Feign client custom interceptor for JWT token validation

Feign client custom interceptor for JWT token validation

To implement a custom interceptor for JWT token validation with Feign clients in a Spring Boot application, follow these steps:

1. Add Dependencies

Ensure that you have the required dependencies in your pom.xml if you're using Maven. If you're using Gradle, the syntax will be similar.

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

2. Create a Feign Configuration Class

You need to create a configuration class for Feign to set up your custom interceptor.

import feign.RequestInterceptor; import feign.RequestTemplate; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; @Configuration public class FeignConfig { @Bean public RequestInterceptor jwtRequestInterceptor() { return new JwtRequestInterceptor(); } }

3. Implement the JWT Interceptor

Create a class that implements RequestInterceptor. This interceptor will add the JWT token to the request header.

import feign.RequestInterceptor; import feign.RequestTemplate; import org.springframework.beans.factory.annotation.Value; import org.springframework.stereotype.Component; @Component public class JwtRequestInterceptor implements RequestInterceptor { @Value("${jwt.token}") private String jwtToken; @Override public void apply(RequestTemplate requestTemplate) { requestTemplate.header("Authorization", "Bearer " + jwtToken); } }

Explanation:

  • The @Value("${jwt.token}") annotation is used to inject the JWT token from your application's configuration. You can replace jwt.token with your actual property key.
  • The apply method is where you set the Authorization header with the JWT token.

4. Configure Feign Clients

Ensure your Feign clients use the configuration class you created.

import org.springframework.cloud.openfeign.FeignClient; @FeignClient(name = "example-client", configuration = FeignConfig.class) public interface ExampleClient { @GetMapping("/api/resource") String getResource(); }

Explanation:

  • The @FeignClient annotation specifies the Feign client and applies the FeignConfig class.

5. Ensure JWT Token Management

Ensure that you have a mechanism to obtain and refresh the JWT token if it's dynamic. You might want to use a service or a component that provides the current token.

import org.springframework.stereotype.Service; @Service public class JwtTokenService { // Method to get JWT token (could be from a secure store or refresh logic) public String getToken() { // Implement token retrieval logic return "your-jwt-token"; } }

Update the JwtRequestInterceptor to use this service:

import feign.RequestInterceptor; import feign.RequestTemplate; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Component; @Component public class JwtRequestInterceptor implements RequestInterceptor { @Autowired private JwtTokenService jwtTokenService; @Override public void apply(RequestTemplate requestTemplate) { String token = jwtTokenService.getToken(); requestTemplate.header("Authorization", "Bearer " + token); } }

6. Run and Test

  • Start your application and test the Feign client to ensure that the JWT token is being correctly included in the request headers.

  • Monitor for any issues related to authentication and token validation.

Summary

  1. Add Feign and web dependencies to your project.
  2. Create a configuration class to define the custom interceptor.
  3. Implement the RequestInterceptor to add the JWT token to requests.
  4. Apply the configuration to your Feign clients.
  5. Manage the JWT token dynamically if needed.

This approach allows you to efficiently add JWT token authentication to your Feign clients in a Spring Boot application.

Examples

  1. How to create a custom Feign client interceptor for JWT token validation?

    • Description: Implement a Feign interceptor that adds a JWT token to the request headers and validates it.
    • Code:
      import feign.RequestInterceptor; import feign.RequestTemplate; import org.springframework.beans.factory.annotation.Value; import org.springframework.stereotype.Component; @Component public class JwtRequestInterceptor implements RequestInterceptor { @Value("${jwt.token}") private String jwtToken; @Override public void apply(RequestTemplate template) { template.header("Authorization", "Bearer " + jwtToken); } }

  2. How to configure Feign client to use a custom interceptor for JWT token validation?

    • Description: Configure the Feign client to use the custom interceptor for adding and validating JWT tokens.
    • Code:
      import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; import feign.Logger; import feign.RequestInterceptor; @Configuration public class FeignConfig { @Bean public RequestInterceptor jwtRequestInterceptor() { return new JwtRequestInterceptor(); } @Bean Logger.Level feignLoggerLevel() { return Logger.Level.FULL; } }

  3. How to validate JWT token in a Feign client request using custom filters?

    • Description: Use custom filters to validate the JWT token and handle exceptions.
    • Code:
      import feign.RequestInterceptor; import feign.RequestTemplate; import org.springframework.stereotype.Component; @Component public class JwtValidationInterceptor implements RequestInterceptor { @Override public void apply(RequestTemplate template) { String token = getToken(); // Implement token retrieval logic validateToken(token); // Implement token validation logic template.header("Authorization", "Bearer " + token); } private String getToken() { // Token retrieval logic return "your-jwt-token"; } private void validateToken(String token) { // Token validation logic } }

