Grails Groovy dynamically invokeMethod with empty/single/multi parameters

You need to first get bean object of your service class.
Create a service like below and get your required service by calling:


serviceFinderService.getServiceByName("serviceName");

 If you have a service named "StudentService.groovy" then replace "serviceName" with "Student" or "student".

package com.pritom.services

import org.codehaus.groovy.grails.web.context.ServletContextHolder
import org.codehaus.groovy.grails.web.servlet.GrailsApplicationAttributes

class ServiceFinderService {
    private static HashMap beanList = new HashMap();
    private def grailsApplication;
    private static def ctx;

    def serviceMethod() {

    }

    public def getServiceByName(String bean) throws Exception {
        if(!ctx) {
            ctx = ServletContextHolder.servletContext.getAttribute(GrailsApplicationAttributes.APPLICATION_CONTEXT)
        }
        bean += "Service";
        bean = bean[0].toLowerCase() + bean.substring(1);
        if(beanList.containsKey(bean)) {
            return beanList.get(bean);
        }
        beanList.put(bean, ctx.getBean(bean));
        if(beanList.containsKey(bean)) {
            return beanList.get(bean);
        }
        throw new Exception("Invalid service");
    }
}

Now check and invoke the method if a specific method existing by such way:

---

def studentService = ServiceFinderService.getServiceByName("Student");

if(studentService.metaClass.respondsTo(studentService, "methodName", [Integer, String, Boolean] as Object[]) {
    def result = studentService.invokeMethod("methodName", [1, "Pritom K Mondal", true] as Object[]);
}

/* If your method is static then call it by: */
if(studentService.metaClass.respondsTo(studentService, "methodName", [Integer, String, Boolean] as Object[]) {
    def result = studentService.metaClass.getTheClass().invokeMethod("methodName", [1, "Pritom K Mondal", true] as Object[]);
}

Grails validate email address

you can use

import org.apache.commons.validator.EmailValidator
...
EmailValidator emailValidator = EmailValidator.getInstance()
if (emailValidator.isValid(valueToTest)) ....

the apache commons validators are included with Grails so you don't need to install another plugin.

Grails Hibernate - null id in entry (don't flush the Session after an exception occurs)

I ran into this issue today when trying to persist one of my objects.  The cause of the problem was interesting.  I was trying to save an object when a property/columns in the table had a unique constraint.  As a result, the object that I was trying to persist would not persist simply because the object's property it failed to meet the unique constraint.

As a result, a call to Save() on the object failed and the ID on the object I was trying to save was not set, but Grails Hibernate still processed the object and associated it with its persistence mechanism leaving it in a "semi-persistent" state with the Grails Hibernate persistence manager (ie: Grails Hibernate now knows about the object you tried to save and it SHOULD have fully evicted the object from its persistence manager because the save failed, but it didn't).

So, the solution that I implemented was to wrap the Save() in a try{} catch{} statement and handling exception.

Basically you need to do something like this:
Create a Filters in conf directory under grails project suppose named 'BaseFilters.groovy' with the following content:
 

import org.codehaus.groovy.grails.commons.spring.GrailsWebApplicationContext
import org.codehaus.groovy.grails.web.context.ServletContextHolder
import org.codehaus.groovy.grails.web.servlet.GrailsApplicationAttributes
import org.hibernate.FlushMode
import org.hibernate.Session
import org.hibernate.SessionFactory

class BaseFilters {
    private static GrailsWebApplicationContext ctx;

    def filters = {
        all(controller:'*', action:'*') {
            before = {
                Session session = getRequestSession();
                session.setFlushMode(FlushMode.MANUAL)
                request.requestSession = session;
            }
            after = { Map model ->
                try {
                    Session session = request.requestSession;
                    session.flush();
                } catch (Exception ex) {
                    ex.printStackTrace()
                }
            }
            afterView = { Exception e ->

            }
        }
    }

    private Session getRequestSession() {
        createCtx();
        SessionFactory sessionFactory = ctx.sessionFactory
        Session session = sessionFactory.currentSession
        return session;
    }

    private def createCtx() {
        if(!ctx) {
            ctx = ServletContextHolder.servletContext.getAttribute(GrailsApplicationAttributes.APPLICATION_CONTEXT)
        }
    }
}

Originally session flush mode initially set to 'FlushMode.AUTO' which cause the error.
So I change the session flush mode to 'FlushMode' to 'MANUAL'.
And also make your service transaction false such: static transactional = false, add this line just below the class definition.

And in the after section, I just manually try to flush, which is not much needed, you can ignore it.
I just add this section to do some logic manually if need.

Grails domain class: unique constraint for multiple columns

Suppose a simple Grails domain class:

class Account {
    String countryId;

    String userName; 

    String areaId;

    String password;

    static constraints = {
        ...???...
    }
}

It is required that user names are unique for a particular countryId and areaId, thus there must be a unique contraint on three columns. And this is the constraints:

userName(unique: ['countryId', 'areaId'])

You can include as many other properties in the array that make up the 
other properties that must be considered in the "unique" constraint on 
the username. 

