Feeds

Get into data with Groovy

Part 2: Object grabber

Top 5 reasons to deploy VMware with Tegile

Of course, under the surface there's still some SQL going on and we can look at it if we want to using the sql and parameters properties of the DataSet. For example, in the case of not_harry this maps to:

println not_harry.sql
println not_harry.parameters

Which gives us:

select * from users where (user_id > ? and user_name != ?)
[2, "harry"]

Can we go further with a DataSet? So far we've restricted ourselves to querying and filtering table data. What if we want to write data back to the database? The good news is that you can add new rows of data, the bad news is that deletes or updates are not yet implemented. We'll have to hope and wait for a future release that adds this functionality.

To illustrate the add row functionality we're going to implement a common enough scenario - we're going to populate our MySQL table with data that's been dumped from a spreadsheet or another RDBMS into a CSV file. It's the kind of data manipulation task that scripting languages traditionally excel at.

The first thing to do is work out how to grab the data from the CSV file and parse it correctly. Here's an extract from our users.csv file:

fred,fred@flintstone.com,10
barney,barney@rubble.net,11
wilma,wilma@flintstone.co.uk,12
bambam,bambam@bambam.org,13
betty,betty@betty.com,14

As should be clear, Groovy is big on iterators, and in this case we can just grab the file and iterate over each line, splitting it on the comma character. As a test we can run the following code:

new File('users.csv').splitEachLine(',') {fields ->
  println fields[0] + " " + fields[1] + " " + fields[2]
  }

Here each line is parsed, tokenised on the comma and bound to a variable that's called fields. The above code will cycle through each line of the file and print the different fields for us. What we want to do next is add each line of data to the database, but instead of INSERT queries we're going to use our DataSet directly:

new File('users.csv').splitEachLine(',') {fields ->
  ds.add(
    user_name: fields[0],
    user_id: fields[2],
    email: fields[1]
  )
}
  
ds.each { println it.user_name }

Running the above code will add the rows from the CSV file and then dump the list of user_names to verify that it's worked.

In just a few lines of code we've managed to read a file, parse it, and then add the data to a database, with minimal amounts of house-keeping code or boilerplate Java.

Of course, the fact the DataSet only works on tables and not on more complex structures (such as the result of a JOIN) means you can't get away from using SQL altogether, but Groovy makes it easy to mix and match approaches. And in the case of complex queries, it's fairly straightforward to use the Sql object to create a database view and then to use the DataSet object to access that.

In all then, Groovy offers a set of high-level objects that make database interaction a relative breeze. ®

Secure remote control for conventional and virtual desktops

More from The Register

next story
Microsoft to bake Skype into IE, without plugins
Redmond thinks the Object Real-Time Communications API for WebRTC is ready to roll
Microsoft promises Windows 10 will mean two-factor auth for all
Sneak peek at security features Redmond's baking into new OS
Mozilla: Spidermonkey ATE Apple's JavaScriptCore, THRASHED Google V8
Moz man claims the win on rivals' own benchmarks
FTDI yanks chip-bricking driver from Windows Update, vows to fight on
Next driver to battle fake chips with 'non-invasive' methods
PEAK APPLE: iOS 8 is least popular Cupertino mobile OS in all of HUMAN HISTORY
'Nerd release' finally staggers past 50 per cent adoption
DEATH by PowerPoint: Microsoft warns of 0-day attack hidden in slides
Might put out patch in update, might chuck it out sooner
Ubuntu 14.10 tries pulling a Steve Ballmer on cloudy offerings
Oi, Windows, centOS and openSUSE – behave, we're all friends here
Was ist das? Eine neue Suse Linux Enterprise? Ausgezeichnet!
Version 12 first major-number Suse release since 2009
prev story

Whitepapers

Why cloud backup?
Combining the latest advancements in disk-based backup with secure, integrated, cloud technologies offer organizations fast and assured recovery of their critical enterprise data.
A strategic approach to identity relationship management
ForgeRock commissioned Forrester to evaluate companies’ IAM practices and requirements when it comes to customer-facing scenarios versus employee-facing ones.
Reg Reader Research: SaaS based Email and Office Productivity Tools
Read this Reg reader report which provides advice and guidance for SMBs towards the use of SaaS based email and Office productivity tools.
Top 5 reasons to deploy VMware with Tegile
Data demand and the rise of virtualization is challenging IT teams to deliver storage performance, scalability and capacity that can keep up, while maximizing efficiency.
Mitigating web security risk with SSL certificates
Web-based systems are essential tools for running business processes and delivering services to customers.