util.LifecycleBase.init(LifecycleBase.java:112)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:140)
at org.apache.catalina.core.StandardService.addConnector(StandardService.java:225)
at org.springframework.boot.context.embedded.tomcat.TomcatEmbeddedServletContainer.addPreviouslyRemovedConnectors(TomcatEmbeddedServletContainer.java:250)
at org.springframework.boot.context.embedded.tomcat.TomcatEmbeddedServletContainer.start(TomcatEmbeddedServletContainer.java:193)
at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.startEmbeddedServletContainer(EmbeddedWebApplicationContext.java:297)
at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.finishRefresh(EmbeddedWebApplicationContext.java:145)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:546)
at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:122)
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:693)
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:360)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:303)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1118)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1107)
at xxx.Application.main(Application.java:17)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.springframework.boot.loader.MainMethodRunner.run(MainMethodRunner.java:48)
at org.springframework.boot.loader.Launcher.launch(Launcher.java:87)
at org.springframework.boot.loader.Launcher.launch(Launcher.java:50)
at org.springframework.boot.loader.JarLauncher.main(JarLauncher.java:51)
Caused by: org.apache.catalina.LifecycleException: The configured protocol [org.apache.coyote.http11.Http11AprProtocol] requires the APR/native library which is not available
at org.apache.catalina.connector.Connector.initInternal(Connector.java:981)
at org.apache.catalina.util.LifecycleBase.init(LifecycleBase.java:107)
... 22 common frames omitted此时你需要在启动spring boot的服务器上安装tomcat-native和apr的模块。可以参考下面的参考文章