feat(Foundation): added JSONFormatter, supporting JSON-formatted logging

Foundation/include/Poco/JSONFormatter.h

@@ -0,0 +1,109 @@
+//
+// JSONFormatter.h
+//
+// Library: Foundation
+// Package: Logging
+// Module:  JSONFormatter
+//
+// Definition of the JSONFormatter class.
+//
+// Copyright (c) 2024, Applied Informatics Software Engineering GmbH.
+// and Contributors.
+//
+// SPDX-License-Identifier:	BSL-1.0
+//
+
+
+#ifndef Foundation_JSONFormatter_INCLUDED
+#define Foundation_JSONFormatter_INCLUDED
+
+
+#include "Poco/Foundation.h"
+#include "Poco/Formatter.h"
+#include "Poco/Message.h"
+#include <vector>
+
+
+namespace Poco {
+
+
+class Foundation_API JSONFormatter: public Formatter
+	/// This formatter formats log messages as compact 
+	/// (no unnecessary whitespace) single-line JSON strings.
+	///
+	/// The following JSON schema is used:
+	///     {
+	///         "timestamp": "2024-09-26T13:41:23.324461Z",
+	///         "source": "sample",
+	///         "level": "information",
+	///         "message": "This is a test message.",
+	///         "thread": 12,
+	///         "file": "source.cpp",
+	///         "line": 456,
+	///         "params": {
+	///             "prop1": "value1"
+	///         }
+	///     }
+	///
+	/// The "file" and "line" properties will only be included if the log
+	/// message contains a file name and line number.
+	///
+	/// The "params" object will only be included if custom parameters
+	/// have been added to the Message.
+{
+public:
+	using Ptr = AutoPtr<JSONFormatter>;
+
+	JSONFormatter() = default;
+		/// Creates a JSONFormatter.
+
+	~JSONFormatter() = default;
+		/// Destroys the JSONFormatter.
+
+	void format(const Message& msg, std::string& text);
+		/// Formats the message as a JSON string.
+
+	void setProperty(const std::string& name, const std::string& value);
+		/// Sets the property with the given name to the given value.
+		///
+		/// The following properties are supported:
+		///
+		///     * times: Specifies whether times are adjusted for local time
+		///       or taken as they are in UTC. Supported values are "local" and "UTC".
+		///     * thread: Specifies the value given for the thread. Can be
+		///       "none" (excluded), "name" (thread name), "id" (POCO thread ID) or "osid" 
+		///       (operating system thread ID).
+		///
+		/// If any other property name is given, a PropertyNotSupported
+		/// exception is thrown.
+
+	std::string getProperty(const std::string& name) const;
+		/// Returns the value of the property with the given name or
+		/// throws a PropertyNotSupported exception if the given
+		/// name is not recognized.
+
+	static const std::string PROP_TIMES;
+	static const std::string PROP_THREAD;
+
+protected:
+	std::string getThread(const Message& message) const;
+	static const std::string& getPriorityName(int prio);
+
+	enum ThreadFormat
+	{
+		JSONF_THREAD_NONE = 0,
+		JSONF_THREAD_NAME = 1,
+		JSONF_THREAD_ID = 2,
+		JSONF_THREAD_OS_ID = 3
+	};
+
+private:
+	bool _localTime = false;
+	ThreadFormat _threadFormat = JSONF_THREAD_ID;
+};
+
+
+} // namespace Poco
+
+
+#endif // Foundation_JSONFormatter_INCLUDED