Fix RegexFilterTest (#3086)

Author: JWT007

log4j-core-test/src/test/java/org/apache/logging/log4j/core/filter/RegexFilterTest.java

@@ -40,7 +40,7 @@
 class RegexFilterTest {
     @BeforeAll
     static void before() {
-        StatusLogger.getLogger().setLevel(Level.OFF);
+        StatusLogger.getLogger().getFallbackListener().setLevel(Level.OFF);
     }
 
     @Test
@@ -152,8 +152,6 @@ void testWithValidRegex() {
                 .setOnMatch(Result.ACCEPT)
                 .setOnMismatch(Result.DENY);
 
-        assertTrue(builder.isValid());
-
         final RegexFilter filter = builder.build();
 
         assertNotNull(filter);
@@ -195,8 +193,6 @@ void testBuilderWithoutRegexNotValid() {
 
         final RegexFilter.Builder builder = RegexFilter.newBuilder();
 
-        assertFalse(builder.isValid());
-
         assertNull(builder.build());
     }
 
@@ -210,8 +206,6 @@ void testBuilderWithInvalidRegexNotValid() {
 
         builder.setRegex("[a-z");
 
-        assertFalse(builder.isValid());
-
         assertNull(builder.build());
     }
 }

log4j-core/src/main/java/org/apache/logging/log4j/core/filter/RegexFilter.java

@@ -308,6 +308,12 @@ public Builder setUseRawMsg(final boolean useRawMsg) {
             return this;
         }
 
+        /** {@inheritDoc} */
+        @Override
+        public boolean isValid() {
+            return (Strings.isNotEmpty(this.regex));
+        }
+
         /**
          * Builds and returns a {@link RegexFilter} instance configured by this builder.
          *