1 files changed, 165 insertions, 0 deletions
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/runtime/parser/LogContext.java b/velocity-engine-core/src/main/java/org/apache/velocity/runtime/parser/LogContext.java
new file mode 100644
index 00000000..c6738cd5
--- /dev/null
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/runtime/parser/LogContext.java
@@ -0,0 +1,165 @@
+package org.apache.velocity.runtime.parser;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import org.apache.velocity.runtime.parser.node.SimpleNode;
+import org.apache.velocity.util.introspection.Info;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.slf4j.MDC;
+
+import java.util.ArrayDeque;
+import java.util.ArrayList;
+import java.util.Deque;
+import java.util.List;
+
+/**
+ * <p>Track location in template files during rendering by populating the slf4j MDC tags <code>file</code>, <code>line</code> and <code>column</code>.</p>
+ * <p>An MDC-aware logger can then use this info to display the template location in the message</p>
+ * <p>For instance with webapp-slf4j-logger, it's enough to use <code>%file</code>, <code>%line</code> and <code>%column</code> in the logger format string.</p>
+ * <p>Since this feature can have a performance impact, it has to be enabled in <code>velocity.properties</code> using:</p>
+ * <pre><code>runtime.log.track_location = true</code></pre>
+ * <p>(typically in a development environment)</p>
+ *
+ * @author Claude Brisson
+ * @version $Id:$
+ * @since 2.2
+ */
+
+public class LogContext
+{
+    protected static Logger logger = LoggerFactory.getLogger("rendering");
+
+    public static final String MDC_FILE = "file";
+    public static final String MDC_LINE = "line";
+    public static final String MDC_COLUMN = "column";
+
+    private boolean trackLocation;
+
+    public LogContext(boolean trackLocation)
+    {
+        this.trackLocation = trackLocation;
+    }
+
+    private static ThreadLocal<Deque<StackElement>> contextStack = new ThreadLocal<Deque<StackElement>>()
+    {
+        @Override
+        public Deque<StackElement> initialValue()
+        {
+            return new ArrayDeque<>();
+        }
+    };
+
+    private static class StackElement
+    {
+        protected StackElement(SimpleNode src, Info info)
+        {
+            this.src = src;
+            this.info = info;
+        }
+
+        protected SimpleNode src;
+        protected int count = 1;
+        protected Info info;
+    }
+
+    public void pushLogContext(SimpleNode src, Info info)
+    {
+        if (!trackLocation)
+        {
+            return;
+        }
+        Deque<StackElement> stack = contextStack.get();
+        StackElement last = stack.peek();
+        if (last != null && last.src == src)
+        {
+            ++last.count;
+        }
+        else
+        {
+            stack.push(new StackElement(src, info));
+            setLogContext(info);
+        }
+    }
+
+    public void popLogContext()
+    {
+        if (!trackLocation)
+        {
+            return;
+        }
+        Deque<StackElement> stack = contextStack.get();
+        StackElement last = stack.peek();
+        if (last == null)
+        {
+            logger.error("log context is already empty");
+            return;
+        }
+        if (--last.count == 0)
+        {
+            stack.pop();
+            last = stack.peek();
+            if (last == null)
+            {
+                clearLogContext();
+            }
+            else
+            {
+                setLogContext(last.info);
+            }
+        }
+    }
+
+    private void setLogContext(Info info)
+    {
+        MDC.put(MDC_FILE, info.getTemplateName());
+        MDC.put(MDC_LINE, String.valueOf(info.getLine()));
+        MDC.put(MDC_COLUMN, String.valueOf(info.getColumn()));
+    }
+
+    private void clearLogContext()
+    {
+        MDC.remove(MDC_FILE);
+        MDC.remove(MDC_LINE);
+        MDC.remove(MDC_COLUMN);
+    }
+
+    private static final String STACKTRACE_LINE = "    %s at %s[line %d, column %d]";
+
+    public String[] getStackTrace()
+    {
+        if (!trackLocation)
+        {
+            return null;
+        }
+        Deque<StackElement> stack = contextStack.get();
+        List<String> levels = new ArrayList<>();
+        for (StackElement level : stack)
+        {
+            String line = String.format(STACKTRACE_LINE,
+                level.src.literal(),
+                level.info.getTemplateName(),
+                level.info.getLine(),
+                level.info.getColumn());
+            levels.add(line);
+        }
+        return levels.size() > 0 ? levels.toArray(new String[levels.size()]) : null;
+    }
+}