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The AWS Java SDK for Amazon DynamoDB module holds the client classes that are used for communicating with Amazon DynamoDB Service

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/*
 * Copyright 2016-2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 *
 * 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:
 *
 *    http://aws.amazon.com/apache2.0
 *
 * This file 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 com.amazonaws.services.dynamodbv2.datamodeling;

import com.amazonaws.annotation.SdkInternalApi;
import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMapperFieldModel.DynamoDBAttributeType;
import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMapperFieldModel.Reflect;
import com.amazonaws.services.dynamodbv2.datamodeling.StandardAnnotationMaps.FieldMap;
import com.amazonaws.services.dynamodbv2.datamodeling.StandardAnnotationMaps.TableMap;
import com.amazonaws.util.StringUtils;

import java.lang.reflect.Method;
import java.util.Collections;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

/**
 * Reflection assistant for {@link DynamoDBMapper}
 */
@SdkInternalApi
final class StandardBeanProperties {

    /**
     * Returns the bean mappings for a given class (caches the results).
     */
    @SuppressWarnings("unchecked")
    static final  Beans of(Class clazz) {
        return ((CachedBeans)CachedBeans.CACHE).getBeans(clazz);
    }

    /**
     * Cache of {@link Beans} by class type.
     */
    private static final class CachedBeans {
        private static final CachedBeans CACHE = new CachedBeans();
        private final ConcurrentMap,Beans> cache = new ConcurrentHashMap,Beans>();

        private final Beans getBeans(Class clazz) {
            if (!cache.containsKey(clazz)) {
                final TableMap annotations = StandardAnnotationMaps.of(clazz);
                final BeanMap map = new BeanMap(clazz, false);
                cache.putIfAbsent(clazz, new Beans(annotations, map));
            }
            return cache.get(clazz);
        }
    }

    /**
     * Cache of {@link Bean} mappings by class type.
     */
    static final class Beans {
        private final DynamoDBMapperTableModel.Properties properties;
        private final Map> map;

        private Beans(TableMap annotations, Map> map) {
            this.properties = new DynamoDBMapperTableModel.Properties.Immutable(annotations);
            this.map = Collections.unmodifiableMap(map);
        }

        final DynamoDBMapperTableModel.Properties properties() {
            return this.properties;
        }

        final Map> map() {
            return this.map;
        }
    }

    /**
     * Holds the reflection bean properties for a given property.
     */
    static final class Bean {
        private final DynamoDBMapperFieldModel.Properties properties;
        private final ConvertibleType type;
        private final Reflect reflect;

        private Bean(FieldMap annotations, Reflect reflect, Method getter) {
            this.properties = new DynamoDBMapperFieldModel.Properties.Immutable(annotations);
            this.type = ConvertibleType.of(getter, annotations);
            this.reflect = reflect;
        }

        final DynamoDBMapperFieldModel.Properties properties() {
            return this.properties;
        }

        final ConvertibleType type() {
            return this.type;
        }

        final Reflect reflect() {
            return this.reflect;
        }
    }

    /**
     * Get/set reflection operations.
     */
    static final class MethodReflect implements Reflect {
        private final Method getter, setter;

        private MethodReflect(Method getter) {
            this.setter = setterOf(getter);
            this.getter = getter;
        }

        @Override
        public V get(T object) {
            try {
                return (V)getter.invoke(object);
            } catch (final Exception e) {
                throw new DynamoDBMappingException("could not invoke " + getter + " on " + object.getClass(), e);
            }
        }

        @Override
        public void set(T object, V value) {
            try {
                setter.invoke(object, value);
            } catch (final Exception e) {
                throw new DynamoDBMappingException("could not invoke " + setter + " on " + object.getClass() +
                    " with value " + value + " of type " + (value == null ? null : value.getClass()), e);
            }
        }

        static Method setterOf(Method getter) {
            try {
                final String name = "set" + getter.getName().replaceFirst("^(get|is)","");
                return getter.getDeclaringClass().getMethod(name, getter.getReturnType());
            } catch (final Exception no) {}
            return null;
        }
    }