  4. How to handle JWT token expiration in a Feign client interceptor?

    • Description: Implement logic to refresh the JWT token if it has expired.
    • Code:
      import feign.RequestInterceptor; import feign.RequestTemplate; import org.springframework.stereotype.Component; @Component public class JwtTokenInterceptor implements RequestInterceptor { @Override public void apply(RequestTemplate template) { String token = getValidToken(); template.header("Authorization", "Bearer " + token); } private String getValidToken() { String token = retrieveToken(); if (isTokenExpired(token)) { token = refreshToken(); } return token; } private String retrieveToken() { // Retrieve current token return "current-jwt-token"; } private boolean isTokenExpired(String token) { // Token expiration check logic return false; } private String refreshToken() { // Token refresh logic return "new-jwt-token"; } }

  5. How to add custom headers to Feign requests for JWT token validation?

    • Description: Add custom headers for JWT token validation in Feign client requests.
    • Code:
      import feign.RequestInterceptor; import feign.RequestTemplate; import org.springframework.stereotype.Component; @Component public class CustomHeaderInterceptor implements RequestInterceptor { @Override public void apply(RequestTemplate template) { template.header("Authorization", "Bearer " + getJwtToken()); template.header("Custom-Header", "Value"); } private String getJwtToken() { // Retrieve JWT token return "your-jwt-token"; } }

  6. How to log JWT token details in Feign client requests?

    • Description: Log details of the JWT token for debugging purposes.
    • Code:
      import feign.RequestInterceptor; import feign.RequestTemplate; import org.springframework.stereotype.Component; import org.slf4j.Logger; import org.slf4j.LoggerFactory; @Component public class JwtLoggingInterceptor implements RequestInterceptor { private static final Logger logger = LoggerFactory.getLogger(JwtLoggingInterceptor.class); @Override public void apply(RequestTemplate template) { String token = getJwtToken(); logger.info("JWT Token: " + token); template.header("Authorization", "Bearer " + token); } private String getJwtToken() { // Retrieve JWT token return "your-jwt-token"; } }

  7. How to refresh JWT token if expired in Feign client interceptor?

    • Description: Implement token refresh logic if the JWT token is expired during a request.
    • Code:
      import feign.RequestInterceptor; import feign.RequestTemplate; import org.springframework.stereotype.Component; @Component public class JwtRefreshInterceptor implements RequestInterceptor { @Override public void apply(RequestTemplate template) { String token = retrieveToken(); if (isTokenExpired(token)) { token = refreshToken(); } template.header("Authorization", "Bearer " + token); } private String retrieveToken() { // Retrieve current JWT token return "current-jwt-token"; } private boolean isTokenExpired(String token) { // Check if the token is expired return false; } private String refreshToken() { // Refresh the token return "new-jwt-token"; } }

  8. How to handle multiple JWT tokens in Feign client interceptor?

    • Description: Manage multiple JWT tokens for different services or roles in the interceptor.
    • Code:
      import feign.RequestInterceptor; import feign.RequestTemplate; import org.springframework.stereotype.Component; @Component public class MultiTokenInterceptor implements RequestInterceptor { @Override public void apply(RequestTemplate template) { String token = getTokenForService(template.url()); template.header("Authorization", "Bearer " + token); } private String getTokenForService(String url) { // Determine and return token based on URL or service return "your-jwt-token"; } }

  9. How to validate JWT token claims in Feign client interceptor?

    • Description: Validate JWT token claims such as expiration, issuer, etc., in the interceptor.
    • Code:
      import feign.RequestInterceptor; import feign.RequestTemplate; import org.springframework.stereotype.Component; @Component public class JwtClaimValidationInterceptor implements RequestInterceptor { @Override public void apply(RequestTemplate template) { String token = getJwtToken(); if (validateClaims(token)) { template.header("Authorization", "Bearer " + token); } else { throw new RuntimeException("Invalid JWT token claims"); } } private String getJwtToken() { // Retrieve JWT token return "your-jwt-token"; } private boolean validateClaims(String token) { // Validate JWT claims return true; } }

  10. How to handle errors during JWT token validation in Feign client interceptor?

    • Description: Implement error handling in case of invalid JWT tokens or failed validations.
    • Code:
      import feign.RequestInterceptor; import feign.RequestTemplate; import org.springframework.stereotype.Component; @Component public class JwtErrorHandlingInterceptor implements RequestInterceptor { @Override public void apply(RequestTemplate template) { try { String token = getJwtToken(); validateToken(token); template.header("Authorization", "Bearer " + token); } catch (Exception e) { // Handle error, e.g., log or throw an exception throw new RuntimeException("JWT token validation failed", e); } } private String getJwtToken() { // Retrieve JWT token return "your-jwt-token"; } private void validateToken(String token) throws Exception { // Token validation logic } }

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