WW-4663 Checks if expression is null to avoid NPE

core/src/main/java/org/apache/struts2/util/ComponentUtils.java

@@ -44,11 +44,11 @@ public class ComponentUtils {
      * @return true if it is an expression
      */
     public static boolean isExpression(String expr) {
-        return expr.startsWith("%{") && expr.endsWith("}");
+        return expr != null && expr.startsWith("%{") && expr.endsWith("}");
     }
 
     public static boolean containsExpression(String expr) {
-        return expr.contains("%{") && expr.contains("}");
+        return expr != null && expr.contains("%{") && expr.contains("}");
     }
 
 }

core/src/test/java/org/apache/struts2/util/ComponentUtilsTest.java

@@ -93,6 +93,10 @@ public class ComponentUtilsTest extends StrutsInternalTestCase {
         assertFalse(actual);
     }
 
+    public void testIsExpressionIsFalseWhenNull() throws Exception {
+        assertFalse(ComponentUtils.isExpression(null));
+    }
+
     public void testContainsExpressionIsTrue() throws Exception {
         // given
         String anExpression = "%{foo}";
@@ -125,6 +129,10 @@ public class ComponentUtilsTest extends StrutsInternalTestCase {
         // then
         assertFalse(actual);
     }
+
+    public void testContainsExpressionIsFalseWhenNull() throws Exception {
+        assertFalse(ComponentUtils.containsExpression(null));
+    }
 }
 
 class MockConfigurationProvider implements ConfigurationProvider {