Return anything other than null

Question

My code used to work until I added the sslEnabled configuration. Since I put "false" as the default value for sslEnabled, it will return null.

And that null causes me the following:

Caused by: org.springframework.beans.factory.BeanNotOfRequiredTypeException: Bean named 'servletContainer' is expected to be of type 'org.springframework.boot.web.servlet.server.ServletWebServerFactory' but was actually of type 'org.springframework.beans.factory.support.NullBean'

I tried to return new ServletWebServerFactory(); but says Cannot instantiate the type ServletWebServerFactory

@Configuration
public class ConnectorConfig {

@Value("${security.ssl.enabled}")
private boolean sslEnabled;

/**
 * Servlet container.
 *
 * @return the servlet web server factory
 */
@Bean
public ServletWebServerFactory servletContainer() {
    if(sslEnabled) {
        TomcatServletWebServerFactory tomcat = new TomcatServletWebServerFactory() {
            @Override
            protected void postProcessContext(Context context) {
                SecurityConstraint securityConstraint = new SecurityConstraint();
                securityConstraint.setUserConstraint("CONFIDENTIAL");
                SecurityCollection collection = new SecurityCollection();
                collection.addPattern("/*");
                securityConstraint.addCollection(collection);
                context.addConstraint(securityConstraint);
            }
        };
        tomcat.addAdditionalTomcatConnectors(redirectConnector());
        return tomcat;
    }
    return null;
}
....

Basically if the flag sslEnabled is false I don't want to enable the SSL and I want to skip that configuration

seeing as you hardcoded your method to return null if that flag is set to false, what did you expect to happen? — Stultuske, Jan 07 '19 at 10:01
Use optional? https://docs.oracle.com/javase/8/docs/api/java/util/Optional.html — bhathiya-perera, Jan 07 '19 at 10:32

Lorelorelore · Accepted Answer · 2019-01-07T10:35:18.347

Maybe the simplest thing to do is declaring a wrapper class and injecting that class. Like creating the following bean:

public class ServletWebServerFactoryWrapper {

    private ServletWebServerFactory servletWebServerFactory;

    public ServletWebServerFactoryWrapper(ServletWebServerFactory servletWebServerFactory){
        this.servletWebServerFactory = servletWebServerFactory;
    }

    public static ServletWebServerFactoryWrapper getWrapper(ServletWebServerFactory servletWebServerFactory){
        return new ServletWebServerFactoryWrapper(servletWebServerFactory);
    }

    public ServletWebServerFactory getFactory(){
        return servletWebServerFactory;
    }
}

and returning it in your code:

@Bean
public ServletWebServerFactoryWrapper servletContainer() {
    if(sslEnabled) {
        TomcatServletWebServerFactory tomcat = new TomcatServletWebServerFactory() {
            @Override
            protected void postProcessContext(Context context) {
                SecurityConstraint securityConstraint = new SecurityConstraint();
                securityConstraint.setUserConstraint("CONFIDENTIAL");
                SecurityCollection collection = new SecurityCollection();
                collection.addPattern("/*");
                securityConstraint.addCollection(collection);
                context.addConstraint(securityConstraint);
            }
        };
        tomcat.addAdditionalTomcatConnectors(redirectConnector());
        return ServletWebServerFactoryWrapper.getWrapper(tomcat);
    }
    return ServletWebServerFactoryWrapper.getWrapper(null);
}

I don't know if you ca use an Optional<ServletWebServerFactory> (Java 8), but you can try, it should be pretty equivalent to this. Your method should become the following:

@Bean
public Optional<ServletWebServerFactory> servletContainer() {
    if(sslEnabled) {
        TomcatServletWebServerFactory tomcat = new TomcatServletWebServerFactory() {
            @Override
            protected void postProcessContext(Context context) {
                SecurityConstraint securityConstraint = new SecurityConstraint();
                securityConstraint.setUserConstraint("CONFIDENTIAL");
                SecurityCollection collection = new SecurityCollection();
                collection.addPattern("/*");
                securityConstraint.addCollection(collection);
                context.addConstraint(securityConstraint);
            }
        };
        tomcat.addAdditionalTomcatConnectors(redirectConnector());
        return Optional.of(tomcat);
    }
    return Optional.empty();
}

Remember that this last alternative works only on Java 8 or superior.

@user10867569 please tell me what issues, I'll be happy to fix them. — Lorelorelore, Jan 07 '19 at 10:14
I don't why it starts SSL configuration anyway, but I suspect that it is related to something else. You should debug your application to understand why it starts SSL anyway. But probably it is another issue and it may not related to the `BeanNotOfRequiredTypeException` you asked for. — Lorelorelore, Jan 07 '19 at 10:24
Why not just use optional? https://docs.oracle.com/javase/8/docs/api/java/util/Optional.html — bhathiya-perera, Jan 07 '19 at 10:31
@BhathiyaPerera I don't know if he uses Java 8 or less... however I added an example with java 8's Optional. — Lorelorelore, Jan 07 '19 at 10:38

Return anything other than null

1 Answers1