So44928052Application.java

package com.stackoverflow.so44928052;

import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.MethodParameter;
import org.springframework.util.StringUtils;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.bind.support.WebArgumentResolver;
import org.springframework.web.bind.support.WebDataBinderFactory;
import org.springframework.web.context.request.NativeWebRequest;
import org.springframework.web.method.support.HandlerMethodArgumentResolver;
import org.springframework.web.method.support.ModelAndViewContainer;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurationSupport;

import io.jsonwebtoken.*;

/**
 * Set your key in application.properties:
 * security.jwt.key=JWTKEY
 */
@SpringBootApplication
public class So44928052Application {

	public static void main(String[] args) {
		SpringApplication.run(So44928052Application.class, args);
	}

	@Bean
	CommandLineRunner runner(@Value("security.jwt.key") String key) {
		return args -> {
			String compactJws = Jwts.builder().setSubject("Joe").signWith(SignatureAlgorithm.HS512, key).compact();
			System.out.println(compactJws);  // prints token just for demo purposes
		};
	}

	@Bean
	JwtParser jwtParser(@Value("security.jwt.key") String key) {
		return Jwts.parser().setSigningKey(key);
	}

	@Configuration
	public static class Mvc extends WebMvcConfigurationSupport {

		@Autowired
		JwtParser jwtParser;

		@Override
		public void addArgumentResolvers(List<HandlerMethodArgumentResolver> argumentResolvers) {
			argumentResolvers.add(new JwtUserHandlerMethodArgumentResolver(jwtParser));
		}
	}

	public static class JwtUserHandlerMethodArgumentResolver implements HandlerMethodArgumentResolver {
		private final JwtParser jwtParser;

		JwtUserHandlerMethodArgumentResolver(JwtParser jwtParser) { this.jwtParser = jwtParser; }

		@Override
		public boolean supportsParameter(MethodParameter methodParameter) {
			return methodParameter.getParameterAnnotation(Autowired.class) != null
					&& methodParameter.getParameterType().equals(String.class);
		}

		@Override
		public Object resolveArgument(MethodParameter methodParameter, ModelAndViewContainer mavContainer,
				NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception {
			if (this.supportsParameter(methodParameter)) {
				final String authorization = webRequest.getHeader("Authorization");
				if (!StringUtils.isEmpty(authorization)) {
					return this.jwtParser.parseClaimsJws(authorization.substring(7)).getBody().getSubject();
				} else {
					return null;
				}
			}
			return WebArgumentResolver.UNRESOLVED;
		}
	}

	@RestController
	public static class GreetingController {
		private static final String template = "Hello, %s!";

		@RequestMapping(value = {"/greeting"}, method = RequestMethod.GET)
		public String index(@Autowired String username) {
			return String.format(template, username);
		}
	}
}