Secure a Spring Boot REST API With JSON Web Token

Secure a Spring Boot REST API With JSON Web Token

In this tutorial, we will be developing a Spring Boot application that makes use of JWT authentication for securing an exposed REST API. In this example, we will be making use of hard-coded user values for user authentication.

In this tutorial, we will be developing a Spring Boot application that makes use of JWT authentication for securing an exposed REST API. In this example, we will be making use of hard-coded user values for user authentication.

Lets Begin?

For better understanding we will be developing the project in stages

  • Develop a Spring Boot Application to expose a Simple REST GET API with mapping /hello.
  • Configure Spring Security for JWT. Expose REST POST API with mapping /authenticate using which User will get a valid JSON Web Token. And then allow the user access to the api /hello only if it has a valid token
  • Develop a Spring Boot Application to expose a GET REST API

Maven Project will be as follows

The pom.xml is as follows-

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.javainuse</groupId>
    <artifactId>spring-boot-jwt</artifactId>
    <version>0.0.1-SNAPSHOT</version>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.1.RELEASE</version>
        <relativePath /> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
    </dependencies>

</project>

Create a Controller class for exposing a GET REST API

package com.javainuse.controller;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class HelloWorldController {

    @RequestMapping({ "/hello" })
    public String firstPage() {
        return "Hello World";
    }

}

Create the bootstrap class with SpringBoot Annotation

package com.javainuse;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class SpringBootHelloWorldApplication {

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

Compile and the run the SpringBootHelloWorldApplication.java as a Java application.

Go to localhost:8080/hello

Spring Security and JWT Configuration

We will be configuring Spring Security and JWT for performing 2 operations-

  • Generating JWT - Expose a POST API with mapping /authenticate. On passing correct username and password it will generate a JSON Web Token(JWT)
  • Validating JWT - If user tries to access GET API with mapping /hello. It will allow access only if request has a valid JSON Web Token(JWT)

Maven Project will be as follows-

The sequence flow for these operations will be as follows-

Generating JWT

Validating JWT

Add the Spring Security and JWT dependencies

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.javainuse</groupId>
    <artifactId>spring-boot-jwt</artifactId>
    <version>0.0.1-SNAPSHOT</version>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.1.RELEASE</version>
        <relativePath /> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-security</artifactId>
        </dependency>
        <dependency>
            <groupId>io.jsonwebtoken</groupId>
            <artifactId>jjwt</artifactId>
            <version>0.9.1</version>
        </dependency>
    </dependencies>

</project>
  • Define the application.properties. The secret key is combined with the header and the payload to create a unique hash. We are only able to verify this hash if you have the secret key.
jwt.secret=javainuse

JwtTokenUtil

  • The JwtTokenUtil is responsible for performing JWT operations like creation and validation.It makes use of the io.jsonwebtoken.Jwts for achieving this.
package com.javainuse.config;

import java.io.Serializable;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;
import java.util.function.Function;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.stereotype.Component;

import io.jsonwebtoken.Claims;
import io.jsonwebtoken.Jwts;
import io.jsonwebtoken.SignatureAlgorithm;

@Component
public class JwtTokenUtil implements Serializable {

    private static final long serialVersionUID = -2550185165626007488L;

    public static final long JWT_TOKEN_VALIDITY = 5 * 60 * 60;

    @Value("${jwt.secret}")
    private String secret;

    //retrieve username from jwt token
    public String getUsernameFromToken(String token) {
        return getClaimFromToken(token, Claims::getSubject);
    }

    //retrieve expiration date from jwt token
    public Date getExpirationDateFromToken(String token) {
        return getClaimFromToken(token, Claims::getExpiration);
    }

    public <T> T getClaimFromToken(String token, Function<Claims, T> claimsResolver) {
        final Claims claims = getAllClaimsFromToken(token);
        return claimsResolver.apply(claims);
    }
    //for retrieveing any information from token we will need the secret key
    private Claims getAllClaimsFromToken(String token) {
        return Jwts.parser().setSigningKey(secret).parseClaimsJws(token).getBody();
    }

    //check if the token has expired
    private Boolean isTokenExpired(String token) {
        final Date expiration = getExpirationDateFromToken(token);
        return expiration.before(new Date());
    }

    //generate token for user
    public String generateToken(UserDetails userDetails) {
        Map<String, Object> claims = new HashMap<>();
        return doGenerateToken(claims, userDetails.getUsername());
    }

