A Groovy parser for CSV files

Parsing CSV these days is pretty straight-forward and not a big deal especially when we have the handy libraries from Apache Commons (I’m talking bout Java world). In this post I will give you an example how to use the Apache Commons CSV with the magic of Groovy and its closures so it can look and feel a little more fun because parsing in general is job for sad people (not kidding).

We’ll make ourself a simple Groovy class that will hold a reference to the CVSParser file, and a reference to the headers and the current record/line of the file that we will iterate with the closure delegate set to the instance of this CSVParserUtils class.

Something like this:

class CSVParseUtils {

    CSVParser csvFile
    def record
    def headers

    CSVParseUtils(String fileLocation) {
        def reader = Paths.get(fileLocation).newReader()
        CSVFormat format = CSVFormat.DEFAULT.withHeader().withDelimiter(delimiter)
        csvFile = new CSVParser(reader, format)
        def header = csvFile.headerMap.keySet().first()
        headers = header.split(delimiter as String)
    }

As we can see it’s a constructor that takes the location to the CSV file that we want to parse, creates some default parsing format and generates new CSVFile that holds the CSV data.

As we see parsing is easy, but it’s better when we can transform the data on the run as we loop it. For that reason we will define a method called eachLine that will take a params Map and a Closure that will have access to the record/line instance and will do something with it.

/**
 * List each line of the csv and execute closure
 * @param params
 * @param closure
 */
def eachLine(Map params = [:], Closure closure) {
    def max = params.max ?: maxLines
    int linesRead = 0
    def rowIterator = csvFile.iterator()
    closure.setDelegate(this)

    while (rowIterator.hasNext() && linesRead++ < max) {
        record = rowIterator.next()
        closure.call(record)
    }
}

It’s nothing special only a simple loop that iterates through the iterator and calls the closure with the given record for that line as a closure argument.

How to use it?

def parser = new CSVParseUtils(fileLocation)
def result = [:]
// first 2 lines without header
parser.eachLine([max: 2]) { CSVRecord record ->
    result.put(record.recordNumber, record.values.size() > 4 ? 
             record.values[0..4] : record.values[0..record.values.size()])
}

We imagine that we need only the first 2 lines and the first 5 columns or something like that.

As you can see this closure loop is not specially connected with CSV, it’s just a clean way to iterate through any textual file line by line and do something with it. As a matter of fact you can use the BufferedReader which has method eachLine too.

The source code for this whole example can be found on github.

Thanks for reading.

Grails and SAPUI5 are friends

Hello reader,

instead of the planned walk through the city park and drinking some beer(s) mother nature swinging moods changed my plans and in place of the shiny sun gave me hard rain and sour mouth. In a situation like that, alone and bored I decided to bore you too and share this short text about two good friends called Grails and SAPUI5 (respect to the OpenUI5 project too). šŸ™‚

I’ve been working hard with the Grails framework this couple of years and different situations led me to different scenarios. Lately I found myself in situation that asked bringing closer the powerful SAP services to the web/mobile clients. And what is better that using the outsourced JavaScript MVC framework made by SAP called SAPUI5 or if you prefer the open source project name OpenUI5 in conjunction with the versatile Grails Framework.

If you’re familiar with Grails then you certainly know that with the latest 3++ versions of Grails there is great support for already established and pretty much famous frameworks/libraries AngularJS and ReactJS in forms of Grails app profiles and plugins. But there is no “official” support for interbridging SAPUI5 and Grails and that is the main motive for writing this blog post and sharing it with you.

SAPUI5 is a single paged application where all the magic is done with JS so what we need is a single html file or in this case a single gsp file. We use that file to define the paths to the SAPUI5 runtime (or sdk) resources and to init the main SAPUI5 application via short JavaScript code. SAPUI5 is best when used with the OData services and that its where this software shines, however it has also great support when working with JSON and provides us with swift JSONModel that we can use to fill up the application data. And because we have JSON then we must have the Restful Grails controllers that will provide us with well defined JSON.

So the situation is pretty simple: Grails connects us with the backend via web services (or else?) or it provides us the data on its own via GORM or something else. Then Grails transforms the data into a JSON format that is a sweet cake for the SAPUI5 to consume and make it look great both on web browsers and on any mobile clients (Smart phones, tablets etc.).

Well this won’t be worth a penny without a working example, right? Because that’s the cause I’ve published a little demo of Grails and SAPUI5 playing together that you can check it on github. In short words we have a Spring Security Core plugin for the authentication and authorization, the JSON Views plugin for making the JSON even easier and also an example how to make it work via rest based http calls if your clients is native app . And of course the SAPUI5 application itself.

Here’s the link to the repo.

Thanks for reading,

cheers.

 

 

Custom Authentication Success Handler with Grails and Spring Security

It’s Sunday and instead of devoting this day to our Lord I will dedicate it to the great Machine and its coding brethren. The jokes aside, this is a quick show up of how to establish custom Authentication Success Handler if you are working with Grails Framework + Spring Security Core Plugin.

Well first, why would you need to alter the ‘normal’ behaviourĀ  of the handler?

The answer: let’s say, you want to change the targetUrl for the specific authenticated user. Is that not enough? šŸ™‚

HOW TO DO IT

With Spring and Java what you need to do is to implement the AuthenticationSuccessHandler interface. It has only one method to be implemented:

void onAuthenticationSuccess(HttpServletRequest var1, HttpServletResponse var2, Authentication var3);

With Grails and Spring Security Core plugin we follow the same path, just the ritual is a little bit different.

