Support continuing log files with same dynamic path segment

configuration/spotbugs-filters.xml

@@ -82,9 +82,12 @@
 		<Bug pattern="SIC_INNER_SHOULD_BE_STATIC_ANON" />
 	</Match>
 	<Match>
-		<!-- Dynamic Policy -->
-		<Class name="org.tinylog.policies.DynamicPolicy" />
-		<!-- Allow writing to static field org.tinylog.policies.DynamicPolicy.reset from instance method org.tinylog.policies.DynamicPolicy.reset -->
+		<!-- Dynamic Path Segment and Dynamic Policy -->
+		<Or>
+			<Class name="org.tinylog.path.DynamicSegment" />
+			<Class name="org.tinylog.policies.DynamicPolicy" />
+		</Or>
+		<!-- Allow the instances to write to their static fields -->
 		<Bug pattern="ST_WRITE_TO_STATIC_FROM_INSTANCE_METHOD" />
 	</Match>
 	<Match>

tinylog-impl/src/main/java/org/tinylog/path/DynamicSegment.java

@@ -21,14 +21,20 @@
  */
 public class DynamicSegment implements Segment {
 
-	private static String text;
 	private static final Object mutex = new Object();
 
+	private static boolean created;
+	private static String text;
+
 	/**
 	 * @param defaultValue Initial value for dynamic text
 	 */
 	DynamicSegment(final String defaultValue) {
-		setText(defaultValue);
+		synchronized (mutex) {
+			if (text == null) {
+				text = defaultValue;
+			}
+		}
 	}
 
 	/**
@@ -57,14 +63,21 @@ public static void setText(final String text) {
 			if (DynamicSegment.text != null && DynamicSegment.text.equals(text)) {
 				return;
 			}
+
 			DynamicSegment.text = text;
-			DynamicPolicy.setReset();
+
+			if (created) {
+				DynamicPolicy.setReset();
+			}
 		}
 	}
 
 	@Override
 	public String getStaticText() {
-		return getText();
+		synchronized (mutex) {
+			created = true;
+			return text;
+		}
 	}
 
 	@Override
@@ -76,7 +89,7 @@ public boolean validateToken(final String token) {
 
 	@Override
 	public String createToken(final String prefix, final Timestamp timestamp) {
-		return getText();
+		return getStaticText();
 	}
 
 }

tinylog-impl/src/test/java/org/tinylog/path/DynamicPathTest.java

@@ -22,12 +22,15 @@
 import java.time.temporal.ChronoUnit;
 import java.util.Date;
 
+import org.junit.After;
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.TemporaryFolder;
 import org.junit.runner.RunWith;
 import org.powermock.core.classloader.annotations.PrepareForTest;
 import org.powermock.modules.junit4.PowerMockRunner;
+import org.powermock.reflect.Whitebox;
+import org.tinylog.policies.DynamicPolicy;
 import org.tinylog.runtime.RuntimeProvider;
 import org.tinylog.runtime.Timestamp;
 
@@ -49,6 +52,17 @@ public final class DynamicPathTest {
 	@Rule
 	public final TemporaryFolder folder = new TemporaryFolder();
 
+
+	/**
+	 * Resets the static dynamic segment and policy fields.
+	 */
+	@After
+	public void reset() {
+		Whitebox.setInternalState(DynamicSegment.class, boolean.class, false, DynamicSegment.class);
+		Whitebox.setInternalState(DynamicSegment.class, String.class, null, DynamicSegment.class);
+		Whitebox.setInternalState(DynamicPolicy.class, boolean.class, false, DynamicPolicy.class);
+	}
+
 	/**
 	 * Verifies that a static path without any patterns can be resolved.
 	 *

tinylog-impl/src/test/java/org/tinylog/path/DynamicSegmentTest.java

@@ -13,7 +13,10 @@
 
 package org.tinylog.path;
 
+import org.junit.After;
 import org.junit.Test;
+import org.powermock.reflect.Whitebox;
+import org.tinylog.policies.DynamicPolicy;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
@@ -23,49 +26,118 @@
 public final class DynamicSegmentTest {
 
 	/**
-	 * Verifies that the passed initial dynamic text as well as the dynamic text set via
-	 * {@link DynamicSegment#setText(String)} will be returned as static text.
+	 * Resets the static dynamic segment and policy fields.
+	 */
+	@After
+	public void reset() {
+		Whitebox.setInternalState(DynamicSegment.class, boolean.class, false, DynamicSegment.class);
+		Whitebox.setInternalState(DynamicSegment.class, String.class, null, DynamicSegment.class);
+		Whitebox.setInternalState(DynamicPolicy.class, boolean.class, false, DynamicPolicy.class);
+	}
+
+	/**
+	 * Verifies that the passed default value will be used as dynamic text, if no other dynamic text is set yet.
+	 */
+	@Test
+	public void useDefaultValueIfTextAbsence() {
+		new DynamicSegment("foo");
+		assertThat(DynamicSegment.getText()).isEqualTo("foo");
+	}
+
+	/**
+	 * Verifies that the passed default value will not be used as dynamic text, if another dynamic text is already set.
+	 */
+	@Test
+	public void useDefaultValueIfTextPresent() {
+		DynamicSegment.setText("bar");
+		new DynamicSegment("foo");
+		assertThat(DynamicSegment.getText()).isEqualTo("bar");
+	}
+
+	/**
+	 * Verifies that the dynamic text can be set globally without triggering a rollover event.
 	 */
 	@Test
-	public void doesHaveStaticText() {
-		DynamicSegment segment = new DynamicSegment("test");
-		assertThat(segment.getStaticText()).isEqualTo("test");
+	public void setTextInitially() {
+		DynamicSegment.setText("foo");
+		assertThat(DynamicSegment.getText()).isEqualTo("foo");
+		assertThat(new DynamicPolicy(null).continueCurrentFile(new byte[0])).isTrue();
+	}
 
