NetHttpTransport.Builder trustCertificates() clobbers any changes made through setSslSocketFactory()

[frankyn]

Environment details

1. OS type and version: any
2. Java version: any
3. version(s): google-http-client-gson:1.40.1

Steps to reproduce

The issue came up for Dataproc Hadoop Connector (GoogleCloudDataproc/hadoop-connectors#782) which uses a custom SslSocketFactory to enable socket level options, e.g. keep-alive. When the builder was used this way it would lose context on trustCertificates or vice-versa depending on which method was called first.

1. Create a builder calling trustCertificates, followed by setSslSocketFactory(); then build.
2. TrustCertificates mutation is lost

Addressing the builder implementation to be more of an intent rather than calling setSslSocketFactory() in trustCertificates would help make the builder easier to use. In addition documentation for these builder methods is non-descriptive beyond what the value means and it would help to call out quirks in implementation.

Code example

// I used defaultSslSocketFactory() but expect that it can be any SslSocketFactory
NetHttpTransport transport = new NetHttpTransport.Builder()
            .trustCertificates(GoogleUtils.getCertificateTrustStore());
            .setSslSocketFactory(HttpsURLConnection.getDefaultSSLSocketFactory()).build();

External references such as API reference guides

• This builder is has no documented guidance which would have helped understand the conflict that could occur.