Enable HTTP2 with Tomcat in Spring Boot

In Spring Boot 2.1 and above it is as simple as adding this property to your .properties (or .yml) file:

server.http2.enabled=true

You can also do it programmatically like this (in one of your configuration classes):

@Bean
public ConfigurableServletWebServerFactory tomcatCustomizer() {
    TomcatServletWebServerFactory factory = new TomcatServletWebServerFactory();
    factory.addConnectorCustomizers(connector -> connector.addUpgradeProtocol(new Http2Protocol()));
    return factory;
}