+	/**
+	 * Verifies that the dynamic text can be overridden globally without triggering a rollover event.
+	 */
+	@Test
+	public void overrideExistingText() {
 		DynamicSegment.setText("foo");
+		DynamicSegment.setText("bar");
+		assertThat(DynamicSegment.getText()).isEqualTo("bar");
+		assertThat(new DynamicPolicy(null).continueCurrentFile(new byte[0])).isTrue();
+	}
+
+	/**
+	 * Verifies setting a new dynamic text will trigger a rollover event, if it is different from the previous dynamic
+	 * text and is already in use.
+	 */
+	@Test
+	public void triggerResetForDifferentText() {
+		DynamicSegment segment = new DynamicSegment("foo");
 		assertThat(segment.getStaticText()).isEqualTo("foo");
+		assertThat(new DynamicPolicy(null).continueCurrentFile(new byte[0])).isTrue();
 
 		DynamicSegment.setText("bar");
 		assertThat(segment.getStaticText()).isEqualTo("bar");
+		assertThat(new DynamicPolicy(null).continueCurrentFile(new byte[0])).isFalse();
 	}
 
 	/**
-	 * Verifies that the passed initial dynamic text as well as the dynamic text set via
-	 * {@link DynamicSegment#setText(String)} will be returned as generated token.
+	 * Verifies setting the same dynamic text again will not trigger a rollover event, even if it is already in use.
 	 */
 	@Test
-	public void createToken() {
-		DynamicSegment segment = new DynamicSegment("test");
-		assertThat(segment.createToken(null, null)).isEqualTo("test");
+	public void preventResetForSameText() {
+		DynamicSegment segment = new DynamicSegment("foo");
+		assertThat(segment.getStaticText()).isEqualTo("foo");
+		assertThat(new DynamicPolicy(null).continueCurrentFile(new byte[0])).isTrue();
 
 		DynamicSegment.setText("foo");
 		assertThat(segment.getStaticText()).isEqualTo("foo");
+		assertThat(new DynamicPolicy(null).continueCurrentFile(new byte[0])).isTrue();
+	}
 
-		DynamicSegment.setText("bar");
-		assertThat(segment.getStaticText()).isEqualTo("bar");
+	/**
+	 * Verifies that the current dynamic text will be returned as generated token.
+	 */
+	@Test
+	public void createToken() {
+		DynamicSegment segment = new DynamicSegment("foo");
+		assertThat(segment.createToken(null, null)).isEqualTo("foo");
 	}
 
 	/**
-	 * Verifies that the dynamic text will be accepted as valid token.
+	 * Verifies that a dynamic segment without a dynamic text will reject tokens.
 	 */
 	@Test
-	public void validateValidToken() {
-		DynamicSegment segment = new DynamicSegment("test");
-		assertThat(segment.validateToken("test")).isTrue();
+	public void validateNonExistingToken() {
+		DynamicSegment segment = new DynamicSegment(null);
 		assertThat(segment.validateToken("foo")).isFalse();
+	}
 
-		DynamicSegment.setText("foo");
-		assertThat(segment.validateToken("test")).isFalse();
+	/**
+	 * Verifies that a dynamic segment with a dynamic text will accept the same tokens.
+	 */
+	@Test
+	public void validateValidToken() {
+		DynamicSegment segment = new DynamicSegment("foo");
 		assertThat(segment.validateToken("foo")).isTrue();
 	}
 
+	/**
+	 * Verifies that a dynamic segment with a dynamic text will reject different tokens.
+	 */
+	@Test
+	public void validateInvalidToken() {
+		DynamicSegment segment = new DynamicSegment("foo");
+		assertThat(segment.validateToken("bar")).isFalse();
+	}
+
 }

tinylog-impl/src/test/java/org/tinylog/policies/DynamicPolicyTest.java

@@ -15,9 +15,12 @@
 
 import java.io.IOException;
 
+import org.junit.After;
 import org.junit.Rule;
 import org.junit.Test;
+import org.powermock.reflect.Whitebox;
 import org.tinylog.configuration.ServiceLoader;
+import org.tinylog.path.DynamicSegment;
 import org.tinylog.rules.SystemStreamCollector;
 import org.tinylog.util.FileSystem;
 
@@ -34,6 +37,16 @@ public final class DynamicPolicyTest {
 	@Rule
 	public final SystemStreamCollector systemStream = new SystemStreamCollector(true);
 
+	/**
+	 * Resets the static dynamic segment and policy fields.
+	 */
+	@After
+	public void reset() {
+		Whitebox.setInternalState(DynamicSegment.class, boolean.class, false, DynamicSegment.class);
+		Whitebox.setInternalState(DynamicSegment.class, String.class, null, DynamicSegment.class);
+		Whitebox.setInternalState(DynamicPolicy.class, boolean.class, false, DynamicPolicy.class);
+	}
+
 	/**
 	 * Verifies that an existing log file will always be continued.
 	 *