Grails pagination on a ArrayList

In my recent grails project, i needed to paginate on an array list, so I wrote a function and thought would share it with you all.

---

public List getFilteredList(int max, int offset) {
    max = Math.min(max ?: 25, 100)
    offset = (offset && offset > 0) ?: 0

    List names = getNames() //Loads the complete list
    int total = names.size()
    int upperLimit = findUpperIndex(offset, max, total)
    List filteredNames = names.getAt(offset..upperLimit)
    return filteredNames
}

private static int findUpperIndex(int offset, int max, int total) {
    max = offset + max - 1
    if (max >= total) {
        max -= max - total + 1
    }
    return max
}

So now if offset=20 and max=10, total = 28 so this will generate a list from 21st to 28th elements of the main list.

Grails: get class object by string/class name

grailsApplication.classLoader.loadClass("au.com.test.package.ClassName")

[Java/Grails] Class ConstrainedProperty

org.codehaus.groovy.grails.validation

[Java/Grails] Class ConstrainedProperty

java.lang.Object
  org.codehaus.groovy.grails.validation.ConstrainedProperty 

Method Summary
void	addMetaConstraint(java.lang.String name, java.lang.Object value) Obtains the value of the named meta constraint.
void	applyConstraint(java.lang.String constraintName, java.lang.Object constrainingValue) Applies a constraint for the specified name and consraint value.
Constraint	getAppliedConstraint(java.lang.String name) @param constraintName The name of the constraint to check
java.util.Collection	getAppliedConstraints() Obtains an applied constraint by name.
java.util.Map	getAttributes()
java.lang.String	getFormat()
java.util.List	getInList() @return Returns the inList.
java.lang.String	getMatches() @return Returns the matches.
java.lang.Comparable	getMax()
java.lang.Integer	getMaxSize()
java.lang.Object	getMetaConstraintValue(java.lang.String name)
java.lang.Comparable	getMin() @return Returns the min.
java.lang.Integer	getMinSize() @return Returns the minSize.
java.lang.Object	getNotEqual() @return Returns the notEqual.
int	getOrder() @param order The order to set.
java.lang.String	getPropertyName() @return Returns the propertyName.
java.lang.Class	getPropertyType() @return Returns the max.
groovy.lang.Range	getRange() @return Returns the range.
java.lang.Integer	getScale() @return The scale, if defined for this property; null, otherwise
groovy.lang.Range	getSize() @param size The size to set.
java.lang.String	getWidget()
boolean	hasAppliedConstraint(java.lang.String constraintName) @return Returns the propertyType.
static boolean	hasRegisteredConstraint(java.lang.String constraintName) @return Returns the appliedConstraints.
boolean	isBlank() @return the blank.
boolean	isCreditCard()
boolean	isDisplay() @return Returns the display.
boolean	isEditable() @param editable The editable to set.
boolean	isEmail() @return Returns the email.
boolean	isNullable() @return Returns the nullable.
boolean	isPassword()
boolean	isUrl()
static void	registerNewConstraint(java.lang.String name, java.lang.Class constraintClass)
static void	registerNewConstraint(java.lang.String name, ConstraintFactory factory)
static void	removeConstraint(java.lang.String name, java.lang.Class constraintClass)
static void	removeConstraint(java.lang.String name)
void	setAttributes(java.util.Map attributes)
void	setBlank(boolean blank)
void	setCreditCard(boolean creditCard)
void	setDisplay(boolean display) @return Returns the editable.
void	setEditable(boolean editable) @return Returns the order.
void	setEmail(boolean email)
void	setFormat(java.lang.String format)
void	setInList(java.util.List inList)
void	setMatches(java.lang.String regex)
void	setMax(java.lang.Comparable max) @param max The max to set.
void	setMaxSize(java.lang.Integer maxSize) @param maxSize The maxSize to set.
void	setMessageSource(org.springframework.context.MessageSource source)
void	setMin(java.lang.Comparable min) @param min The min to set.
void	setMinSize(java.lang.Integer minSize) @param minSize The minLength to set.
void	setNotEqual(java.lang.Object notEqual) @param notEqual The notEqual to set.
void	setNullable(boolean nullable)
void	setOrder(int order)
void	setPassword(boolean password)
void	setPropertyName(java.lang.String propertyName) @return Returns the url.
void	setRange(groovy.lang.Range range)
void	setSize(groovy.lang.Range size)
void	setUrl(boolean url)
void	setWidget(java.lang.String widget)
boolean	supportsContraint(java.lang.String constraintName) Checks with this ConstraintedProperty instance supports applying the specified constraint.
java.lang.String	toString()
void	validate(java.lang.Object target, java.lang.Object propertyValue, org.springframework.validation.Errors errors)