fix SLF4J-463

qos-ch · Aug 9, 2019 · acc9150 · degroves · Aug 9, 2019 · acc9150
1 parent d507426
commit acc9150
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Showing 5 changed files with 73 additions and 6 deletions.
diff --git a/slf4j-api/src/main/java/org/slf4j/LoggerFactory.java b/slf4j-api/src/main/java/org/slf4j/LoggerFactory.java
@@ -148,6 +148,7 @@ private final static void bind() {
             reportMultipleBindingAmbiguity(providersList);
             if (providersList != null && !providersList.isEmpty()) {
             	PROVIDER = providersList.get(0);
+            	// SLF4JServiceProvider.initialize() is intended to be called here and nowhere else.
             	PROVIDER.initialize();
             	INITIALIZATION_STATE = SUCCESSFUL_INITIALIZATION;
                 reportActualBinding(providersList);

diff --git a/slf4j-api/src/main/java/org/slf4j/MarkerFactory.java b/slf4j-api/src/main/java/org/slf4j/MarkerFactory.java
@@ -52,7 +52,6 @@ private MarkerFactory() {
     static {
         SLF4JServiceProvider provider = LoggerFactory.getProvider();
         if (provider != null) {
-        	provider.initialize();
             MARKER_FACTORY = provider.getMarkerFactory();
         } else {
             Util.report("Failed to find provider");

diff --git a/slf4j-api/src/main/java/org/slf4j/spi/SLF4JServiceProvider.java b/slf4j-api/src/main/java/org/slf4j/spi/SLF4JServiceProvider.java
@@ -2,32 +2,51 @@
 
 import org.slf4j.ILoggerFactory;
 import org.slf4j.IMarkerFactory;
+import org.slf4j.LoggerFactory;
 
+/**
+ * This interface based on {@link java.util.ServiceLoader} paradigm. 
+ * 
+ * <p>It replaces the old static-binding mechanism used in SLF4J versions 1.0.x to 1.7.x.
+ *
+ * @author Ceki G&uml;lc&uml;
+ * @since 1.8
+ */
 public interface SLF4JServiceProvider {
 
 
     /**
      * Return the instance of {@link ILoggerFactory} that 
      * {@link org.slf4j.LoggerFactory} class should bind to.
      * 
-     * @return the instance of {@link ILoggerFactory} that 
-     * {@link org.slf4j.LoggerFactory} class should bind to.
+     * @return instance of {@link ILoggerFactory} 
      */
     public ILoggerFactory getLoggerFactory();
 
     /**
      * Return the instance of {@link IMarkerFactory} that 
      * {@link org.slf4j.MarkerFactory} class should bind to.
      * 
-     * @return the instance of {@link IMarkerFactory} that 
-     * {@link org.slf4j.MarkerFactory} class should bind to.
+     * @return instance of {@link IMarkerFactory} 
      */
     public IMarkerFactory getMarkerFactory();
 
-
+    /**
+     * Return the instnace of {@link MDCAdapter} that
+     * {@link MDC} should bind to.
+     * 
+     * @return instance of {@link MDCAdapter} 
+     */
     public MDCAdapter getMDCAdapter();
 
     public String getRequesteApiVersion();
 
+    /**
+     * Initialize the logging back-end.
+     * 
+     * <p><b>WARNING:</b> This method is intended to be called once by 
+     * {@link LoggerFactory} class and from nowhere else. 
+     * 
+     */
     public void initialize();
 }
diff --git a/slf4j-simple/src/main/java/org/slf4j/simple/DoubleInitializationPitfallTest.java b/slf4j-simple/src/main/java/org/slf4j/simple/DoubleInitializationPitfallTest.java
@@ -0,0 +1,37 @@
+package org.slf4j.simple;
+
+import static org.junit.Assert.fail;
+
+import org.junit.Test;
+import org.slf4j.ILoggerFactory;
+import org.slf4j.LoggerFactory;
+import org.slf4j.MDC;
+import org.slf4j.MarkerFactory;
+
+public class DoubleInitializationPitfallTest {
+
+
+	@Test
+	public void verifyImpactOfMarkerFactory() {
+		ILoggerFactory firstFactory = LoggerFactory.getILoggerFactory();
+		MarkerFactory.getMarker("DOUBLE_INIT");
+		ILoggerFactory secondFactory = LoggerFactory.getILoggerFactory();
+
+		if(firstFactory != secondFactory) {
+			fail("MarkerFactory.getMarker causes multiple provider initialization");
+		}
+	}
+
+	@Test
+	public void verifyImpactOfMDC() {
+		ILoggerFactory firstFactory = LoggerFactory.getILoggerFactory();
+		MDC.put("DoubleInitializationPitfallTest", "a");
+		ILoggerFactory secondFactory = LoggerFactory.getILoggerFactory();
+
+		if(firstFactory != secondFactory) {
+			fail("MarkerFactory.getMarker causes multiple provider initialization");
+		}
+	}
+
+
+}
diff --git a/slf4j-site/src/site/pages/news.html b/slf4j-site/src/site/pages/news.html
@@ -37,6 +37,17 @@ <h1>SLF4J News</h1>
      class names in <code/>
    -->
 
+
+   <hr noshade="noshade" size="1"/>
+   <h3> 2019  - Release of SLF4J 2.0.0-alpha1</h3>
+
+
+   <p>&bull; Fix the double back-end initializatoin problem reported
+   in <a href="https://jira.qos.ch/browse/SLF4J-463">SLF4J-463</a> by
+   Dan Groves who also provided a test-case to reptoduce the problem
+   and a relevant fix.
+   </p>
+
    <hr noshade="noshade" size="1"/>
 
    <h3>6th of August, 2019 - Release of SLF4J 1.7.27</h3>