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java/org/apache/tomcat/dbcp/pool2/impl/SecurityManagerCallStack.java

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+/*
+ * 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.
+ */
+package org.apache.tomcat.dbcp.pool2.impl;
+
+import java.io.PrintWriter;
+import java.lang.ref.WeakReference;
+import java.security.AccessController;
+import java.security.PrivilegedAction;
+import java.text.DateFormat;
+import java.text.SimpleDateFormat;
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * CallStack strategy using a {@link SecurityManager}. Obtaining the current call stack is much faster via a
+ * SecurityManger, but access to the underlying method may be restricted by the current SecurityManager. In environments
+ * where a SecurityManager cannot be created, {@link ThrowableCallStack} should be used instead.
+ *
+ * @see RuntimePermission
+ * @see SecurityManager#getClassContext()
+ * @since 2.4.3
+ */
+public class SecurityManagerCallStack implements CallStack {
+
+    private final String messageFormat;
+    //@GuardedBy("dateFormat")
+    private final DateFormat dateFormat;
+    private final PrivateSecurityManager securityManager;
+
+    private volatile Snapshot snapshot;
+
+    /**
+     * Create a new instance.
+     *
+     * @param messageFormat message format
+     * @param useTimestamp whether to format the dates in the output message or not
+     */
+    public SecurityManagerCallStack(final String messageFormat, final boolean useTimestamp) {
+        this.messageFormat = messageFormat;
+        this.dateFormat = useTimestamp ? new SimpleDateFormat(messageFormat) : null;
+        this.securityManager = AccessController.doPrivileged(new PrivilegedAction<PrivateSecurityManager>() {
+            @Override
+            public PrivateSecurityManager run() {
+                return new PrivateSecurityManager();
+            }
+        });
+    }
+
+    @Override
+    public boolean printStackTrace(final PrintWriter writer) {
+        final Snapshot snapshotRef = this.snapshot;
+        if (snapshotRef == null) {
+            return false;
+        }
+        final String message;
+        if (dateFormat == null) {
+            message = messageFormat;
+        } else {
+            synchronized (dateFormat) {
+                message = dateFormat.format(Long.valueOf(snapshotRef.timestamp));
+            }
+        }
+        writer.println(message);
+        for (final WeakReference<Class<?>> reference : snapshotRef.stack) {
+            writer.println(reference.get());
+        }
+        return true;
+    }
+
+    @Override
+    public void fillInStackTrace() {
+        snapshot = new Snapshot(securityManager.getCallStack());
+    }
+
+    @Override
+    public void clear() {
+        snapshot = null;
+    }
+
+    /**
+     * A custom security manager.
+     */
+    private static class PrivateSecurityManager extends SecurityManager {
+        /**
+         * Get the class stack.
+         *
+         * @return class stack
+         */
+        private List<WeakReference<Class<?>>> getCallStack() {
+            final Class<?>[] classes = getClassContext();
+            final List<WeakReference<Class<?>>> stack = new ArrayList<>(classes.length);
+            for (final Class<?> klass : classes) {
+                stack.add(new WeakReference<Class<?>>(klass));
+            }
+            return stack;
+        }
+    }
+
+    /**
+     * A snapshot of a class stack.
+     */
+    private static class Snapshot {
+        private final long timestamp = System.currentTimeMillis();
+        private final List<WeakReference<Class<?>>> stack;
+
+        /**
+         * Create a new snapshot with a class stack.
+         *
+         * @param stack class stack
+         */
+        private Snapshot(final List<WeakReference<Class<?>>> stack) {
+            this.stack = stack;
+        }
+    }
+}