contract PostgreSQLSample{
  function onCreate(){
    Global.dbArg= "jdbc:postgresql://127.0.0.1:5432/huaqiancai";
  }
  export function selectStudent(arg){
    var conn = org.test.PostgreSQLUtil.connect(Global.dbArg);
    if (conn!=undefined && !conn.isClosed()){
      print("successfully connected");
    }
    else return "connect failed";
    var  sql = "select * from student;";
    var statement = conn.createStatement();
    var resultSet = statement.executeQuery(sql);
    ret  = [];
    var meta = resultSet.getMetaData();
    for (;resultSet.next();){
      var line = {
      };
      for (var j=1;j<=meta.getColumnCount();j++){
        line[meta.getColumnName(j)] = resultSet.getString(j);
      }
      ret.push(line);
    }
    return JSON.stringify(ret);
  }
}