Merge pull request #776 from CJSCommonPlatform/add-debug-logger

Add debug logger

Author: mapingo

CHANGELOG.md

@@ -4,6 +4,8 @@ on [Keep a CHANGELOG](http://keepachangelog.com/). This project adheres to
 [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased]
+### Added
+- Injectable debug logger that logs only if debug logging is set. 
 
 ## [6.1.0] - 2018-09-28
 ### Changed

messaging/messaging-core/src/main/java/uk/gov/justice/services/messaging/logging/DebugLogger.java

@@ -0,0 +1,19 @@
+package uk.gov.justice.services.messaging.logging;
+
+import java.util.function.Supplier;
+
+import org.slf4j.Logger;
+
+public class DebugLogger {
+
+    public void debug(final Logger logger, final Supplier<String> message) {
+
+        if (logger.isDebugEnabled()) {
+            try {
+                logger.debug(message.get());
+            } catch (final Exception e) {
+                logger.error("Could not generate debug log message", e);
+            }
+        }
+    }
+}

messaging/messaging-core/src/test/java/uk/gov/justice/services/messaging/logging/DebugLoggerTest.java

@@ -0,0 +1,58 @@
+package uk.gov.justice.services.messaging.logging;
+
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoMoreInteractions;
+import static org.mockito.Mockito.when;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.InjectMocks;
+import org.mockito.Mock;
+import org.mockito.runners.MockitoJUnitRunner;
+import org.slf4j.Logger;
+
+@RunWith(MockitoJUnitRunner.class)
+public class DebugLoggerTest {
+
+    @Mock
+    private Logger logger;
+
+    @InjectMocks
+    private DebugLogger debugLogger;
+
+    @Test
+    public void shouldLogNameIfDebugIsTrue() {
+
+        when(logger.isDebugEnabled()).thenReturn(true);
+
+        debugLogger.debug(logger, () -> "Test Message");
+
+        verify(logger).debug("Test Message");
+    }
+
+    @Test
+    public void shouldNotLogNameIfDebugIsFalse() {
+
+        when(logger.isDebugEnabled()).thenReturn(false);
+
+        debugLogger.debug(logger, () -> "Test Message");
+
+        verify(logger).isDebugEnabled();
+        verifyNoMoreInteractions(logger);
+    }
+
+    @Test
+    public void shouldLogErrorIfExceptionIsThrownWhenLogging() {
+
+        final RuntimeException runtimeException = new RuntimeException();
+
+        when(logger.isDebugEnabled()).thenReturn(true);
+
+        debugLogger.debug(logger, () -> {
+            throw runtimeException;
+        });
+
+        verify(logger).isDebugEnabled();
+        verify(logger).error("Could not generate debug log message", runtimeException);
+    }
+}