Throw IllegalArgumentException at invalid time zone textual representation instead of defaulting to GMT

README.md

@@ -1639,7 +1639,9 @@ You can change the timezone like this:
 </encoder>
 ```
 
-The value of the `timeZone` element can be any string accepted by java's  `TimeZone.getTimeZone(String id)` method.
+The value of the `timeZone` element can be any string accepted by java's `TimeZone.getTimeZone(String id)` method.
+For example `America/Los_Angeles`, `GMT+10` or `UTC`.
+Use the special value `[DEFAULT]` to use the default TimeZone of the system.
 
 
 ## Customizing LoggingEvent Message

src/main/java/net/logstash/logback/composite/FormattedTimestampJsonProvider.java

@@ -23,6 +23,7 @@
 import java.util.TimeZone;
 
 import net.logstash.logback.fieldnames.LogstashCommonFieldNames;
+import net.logstash.logback.util.TimeZoneUtils;
 
 import ch.qos.logback.core.spi.DeferredProcessingAware;
 import com.fasterxml.jackson.core.JsonGenerator;
@@ -31,8 +32,8 @@
  * Writes the timestamp field as either:
  * <ul>
  *      <li>A string value formatted by a {@link DateTimeFormatter} pattern</li>
- *      <li>A string value representing the number of milliseconds since unix epoch  (designated by specifying the pattern value as {@value #UNIX_TIMESTAMP_AS_STRING})</li>
- *      <li>A number value of the milliseconds since unix epoch  (designated by specifying the pattern value as {@value #UNIX_TIMESTAMP_AS_NUMBER})</li>
+ *      <li>A string value representing the number of milliseconds since unix epoch (designated by specifying the pattern value as {@value #UNIX_TIMESTAMP_AS_STRING})</li>
+ *      <li>A number value of the milliseconds since unix epoch (designated by specifying the pattern value as {@value #UNIX_TIMESTAMP_AS_NUMBER})</li>
  * </ul>
  */
 public abstract class FormattedTimestampJsonProvider<Event extends DeferredProcessingAware, FieldNames extends LogstashCommonFieldNames> extends AbstractFieldJsonProvider<Event> implements FieldNamesAware<FieldNames> {
@@ -51,9 +52,16 @@ public abstract class FormattedTimestampJsonProvider<Event extends DeferredProce
      */
     public static final String UNIX_TIMESTAMP_AS_STRING = "[UNIX_TIMESTAMP_AS_STRING]";
 
+    /**
+     * The default {@link #pattern} value.
+     */
     private static final String DEFAULT_PATTERN = "[ISO_OFFSET_DATE_TIME]";
-    private static final TimeZone DEFAULT_TIMEZONE = TimeZone.getDefault();
 
+    /**
+     * Keyword used by {@link #setTimeZone(String)} to denote the system default time zone.
+     */
+    public static final String DEFAULT_TIMEZONE_KEYWORD = "[DEFAULT]";
+
     /**
      * The pattern in which to format the timestamp.
      *
@@ -72,7 +80,7 @@ public abstract class FormattedTimestampJsonProvider<Event extends DeferredProce
      * The timezone for which to write the timestamp.
      * Only applicable if the pattern is not {@value #UNIX_TIMESTAMP_AS_NUMBER} or {@value #UNIX_TIMESTAMP_AS_STRING}
      */
-    private TimeZone timeZone = DEFAULT_TIMEZONE;
+    private TimeZone timeZone = TimeZone.getDefault();
 
     /**
      * Writes the timestamp to the JsonGenerator.
@@ -204,11 +212,35 @@ public void setPattern(String pattern) {
         this.pattern = pattern;
         updateTimestampWriter();
     }
+
+    /**
+     * Get the time zone used to write the timestamp.
+     * 
+     * @return the time zone used to write the timestamp
+     */
     public String getTimeZone() {
         return timeZone.getID();
     }
-    public void setTimeZone(String timeZoneId) {
-        this.timeZone = TimeZone.getTimeZone(timeZoneId);
+
+
+    /**
+     * Set the timezone for which to write the timestamp.
+     * Only applicable if the pattern is not {@value #UNIX_TIMESTAMP_AS_NUMBER} or {@value #UNIX_TIMESTAMP_AS_STRING}.
+     * 
+     * <p>The value of the {@code timeZone} can be any string accepted by java's {@link TimeZone#getTimeZone(String)} method.
