Add Exception Type and Message to JSON Logs

Adds the two fields exception_type and exception_message to
the BaseFieldSuppliers for Log4j and Logback. This allows users
to override the provided values with custom FieldSuppliers. Basic
Unit Tests were added.

Performance implications should be minimal for events without
exceptions. If there are exceptions, the only longer check is for
the message to be non-blank.

Signed-off-by: Karsten Schnitter <k.schnitter@sap.com>

Author: KarstenSchnitter

cf-java-logging-support-log4j2/src/main/java/com/sap/hcp/cf/log4j2/layout/supppliers/BaseFieldSupplier.java

@@ -4,6 +4,7 @@
 import java.util.HashMap;
 import java.util.Map;
 
+import org.apache.commons.lang3.StringUtils;
 import org.apache.logging.log4j.core.LogEvent;
 
 import com.sap.hcp.cf.log4j2.converter.api.Log4jContextFieldSupplier;
@@ -24,6 +25,13 @@ public Map<String, Object> map(LogEvent event) {
         if (!LogEventUtilities.isRequestLog(event) && event.getMessage() != null) {
             fields.put(Fields.MSG, LogEventUtilities.getFormattedMessage(event));
         }
+        if (event.getThrown() != null) {
+            Throwable throwable = event.getThrown();
+            fields.put(Fields.EXCEPTION_TYPE, throwable.getClass().getName());
+            if (StringUtils.isNotBlank(throwable.getMessage())) {
+                fields.put(Fields.EXCEPTION_MESSAGE, throwable.getMessage());
+            }
+        }
         return fields;
     }
 

cf-java-logging-support-log4j2/src/test/java/com/sap/hcp/cf/log4j2/layout/suppliers/BaseFieldSupplierTest.java

@@ -0,0 +1,58 @@
+package com.sap.hcp.cf.log4j2.layout.suppliers;
+
+import com.sap.hcp.cf.log4j2.converter.api.Log4jContextFieldSupplier;
+import com.sap.hcp.cf.log4j2.layout.supppliers.BaseFieldSupplier;
+import com.sap.hcp.cf.logging.common.Fields;
+import org.apache.logging.log4j.core.LogEvent;
+import org.apache.logging.log4j.core.time.Instant;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.Mockito;
+import org.mockito.runners.MockitoJUnitRunner;
+
+import java.time.Clock;
+import java.util.Map;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.junit.Assert.*;
+
+import static org.hamcrest.Matchers.hasEntry;
+import static org.hamcrest.MatcherAssert.*;
+import static org.hamcrest.Matchers.*;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+@RunWith(MockitoJUnitRunner.class)
+public class BaseFieldSupplierTest {
+
+    @Mock
+    private LogEvent event;
+
+    private Log4jContextFieldSupplier baseFieldSupplier = new BaseFieldSupplier();
+
+    @Before
+    public void initializeEvent() {
+        when(event.getInstant()).thenReturn(mock(Instant.class));
+    }
+
+    @Test
+    public void addsNoExceptionFieldsWithoutException() {
+        Map<String, Object> fields = baseFieldSupplier.map(event);
+
+        assertThat(fields, not(hasKey(Fields.EXCEPTION_TYPE)));
+        assertThat(fields, not(hasKey(Fields.EXCEPTION_MESSAGE)));
+    }
+
+    @Test
+    public void mapsException() {
+        Exception exception = new RuntimeException("exception message");
+        when(event.getThrown()).thenReturn(exception);
+
+        Map<String, Object> fields = baseFieldSupplier.map(event);
+
+        assertThat(fields, hasEntry(Fields.EXCEPTION_TYPE, RuntimeException.class.getName()));
+        assertThat(fields, hasEntry(Fields.EXCEPTION_MESSAGE, "exception message"));
+    }
+}

cf-java-logging-support-logback/src/main/java/com/sap/hcp/cf/logback/encoder/BaseFieldSupplier.java

@@ -4,12 +4,14 @@
 import java.util.HashMap;
 import java.util.Map;
 
+import ch.qos.logback.classic.spi.ThrowableProxy;
 import com.sap.hcp.cf.logback.converter.api.LogbackContextFieldSupplier;
 import com.sap.hcp.cf.logging.common.Defaults;
 import com.sap.hcp.cf.logging.common.Fields;
 import com.sap.hcp.cf.logging.common.Markers;
 
 import ch.qos.logback.classic.spi.ILoggingEvent;
+import org.apache.commons.lang3.StringUtils;
 
 public class BaseFieldSupplier implements LogbackContextFieldSupplier {
 
@@ -25,6 +27,13 @@ public Map<String, Object> map(ILoggingEvent event) {
         if (!isRequestLog(event)) {
             fields.put(Fields.MSG, event.getFormattedMessage());
         }
+        if (event.getThrowableProxy() != null && event.getThrowableProxy() instanceof ThrowableProxy) {
+            Throwable throwable = ((ThrowableProxy) event.getThrowableProxy()).getThrowable();
+            fields.put(Fields.EXCEPTION_TYPE, throwable.getClass().getName());
+            if (StringUtils.isNotBlank(throwable.getMessage())) {
+                fields.put(Fields.EXCEPTION_MESSAGE, throwable.getMessage());
+            }
+        }
         return fields;
     }
 

cf-java-logging-support-logback/src/test/java/com/sap/hcp/cf/logback/encoder/BaseFieldSupplierTest.java

@@ -0,0 +1,49 @@
+package com.sap.hcp.cf.logback.encoder;
+
+import ch.qos.logback.classic.spi.ILoggingEvent;
+import ch.qos.logback.classic.spi.ThrowableProxy;
+import com.sap.hcp.cf.logback.converter.api.LogbackContextFieldSupplier;
+import com.sap.hcp.cf.logging.common.Fields;
+import org.apache.commons.math3.stat.inference.GTest;
+import org.hamcrest.MatcherAssert;
+import org.hamcrest.Matchers;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.Mockito;
+import org.mockito.runners.MockitoJUnitRunner;
+
+import java.util.Map;
+
+import static org.hamcrest.Matchers.hasEntry;
+import static org.hamcrest.MatcherAssert.*;
+import static org.hamcrest.Matchers.*;
+import static org.mockito.Mockito.when;
+
+@RunWith(MockitoJUnitRunner.class)
+public class BaseFieldSupplierTest {
+
+    @Mock
+    private ILoggingEvent event;
+
+    private LogbackContextFieldSupplier baseFieldSupplier = new BaseFieldSupplier();
+
+    @Test
+    public void addsNoExceptionFieldsWithoutException() {
+        Map<String, Object> fields = baseFieldSupplier.map(event);
+
+        assertThat(fields, not(hasKey(Fields.EXCEPTION_TYPE)));
+        assertThat(fields, not(hasKey(Fields.EXCEPTION_MESSAGE)));
+    }
+
+    @Test
+    public void mapsException() {
+        Exception exception = new RuntimeException("exception message");
+        when(event.getThrowableProxy()).thenReturn(new ThrowableProxy(exception));
+
+        Map<String, Object> fields = baseFieldSupplier.map(event);
+
+        assertThat(fields, hasEntry(Fields.EXCEPTION_TYPE, RuntimeException.class.getName()));
+        assertThat(fields, hasEntry(Fields.EXCEPTION_MESSAGE, "exception message"));
+    }
+}