Volleyで自己署名証明書を使ったHTTPS通信

1. 証明書をres/rawに置く (この例ではself.cerとします)
2. その証明書を利用してTrustManagerを生成し，SSLSocketFactoryのインスタンスを得る.
   参考: http://developer.android.com/training/articles/security-ssl.html#UnknownCa (英語)
3. SSLSocketFactoryのインスタンスから，VolleyのBasicNetworkインスタンスを生成し，RequestQueueに渡す．

最終的に以下のようなソースコードになる．

public class MySSL {
    public static SSLSocketFactory getSocketFactory(Context context) {
        try {
            CertificateFactory certificateFactory = CertificateFactory.getInstance("X.509");
            Certificate certificate = certificateFactory.generateCertificate(
                    context.getResources().openRawResource(R.raw.self));
            Log.d("ca=" + ((X509Certificate) certificate).getSubjectDN());

            String keyStoreType = KeyStore.getDefaultType();
            KeyStore keyStore = KeyStore.getInstance(keyStoreType);
            keyStore.load(null, null);
            keyStore.setCertificateEntry("ca", certificate);

            TrustManagerFactory managerFactory = TrustManagerFactory.getInstance(
                    TrustManagerFactory.getDefaultAlgorithm());
            managerFactory.init(keyStore);

            SSLContext sslContext = SSLContext.getInstance("TLS");
            sslContext.init(null, managerFactory.getTrustManagers(), null);
            return sslContext.getSocketFactory();
        } catch (Exception e) {
            // TODO: handle error
        }
        return null;
    }
}

/*
 * 自己署名証明書のために，カスタム{@link SSLSocketFactory}を利用する{@link RequestQueue}.
 * Volley本家の実装を流用
**/
public class MyRequestQueue extends RequestQueue {
    private static final String DEFAULT_CACHE_DIR = "volley";
    private final Context context;

    public MyRequestQueue(final Context context) {
        super(
                new DiskBasedCache(new File(context.getCacheDir(), DEFAULT_CACHE_DIR)),
                createNetwork(context));
        this.context = context;
    }

    private static Network createNetwork(Context context) {
        String userAgent = "volley/0";
        try {
            String packageName = context.getPackageName();
            PackageInfo info = context.getPackageManager().getPackageInfo(packageName, 0);
            userAgent = packageName + "/" + info.versionCode;
        } catch (PackageManager.NameNotFoundException e) {
        }
        // Gingerbread以前のHttpUrlConnectionにはバグがあるので注意とのこと，今回は気にしない
        // See: http://android-developers.blogspot.com/2011/09/androids-http-clients.html
        return new BasicNetwork(new HurlStack(null, MySSL.getSocketFactory(context)));
    }
}