What is the difference between /* and /** pattern in Spring boot?

Question

I was trying to register certain URLs for a Filter when I noticed that there is a difference between /* and /** patterns.

    @Bean
    public FilterRegistrationBean tokenAuthenticationFilterBean() {
        FilterRegistrationBean registration = new FilterRegistrationBean(tokenAuthenticationFilter);
        registration.addUrlPatterns("/api/**","/ping","/api/*");
        return registration;
    }

What is the difference between these patterns?

Answer 1

Spring normally uses ant-style path matching patterns for URLs - if you look at the java docs for the AntPathMatcher you will see the explanation

The mapping matches URLs using the following rules: ? matches one character
* matches zero or more characters
** matches zero or more directories in a path 
{spring:[a-z]+} matches the regexp [a-z]+ as a path variable named "spring"

http://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/util/AntPathMatcher.html