    //while creating the token -
    //1. Define  claims of the token, like Issuer, Expiration, Subject, and the ID
    //2. Sign the JWT using the HS512 algorithm and secret key.
    //3. According to JWS Compact Serialization(https://tools.ietf.org/html/draft-ietf-jose-json-web-signature-41#section-3.1)
    //   compaction of the JWT to a URL-safe string 
    private String doGenerateToken(Map<String, Object> claims, String subject) {

        return Jwts.builder().setClaims(claims).setSubject(subject).setIssuedAt(new Date(System.currentTimeMillis()))
                .setExpiration(new Date(System.currentTimeMillis() + JWT_TOKEN_VALIDITY * 1000))
                .signWith(SignatureAlgorithm.HS512, secret).compact();
    }

    //validate token
    public Boolean validateToken(String token, UserDetails userDetails) {
        final String username = getUsernameFromToken(token);
        return (username.equals(userDetails.getUsername()) && !isTokenExpired(token));
    }
}

JWTUserDetailsService

JWTUserDetailsService implements the Spring Security UserDetailsService interface. It overrides the loadUserByUsername for fetching user details from the database using the username. The Spring Security Authentication Manager calls this method for getting the user details from the database when authenticating the user details provided by the user. Here we are getting the user details from a hardcoded User List. In the next tutorial we will be adding the DAO implementation for fetching User Details from the Database. Also the password for a user is stored in encrypted format using BCrypt. Previously we have seen Spring Boot Security - Password Encoding Using Bcrypt. Here using the Online Bcrypt Generator you can generate the Bcrypt for a password.package com.javainuse.service;

import java.util.ArrayList;

import org.springframework.security.core.userdetails.User;
import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.security.core.userdetails.UserDetailsService;
import org.springframework.security.core.userdetails.UsernameNotFoundException;
import org.springframework.stereotype.Service;

@Service
public class JwtUserDetailsService implements UserDetailsService {

    @Override
    public UserDetails loadUserByUsername(String username) throws UsernameNotFoundException {
        if ("javainuse".equals(username)) {
            return new User("javainuse", "$2aJWTUserDetailsService implements the Spring Security UserDetailsService interface. It overrides the loadUserByUsername for fetching user details from the database using the username. The Spring Security Authentication Manager calls this method for getting the user details from the database when authenticating the user details provided by the user. Here we are getting the user details from a hardcoded User List. In the next tutorial we will be adding the DAO implementation for fetching User Details from the Database. Also the password for a user is stored in encrypted format using BCrypt. Previously we have seen Spring Boot Security - Password Encoding Using Bcrypt. Here using the Online Bcrypt Generator you can generate the Bcrypt for a password.package com.javainuse.service;

import java.util.ArrayList;

import org.springframework.security.core.userdetails.User;
import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.security.core.userdetails.UserDetailsService;
import org.springframework.security.core.userdetails.UsernameNotFoundException;
import org.springframework.stereotype.Service;

@Service
public class JwtUserDetailsService implements UserDetailsService {

    @Override
    public UserDetails loadUserByUsername(String username) throws UsernameNotFoundException {
        if ("javainuse".equals(username)) {
            return new User("javainuse", "$2a$10$slYQmyNdGzTn7ZLBXBChFOC9f6kFjAqPhccnP6DxlWXx2lPk1C3G6",
                    new ArrayList<>());
        } else {
            throw new UsernameNotFoundException("User not found with username: " + username);
        }
    }
}
0$slYQmyNdGzTn7ZLBXBChFOC9f6kFjAqPhccnP6DxlWXx2lPk1C3G6",
                    new ArrayList<>());
        } else {
            throw new UsernameNotFoundException("User not found with username: " + username);
        }
    }
}

JwtAuthenticationController

  • Expose a POST API /authenticate using the JwtAuthenticationController. The POST API gets username and password in the body- Using Spring Authentication Manager we authenticate the username and password.If the credentials are valid, a JWT token is created using the JWTTokenUtil and provided to the client.
package com.javainuse.controller;

import java.util.Objects;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.ResponseEntity;
import org.springframework.security.authentication.AuthenticationManager;
import org.springframework.security.authentication.BadCredentialsException;
import org.springframework.security.authentication.DisabledException;
import org.springframework.security.authentication.UsernamePasswordAuthenticationToken;
import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.web.bind.annotation.CrossOrigin;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
import com.javainuse.service.JwtUserDetailsService;


import com.javainuse.config.JwtTokenUtil;
import com.javainuse.model.JwtRequest;
import com.javainuse.model.JwtResponse;

