PrintingResultHandler defensively accesses session.getAttributeNames()

Issue: SPR-16164

spring-test/src/main/java/org/springframework/test/web/servlet/result/PrintingResultHandler.java

@@ -59,7 +59,6 @@ public class PrintingResultHandler implements ResultHandler {
 
 	private static final String MISSING_CHARACTER_ENCODING = "<no character encoding set>";
 
-
 	private final ResultValuePrinter printer;
 
 
@@ -148,9 +147,14 @@ protected final MultiValueMap<String, String> getParamsMultiValueMap(MockHttpSer
 
 	protected final Map<String, Object> getSessionAttributes(MockHttpServletRequest request) {
 		HttpSession session = request.getSession(false);
-		return session == null ? Collections.emptyMap() :
-				Collections.list(session.getAttributeNames()).stream()
-						.collect(Collectors.toMap(n -> n, session::getAttribute));
+		if (session != null) {
+			Enumeration<String> attrNames = session.getAttributeNames();
+			if (attrNames != null) {
+				return Collections.list(attrNames).stream().
+						collect(Collectors.toMap(n -> n, session::getAttribute));
+			}
+		}
+		return Collections.emptyMap();
 	}
 
 	protected void printAsyncResult(MvcResult result) throws Exception {
@@ -169,7 +173,9 @@ protected void printAsyncResult(MvcResult result) throws Exception {
 	/**
 	 * Print the handler.
 	 */
-	protected void printHandler(@Nullable Object handler, @Nullable HandlerInterceptor[] interceptors) throws Exception {
+	protected void printHandler(@Nullable Object handler, @Nullable HandlerInterceptor[] interceptors)
+			throws Exception {
+
 		if (handler == null) {
 			this.printer.printValue("Type", null);
 		}

spring-test/src/test/java/org/springframework/test/web/servlet/result/PrintingResultHandlerTests.java

@@ -22,8 +22,10 @@
 import java.util.List;
 import java.util.Map;
 import javax.servlet.http.Cookie;
+import javax.servlet.http.HttpSession;
 
 import org.junit.Test;
+import org.mockito.Mockito;
 
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.MediaType;
@@ -40,8 +42,7 @@
 import org.springframework.web.servlet.FlashMap;
 import org.springframework.web.servlet.ModelAndView;
 
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.*;
 
 /**
  * Unit tests for {@link PrintingResultHandler}.
@@ -93,6 +94,55 @@ public void printRequest() throws Exception {
 		assertValue("MockHttpServletRequest", "Session Attrs", Collections.singletonMap("foo", "bar"));
 	}
 
+	@Test
+	public void printRequestWithoutSession() throws Exception {
+		this.request.addParameter("param", "paramValue");
+		this.request.addHeader("header", "headerValue");
+		this.request.setCharacterEncoding("UTF-16");
+		String palindrome = "ablE was I ere I saw Elba";
+		byte[] bytes = palindrome.getBytes("UTF-16");
+		this.request.setContent(bytes);
+
+		this.handler.handle(this.mvcResult);
+
+		HttpHeaders headers = new HttpHeaders();
+		headers.set("header", "headerValue");
+
+		MultiValueMap<String, String> params = new LinkedMultiValueMap<>();
+		params.add("param", "paramValue");
+
+		assertValue("MockHttpServletRequest", "HTTP Method", this.request.getMethod());
+		assertValue("MockHttpServletRequest", "Request URI", this.request.getRequestURI());
+		assertValue("MockHttpServletRequest", "Parameters", params);
+		assertValue("MockHttpServletRequest", "Headers", headers);
+		assertValue("MockHttpServletRequest", "Body", palindrome);
+	}
+
+	@Test
+	public void printRequestWithEmptySessionMock() throws Exception {
+		this.request.addParameter("param", "paramValue");
+		this.request.addHeader("header", "headerValue");
+		this.request.setCharacterEncoding("UTF-16");
+		String palindrome = "ablE was I ere I saw Elba";
+		byte[] bytes = palindrome.getBytes("UTF-16");
+		this.request.setContent(bytes);
+		this.request.setSession(Mockito.mock(HttpSession.class));
+
+		this.handler.handle(this.mvcResult);
+
+		HttpHeaders headers = new HttpHeaders();
+		headers.set("header", "headerValue");
+
+		MultiValueMap<String, String> params = new LinkedMultiValueMap<>();
+		params.add("param", "paramValue");
+
+		assertValue("MockHttpServletRequest", "HTTP Method", this.request.getMethod());
+		assertValue("MockHttpServletRequest", "Request URI", this.request.getRequestURI());
+		assertValue("MockHttpServletRequest", "Parameters", params);
+		assertValue("MockHttpServletRequest", "Headers", headers);
+		assertValue("MockHttpServletRequest", "Body", palindrome);
+	}
+
 	@Test
 	@SuppressWarnings("deprecation")
 	public void printResponse() throws Exception {
@@ -325,6 +375,7 @@ public void printValue(String label, Object value) {
 		}
 	}
 
+
 	public void handle() {
 	}