Spring Security Plugin use the AjaxAwareAuthenticationSuccessHandlerĀ  bean that extends SavedRequestAwareAuthenticationSuccessHandler and if you follow the hierarchy tree you will notice that at some point the needed interface is implemented at the upper classes. So what we need to do is just extend AjaxAwareAuthenticationSuccessHandler and define the bean in resources.groovy (Š¾r .xml).

package com.wordpress.groggystuff.grails

import grails.plugin.springsecurity.web.authentication.AjaxAwareAuthenticationSuccessHandler
import org.springframework.security.core.Authentication

import javax.servlet.ServletException
import javax.servlet.http.HttpServletRequest
import javax.servlet.http.HttpServletResponse
import javax.servlet.http.HttpSession

class GroggySuccessHandler extends AjaxAwareAuthenticationSuccessHandler {

    boolean userIsBadPerson = false

    @Override
    protected String determineTargetUrl(HttpServletRequest request,HttpServletResponse response) {

        if(userIsBadPerson){
            logger.info(&quot;This user is very nasty. Send him to /dev/null to rot.&quot;)
            return &quot;/dev/null&quot;
        }
        else {
            return super.determineTargetUrl(request, response)
        }
    }

    @Override
    public void onAuthenticationSuccess(final HttpServletRequest request, final HttpServletResponse response,
                                        final Authentication authentication) throws ServletException, IOException {
        try {
            checkIfTheUserIsBadPerson(request.getSession(),authentication)
            handle(request,response,authentication)
            super.clearAuthenticationAttributes(request)
        }
        finally {
            // always remove the saved request
            requestCache.removeRequest(request, response)
        }
    }

    protected void handle(HttpServletRequest request, HttpServletResponse response, Authentication authentication)
            throws IOException, ServletException {
        String targetUrl = determineTargetUrl(request, response)

        if (response.isCommitted()) {
            logger.debug(&quot;Response has already been committed. Unable to redirect to &quot; + targetUrl)
            return
        }

        redirectStrategy.sendRedirect(request, response, targetUrl)
    }


    private void checkIfTheUserIsBadPerson(HttpSession session, Authentication authentication){

        // do the groggy check to find if the user is a bad person
        // presume that the user is always a bad person
        userIsBadPerson = true
    }
}

When the user authenticates successfully onAuthenticationSuccess method is called. With this code the method determineTargetUrl will be always referenced when the user logins and from there we can easily change the targetUrl that the handle method redirects to. I wrote a logical check with which I check when to redirect and how to build my targetUrl in determineTargetUrl. Don’t forget to define the bean in resources.groovy .Ā  The bean id must be the same as in the plugin, otherwise this class will be just ignored.

beans = {
    // other beans
    authenticationSuccessHandler(GroggySuccessHandler) {
        /* Reusing the security configuration */
        def conf = SpringSecurityUtils.securityConfig
        /* Configuring the bean */
        requestCache = ref('requestCache')
        redirectStrategy = ref('redirectStrategy')
        defaultTargetUrl = conf.successHandler.defaultTargetUrl
        alwaysUseDefaultTargetUrl = conf.successHandler.alwaysUseDefault
        targetUrlParameter = conf.successHandler.targetUrlParameter
        ajaxSuccessUrl = conf.successHandler.ajaxSuccessUrl
        useReferer = conf.successHandler.useReferer
    }
}

And that’s it my lads and gals. (tested with Grails 2.5.0 and spring-security-core:2.0-RC4)

And a song as always.

Cool usage of TimeCategory in Groovy

Groovy, the programming language based on JVM implements a feature called Categories. It is originally borrowed from Objective-C . Simple explanation for this feature can be the ability to implement new methods in existing classes without modifying their original code which in some way is injecting new methods through a Category class. For more information official documentation can be found here .

Rather interesting for me was playing with the TimeCategory class for writing a short and easy script for fixing some datetime columns in database. This class offers a convenient way of Date and Time manipulation.

General syntax for categories is the following:

use ( Class ) {
// Some code
}

Concrete usage of TimeCategory:

use ( TimeCategory ) {
// application on numbers:
println 1.minute.from.now
println 10.hours.ago
// application on dates
def someDate = new Date()
println someDate - 3.months
}

Seems weird? From when Integer has months, minutes, hours etc. methods ? Well it still doesn’t have any of that, however those methods are dynamically added with the TimeCategory use.

If you are interested how is this possible I suggest you to go through TimeCategoryĀ API and source code if possible. Also this forum post can be useful for deeper understanding of the groovy magic.

And last but not least, an example groovy script for your pleasure.


@GrabConfig(systemClassLoader=true)
@Grab(group='mysql', module='mysql-connector-java', version='5.1.27')

import groovy.time.TimeCategory
import java.sql.Timestamp

sql = groovy.sql.Sql.newInstance(
"jdbc:mysql://hostname:3306/DB_name?autoReconnect=true",
"user",
"password",
"com.mysql.jdbc.Driver")

def rows= [:]

// Select Data
sql.eachRow("select * from Table_Name"){
def impDates = new ImportedDates() // This is some custom Class found in the same package/directory if script
impDates.dateColumn = it.dateColumn

if(impDates.dateColumn!=null){
use(TimeCategory){
impDates.dateColumn = impDates.dateColumn - 1.day // Shift dateColumn for one day backwards in time
}
}

rows.put(it.UID,impDates) // Put private key and ImportedDate object in Map

}

// Update Data
rows.each {row-&gt;
ImportedDates id = row.value
// Check if value is different from null, if it is convert it to Timestamp(we use datetime column in db) and execute update query
dateColumnĀ  = null
if(id.dateColumn) dateColumn = new Timestamp(id.dateColumn.getTime())

// Actual update query
sql.executeUpdate('update Table_Name set dateColumn = ? ' +
'where UID like ?',
[dateColumn, row.key.toString()])

}

Cheers.