Use less gson internally.

org.jdrupes.vmoperator.util/src/org/jdrupes/vmoperator/util/DataPath.java

@@ -0,0 +1,176 @@
+/*
+ * VM-Operator
+ * Copyright (C) 2023 Michael N. Lipp
+ * 
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package org.jdrupes.vmoperator.util;
+
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.logging.Logger;
+
+/**
+ * Utility class that supports navigation through arbitrary data structures.
+ */
+public final class DataPath {
+
+    private static final Logger logger
+        = Logger.getLogger(DataPath.class.getName());
+
+    private DataPath() {
+    }
+
+    /**
+     * Apply the given selectors on the given object and return the
+     * value reached.
+     * 
+     * Selectors can be if type {@link String} or {@link Number}. The
+     * former are used to access a property of an object, the latter to
+     * access an element in an array or a {@link List}.
+     * 
+     * Depending on the object currently visited, a {@link String} can
+     * be the key of a {@link Map}, the property part of a getter method
+     * or the name of a method that has an empty parameter list.
+     *
+     * @param <T> the generic type
+     * @param from the from
+     * @param selectors the selectors
+     * @return the result
+     */
+    @SuppressWarnings("PMD.UseLocaleWithCaseConversions")
+    public static <T> Optional<T> get(Object from, Object... selectors) {
+        Object cur = from;
+        for (var selector : selectors) {
+            if (cur == null) {
+                return Optional.empty();
+            }
+            if (selector instanceof String && cur instanceof Map map) {
+                cur = map.get(selector);
+                continue;
+            }
+            if (selector instanceof Number index && cur instanceof List list) {
+                cur = list.get(index.intValue());
+                continue;
+            }
+            if (selector instanceof String property) {
+                var retrieved = tryAccess(cur, property);
+                if (retrieved.isEmpty()) {
+                    return Optional.empty();
+                }
+                cur = retrieved.get();
+            }
+        }
+        @SuppressWarnings("unchecked")
+        var result = Optional.ofNullable((T) cur);
+        return result;
+    }
+
+    @SuppressWarnings("PMD.UseLocaleWithCaseConversions")
+    private static Optional<Object> tryAccess(Object obj, String property) {
+        Method acc = null;
+        try {
+            // Try getter
+            acc = obj.getClass().getMethod("get" + property.substring(0, 1)
+                .toUpperCase() + property.substring(1));
+        } catch (SecurityException e) {
+            return Optional.empty();
+        } catch (NoSuchMethodException e) { // NOPMD
+            // Can happen...
+        }
+        if (acc == null) {
+            try {
+                // Try method
+                acc = obj.getClass().getMethod(property);
+            } catch (SecurityException | NoSuchMethodException e) {
+                return Optional.empty();
+            }
+        }
+        if (acc != null) {
+            try {
+                return Optional.ofNullable(acc.invoke(obj));
+            } catch (IllegalAccessException
+                    | InvocationTargetException e) {
+                return Optional.empty();
+            }
+        }
+        return Optional.empty();
+    }
+
+    /**
+     * Attempts to make a as-deep-as-possible copy of the given
+     * container. New containers will be created for Maps, Lists and
+     * Arrays. The method is invoked recursively for the entries/items.
+     * 
+     * If invoked with an object that is neither a map, list or array,
+     * the methods checks if the object implements {@link Cloneable}
+     * and if it does, invokes its {@link Object#clone()} method.
+     * Else the method return the object.
+     *
+     * @param <T> the generic type
+     * @param object the container
+     * @return the t
+     */
+    @SuppressWarnings({ "PMD.CognitiveComplexity", "unchecked" })
+    public static <T> T deepCopy(T object) {
+        if (object instanceof Map map) {
+            @SuppressWarnings("PMD.UseConcurrentHashMap")
+            Map<Object, Object> copy;
+            try {
+                copy = (Map<Object, Object>) object.getClass().getConstructor()
+                    .newInstance();
+            } catch (InstantiationException | IllegalAccessException
+                    | IllegalArgumentException | InvocationTargetException
+                    | NoSuchMethodException | SecurityException e) {
+                logger.severe(
+                    () -> "Cannot create new instance of " + object.getClass());
+                return null;
+            }
+            for (var entry : ((Map<?, ?>) map).entrySet()) {
+                copy.put(entry.getKey(),
+                    deepCopy(entry.getValue()));
+            }
+            return (T) copy;
+        }
+        if (object instanceof List list) {
+            List<Object> copy = new ArrayList<>();
+            for (var item : list) {
+                copy.add(deepCopy(item));
+            }
+            return (T) copy;
+        }
+        if (object.getClass().isArray()) {
+            var copy = new ArrayList<>();
+            for (var item : (Object[]) object) {
+                copy.add(deepCopy(item));
+            }
+            return (T) copy.toArray();
+        }
+        if (object instanceof Cloneable) {
+            try {
+                return (T) object.getClass().getMethod("clone")
+                    .invoke(object);
+            } catch (IllegalAccessException | InvocationTargetException
+                    | NoSuchMethodException | SecurityException e) {
+                return object;
+            }
+        }
+        return object;
+    }
+}