Passing keycloak configuration parameters in the code rather than reading from application.properties

wish help you to fix your issue The xsd schema definition of the security namespace only allows boolean values in the use-secure-cookie attribute. If you don't specify one of the allowed literals ("true" or "false"), your xml won't pass the schema validation, and won't get even parsed.
So if you use the security namespace configuration, you won't be able to use external properties to set this value. To prove my point, here is the relevant code snippet from RememberMeBeanDefinitionParser.parse():

String useSecureCookie = element.getAttribute("use-secure-cookie");
if (StringUtils.hasText(useSecureCookie)) {
    services.getPropertyValues().addPropertyValue(
                    "useSecureCookie", Boolean.valueOf(useSecureCookie));
}

wish helps you Let us assume up to runtime we do not know what are the details of configuration(may user need to configure these parameters in config file before running the application. ,
I am thinking it will impact performance.

public final class Config { 
    public static final int CONST_1;
    public static final String CONST_2;

    static {
        int c1;
        String c2;
        try (Scanner s = new Scanner(new File("config.txt"))) {
            c1 = s.nextInt();
            c2 = s.next();
        } catch (IOException ex) {
            throw RuntimeException("Cannot load config properties", ex);
        }
        CONST_1 = c1;
        CONST_2 = c2; 
    }
}

public final class Config { 
    public final int CONST_1;
    public final String CONST_2;

    public Config(File file) throws IOException {
        try (Scanner s = new Scanner(file)) {
            CONST_1 = s.nextInt();
            CONST_2 = s.next();
        } 
    }
}

wish helps you The error is because you have used a lower version of spring boot.You must have spring boot 2.0 or above for integrating with keycloak.

hope this fix your issue It is not necessary to keycloak.json.But you have to use spring boot version 2.0 and above.That will work.

wish help you to fix your issue Use a base configuration file
Having a base configuration file and another file that extends from it might be a better approach. For this example, we will look at my base configuration file:

var env = require('./environment');

// This is the configuration for a smoke test for an Angular TypeScript application.
exports.config = {
  seleniumAddress: env.seleniumAddress,

  framework: 'jasmine',

  specs: [
    'ng2/async_spec.js'
  ],

  capabilities: env.capabilities,

  baseUrl: env.baseUrl,
  allScriptsTimeout: 120000,
  getPageTimeout: 120000,
  jasmineNodeOpts: {
    defaultTimeoutInterval: 120000
  }
};

exports.config = require('./angular2Conf.js').config;

exports.config.sauceUser = process.env.SAUCE_USERNAME;
exports.config.sauceKey = process.env.SAUCE_ACCESS_KEY;
exports.config.seleniumAddress = undefined;

// TODO: add in firefox when issue #2784 is fixed
exports.config.multiCapabilities = [{
    'browserName': 'chrome',
    'tunnel-identifier': process.env.TRAVIS_JOB_NUMBER,
    'build': process.env.TRAVIS_BUILD_NUMBER,
    'name': 'Protractor suite tests',
    'version': '54',
    'selenium-version': '2.53.1',
    'chromedriver-version': '2.26',
    'platform': 'OS X 10.11'
  }];
exports.config.capabilities = undefined;
exports.config.allScriptsTimeout = 120000;
exports.config.getPageTimeout = 120000;
exports.config.jasmineNodeOpts.defaultTimeoutInterval = 120000;