org.springframework.vault.core.util.PropertyTransformers.java Source code

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/*
 * Copyright 2017-2019 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.vault.core.util;

import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Map.Entry;

import org.springframework.util.Assert;

/**
 * Implementations of {@link PropertyTransformer} that provide various useful property
 * transformation operations, prefixing, etc.
 *
 * @author Mark Paluch
 */
public abstract class PropertyTransformers {

    /**
     * @return "no-operation" transformer which simply returns given name as is. Used
     * commonly as placeholder or marker.
     */
    public static PropertyTransformer noop() {
        return NoOpPropertyTransformer.instance();
    }

    /**
     * @return removes {@literal null} value properties.
     */
    public static PropertyTransformer removeNullProperties() {
        return RemoveNullProperties.instance();
    }

    /**
     * @param propertyNamePrefix the prefix to add to each property name.
     * @return {@link PropertyTransformer} to add {@code propertyNamePrefix} to each
     * property name.
     */
    public static PropertyTransformer propertyNamePrefix(String propertyNamePrefix) {
        return KeyPrefixPropertyTransformer.forPrefix(propertyNamePrefix);
    }

    /**
     * {@link PropertyTransformer} that passes the given properties through without
     * returning changed properties.
     */
    static class NoOpPropertyTransformer implements PropertyTransformer {

        static NoOpPropertyTransformer INSTANCE = new NoOpPropertyTransformer();

        private NoOpPropertyTransformer() {
        }

        /**
         * @return the {@link PropertyTransformer} instance.
         */
        public static PropertyTransformer instance() {
            return INSTANCE;
        }

        @Override
        public Map<String, Object> transformProperties(Map<String, ? extends Object> input) {
            return (Map) input;
        }
    }

    /**
     * {@link PropertyTransformer} to remove {@literal null}-value properties.
     */
    static class RemoveNullProperties implements PropertyTransformer {

        static RemoveNullProperties INSTANCE = new RemoveNullProperties();

        private RemoveNullProperties() {
        }

        /**
         * @return the {@link PropertyTransformer} instance.
         */
        public static PropertyTransformer instance() {
            return INSTANCE;
        }

        @Override
        public Map<String, Object> transformProperties(Map<String, ? extends Object> input) {

            Map<String, Object> target = new LinkedHashMap<>(input.size(), 1);

            for (Entry<String, ? extends Object> entry : input.entrySet()) {

                if (entry.getValue() == null) {
                    continue;
                }

                target.put(entry.getKey(), entry.getValue());
            }

            return target;
        }
    }

    /**
     * {@link PropertyTransformer} that adds a prefix to each key name.
     */
    static class KeyPrefixPropertyTransformer implements PropertyTransformer {

        private final String propertyNamePrefix;

        private KeyPrefixPropertyTransformer(String propertyNamePrefix) {

            Assert.notNull(propertyNamePrefix, "Property name prefix must not be null");

            this.propertyNamePrefix = propertyNamePrefix;
        }

        /**
         * Create a new {@link KeyPrefixPropertyTransformer} that adds a prefix to each
         * key name.
         * @param propertyNamePrefix the property name prefix to be added in front of each
         *     property name, must not be {@literal null}.
         * @return a new {@link KeyPrefixPropertyTransformer} that adds a prefix to each
         * key name.
         */
        public static PropertyTransformer forPrefix(String propertyNamePrefix) {
            return new KeyPrefixPropertyTransformer(propertyNamePrefix);
        }

        @Override
        public Map<String, Object> transformProperties(Map<String, ? extends Object> input) {

            Map<String, Object> target = new LinkedHashMap<>(input.size(), 1);

            for (Entry<String, ? extends Object> entry : input.entrySet()) {
                target.put(propertyNamePrefix + entry.getKey(), entry.getValue());
            }

            return target;
        }
    }
}