Enable additional JVM parameters on JDBC() instantiation

[hjort]

When additional JVM parameters must be passed during the database connection, JDBC() class might accept an additional argument.

For instance, in order to connect to a Teiid data source constrained by SSL security requirements, one must specify the private JKS key through -Djavax.net.ssl.trustStore argument.

With the current pull request, RJDBC is able to accept JVM additional arguments seamlessly, as it was already available in rJava package.

Here is an example of that functionality:

library(RJDBC)

drv<-JDBC('org.teiid.jdbc.TeiidDriver', '/opt/jdbc/teiid-8.7.1.redhat-8-jdbc.jar', '"', '-Djavax.net.ssl.trustStore=/opt/jdbc/truststore-pro-2014.jks')

[kafran]

Will this be merged?

[hjort]

Well, I don't know. It's been a while.

[s-u]

Well, it's not that simple. Unlike that classpath, there is no guarantee that you can set the JVM parameters - if JVM is already initialized (either by another package or because you're embedded in running Java) it's a no-op so the patch certainly isn't complete. Part of the issue that we're now going quite low-level - if this is about Java properties then you can set them in the runtime as well. So I think this is simply the wrong approach. If I read the original issue correctly, it may make more sense to allow setting Java properties (which can be done at runtime) instead of JVM startup-flags.

[tsykes]

I came across this as I was trying to set a truststore on my RJDBC connection. Here's how I ended up doing it:

# install.packages("RJDBC")
props <-  c("-Djavax.net.ssl.trustStore=C:\\windows\\path\\to\\truststore.jks",
            "-Djavax.net.ssl.trustStorePassword=changeit",
            "-Djavax.net.ssl.trustStoreType=jks",
            "-Doracle.net.ssl_version=1.2")

options(java.parameters = props) 

library(RJDBC)

drv <- JDBC("oracle.jdbc.driver.OracleDriver","C:\\windows\\path\\to\\oracle\\driver\\ojdbc8-12.2.0.1.jar")

url <- "jdbc:oracle:thin:@(DESCRIPTION=(ADDRESS=(PROTOCOL=tcps)(HOST=servername) PORT=2494))(CONNECT_DATA=(SERVICE_NAME=servicename)))"

conn <- dbConnect(drv, url, "user", "password")

chk <- dbGetQuery(conn, "SELECT 5432 betterport FROM DUAL ") 

chk

[s-u]

@tsykes yes, that only works if no other package has started Java before.

What I was saying is that it may be better to set properties instead as they can be set even in a running JVM. So what I had in mind was something like:

setProps <- function(...) {
   l=list(...)
   for (k in names(l))
      J("java.lang.System")$setProperty(k, l[[k]])
}

setProps(
        oracle.net.ssl_version="1.2",
        javax.net.ssl.trustStoreType="jks",
        javax.net.ssl.trustStorePassword="changeit",
        javax.net.ssl.trustStore="C:\\windows\\path\\to\\truststore.jks")

Does that work for you? That's what I was suggesting so if it works for you that's easy to add...

Perhaps to clarify: if this is about run-time Java properties that's easy to implement, but that's not what this PR was addressing. This PR was about setting JVM start-up arguments which are a different beast since you can't change them once the JVM is running (e.g. the stack, heap etc.), so the approach in this PR doesn't work. If setting run-time properties is sufficient for the examples people use then that's a different, but much easier issue.