Base Controller #springboot

BaseController.java

import jakarta.servlet.ServletContext;
import jakarta.servlet.http.HttpServletRequest;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.env.Environment;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.Objects;

/**
 * This controller returns the JavaScript code to set the <base href="/server.contextPath"/>.
 */
@Configuration
@RestController
class BaseController {

    // Logger
    private static final Logger LOG = LoggerFactory.getLogger(BaseController.class);


    private final Environment environment;
    private final ServletContext servletContext;

    BaseController(Environment environment, ServletContext servletContext) {
        this.environment = environment;
        this.servletContext = servletContext;
    }

    @GetMapping(value = "/base", produces = { "text/javascript" })
    public String contextPath(HttpServletRequest request) {
        // This header is set by the load balancer proxy
        String xForwardedServer = request.getHeader("x-forwarded-server");

        // header must be set by the load balancer proxy if the context path at LB is not /
        String xForwardedPrefix = request.getHeader("x-forwarded-prefix");

        // If it is set we should not consider our own context path
        String contextPath = servletContext.getContextPath();
        if (xForwardedServer != null) {
            contextPath = xForwardedPrefix == null ? "" : xForwardedPrefix;
        }
        contextPath = simpleSanitize(contextPath);
        contextPath = contextPath + "/";
        return "(function () {\n"
                + "    var head = document.getElementsByTagName('head').item(0);\n"
                + "    var base = document.createElement('base');\n" + "    base.href = '" + contextPath + "';\n"
                + "    head.appendChild(base);\n" + "})();\n";
    }

    // IA-11973 - Very simple sanitizer for now. At some point we should try to leverage
    // some other library to do more sophisticated sanitization/validation. I do not know enough
    // about the context path here and want to avoid breaking it for valid characters.
    private static String simpleSanitize(String input) {
        if (Objects.isNull(input) || input.length() == 0) {
            return input;
        }
        return input.replaceAll("(?i)<script.*?>.*?</script.*?>", "")
                .replaceAll("(?i)<.*?javascript:.*?>.*?</.*?>", "");
    }
}