+     * For example "America/Los_Angeles" or "GMT+10".
+     * 
+     * <p>Use a blank string, {@code null} or the value {@value #DEFAULT_TIMEZONE_KEYWORD} to use the default TimeZone of the system.
+     * 
+     * @param timeZone the textual representation of the desired time zone
+     * @throws IllegalArgumentException if the input string is not a valid TimeZone representation
+     */
+    public void setTimeZone(String timeZone) {
+        if (timeZone == null || timeZone.trim().isEmpty() || DEFAULT_TIMEZONE_KEYWORD.equalsIgnoreCase(timeZone)) {
+            this.timeZone = TimeZone.getDefault();
+        } else {
+            this.timeZone = TimeZoneUtils.parseTimeZone(timeZone);
+        }
         updateTimestampWriter();
     }
 }

src/main/java/net/logstash/logback/util/TimeZoneUtils.java

@@ -0,0 +1,56 @@
+/*
+ * Copyright 2013-2021 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package net.logstash.logback.util;
+
+import java.util.Objects;
+import java.util.TimeZone;
+
+public class TimeZoneUtils {
+
+    private TimeZoneUtils() {
+        // utility class
+    }
+
+
+    /**
+     * Parse a string into the corresponding {@link TimeZone} using the format described by
+     * {@link TimeZone#getTimeZone(String)}.
+     * 
+     * <p>The value of the {@code timeZone} can be any string accepted by java's {@link TimeZone#getTimeZone(String)}
+     * method. For example "America/Los_Angeles" or "GMT+10".
+     * 
+     * @param str the string to parse into a valid {@link TimeZone}.
+     * @return the {@link TimeZone} corresponding to the input string
+     * @throws IllegalArgumentException thrown when the string is not a valid TimeZone textual
+     *                                  representation.
+     */
+    public static TimeZone parseTimeZone(String str) {
+        TimeZone tz = TimeZone.getTimeZone(Objects.requireNonNull(str));
+
+        /*
+         * Instead of throwing an exception when it fails to parse the string into a valid
+         * TimeZone, getTimeZone() returns a TimeZone with id "GMT".
+         * 
+         * If the returned TimeZone is GMT but the input string is not, then the input string
+         * was not a valid time zone representation.
+         */
+        if ("GMT".equals(tz.getID()) && !"GMT".equals(str)) {
+            throw new IllegalArgumentException("Invalid TimeZone value (was '" + str + "')");
+        }
+
+        return tz;
+    }
+}

src/test/java/net/logstash/logback/util/TimeZoneUtilsTest.java

@@ -0,0 +1,54 @@
+/*
+ * Copyright 2013-2021 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package net.logstash.logback.util;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+import org.junit.jupiter.api.Test;
+
+/**
+ * @author brenuart
+ *
+ */
+public class TimeZoneUtilsTest {
+
+    @Test
+    public void standardTimeZones() {
+        assertThat(TimeZoneUtils.parseTimeZone("GMT").getID()).isEqualTo("GMT");
+        assertThat(TimeZoneUtils.parseTimeZone("Europe/Brussels").getID()).isEqualTo("Europe/Brussels");
+    }
+
+
+    @Test
+    public void customTimeZones() {
+        assertThat(TimeZoneUtils.parseTimeZone("GMT+00").getID()).isEqualTo("GMT+00:00");
+        assertThat(TimeZoneUtils.parseTimeZone("GMT+00:00").getID()).isEqualTo("GMT+00:00");
+
+        assertThat(TimeZoneUtils.parseTimeZone("GMT-00").getID()).isEqualTo("GMT-00:00");
+        assertThat(TimeZoneUtils.parseTimeZone("GMT-00:00").getID()).isEqualTo("GMT-00:00");
+
+        assertThat(TimeZoneUtils.parseTimeZone("GMT+01:12").getID()).isEqualTo("GMT+01:12");
+    }
+
+
+    @Test
+    public void invalidTimeZone() {
+        assertThatThrownBy(() -> TimeZoneUtils.parseTimeZone("foo")).isInstanceOf(IllegalArgumentException.class);
+        assertThatThrownBy(() -> TimeZoneUtils.parseTimeZone("")).isInstanceOf(IllegalArgumentException.class);
+        assertThatThrownBy(() -> TimeZoneUtils.parseTimeZone(null)).isInstanceOf(NullPointerException.class);
+    }
+}