/home/kai/Dokumente/yourshouter/http-resources/src/test/java/de/juplo/httpresources/ThymeleafWithHttpResourceProtocolResolverIT.java

+    package de.juplo.httpresources;
+
+    import org.apache.http.entity.StringEntity;
+    import org.junit.jupiter.api.BeforeEach;
+    import org.junit.jupiter.api.Test;
+    import org.mockserver.integration.ClientAndServer;
+    import org.slf4j.Logger;
+    import org.slf4j.LoggerFactory;
+    import org.springframework.beans.factory.annotation.Autowired;
+    import org.springframework.boot.autoconfigure.SpringBootApplication;
+    import org.springframework.boot.autoconfigure.thymeleaf.ThymeleafProperties;
+    import org.springframework.boot.test.context.SpringBootTest;
+    import org.springframework.cache.Cache;
+    import org.springframework.context.ApplicationContext;
+    import org.springframework.context.annotation.Bean;
+    import org.springframework.core.io.Resource;
+    import org.springframework.stereotype.Controller;
+    import org.springframework.test.web.servlet.MockMvc;
+    import org.springframework.test.web.servlet.setup.MockMvcBuilders;
+    import org.springframework.ui.Model;
+    import org.springframework.web.bind.annotation.RequestMapping;
+    import org.springframework.web.bind.annotation.RequestParam;
+    import org.springframework.web.context.WebApplicationContext;
+    import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
+    import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
+    import org.springframework.web.util.NestedServletException;
+    import org.thymeleaf.spring5.templateresolver.SpringResourceTemplateResolver;
+
+    import java.io.IOException;
+    import java.net.URI;
+    import java.net.URISyntaxException;
+    import java.nio.file.Files;
+    import java.nio.file.Paths;
+    import java.time.Duration;
+    import java.util.Scanner;
+    import java.util.stream.Collectors;
+
+    import static org.junit.jupiter.api.Assertions.assertThrows;
+    import static org.mockserver.model.HttpRequest.request;
+    import static org.mockserver.verify.VerificationTimes.exactly;
+    import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
+    import static org.springframework.test.web.servlet.result.MockMvcResultHandlers.print;
+    import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.content;
+    import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
+
+
+    /**
+     * This test-case showcases the usage of the {@link HttpResourceProtocolResolver}
+     * with Thymeleaf.
+     *
+     * Since Thymeleaf does not use the Resource-Chain mechanism, that Spring introduced
+     * for the handling of static resources, the {@code HttpResourceProtocolResolver} has
+     * to be used and the protocol has to be hardwired into the configuration as
+     * {@code spring.thymeleaf.prefix}.
+     * The downside of this approach is, that the templates are only resolved against
+     * the configured remote-URI and do not take part in the fallback-mechanism, that
+     * can be configured through {@code spring.resources.static-locations}.
+     *
+     * The test-case was addapted accordingly, to show the changed behaviour.
+     */
+    @SpringBootTest({
+        "juplo.http-resources.protocol-resolver.enabled=true",
+        "spring.thymeleaf.cache=true" })
+    public class ThymeleafWithHttpResourceProtocolResolverIT extends IntegrationTestBase
+    {
+      private static final Logger LOG =
+          LoggerFactory.getLogger(ThymeleafWithHttpResourceProtocolResolverIT.class);
+
+
+      @Autowired
+      HttpResources resources;
+      @Autowired
+      Cache cache;
+      @Autowired
+      WebApplicationContext context;
+
+      MockMvc mvc;
+
+
+      @BeforeEach
+      public void setUp()
+      {
+        cache.clear();
+        mvc = MockMvcBuilders
+            .webAppContextSetup(context)
+            .alwaysDo(print())
+            .build();
+      }
+
+
+      @Test
+      public void testRenderLocalTemplate() throws Exception
+      {
+        LOG.info("<-- start of test-case");
+
+        assertThrows(
+            NestedServletException.class,
+            () -> mvc.perform(get(URI.create("http://test/controller.html?template=local"))));
+
+        server.verify(FETCH("/local.html"), exactly(2));
+      }
+
+      @Test
+      public void testRenderRemoteTemplate() throws Exception
+      {
+        LOG.info("<-- start of test-case");
+
+        mvc
+            .perform(get(URI.create("http://test/controller.html?template=remote")))
+            .andExpect(status().isOk())
+            .andExpect(content().string(read("/rendered/remote.html")));
+
+        server.verify(FETCH("/remote.html"), exactly(1));
+      }
+
+      @Test
+      public void testRenderCachedRemoteTemplate() throws Exception
+      {
+        LOG.info("<-- start of test-case");
+
+        mvc
+            .perform(get(URI.create("http://test/controller.html?template=remote")))
+            .andExpect(status().isOk())
+            .andExpect(content().string(read("/rendered/remote.html")));
