Make Feign client to take truststore from custom property

Feign client in our app is communicating with a self-signed server. We are able to make Feign client use the custom truststore using the property javax.net.ssl.trustStore system property. But because my app also communicates with standard CA certified sites, the default truststore shouldn’t be overridden.

How can I use the custom truststore without using javax.net.ssl.trustStore system property? Or else how can I have my Feign client use the truststore from a property other than standard javax.net.ssl.trustStore system property?

Answer

I ended up handcrafting my own instance of SSLSocketFactory that I pass to my Feign client, using the below code,

/**
 * Gets the {@link SSLSocketFactory} instance for the client communication
 * using the given truststore file and password.
 * 
 * Since the instance is used as client, this is instantiated with empty
 * keystore and the truststore represented by the given truststore file.
 * 
 * 
 * @param theTrustStoreFile
 *            The complete file path of the truststore.
 * @return {@link SSLSocketFactory} instance that internally uses the given
 *         truststore.
 * @throws Exception
 *             When there is an error in the creating the
 *             {@link SSLSocketFactory} instance.
 */
public static SSLSocketFactory getClientSSLSocketFactory(File theTrustStoreFile)
        throws Exception
{
    // This supports TLSv1.2
    SSLContext sslContext = SSLContext.getInstance("TLS");

    KeyStore kStore = KeyStore.getInstance(KeyStore.getDefaultType());

    FileInputStream file = getFileInputStream(theTrustStoreFile);
    kStore.load(file, null);

    TrustManagerFactory tmf = TrustManagerFactory
            .getInstance(TrustManagerFactory.getDefaultAlgorithm());
    tmf.init(kStore);

    sslContext.init(new KeyManager[] {}, tmf.getTrustManagers(), null);

    return sslContext.getSocketFactory();
}

/**
 * Reads the file into {@link FileInputStream} instance.
 * 
 * @param file
 *            The file to be read.
 * @return {@link FileInputStream} that represents the file content/
 * @throws Exception
 *             When there is any error in reading the file.
 */
private static FileInputStream getFileInputStream(final File file) throws Exception
{
    return AccessController.doPrivileged(new PrivilegedExceptionAction<FileInputStream>()
    {
        @Override
        public FileInputStream run() throws Exception
        {
            try
            {
                if (file.exists())
                {
                    return new FileInputStream(file);
                } else
                {
                    return null;
                }
            } catch (FileNotFoundException e)
            {
                // couldn't find it, oh well.
                return null;
            }
        }
    });
}

And when I instantiate my client, I do it like,

Feign.builder().client(getClientSSLSocketFactory(trustFile),null)...

This gist contains sample code and its usage.