assessment.html

....
<form action="#" th:action="@{/greeting}" method="post">
  .....
  

controller.java

@org.springframework.stereotype.Controller
@EnableAutoConfiguration

public class Controller {
    @Autowired
    nz.org.needsassessment.PdfGeneratorUtil pdfGenaratorUtil;

    @GetMapping ("/")
    String home() {
        return "static/assessment.html";
    }

    @PostMapping("/greeting")
    public String greetingSubmit() {

        Map<String,String> data = new HashMap<String,String>();
        data.put("name","James");
        try {
            pdfGenaratorUtil.createPdf("greeting",data);
        } catch (Exception e) {
            e.printStackTrace();
        }

        return "finished";
    }