add option to encode Throwable in a raw format for easy ingestion into logging backends

Author: zeitlinger

logback-classic/src/main/java/ch/qos/logback/classic/encoder/JsonEncoder.java

@@ -103,6 +103,8 @@ public class JsonEncoder extends EncoderBase<ILoggingEvent> {
 
     private static final char VALUE_SEPARATOR = COMMA_CHAR;
 
+    private static final String NEWLINE = "\\\\n";
+
     private boolean withSequenceNumber = true;
 
     private boolean withTimestamp = true;
@@ -119,6 +121,7 @@ public class JsonEncoder extends EncoderBase<ILoggingEvent> {
     private boolean withMessage = true;
     private boolean withArguments = true;
     private boolean withThrowable = true;
+    private boolean withRawThrowable = false;
     private boolean withFormattedMessage = false;
 
 
@@ -190,6 +193,11 @@ public byte[] encode(ILoggingEvent event) {
         if (withArguments)
             appendArgumentArray(sb, event);
 
+        if (withRawThrowable) {
+            appenderMember(sb, "rawThrowable", event.getThrowableProxy() != null ? getRawThrowable(event.getThrowableProxy()) : NULL_STR);
+            sb.append(VALUE_SEPARATOR);
+        }
+
         if (withThrowable)
             appendThrowableProxy(sb, THROWABLE_ATTR_NAME, event.getThrowableProxy());
 
@@ -298,6 +306,26 @@ private void appendThrowableProxy(StringBuilder sb, String attributeName, IThrow
 
     }
 
+    private static String getRawThrowable(IThrowableProxy throwableProxy) {
+        StringBuilder sb = new StringBuilder();
+        getRawThrowable(throwableProxy, sb, 0);
+        return sb.toString();
+    }
+
+    private static void getRawThrowable(IThrowableProxy throwable, StringBuilder sb, int depth) {
+        if (throwable == null) {
+            return;
+        }
+        if (depth > 0) {
+            sb.append("Caused by: ");
+        }
+        sb.append(throwable.getClassName()).append(": ").append(throwable.getMessage()).append(NEWLINE);
+        for (StackTraceElementProxy step : throwable.getStackTraceElementProxyArray()) {
+            sb.append("  ").append(step).append(NEWLINE);
+        }
+        getRawThrowable(throwable.getCause(), sb, depth + 1);
+    }
+
     private void appendSTEPArray(StringBuilder sb, StackTraceElementProxy[] stepArray, int commonFrames) {
         sb.append(QUOTE).append(STEP_ARRAY_NAME_ATTRIBUTE).append(QUOTE_COL).append(OPEN_ARRAY);
 
@@ -512,8 +540,15 @@ public void setWithThrowable(boolean withThrowable) {
         this.withThrowable = withThrowable;
     }
 
+    /**
+     * @param withRawThrowable
+     * @since 1.5.7
+     */
+    public void setWithRawThrowable(boolean withRawThrowable) {
+        this.withRawThrowable = withRawThrowable;
+    }
+
     public void setWithFormattedMessage(boolean withFormattedMessage) {
         this.withFormattedMessage = withFormattedMessage;
     }
-
 }

logback-classic/src/test/java/ch/qos/logback/classic/encoder/JsonEncoderTest.java

@@ -29,7 +29,6 @@
 import ch.qos.logback.core.read.ListAppender;
 import ch.qos.logback.core.status.testUtil.StatusChecker;
 import ch.qos.logback.core.testUtil.RandomUtil;
-import ch.qos.logback.core.util.StatusPrinter;
 import com.fasterxml.jackson.core.JsonProcessingException;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
@@ -48,6 +47,7 @@
 import java.util.Map;
 import java.util.Objects;
 
+import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
@@ -257,6 +257,22 @@ void withThrowable() throws JsonProcessingException {
         compareEvents(event, resultEvent);
     }
 
+    @Test
+    void withRawThrowable() throws IOException {
+        Throwable t = new RuntimeException("test", new IllegalStateException("test cause"));
+        LoggingEvent event = new LoggingEvent("in withThrowable test", logger, Level.WARN, "hello kvp", t, null);
+
+        jsonEncoder.setWithRawThrowable(true);
+        byte[] resultBytes = jsonEncoder.encode(event);
+        String resultString = new String(resultBytes, StandardCharsets.UTF_8).trim();
+
+        //testing the whole stack trace is brittle - depends on the tool used, e.g. is different in an IDE
+        //and contains line numbers that can easily change
+
+        assertThat(resultString).contains("\"java.lang.RuntimeException: test\\\\n  at ch.qos.logback.classic");
+        assertThat(resultString).contains("Caused by: java.lang.IllegalStateException: test cause\\\\n  at ch.qos.logback.classic");
+    }
+
     @Test
     void withThrowableHavingCause() throws JsonProcessingException {
         Throwable cause = new IllegalStateException("test cause");
@@ -371,4 +387,4 @@ void withJoranAndEnabledFormattedMessage() throws JoranException, IOException {
 
         assertEquals(withness, lines.get(0));
     }
-}
+}