    /**
     * Get/set reflection operations with a declaring property.
     */
    static final class DeclaringReflect implements Reflect {
        private final Reflect reflect;
        private final Reflect declaring;
        private final Class targetType;

        private DeclaringReflect(Method getter, Reflect declaring, Class targetType) {
            this.reflect = new MethodReflect(getter);
            this.declaring = declaring;
            this.targetType = targetType;
        }

        @Override
        public V get(T object) {
            final T declaringObject = declaring.get(object);
            if (declaringObject == null) {
                return null;
            }
            return reflect.get(declaringObject);
        }

        @Override
        public void set(T object, V value) {
            T declaringObject = declaring.get(object);
            if (declaringObject == null) {
                declaring.set(object, (declaringObject = newInstance(targetType)));
            }
            reflect.set(declaringObject, value);
        }

        static  T newInstance(Class targetType) {
            try {
                return targetType.newInstance();
            } catch (final Exception e) {
                throw new DynamoDBMappingException("could not instantiate " + targetType, e);
            }
        }
    }

    /**
     * {@link Map} of {@link Bean}
     */
    static final class BeanMap extends LinkedHashMap> {
        private final Class clazz;

        BeanMap(Class clazz, boolean inherited) {
            this.clazz = clazz;
            putAll(clazz, inherited);
        }

        private void putAll(Class clazz, boolean inherited) {
            for (final Method method : clazz.getMethods()) {
                if (canMap(method, inherited)) {
                    final FieldMap annotations = StandardAnnotationMaps.of(method, null);
                    if (!annotations.ignored()) {
                        final Reflect reflect = new MethodReflect(method);
                        putOrFlatten(annotations, reflect, method);
                    }
                }
            }
        }

        private void putOrFlatten(FieldMap annotations, Reflect reflect, Method getter) {
            if (annotations.flattened()) {
                flatten((Class)annotations.targetType(), annotations.attributes(), (Reflect)reflect);
            } else {
                final Bean bean = new Bean(annotations, reflect, getter);
                if (put(bean.properties().attributeName(), bean) != null) {
                    throw new DynamoDBMappingException("duplicate attribute name " + bean.properties().attributeName());
                }
            }
        }

        private void flatten(Class targetType, Map attributes, Reflect declaring) {
            for (final Method method : targetType.getMethods()) {
                if (canMap(method, true)) {
                    String name = fieldNameOf(method);
                    if ((name = attributes.remove(name)) == null) {
                        continue;
                    }
                    final FieldMap annotations = StandardAnnotationMaps.of(method, name);
                    if (!annotations.ignored()) {
                        final Reflect reflect = new DeclaringReflect(method, declaring, targetType);
                        putOrFlatten(annotations, reflect, method);
                    }
                }
            }
            if (!attributes.isEmpty()) { //<- this should be empty by now
                throw new DynamoDBMappingException("contains unknown flattened attribute(s): " + attributes);
            }
        }

        private boolean canMap(Method method, boolean inherited) {
            if (method.getName().matches("^(get|is).+") == false) {
                return false;
            } else if (method.getParameterTypes().length != 0) {
                return false;
            } else if (method.isBridge() || method.isSynthetic()) {
                return false;
            } else if (method.getDeclaringClass() == Object.class) {
                return false;
            } else if (!inherited && method.getDeclaringClass() != this.clazz &&
                StandardAnnotationMaps.of(method.getDeclaringClass()).attributeType() == null) {
                return false;
            } else {
                return true;
            }
        }
    }

    /**
     * Gets the field name given the getter method.
     */
    static final String fieldNameOf(Method getter) {
        final String name = getter.getName().replaceFirst("^(get|is)","");
        return StringUtils.lowerCase(name.substring(0, 1)) + name.substring(1);
    }

}