GH-1140 Add data masking capabilities for JSON logging

Resolves #1140

spring-cloud-function-context/src/main/java/org/springframework/cloud/function/utils/JsonMasker.java

@@ -0,0 +1,140 @@
+/*
+ * Copyright 2024-2024 the original author or authors.
+ *
+ * Licensed 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
+ *
+ *      https://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.springframework.cloud.function.utils;
+
+import java.net.URI;
+import java.net.URL;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Collection;
+import java.util.Enumeration;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.TreeSet;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.SerializationFeature;
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+
+import org.springframework.cloud.function.json.JacksonMapper;
+import org.springframework.cloud.function.json.JsonMapper;
+import org.springframework.util.ClassUtils;
+
+
+/**
+ * @author Oleg Zhurakousky
+ */
+public final class JsonMasker {
+
+	private static final Log logger = LogFactory.getLog(JsonMasker.class);
+
+	private static JsonMasker jsonMasker;
+
+	private final JacksonMapper mapper;
+
+	private final Set<String> keysToMask;
+
+	private JsonMasker() {
+		this.keysToMask = loadKeys();
+		this.mapper = new JacksonMapper(new ObjectMapper().enable(SerializationFeature.INDENT_OUTPUT));
+
+	}
+
+	public synchronized static JsonMasker INSTANCE() {
+		if (jsonMasker == null) {
+			jsonMasker = new JsonMasker();
+		}
+		return jsonMasker;
+	}
+
+	public synchronized static JsonMasker INSTANCE(Set<String> keysToMask) {
+		INSTANCE().addKeys(keysToMask);
+		return jsonMasker;
+	}
+
+	public String[] getKeysToMask() {
+		return keysToMask.toArray(new String[0]);
+	}
+
+	public String mask(Object json) {
+		if (!JsonMapper.isJsonString(json)) {
+			return (String) json;
+		}
+		Object map = this.mapper.fromJson(json, Object.class);
+		return this.iterate(map);
+	}
+
+	@SuppressWarnings({ "unchecked" })
+	private String iterate(Object json) {
+		if (json instanceof Collection arrayValue) {
+			for (Object element : arrayValue) {
+				if (element instanceof Map mapElement) {
+					for (Map.Entry<String, Object> entry : ((Map<String, Object>) mapElement).entrySet()) {
+						this.doMask(entry.getKey(), entry);
+					}
+				}
+			}
+		}
+		else if (json instanceof Map mapElement) {
+			for (Map.Entry<String, Object> entry : ((Map<String, Object>) mapElement).entrySet()) {
+				this.doMask(entry.getKey(), entry);
+			}
+		}
+		return new String(this.mapper.toJson(json), StandardCharsets.UTF_8);
+	}
+
+	private void doMask(String key, Map.Entry<String, Object> entry) {
+		if (this.keysToMask.contains(key)) {
+			entry.setValue("*******");
+		}
+		else if (entry.getValue() instanceof Map) {
+			this.iterate(entry.getValue());
+		}
+		else if (entry.getValue() instanceof Collection) {
+			this.iterate(entry.getValue());
+		}
+	}
+
+	private static Set<String> loadKeys() {
+		Set<String> finalKeysToMask = new TreeSet<>();
+		try {
+			Enumeration<URL> resources = ClassUtils.getDefaultClassLoader().getResources("META-INF/mask.keys");
+			while (resources.hasMoreElements()) {
+				URI uri = resources.nextElement().toURI();
+				List<String> lines = Files.readAllLines(Path.of(uri));
+				for (String line : lines) {
+					// need to split in case if delimited
+					String[] keys = line.split(",");
+					for (int i = 0; i < keys.length; i++) {
+						finalKeysToMask.add(keys[i].trim());
+					}
+				}
+			}
+		}
+		catch (Exception e) {
+			logger.warn("Failed to load keys to mask. No keys will be masked", e);
+		}
+		return finalKeysToMask;
+	}
+
+	private void addKeys(Set<String> keys) {
+		this.keysToMask.addAll(keys);
+	}
+}