Reset Pragma header in WebContentGenerator

As filter-based libraries and projects (such as Spring Security) may
use the "Pragma" header in HTTP responses, WebContentGenerator should
make sure that such headers are overwritten to avoid clashes with
the HTTP caching headers set by the HTTP caching configuration.

Issue: SPR-13252

spring-webmvc/src/test/java/org/springframework/web/servlet/mvc/WebContentInterceptorTests.java

@@ -105,6 +105,34 @@ public class WebContentInterceptorTests {
 		assertThat(cacheControlHeaders, Matchers.emptyIterable());
 	}
 
+	// SPR-13252
+	@Test
+	public void cachingConfigAndPragmaHeader() throws Exception {
+		WebContentInterceptor interceptor = new WebContentInterceptor();
+		interceptor.setCacheSeconds(10);
+		response.setHeader("Pragma", "no-cache");
+
+		interceptor.preHandle(request, response, null);
+
+		Iterable<String> pragmaHeaders = response.getHeaders("Pragma");
+		assertThat(pragmaHeaders, Matchers.contains(""));
+	}
+
+	// SPR-13252
+	@SuppressWarnings("deprecation")
+	@Test
+	public void http10CachingConfigAndPragmaHeader() throws Exception {
+		WebContentInterceptor interceptor = new WebContentInterceptor();
+		interceptor.setCacheSeconds(10);
+		interceptor.setAlwaysMustRevalidate(true);
+		response.setHeader("Pragma", "no-cache");
+
+		interceptor.preHandle(request, response, null);
+
+		Iterable<String> pragmaHeaders = response.getHeaders("Pragma");
+		assertThat(pragmaHeaders, Matchers.contains(""));
+	}
+
 	@SuppressWarnings("deprecation")
 	@Test
 	public void http10CachingConfigAndSpecificMapping() throws Exception {