Commit Session on Include Dispatch

The servlet spec disallows any writing of headers after an include has been issued.

This commit intercepts the include and commits the session, then
allowing the include to proceed.

See: #1243

spring-session-core/src/main/java/org/springframework/session/web/http/SessionRepositoryFilter.java

@@ -21,8 +21,11 @@ import java.time.Instant;
 import java.util.List;
 
 import javax.servlet.FilterChain;
+import javax.servlet.RequestDispatcher;
 import javax.servlet.ServletContext;
 import javax.servlet.ServletException;
+import javax.servlet.ServletRequest;
+import javax.servlet.ServletResponse;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletRequestWrapper;
 import javax.servlet.http.HttpServletResponse;
@@ -358,6 +361,12 @@ public class SessionRepositoryFilter<S extends Session> extends OncePerRequestFi
 			return this.requestedSessionId;
 		}
 
+		@Override
+		public RequestDispatcher getRequestDispatcher(String path) {
+			RequestDispatcher requestDispatcher = super.getRequestDispatcher(path);
+			return new SessionCommittingRequestDispatcher(requestDispatcher);
+		}
+
 		private S getRequestedSession() {
 			if (!this.requestedSessionCached) {
 				List<String> sessionIds = SessionRepositoryFilter.this.httpSessionIdResolver
@@ -407,6 +416,25 @@ public class SessionRepositoryFilter<S extends Session> extends OncePerRequestFi
 			}
 		}
 
+		private final class SessionCommittingRequestDispatcher implements RequestDispatcher {
+			private final RequestDispatcher delegate;
+
+			SessionCommittingRequestDispatcher(RequestDispatcher delegate) {
+				this.delegate = delegate;
+			}
+
+			@Override
+			public void forward(ServletRequest request, ServletResponse response) throws ServletException, IOException {
+				this.delegate.forward(request, response);
+			}
+
+			@Override
+			public void include(ServletRequest request, ServletResponse response) throws ServletException, IOException {
+				SessionRepositoryRequestWrapper.this.commitSession();
+				this.delegate.include(request, response);
+			}
+		}
+
 	}
 
 }

spring-session-core/src/test/java/org/springframework/session/web/http/SessionRepositoryFilterTests.java

@@ -1170,6 +1170,21 @@ public class SessionRepositoryFilterTests {
 		});
 	}
 
+	@Test
+	public void doFilterInclude() throws Exception {
+		doFilter(new DoInFilter() {
+			@Override
+			public void doFilter(HttpServletRequest wrappedRequest,
+					HttpServletResponse wrappedResponse) throws IOException, ServletException {
+				String id = wrappedRequest.getSession().getId();
+				wrappedRequest.getRequestDispatcher("/").include(wrappedRequest, wrappedResponse);
+				assertThat(
+						SessionRepositoryFilterTests.this.sessionRepository.findById(id))
+						.isNotNull();
+			}
+		});
+	}
+
 	// --- HttpSessionIdResolver
 
 	@Test