Java – How to serve static html from spring boot

I ran the spring-boot-sample-web-static project from here, made this alteration to the pom

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-tomcat</artifactId>
</dependency>

And added this class to serve a duplicate page index2.html from the same static folder location:

import org.springframework.http.MediaType;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller
public class Rester {

    @RequestMapping(value = "/rand", produces = MediaType.APPLICATION_JSON_VALUE)
    @ResponseBody
    private RandomObj jsonEndpoint() {
        return new RandomObj();
    }

    @RequestMapping(value = "/tw")
    public String somePg() {
        return "index2";
    }
}

The json url works fine, but when I try to access localhost:8080/tw I get a blank page, and this error in the console:

2017-02-22 15:37:22.076 ERROR 21494 --- [nio-8080-exec-9] o.s.boot.web.support.ErrorPageFilter     : Cannot forward to error page for request [/tw] as the response has already been committed. As a result, the response may have the wrong status code. If your application is running on WebSphere Application Server you may be able to resolve this problem by setting com.ibm.ws.webcontainer.invokeFlushAfterService to false

Am I doing something wrong?