第5回 #渋谷Java http://connpass.com/event/4549/ で発表する内容に関するコードです。

CFnTemplateBuilder.java

package biz.k11i.demo;

import biz.k11i.demo.CFnTemplateBuilder.Subnet;
import biz.k11i.demo.CFnTemplateBuilder.VPC;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;

/**
 * Java で CloudFormation テンプレートの DSL を実現してみる試み。
 * <p>
 * 実行には google-gson を必要とします。Gradle なら次の行を build.gradle に追記してください。
 * </p>
 * <p>
 * <code>compile group: 'com.google.code.gson', name: 'gson', version: '2.2.4'</code>
 * </p>
 *
 * @author KOMIYA Atsushi
 */
public class CFnTemplateBuilder {
    private static final Gson GSON = new Gson();
    private static final Gson PP_GSON = new GsonBuilder().setPrettyPrinting().create();

    private List<Jsonable> resources = new ArrayList<>();

    public VPC newVPC(String ip, int subnetMaskBits) {
        VPC vpc = new VPC(ip, subnetMaskBits);
        resources.add(vpc);
        return vpc;
    }

    public String build() {
        StringBuilder sb = new StringBuilder()
                .append('{')
                .append("\"AWSTemplateFormatVersion\": \"2010-09-09\",")
                .append("\"Resources\": {");

        boolean needCommaSeparation = false;
        for (Jsonable resource : resources) {
            if (needCommaSeparation) {
                sb.append(",");
            }
            needCommaSeparation = true;
            sb.append(resource.toJson());
        }

        sb.append("} }");

        return PP_GSON.toJson(GSON.fromJson(sb.toString(), Map.class));
    }

    // ----

    public static interface Function<P> {
        void call(P param);
    }

    public static interface Jsonable {
        String toJson();
    }

    public static interface HasResourceName {
        String resourceName();
    }

    public static class JsonBuilder implements Jsonable {
        private final String resourceName;
        private final Map<String, Object> object = new LinkedHashMap<>();
        private final Map<String, Object> properties = new LinkedHashMap<>();

        public JsonBuilder(String resourceName, String type) {
            this.resourceName = resourceName;
            this.object.put("Type", type);
        }

        public JsonBuilder add(String key, Object value) {
            this.properties.put(key, value);
            return this;
        }

        public JsonBuilder addMap(String key, Function<Map<String, Object>> initializer) {
            this.properties.put(key, map(initializer));
            return this;
        }

        public static Map<String, Object> map(Function<Map<String, Object>> initializer) {
            Map<String, Object> map = new LinkedHashMap<>();
            initializer.call(map);
            return map;
        }

        public JsonBuilder addList(String key, Function<List<Object>> initializer) {
            this.properties.put(key, list(initializer));
            return this;
        }

        public static List<Object> list(Function<List<Object>> initializer) {
            List<Object> list = new ArrayList<>();
            initializer.call(list);
            return list;
        }

        @Override
        public String toJson() {
            if (!properties.isEmpty()) {
                this.object.put("Properties", properties);
            } else {
                this.object.remove("Properties");
            }

            return String.format("\"%s\": %s", resourceName, GSON.toJson(object));
        }
    }

    private static class Cidr {
        private final String ip;
        private final int subnetMaskBits;

        Cidr(String ip, int subnetMaskBits) {
            this.ip = ip;
            this.subnetMaskBits = subnetMaskBits;
        }

        public String toString() {
            return String.format("%s/%d", ip, subnetMaskBits);
        }
    }

    public static class VPC implements Jsonable, HasResourceName {
        private static int sequence = 1;

        private final String resourceName = "Vpc" + sequence++;
        private final Cidr cidrBlock;

        private List<Subnet> subnets = new ArrayList<>();
        private List<RouteTable> routeTables = new ArrayList<>();

        public VPC(String ip, int subnetMaskBits) {
            cidrBlock = new Cidr(ip, subnetMaskBits);
        }

        public RouteTable newRouteTable() {
            RouteTable routeTable = new RouteTable(this);
            routeTables.add(routeTable);
            return routeTable;
        }

        public Subnet newSubnet(String ip, int subnetMaskBits) {
            Subnet subnet = new Subnet(this, ip, subnetMaskBits);
            subnets.add(subnet);
            return subnet;
        }

        public VPC subnet(String ip, int subnetMaskBits, Function<Subnet> initializer) {
            initializer.call(newSubnet(ip, subnetMaskBits));
            return this;
        }

        @Override
        public String toJson() {
            StringBuilder sb = new StringBuilder();

            sb.append(new JsonBuilder(resourceName, "AWS::EC2::VPC")
                    .add("CidrBlock", cidrBlock.toString())
                    .toJson());

            for (Subnet subnet : subnets) {
                sb.append(",\n")
                        .append(subnet.toJson());
            }

            for (RouteTable routeTable : routeTables) {
                sb.append(",\n")
                        .append(routeTable.toJson());
            }

            return sb.toString();
        }

        @Override
        public String resourceName() {
            return resourceName;
        }
    }

    public static class Subnet implements Jsonable, HasResourceName {
        private static int sequence = 1;

        private final String resourceName = "Subnet" + sequence++;
        private final VPC vpc;
        private final Cidr cidr;
        private String availabilityZone;

        public Subnet(VPC vpc, String ip, int subnetMaskBits) {
            this.vpc = vpc;
            this.cidr = new Cidr(ip, subnetMaskBits);
        }

        public Subnet availabilityZone(String availabilityZone) {
            this.availabilityZone = availabilityZone;
            return this;
        }

