Provide servlet request listener which fill the MDC

This is seen as superior to a filter as the MDC is not cleared before an error handler servlet is executed.

Signed-off-by: Sven Strickroth <[email protected]>

logback-classic/src/main/java/ch/qos/logback/classic/helpers/MDCInsertingServletRequestListener.java

@@ -0,0 +1,73 @@
+/**
+ * Logback: the reliable, generic, fast and flexible logging framework.
+ * Copyright (C) 1999-2015, 2024, QOS.ch. All rights reserved.
+ *
+ * This program and the accompanying materials are dual-licensed under
+ * either the terms of the Eclipse Public License v1.0 as published by
+ * the Eclipse Foundation
+ *
+ *   or (per the licensee's choosing)
+ *
+ * under the terms of the GNU Lesser General Public License version 2.1
+ * as published by the Free Software Foundation.
+ */
+package ch.qos.logback.classic.helpers;
+
+import javax.servlet.ServletRequest;
+import javax.servlet.ServletRequestEvent;
+import javax.servlet.ServletRequestListener;
+import javax.servlet.http.HttpServletRequest;
+
+import org.slf4j.MDC;
+
+import ch.qos.logback.classic.ClassicConstants;
+
+/**
+ * A simple servlet request listener that stores the remote address,
+ * used HTTP method, and 
+ *
+ * <p> The value is removed from the MDC once the request has
+ * been fully processed (including an error handler servlet).
+ *
+ * @author Sven Strickroth
+ * @author Ceki G&uuml;lc&uuml;
+ */
+public class MDCInsertingServletRequestListener implements ServletRequestListener {
+    @Override
+    public void requestInitialized(ServletRequestEvent sre) {
+        insertIntoMDC(sre.getServletRequest());
+    }
+
+    @Override
+    public void requestDestroyed(ServletRequestEvent sre) {
+        clearMDC();
+    }
+
+    private void insertIntoMDC(final ServletRequest request) {
+        MDC.put(ClassicConstants.REQUEST_REMOTE_HOST_MDC_KEY, request.getRemoteHost());
+
+        if (request instanceof HttpServletRequest) {
+            HttpServletRequest httpServletRequest = (HttpServletRequest) request;
+            MDC.put(ClassicConstants.REQUEST_REQUEST_URI, httpServletRequest.getRequestURI());
+            StringBuffer requestURL = httpServletRequest.getRequestURL();
+            if (requestURL != null) {
+                MDC.put(ClassicConstants.REQUEST_REQUEST_URL, requestURL.toString());
+            }
+            MDC.put(ClassicConstants.REQUEST_METHOD, httpServletRequest.getMethod());
+            MDC.put(ClassicConstants.REQUEST_QUERY_STRING, httpServletRequest.getQueryString());
+            MDC.put(ClassicConstants.REQUEST_USER_AGENT_MDC_KEY, httpServletRequest.getHeader("User-Agent"));
+            MDC.put(ClassicConstants.REQUEST_X_FORWARDED_FOR, httpServletRequest.getHeader("X-Forwarded-For"));
+        }
+    }
+
+    private void clearMDC() {
+        MDC.remove(ClassicConstants.REQUEST_REMOTE_HOST_MDC_KEY);
+        MDC.remove(ClassicConstants.REQUEST_REQUEST_URI);
+        MDC.remove(ClassicConstants.REQUEST_QUERY_STRING);
+        // removing possibly nonexistent item is OK
+        MDC.remove(ClassicConstants.REQUEST_REQUEST_URL);
+        MDC.remove(ClassicConstants.REQUEST_METHOD);
+        MDC.remove(ClassicConstants.REQUEST_USER_AGENT_MDC_KEY);
+        MDC.remove(ClassicConstants.REQUEST_X_FORWARDED_FOR);
+    }
+}

logback-examples/src/main/java/chapters/mdc/UserServletRequestListener.java

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+/**
+ * Logback: the reliable, generic, fast and flexible logging framework.
+ * Copyright (C) 1999-2015, 2024, QOS.ch. All rights reserved.
+ *
+ * This program and the accompanying materials are dual-licensed under
+ * either the terms of the Eclipse Public License v1.0 as published by
+ * the Eclipse Foundation
+ *
+ *   or (per the licensee's choosing)
+ *
+ * under the terms of the GNU Lesser General Public License version 2.1
+ * as published by the Free Software Foundation.
+ */
+package ch.qos.logback.classic.helpers;
+
+import java.security.Principal;
+
+import javax.servlet.ServletRequestEvent;
+import javax.servlet.ServletRequestListener;
+import javax.servlet.annotation.WebListener;
+import javax.servlet.http.HttpServletRequest;
+
+import org.slf4j.MDC;
+
+/**
+ * A simple servlet request listener that stores the username
+ * found in the Principal in the MDC.
+ *
+ * <p> The value is removed from the MDC once the request has
+ * been fully processed (including an error handler servlet).
+ *
+ * @author Sven Strickroth
+ * @author S&eacute;bastien Pennec
+ */
+@WebListener
+public class UserServletRequestListener implements ServletRequestListener {
+
+    private final String USER_KEY = "username";
+
+    @Override
+    public void requestDestroyed(ServletRequestEvent sre) {
+        MDC.clear();
+    }
+
+    @Override
+    public void requestInitialized(ServletRequestEvent sre) {
+        if (sre.getServletRequest() instanceof HttpServletRequest) {
+            HttpServletRequest request = (HttpServletRequest) sre.getServletRequest();
+            Principal principal = request.getUserPrincipal();
+            if (principal != null) {
+                String username = principal.getName();
+                registerUsername(username);
+            }
+        }
+    }
+
+    private void registerUsername(final String username) {
+        if (username != null && !username.trim().isEmpty()) {
+            MDC.put(USER_KEY, username);
+        }
+    }
+}