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• DynamoDBDelimited.java

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com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBDelimited Maven / Gradle / Ivy

/*
 * Copyright 2016-2016 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.services.dynamodbv2.datamodeling.DynamoDBMapperFieldModel.Id;
import com.amazonaws.services.dynamodbv2.datamodeling.StandardBeanProperties.Bean;
import com.amazonaws.services.dynamodbv2.datamodeling.StandardBeanProperties.Builder;
import com.amazonaws.services.dynamodbv2.datamodeling.StandardTypeConverters.Scalar;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

import java.util.Map;
import java.util.regex.Pattern;

/**
 * Annotation to convert an object into a single delimited {@link String}
 * attribute.
 *
 * A minimal example using getter annotations,
 * 
 * @DynamoDBTable(tableName="TestTable")
 * public class TestClass {
 *     private String key;
 *     private PhoneNumber phoneNumber;
 *
 *     @DynamoDBHashKey
 *     public String getKey() { return key; }
 *     public void setKey(String key) { this.key = key; }
 *
 *     @DynamoDBDelimited(attributeNames={"areaCode","exchange","subscriber"}, delimiter='-')
 *     public PhoneNumber getPhoneNumber() { return phoneNumber; }
 *     public void setPhoneNumber(PhoneNumber phoneNumber) { this.phoneNumber = phoneNumber; }
 * }
 * 
 *
 * With the following complex type to string delimit,
 * 
 * public class PhoneNumber {
 *     private String areaCode;
 *     private String exchange;
 *     private String subscriber;
 *
 *     public String getAreaCode() { return areaCode; }
 *     public void setAreaCode(String areaCode) { this.areaCode = areaCode; }
 *
 *     public String getExchange() { return exchange; }
 *     public void setExchange(String exchange) { this.exchange = exchange; }
 *
 *     public String getSubscriber() { return subscriber; }
 *     public void setSubscriber(String subscriber) { this.subscriber = subscriber; }
 * }
 * 
 *
 * Would write the following value to DynamoDB given,
 * 

 *     
PhoneNumber("206","266","1000") = "206-266-1000"
 *     
PhoneNumber("206",null,"1000") = "206--1000"
 *     
PhoneNumber("206",null,null) = "206--"
 *     
PhoneNumber(null,"266","1000") = "-266-1000"
 *     
PhoneNumber(null,"266",null) = "-266-"
 *     
PhoneNumber(null,null,"1000") = "--1000"
 *     
PhoneNumber(null,null,null) = null
 *     
null = null
 * 
 *
 * Conversely, reading not fully formatted values from DynamoDB given,
 * 

 *     
"" = empty string not allowed by DDB but would produce empty object
 *     
"--" = PhoneNumber(null,null,null)
 *     
"-----" = PhoneNumber(null,null,null)
 *     
"206" = PhoneNumber("206",null,null)
 *     
"206-266" = PhoneNumber("206","266",null)
 *     
"206-266-1000-1234-5678" = PhoneNumber("206","266","1000")
 * 
 *
 * Please note,
 *
 * The converter does not protect against values which may also contain the
 * delimiter. If more advanced conversion is required, consider implementing,
 * a custom {@link DynamoDBTypeConverter}.
 *
 * New delimited values may always be appended to the string, however, there
 * are some risks in distributed systems where, if one system has updated
 * delimiting instructions and begins to persist new values, other systems,
 * which also persist that same data, would effectively truncate it back to the
 * original format.
 *
 * Auto-generated annotations are not supported on field/property. However,
 * conversion annotations such as {@link DynamoDBTypeConvertedTimestamp} and
 * {@link DynamoDBTypeConverted} where the output type is {@link String} are
 * supported.
 *
 * @see com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBTypeConverted
 * @see com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBTypeConvertedTimestamp
 */
@DynamoDBTypeConverted(converter=DynamoDBDelimited.Converter.class)
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE, ElementType.FIELD, ElementType.METHOD})
public @interface DynamoDBDelimited {

    /**
     * The delimiter for separating attribute values; default is |.
     */
    char delimiter() default '|';

    /**
     * The ordered list of attribute/field names.
     */
    String[] attributeNames();

    /**
     * Type converter for string delimited attributes.
     */
    static final class Converter implements DynamoDBTypeConverter {
        private final Field[] fields;
        private final Class targetType;
        private final String delimiter;

        /**
         * Constructs a new delimited converter.
         * @param targetType The target type.
         * @param annotation The annotation.
         */
        public Converter(final Class targetType, final DynamoDBDelimited annotation) {
            final String[] names = annotation.attributeNames();
            if (names.length <= 1) {
                throw new DynamoDBMappingException("@DynamoDBDelimited missing attributeNames" +
                    "; must specify two or more attribute names");
            }
            final Map> beans = new Builder(targetType, true).build();
            this.fields = new Field[names.length];
            for (int i = 0; i < fields.length; i ++) {
                if (!beans.containsKey(names[i])) {
                    throw new DynamoDBMappingException(new Id(targetType, names[i])
                        .format("not mapped on object model %s", beans.keySet()));
                }
                this.fields[i] = new Field(targetType, beans.get(names[i]));
            }
            this.delimiter = String.valueOf(annotation.delimiter());
            this.targetType = targetType;
        }

        /**
         * {@inheritDoc}
         */
        @Override
        public final String convert(final T object) {
            final StringBuilder string = new StringBuilder();
            for (int i = 0; i < fields.length; i++) {
                if (i > 0) {
                    string.append(delimiter);
                }
                final String value = fields[i].get(object);
                if (value != null) {
                    if (value.contains(delimiter)) {
                        throw new DynamoDBMappingException(fields[i].bean.id()
                            .format("must not contain delimiter %s" + delimiter));
                    }
                    string.append(value);
                }
            }
            return string.length() < fields.length ? null : string.toString();
        }

        /**
         * {@inheritDoc}
         */
        @Override
        public final T unconvert(final String string) {
            final T object;
            try {
                object = targetType.newInstance();
            } catch (final Exception e) {
                throw new DynamoDBMappingException("unable to instantiate " + targetType, e);
            }
            final String[] values = string.split(Pattern.quote(delimiter));
            for (int i = 0, its = Math.min(fields.length, values.length); i < its; i++) {
                fields[i].set(object, values[i]);
            }
            return object;
        }
    
        /**
         * Field conversion.
         */
        private static final class Field {
            private final DynamoDBTypeConverter converter;
            private final Bean bean;

            private Field(final Class type, final Bean bean) {
                if (bean.annotations().typeConverted() == null) {
                    this.converter = Scalar.STRING.getConverter(bean.type().type());
                } else {
                    this.converter = bean.annotations().typeConverter();
                }
                this.bean = bean;
            }

            private final String get(final T object) {
                final V value = bean.reflect().get(object);
                if (value == null) {
                    return null;
                }
                return converter.convert(value);
            }

            private final void set(final T object, final String string) {
                if (!string.isEmpty()) {
                    final V value = converter.unconvert(string);
                    if (value != null) {
                        bean.reflect().set(object, value);
                    }
                }
            }
        }
    }

}