path name provider

PathNameProvider.java

package com.getbase.tracing4j.spring;

import lombok.extern.slf4j.Slf4j;
import org.springframework.context.ApplicationListener;
import org.springframework.context.event.ContextRefreshedEvent;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.mvc.condition.PatternsRequestCondition;
import org.springframework.web.servlet.mvc.method.RequestMappingInfo;
import org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping;

import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;

@Slf4j
public class PathNameProvider implements ApplicationListener<ContextRefreshedEvent> {
    private Map<Method, String> mappingNames;
    
    // Event is used instead of regular injection because RequestMappingHandlerMapping is not available early enough
    @Override
    public void onApplicationEvent(ContextRefreshedEvent event) {
        RequestMappingHandlerMapping mappings = event.getApplicationContext().getBean(RequestMappingHandlerMapping.class);
        mappingNames = new HashMap<>();
        for(Entry<RequestMappingInfo, HandlerMethod> entry : mappings.getHandlerMethods().entrySet()) {
            PatternsRequestCondition patterns = entry.getKey().getPatternsCondition();
            String pattern = patterns.getPatterns().iterator().next();
            mappingNames.put(entry.getValue().getMethod(), pattern);
        }
    }
    
    /**
     * Extract RequestMapping corresponding to given HandlerMethod.
     * @param handler handler object obtained from HandlerInterceptorAdapter.preHandle argument
     * @return mapping name, e.g. "/api/v1/orders"
     */
    public String getPathName(Object handler) {
        if (handler instanceof HandlerMethod) {
            HandlerMethod handlerMethod = (HandlerMethod) handler;
            String name = mappingNames.get(handlerMethod.getMethod());
            if (name != null) {
                return name;
            }
        }
        log.warn("unknown handler {}", handler);
        return "<unknown>";
    }
}