Groovy syntax for enter/exit block - groovy

Question

Is there a way to define a block/environment with custom open and close methods? Currently, I have:
script {
withCredentials([usernamePassword(credentialsId: '...', usernameVariable: 'CONFIG_USER', passwordVariable: 'CONFIG_PASS')]) {
def sql = Sql.newInstance("...", CONFIG_USER, CONFIG_PASS, "com.mysql.jdbc.Driver")
sql.rows("SELECT * FROM visualization").each { row ->
println "row ${row.branch}"
}
sql.close()
}
}
I would like to be able to do:
with sqlConnection() { sql ->
sql.rows("SELECT * FROM visualization").each { row ->
println "row ${row.branch}"
}
}
Where it automatically opens/closes the connection accordingly. I am new to Groovy, so it's the syntax I'm concerned about. In Python I would do this using an object __enter__/__exit__.

Answer 1

If I understand you correctly you want a new method sqlConnection() that does the withCredentials part?
You can use a closure parameter to do something before or after something else.
def sqlConnection(Closure withSqlClosure) {
withCredentials([usernamePassword(credentialsId: '...', usernameVariable: 'CONFIG_USER', passwordVariable: 'CONFIG_PASS')]) {
Sql.newInstance("...", CONFIG_USER, CONFIG_PASS, "com.mysql.jdbc.Driver").withCloseable {sql ->
withSqlClosure(sql)
}
}
}
Can be used like this
sqlConnection() { sql ->
sql.rows("SELECT * FROM visualization").each { row ->
println "row ${row.branch}"
}
}
So everything before the call to the closure (withSqlClosure(sql)) corresponds to __enter__ everything after the call is your __exit__. Note that you will need to lookout for exceptions. Usually you will want to wrap the closure call in a try { ... } finally { ... } Statement. Here I used withCloseable which does that for us (assuming Sql.newInstance returns a Closeable).
To aid your IDE and enable #CompileStatic you should also add a #ClosureParams
def sqlConnection(
#ClosureParams(value = groovy.transform.stc.SimpleType,
options = ["your.sql.type"]) Closure withSqlClosure) {
withCredentials([usernamePassword(credentialsId: '...', usernameVariable: 'CONFIG_USER', passwordVariable: 'CONFIG_PASS')]) {
Sql.newInstance("...", CONFIG_USER, CONFIG_PASS, "com.mysql.jdbc.Driver").withCloseable {sql ->
withSqlClosure(sql)
}
}
}
Here your.sql.type is the return type of Sql.newInstance.