@RestController
@CrossOrigin
public class JwtAuthenticationController {

    @Autowired
    private AuthenticationManager authenticationManager;

    @Autowired
    private JwtTokenUtil jwtTokenUtil;

    @Autowired
    private JwtUserDetailsService userDetailsService;

    @RequestMapping(value = "/authenticate", method = RequestMethod.POST)
    public ResponseEntity<?> createAuthenticationToken(@RequestBody JwtRequest authenticationRequest) throws Exception {

        authenticate(authenticationRequest.getUsername(), authenticationRequest.getPassword());

        final UserDetails userDetails = userDetailsService
                .loadUserByUsername(authenticationRequest.getUsername());

        final String token = jwtTokenUtil.generateToken(userDetails);

        return ResponseEntity.ok(new JwtResponse(token));
    }

    private void authenticate(String username, String password) throws Exception {
        try {
            authenticationManager.authenticate(new UsernamePasswordAuthenticationToken(username, password));
        } catch (DisabledException e) {
            throw new Exception("USER_DISABLED", e);
        } catch (BadCredentialsException e) {
            throw new Exception("INVALID_CREDENTIALS", e);
        }
    }
}

JwtRequest

  • This class is required for storing the username and password we recieve from the client.
package com.javainuse.model;

import java.io.Serializable;

public class JwtRequest implements Serializable {

    private static final long serialVersionUID = 5926468583005150707L;

    private String username;
    private String password;

    //need default constructor for JSON Parsing
    public JwtRequest()
    {

    }

    public JwtRequest(String username, String password) {
        this.setUsername(username);
        this.setPassword(password);
    }

    public String getUsername() {
        return this.username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return this.password;
    }

    public void setPassword(String password) {
        this.password = password;
    }
}

JwtResponse

  • This is class is required for creating a response containing the JWT to be returned to the user.
package com.javainuse.model;

import java.io.Serializable;

public class JwtResponse implements Serializable {

    private static final long serialVersionUID = -8091879091924046844L;
    private final String jwttoken;

    public JwtResponse(String jwttoken) {
        this.jwttoken = jwttoken;
    }

    public String getToken() {
        return this.jwttoken;
    }
}

JwtRequestFilter

  • The JwtRequestFilter extends the Spring Web Filter OncePerRequestFilter class. For any incoming request this Filter class gets executed. It checks if the request has a valid JWT token. If it has a valid JWT Token then it sets the Authentication in the context, to specify that the current user is authenticated.
package com.javainuse.config;

import java.io.IOException;

import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.security.authentication.UsernamePasswordAuthenticationToken;
import org.springframework.security.core.context.SecurityContextHolder;
import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.security.web.authentication.WebAuthenticationDetailsSource;
import org.springframework.stereotype.Component;
import org.springframework.web.filter.OncePerRequestFilter;

import com.javainuse.service.JwtUserDetailsService;

import io.jsonwebtoken.ExpiredJwtException;

@Component
public class JwtRequestFilter extends OncePerRequestFilter {

    @Autowired
    private JwtUserDetailsService jwtUserDetailsService;

    @Autowired
    private JwtTokenUtil jwtTokenUtil;

    @Override
    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain chain)
            throws ServletException, IOException {

        final String requestTokenHeader = request.getHeader("Authorization");

        String username = null;
        String jwtToken = null;
        // JWT Token is in the form "Bearer token". Remove Bearer word and get
        // only the Token
        if (requestTokenHeader != null && requestTokenHeader.startsWith("Bearer ")) {
            jwtToken = requestTokenHeader.substring(7);
            try {
                username = jwtTokenUtil.getUsernameFromToken(jwtToken);
            } catch (IllegalArgumentException e) {
                System.out.println("Unable to get JWT Token");
            } catch (ExpiredJwtException e) {
                System.out.println("JWT Token has expired");
            }
        } else {
            logger.warn("JWT Token does not begin with Bearer String");
        }

        // Once we get the token validate it.
        if (username != null && SecurityContextHolder.getContext().getAuthentication() == null) {

            UserDetails userDetails = this.jwtUserDetailsService.loadUserByUsername(username);

            // if token is valid configure Spring Security to manually set
            // authentication
            if (jwtTokenUtil.validateToken(jwtToken, userDetails)) {

