Is there any option to add a default value to all @RequestHeaders in spring boot?

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Is there any option to add a default value to all @RequestHeader's in spring boot?

@RequestHeader(value = "User-Accept-Language", defaultValue = "en-IN") String localeCd

I am copy/pasting to all the API's. Any help to avoid code duplication!!

2 Answers

I didn't find anything already done for having an annotation for adding a header with a value so I did my own. Here is the code, is very simple, I did it using spring AOP

  1. I created the annotation classes

    import java.lang.annotation.ElementType;
    import java.lang.annotation.Retention;
    import java.lang.annotation.RetentionPolicy;
    import java.lang.annotation.Target;
    
    @Retention(RetentionPolicy.RUNTIME)
    @Target(ElementType.METHOD)
    public @interface ResponseHeader {
    
        public String key() default "";
    
        public String value() default "";
    }
    

    and the one for containing an array of Headers annotations

    import java.lang.annotation.ElementType;
    import java.lang.annotation.Retention;
    import java.lang.annotation.RetentionPolicy;
    import java.lang.annotation.Target;
    
    
    @Retention(RetentionPolicy.RUNTIME)
    @Target(ElementType.METHOD)
    public @interface ResponseHeaders {
    
        public ResponseHeader[] headers();
    }
    
  2. The AOP class for catching the restControllers (you can customise the AOP for setting you own pointcut as you wish:

    import YOUR_PACKAGE_ANNOTATION.ResponseHeaders;
    import org.aspectj.lang.annotation.After;
    import org.aspectj.lang.annotation.Aspect;
    import org.aspectj.lang.annotation.Pointcut;
    import org.springframework.stereotype.Component;
    import org.springframework.web.context.request.RequestContextHolder;
    import org.springframework.web.context.request.ServletRequestAttributes;
    
    import javax.servlet.http.HttpServletResponse;
    import java.util.List;
    
    /**
     * Aspect for inserting headers on the methods of the @RestController         
     annotated classes
     */
     @Aspect
     @Component
     public class ResponseHeadersAnnotation {
    
     /**
     * Pointcut for filtering just classes with @RestController annotation
     */
    @Pointcut("@within(org.springframework.web.bind.annotation.RestController)")
    public void restControllerClass() {
    }
    
    /**
     * It adds the headers to the response of the method of the controller
     *
     * @param responseHeaders
     */
    @After("restControllerClass() && @annotation(responseHeaders)")
    public void addHeaders(final ResponseHeaders responseHeaders) {
        final HttpServletResponse response = ((ServletRequestAttributes) RequestContextHolder.getRequestAttributes()).getResponse();
        List.of(responseHeaders.headers()).forEach(responseHeader -> response.setHeader(responseHeader.key(), responseHeader.value()));
     }
    }
    
  3. Here is an example of how to use it in a controller:

    @GetMapping(value = {"/ServiceTicketCollection", "/ServiceRequestCollection"})
    @ResponseHeaders(headers = {
            @ResponseHeader(key = "cookie1", value = "value1"),
            @ResponseHeader(key = "cookie2, value = "value2")
    })
    public Object restControllerMethod() {
        ...
    }
    

This is an example on how to provide a default value for a header using spring WebFlux

@Component
public class CorrelationIdFilter implements WebFilter {

    @Override
    public Mono<Void> filter(ServerWebExchange exchange, WebFilterChain chain) {
        var correlationId = exchange.getRequest().getHeaders().getFirst(CORRELATION_ID_HEADER);
        if (correlationId == null || correlationId.isEmpty()) {
            correlationId = UUID.randomUUID().toString();
            ServerHttpRequest mutatedRequest = exchange.getRequest()
                    .mutate()
                    .header(CORRELATION_ID_HEADER, correlationId)
                    .build();
            exchange = exchange
                    .mutate()
                    .request(mutatedRequest)
                    .build();
        }
        exchange.getResponse().getHeaders().add(CORRELATION_ID_HEADER, correlationId);
        return chain.filter(exchange);
    }
}

And this is for Spring web

@Component
public class CorrelationIdFilter implements Filter {

    static final String CORRELATION_ID_HEADER = "X-Correlation-ID";

    @Override
    public void init(FilterConfig filterConfig) {
        // empty
    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
            throws IOException, ServletException {

        HttpServletRequest httpRequest = (HttpServletRequest) request;
        String correlationId = httpRequest.getHeader(CORRELATION_ID_HEADER);
        if (correlationId == null) {
           correlationId = XidFactory.nextXid();
           ((HttpServletResponse) response).addHeader(CORRELATION_ID_HEADER, correlationId);
        }
        
        chain.doFilter(request, response);
    }

    @Override
    public void destroy() {
        // empty
    }
}
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