        @Override
        public String toJson() {
            JsonBuilder builder = new JsonBuilder(resourceName, "AWS::EC2::Subnet")
                    .add("CidrBlock", cidr.toString())
                    .add("VpcId", JsonBuilder.map(m -> m.put("Ref", vpc.resourceName())));

            if (availabilityZone != null) {
                builder.add("AvailabilityZone", availabilityZone);
            }

            return builder.toJson();
        }

        @Override
        public String resourceName() {
            return resourceName;
        }
    }

    public static class RouteTable implements Jsonable, HasResourceName {
        private static int sequence = 1;

        private final String resourceName = "RouteTable" + sequence++;
        private final VPC vpc;
        private InternetGateway internetGateway;
        private List<Subnet> subnets = new ArrayList<>();

        public RouteTable(VPC vpc) {
            this.vpc = vpc;
        }

        public RouteTable attachInternetGateway() {
            this.internetGateway = new InternetGateway(vpc);
            return this;
        }

        public RouteTable addRoute(Subnet subnet) {
            this.subnets.add(subnet);
            return this;
        }

        @Override
        public String toJson() {
            StringBuilder sb = new StringBuilder();

            sb.append(new JsonBuilder(resourceName, "AWS::EC2::RouteTable")
                    .addMap("VpcId", m -> m.put("Ref", vpc.resourceName))
                    .toJson())
                    .append(",\n")
                    .append(internetGateway.toJson());

            int count = 0;
            for (Subnet subnet : subnets) {
                sb.append(",\n")
                        .append(new JsonBuilder(resourceName + "Association" + count++, "AWS::EC2::SubnetRouteTableAssociation")
                                .addMap("RouteTableId", m -> m.put("Ref", resourceName))
                                .addMap("SubnetId", m -> m.put("Ref", subnet.resourceName()))
                                .toJson());
            }

            return sb.toString();
        }

        @Override
        public String resourceName() {
            return resourceName;
        }
    }

    public static class InternetGateway implements Jsonable, HasResourceName {
        private static int sequence = 1;

        private final String resourceName = "Igw" + sequence++;
        private final VPC vpc;

        public InternetGateway(VPC vpc) {
            this.vpc = vpc;
        }

        @Override
        public String toJson() {
            String selfJson = new JsonBuilder(resourceName, "AWS::EC2::InternetGateway")
                    .toJson();

            String attachJson = new JsonBuilder(resourceName + "Attachment", "AWS::EC2::VPCGatewayAttachment")
                    .addMap("InternetGatewayId", m -> m.put("Ref", resourceName))
                    .addMap("VpcId", m -> m.put("Ref", vpc.resourceName()))
                    .toJson();

            return String.format("%s,\n%s", selfJson, attachJson);
        }

        @Override
        public String resourceName() {
            return resourceName;
        }
    }
}

/**
 * クラスメソッド社の技術ブログエントリ「Amazon VPCを使ったミニマム構成のサーバ環境を構築する」
 *
 *   http://dev.classmethod.jp/cloud/aws/minimum-amazon-vpc-server-environment/
 *
 * の記事にある VPC を構築するための CloudFormation テンプレートを、上記のクラスを
 * 利用して実際に作ってみようと思います。
 */
class HowToUse {
    public static void main(String[] args) {
        CFnTemplateBuilder builder = new CFnTemplateBuilder();

        // 10.0.0.0/16 の VPC 上に、
        //   10.0.1.0/24
        //   10.0.2.0/24
        // の二つのプライベートなサブネットを作成します
        VPC vpc = builder
                .newVPC("10.0.0.0", 16)
                .subnet("10.0.1.0", 24,
                        privateSubnet -> privateSubnet.availabilityZone("ap-northeast-1a"))
                .subnet("10.0.2.0", 24,
                        anotherPrivateSubnet -> anotherPrivateSubnet.availabilityZone("ap-northeast-1c"));

        // 上記のサブネットとは別に、 10.0.0.0/24 のパブリックなサブネットを作成します
        Subnet publicSubnet = vpc
                .newSubnet("10.0.0.0", 24)
                .availabilityZone("ap-northeast-1a");

        // 10.0.0.0/24 のパブリックなサブネットについては、
        // インターネットとの疎通ができるようにゲートウェイを用意します
        vpc.newRouteTable()
                .attachInternetGateway()
                .addRoute(publicSubnet);

        // 本来はこの後にセキュリティグループを作成するなどまだまだ続くのですが、
        // 実装が追いつかなかったので断念しました。

        System.out.println(builder.build());
    }
}