Update NamePatternFilter to detect regular expression character class

Previously, NamePatternFilter looked for “*”, “$”, “^”, or “+” when
trying to identify a string as being a regular expression. This meant
that it missed the use of a character class ([a-z], for example). This
commit adds “[“} to the list of characters that are considered to be
part of a regular expression.

Closes gh-4233

spring-boot-actuator/src/main/java/org/springframework/boot/actuate/endpoint/mvc/NamePatternFilter.java

@@ -35,7 +35,7 @@ import java.util.regex.Pattern;
  */
 abstract class NamePatternFilter<T> {
 
-	private static final String[] REGEX_PARTS = { "*", "$", "^", "+" };
+	private static final String[] REGEX_PARTS = { "*", "$", "^", "+", "[" };
 
 	private final T source;
 

spring-boot-actuator/src/test/java/org/springframework/boot/actuate/endpoint/mvc/NamePatternFilterTests.java

@@ -22,6 +22,8 @@ import org.junit.Test;
 
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.hasEntry;
+import static org.hamcrest.Matchers.is;
+import static org.hamcrest.Matchers.nullValue;
 import static org.junit.Assert.assertThat;
 
 /**
@@ -41,13 +43,48 @@ public class NamePatternFilterTests {
 	}
 
 	@Test
-	public void regex() throws Exception {
+	public void regexRepetitionZeroOrMore() {
 		MockNamePatternFilter filter = new MockNamePatternFilter();
 		Map<String, Object> results = filter.getResults("fo.*");
 		assertThat(results.get("foo"), equalTo((Object) "foo"));
 		assertThat(results.get("fool"), equalTo((Object) "fool"));
 		assertThat(filter.isGetNamesCalled(), equalTo(true));
+	}
+
+	@Test
+	public void regexRepetitionOneOrMore() {
+		MockNamePatternFilter filter = new MockNamePatternFilter();
+		Map<String, Object> results = filter.getResults("fo.+");
+		assertThat(results.get("foo"), equalTo((Object) "foo"));
+		assertThat(results.get("fool"), equalTo((Object) "fool"));
+		assertThat(filter.isGetNamesCalled(), equalTo(true));
+	}
+
+	@Test
+	public void regexEndAnchor() {
+		MockNamePatternFilter filter = new MockNamePatternFilter();
+		Map<String, Object> results = filter.getResults("foo$");
+		assertThat(results.get("foo"), equalTo((Object) "foo"));
+		assertThat(results.get("fool"), is(nullValue()));
+		assertThat(filter.isGetNamesCalled(), equalTo(true));
+	}
+
+	@Test
+	public void regexStartAnchor() {
+		MockNamePatternFilter filter = new MockNamePatternFilter();
+		Map<String, Object> results = filter.getResults("^foo");
+		assertThat(results.get("foo"), equalTo((Object) "foo"));
+		assertThat(results.get("fool"), is(nullValue()));
+		assertThat(filter.isGetNamesCalled(), equalTo(true));
+	}
 
+	@Test
+	public void regexCharacterClass() {
+		MockNamePatternFilter filter = new MockNamePatternFilter();
+		Map<String, Object> results = filter.getResults("fo[a-z]l");
+		assertThat(results.get("foo"), is(nullValue()));
+		assertThat(results.get("fool"), equalTo((Object) "fool"));
+		assertThat(filter.isGetNamesCalled(), equalTo(true));
 	}
 
 	private static class MockNamePatternFilter extends NamePatternFilter<Object> {