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是一种基于JNI的文件和网络读写模式，现在很多高版本的tomcat，都默认走它了。

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

参考

TOMCAT开启APR模式

tomcat bio nio apr 模式性能测试与个人看法（强烈推荐）

Spring boot 官方文档

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