                UsernamePasswordAuthenticationToken usernamePasswordAuthenticationToken = new UsernamePasswordAuthenticationToken(
                        userDetails, null, userDetails.getAuthorities());
                usernamePasswordAuthenticationToken
                        .setDetails(new WebAuthenticationDetailsSource().buildDetails(request));
                // After setting the Authentication in the context, we specify
                // that the current user is authenticated. So it passes the
                // Spring Security Configurations successfully.
                SecurityContextHolder.getContext().setAuthentication(usernamePasswordAuthenticationToken);
            }
        }
        chain.doFilter(request, response);
    }

}

JwtAuthenticationEntryPoint

  • This class will extend Spring's AuthenticationEntryPoint class and override its method commence. It rejects every unauthenticated request and send error code 401
package com.javainuse.config;

import java.io.IOException;
import java.io.Serializable;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.security.core.AuthenticationException;
import org.springframework.security.web.AuthenticationEntryPoint;
import org.springframework.stereotype.Component;

@Component
public class JwtAuthenticationEntryPoint implements AuthenticationEntryPoint, Serializable {

    private static final long serialVersionUID = -7858869558953243875L;

    @Override
    public void commence(HttpServletRequest request, HttpServletResponse response,
            AuthenticationException authException) throws IOException {

        response.sendError(HttpServletResponse.SC_UNAUTHORIZED, "Unauthorized");
    }
}

WebSecurityConfig

  • This class extends the WebSecurityConfigurerAdapter is a convenience class that allows customization to both WebSecurity and HttpSecurity.
package com.javainuse.config;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.security.authentication.AuthenticationManager;
import org.springframework.security.config.annotation.authentication.builders.AuthenticationManagerBuilder;
import org.springframework.security.config.annotation.method.configuration.EnableGlobalMethodSecurity;
import org.springframework.security.config.annotation.web.builders.HttpSecurity;
import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity;
import org.springframework.security.config.annotation.web.configuration.WebSecurityConfigurerAdapter;
import org.springframework.security.config.http.SessionCreationPolicy;
import org.springframework.security.core.userdetails.UserDetailsService;
import org.springframework.security.crypto.bcrypt.BCryptPasswordEncoder;
import org.springframework.security.crypto.password.PasswordEncoder;
import org.springframework.security.web.authentication.UsernamePasswordAuthenticationFilter;

@Configuration
@EnableWebSecurity
@EnableGlobalMethodSecurity(prePostEnabled = true)
public class WebSecurityConfig extends WebSecurityConfigurerAdapter {

    @Autowired
    private JwtAuthenticationEntryPoint jwtAuthenticationEntryPoint;

    @Autowired
    private UserDetailsService jwtUserDetailsService;

    @Autowired
    private JwtRequestFilter jwtRequestFilter;

    @Autowired
    public void configureGlobal(AuthenticationManagerBuilder auth) throws Exception {
        // configure AuthenticationManager so that it knows from where to load
        // user for matching credentials
        // Use BCryptPasswordEncoder
        auth.userDetailsService(jwtUserDetailsService).passwordEncoder(passwordEncoder());
    }

    @Bean
    public PasswordEncoder passwordEncoder() {
        return new BCryptPasswordEncoder();
    }

    @Bean
    @Override
    public AuthenticationManager authenticationManagerBean() throws Exception {
        return super.authenticationManagerBean();
    }

    @Override
    protected void configure(HttpSecurity httpSecurity) throws Exception {
        // We don't need CSRF for this example
        httpSecurity.csrf().disable()
                // dont authenticate this particular request
                .authorizeRequests().antMatchers("/authenticate").permitAll().
                // all other requests need to be authenticated
                anyRequest().authenticated().and().
                // make sure we use stateless session; session won't be used to
                // store user's state.
                exceptionHandling().authenticationEntryPoint(jwtAuthenticationEntryPoint).and().sessionManagement()
                .sessionCreationPolicy(SessionCreationPolicy.STATELESS);

        // Add a filter to validate the tokens with every request
        httpSecurity.addFilterBefore(jwtRequestFilter, UsernamePasswordAuthenticationFilter.class);
    }
}

Start the Spring Boot Application

Generate a JSON Web Token

  • Create a POST request with url localhost:8080/authenticate. Body should have valid username and password. In our case username is javainuse and password is password.
  • Validate the JSON Web Token

    • Try accessing the url localhost:8080/hello using the above generated token in the header as follows

Download Source Code

And there you have it! We hope you enjoyed this demonstration on how to implement Spring Boot security via a JSON Web Token (JWT).

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