Spring MVC model not forwarded

[blaluc]

It seems that while forwarding requests, the model instance is not injected from the request scope.

e.g.:

@Controller
@RequestMapping("/second")
public class OtherController {

	@GetMapping
	public String view2(Model model) {
		model.addAttribute("key2", "second value");
		return "forward:/";
	}

@Controller
@RequestMapping("/")
public class TestController {

	@GetMapping
	public String index(Model model) {
		model.addAttribute("key1", "first value");
		return "index";
	}
}

index.jte:

@param String key1
@param String key2

key1: ${key1} <br>
key2: ${key2}

By calling http://localhost:8080/second, the key2 value should be propagated to the template and displayed, but it is not, and the following page is shown instead:

key1: first value
key2:

The same example with thymeleaf works as expected giving the result:

key1: first value
key2: second value

[blaluc]

it seems that can be solved by adding

this.setExposeRequestAttributes(true);

in the JteViewResolver class, i.e.:

public class JteViewResolver extends AbstractTemplateViewResolver {
...
    public JteViewResolver(TemplateEngine templateEngine, final String templateSuffix) {
        this.templateEngine = templateEngine;
        this.setSuffix(templateSuffix);
        this.setViewClass(JteView.class);
        this.setContentType(MediaType.TEXT_HTML_VALUE);
        this.setOrder(Ordered.HIGHEST_PRECEDENCE);
        this.setExposeRequestAttributes(true);
    }
...

[casid]

@blaluc thanks for sharing. Your suggested fix looks good to me.

However I'm not a heavy spring user and don't know if this has any unintended side effects.

@atomfrede, @tschuehly would this change be okay with you?

[atomfrede]

At first glance it looks okay. Found similar issues with pebble for example. Not sure why it works for thymeleaf out of the box because it looks like the exposeRequestAttributes is not set (at least not explicitly).

[atomfrede]

I have found why it works with thymeleaf. In case it is forwarded, thymeleaf creates an InternalViewResourceView and in there it exposes the model attributes as request attributes (always). So setting it looks fine to me (maybe check if that has any implications on normal view resolving)

[atomfrede]

@blaluc Just curious, whats the use case for the forward (instead e.g. redirect with flash attributes for example), besides being the forward totally server side?

[blaluc]

Hi @atomfrede, the use case I’m working on involves integrating with the htmx library (https://htmx.org/). To handle a full-page reload, it might be useful to forward the model built in a 'partial' controller method (server-side) to another controller method responsible for rendering the full page.

[casid]

@blaluc did you check if it has any impact on normal view resolving? And, would you be up to submit a Pull Request with your suggested fix?

[blaluc]

Done (#383).

To avoid any impact I have added a configuration parameter (the default behavior is the previous one).

Cheers!

[casid]

This is now released with jte 3.1.13