+
+        mvc
+            .perform(get(URI.create("http://test/controller.html?template=remote")))
+            .andExpect(status().isOk())
+            .andExpect(content().string(read("/rendered/remote.html")));
+
+        mvc
+            .perform(get(URI.create("http://test/controller.html?template=remote")))
+            .andExpect(status().isOk())
+            .andExpect(content().string(read("/rendered/remote.html")));
+
+        mvc
+            .perform(get(URI.create("http://test/controller.html?template=remote")))
+            .andExpect(status().isOk())
+            .andExpect(content().string(read("/rendered/remote.html")));
+
+        server.verify(FETCH("/remote.html"), exactly(1));
+      }
+
+      @Test
+      public void testRenderModifiedRemoteTemplate() throws Exception
+      {
+        LOG.info("<-- start of test-case");
+
+        mvc
+            .perform(get(URI.create("http://test/controller.html?template=remote")))
+            .andExpect(status().isOk())
+            .andExpect(content().string(read("/rendered/remote.html")));
+
+        CLOCK.timetravel(Duration.ofSeconds(10));
+        server.when(FETCH("/remote.html")).forward(NGINX("/modified.html"));
+
+        mvc
+            .perform(get(URI.create("http://test/controller.html?template=remote")))
+            .andExpect(status().isOk())
+            .andExpect(content().string(read("/rendered/modified.html")));
+
+        server.verify(FETCH("/remote.html"), exactly(2));
+        server.verify(
+            request()
+                .withPath("/remote.html")
+                .withHeader("If-Modified-Since")
+                .withHeader("If-None-Match"),
+            exactly(1));
+      }
+
+
+      @Controller
+      public static class TestController
+      {
+
+        @RequestMapping("/controller.html")
+        public String controller(
+            @RequestParam String template,
+            Model model
+            )
+        {
+          model.addAttribute("template", template);
+          return template;
+        }
+
+      }
+
+
+      static StringEntity body(String resource) throws URISyntaxException, IOException
+      {
+        return new StringEntity(read(resource));
+      }
+
+      static String read(String resource) throws URISyntaxException, IOException
+      {
+        URI uri = ThymeleafWithHttpResourceProtocolResolverIT.class.getResource(resource).toURI();
+        return Files.readAllLines(Paths.get(uri)).stream().collect(Collectors.joining("\n"));
+      }
+
+      static String read(Resource resource) throws URISyntaxException, IOException
+      {
+        Scanner s = new Scanner(resource.getInputStream()).useDelimiter("\\A");
+        return s.hasNext() ? s.next() : "";
+      }
+
+
+      @SpringBootApplication
+      public static class Application implements WebMvcConfigurer
+      {
+        @Autowired
+        ClientAndServer server;
+
+        /**
+         * This mimics the autoconfiguration of Thymeleaf in Spring-Boot.
+         * Reason: Found no other way to inject the property {@code spring.thymeleaf.prefix} dynamically
+         */
+        @Bean
+        public SpringResourceTemplateResolver defaultTemplateResolver(
+            ThymeleafProperties properties,
+            ApplicationContext applicationContext,
+            ClientAndServer server)
+        {
+          SpringResourceTemplateResolver resolver = new SpringResourceTemplateResolver();
+          resolver.setApplicationContext(applicationContext);
+          resolver.setPrefix("http://localhost:" + server.getLocalPort() + "/"); // << Cannot be passed in via properties
+          resolver.setSuffix(properties.getSuffix());
+          resolver.setTemplateMode(properties.getMode());
+          if (properties.getEncoding() != null)
+          {
+            resolver.setCharacterEncoding(properties.getEncoding().name());
+          }
+          resolver.setCacheable(false); // << With caching enabled, the caching of HttpResources cannot be tested
+          Integer order = properties.getTemplateResolverOrder();
+          if (order != null)
+          {
+            resolver.setOrder(order);
+          }
+          resolver.setCheckExistence(properties.isCheckTemplate());
+          return resolver;
+        }
+
+        @Bean
+        public TestController testController()
+        {
+          return new TestController();
+        }
+
+        @Override
+        public void addResourceHandlers(ResourceHandlerRegistry registry)
+        {
+          LOG.info(
+              "{} resource-handler for static location {}",
+              registry.hasMappingForPattern("/**") ? "Overwriting" : "Setting",
+              "/**"
+          );
+          registry
+              .addResourceHandler("/**")
+              .addResourceLocations(
+                  "classpath:/static/",
+                  "classpath:/public/",
+                  "http://localhost:" + server.getLocalPort(),
+                  "classpath:/fallback/")
+              .resourceChain(false);
+        }
+      }
+    }
+