Spring Boot: How to add another WAR files to the embedded tomcat?

You can add a war file to embedded Tomcat using Tomcat.addWebapp. As its javadoc says, it’s the “equivalent to adding a web application to Tomcat’s web apps directory”. To use this API in Spring Boot, you need to use a custom TomcatEmbeddedServletContainerFactory subclass:

@Bean
public EmbeddedServletContainerFactory servletContainerFactory() {
    return new TomcatEmbeddedServletContainerFactory() {

        @Override
        protected TomcatEmbeddedServletContainer getTomcatEmbeddedServletContainer(
                Tomcat tomcat) {
            // Ensure that the webapps directory exists
            new File(tomcat.getServer().getCatalinaBase(), "webapps").mkdirs();

            try {
                Context context = tomcat.addWebapp("/foo", "/path/to/foo.war");
                // Allow the webapp to load classes from your fat jar
                context.setParentClassLoader(getClass().getClassLoader());
            } catch (ServletException ex) {
                throw new IllegalStateException("Failed to add webapp", ex);
            }
            return super.getTomcatEmbeddedServletContainer(tomcat);
        }

    };
}

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