library(shiny)
library(rJava)
library(RJDBC)

jdbcConnection <- NULL

shinyServer(function(input, output, session) {

  # Create connection driver and open connection
  #jdbcDriver <- JDBC(driverClass="oracle.jdbc.OracleDriver", classPath="lib/ojdbc6.jar")
  #jdbcConnection <- dbConnect(jdbcDriver, "jdbc:oracle:thin:@//database.hostname.com:port/service_name_or_sid", "username", "password")

  # Query on the Oracle instance name.
  #instanceName <- dbGetQuery(jdbcConnection, "SELECT instance_name FROM v$instance")
  #print(instanceName)

  # Close connection
  #dbDisconnect(jdbcConnection)

  jdbcDriver <- JDBC(driverClass="oracle.jdbc.OracleDriver", classPath="C:/Program Files/Java/jdk1.8.0_91/lib/ojdbc6.jar")

  connectToDb <- reactive({
    jdbcConnection <<- dbConnect(
      jdbcDriver,
      "jdbc:oracle:thin:@//localhost:1521/orc",
      "rusa2",
      "admin"
      )
    if (is.null(jdbcConnection)) {
      print("Could not connect to DB")
      return(NULL)
    }
    print("Connection to DB successfuly established")
  })

  testQuery <- function()({
    # Query on the Oracle instance name.
    instanceName <- dbGetQuery(jdbcConnection, "SELECT * FROM rusa2.tbl_routes")
    print(instanceName)
  })

  printJavaVersion <- reactive({
    # Set JAVA_HOME, set max. memory, and load rJava library
    #Sys.setenv(JAVA_HOME='/path/to/java_home')
    options(java.parameters="-Xmx2g")

    # Output Java version
    .jinit()
    v <- .jcall("java/lang/System", "S", "getProperty", "java.version")
    version <- paste("Java version is", v, sep=" ")
    print(version)
  })

  observeEvent(input$test, {
    connectToDb()
    testQuery()
  })

})