Introduction

First draft of some refactoring done on Grails projects. Created an "InstanceController", an "InstanceService" and "crud.gsp", "list.gsp" to cut down editing and code duplication across domain classes.

Details

This is the code for the blog at http://fjanon.blogspot.com/2009/10/over-my-last-few-grails-projects.html

in /domainclass/Streettype.groovy

class Streettype {
	String name

	static constraints = {
		name('unique': true, 'nullable': false, 'maxSize': 15)
		}

	static mapping = {
		version false
	}

public String toMessage()	// Needed for the InstanceController to display error messages
	{
	 return this.toString()
	}

public String toString()
	{
	 def str = (name?: '-no streettype name-')
	 return str
	}
}

in Bootstrap.groovy:

class BootStrap {

def streettypeService

def init =
	{
	 streettypeService.setup()
	}
}

in /config/Constants.groovy

public class Constants {
//  Used in the controllers and 'crud.gsp'
public static final SHOW = 'show'
public static final EDIT = 'edit'
public static final CREATE = 'create'
}

in /controllers/InstanceController.groovy

// Generic controller
abstract class InstanceController {

def service = null // MUST be initialized in the subclass
def instancename = null // MUST be initialized in the subclass

def beforeInterceptor = {
	setup()
}

abstract def setup();

def index = { index() }
def index () { list() }	// a bit faster, no need for the redirect

def list = { list() }
def list()
	{
	 // if there is an 'id' in the 'params', use it to highlight that item in the list
	 def instance = service.getById(params.id)
	 // 'selected' is used to highlight the instance last edited/saved. Caution: uniform can be null when the list is called by list or index
	 render('view': 'list', 'model': ['instancelist': service.list(), 'selectedid': instance?.id, 'instancename': instancename])
	}

def show = { show() }
def show()
	{
	 def instance = service.getById(params.id)
	 if (!instance)
		{
		 flash.message = "$instancename not found with id ${params.id}"
		 redirect('action': 'list')
		}
	 render('view': 'crud', 'model': ['instance': instance, 'edit': false, 'mode': Constants.SHOW, 'instancename': instancename])
	}

def delete = { delete() }
def delete()
	{
	def instance = service.getById(params.id)
	def name = instance?.toMessage()	// Save it for use in the message after the instance is deleted
	if (!instance)
		{
		 flash.message = name?:'Element' + " not found with id '${params.id}'"
		 redirect('action': 'list')
		 return
		}

	if (service.metaClass.respondsTo(service, "isUsed") && service.isUsed(instance))
		{
		 flash.message = name?:'Element' + ' is still used by other elements, it cannot be deleted.'
		 redirect('action': 'show', 'id': params.id)
		 return
		}
	 if (service.delete(instance))
		{
		 flash.message = "Element ${name?'\'' + name + '\'':''} deleted"
		 redirect('action': 'list')
		 return
		}
	 else
		{
		 flash.message = "Element ${name?'$name':''} could not be deleted"
		 redirect('action': 'show', 'id': params.id)
		 return
		}
	}

def edit = { edit() }
def edit()
	{
	def instance = service.getById(params.id)
	if (!instance)
		{
		 flash.message = "Element not found with id ${params.id}"
		 redirect('action': 'list')
		}
	else
		{
		 render('view': 'crud', 'model': ['instance': instance, 'edit': true, 'mode': Constants.EDIT, '$instancename': instancename])
		}
	}

def update = { update() }
def update()
	{
	def instance = service.getById(params.id)
	if (!instance)
		{
		 flash.message = "Element not found with id ${params.id}"
		 redirect('action': 'list')
		 return
		}

	instance.properties = params
	bindmore(instance, params)

	instance = service.update(instance)
	if (instance.hasErrors())
		{
		 render('view': 'crud', 'model': ['instance': instance, 'edit': true, 'mode': Constants.EDIT, 'instancename': instancename])
		}
	else
		{
		 flash.message = "$instancename '${instance.toMessage()}' updated"
		 redirect('action': 'list', 'id': instance?.id)	// The id used to highlight the instance in the list
		}
	}

def void bindmore(instance, params)
	{
	 // Overriden by subclasses if extra binding is needed
	 // example: if (params.defaultcolor) instance.defaultcolor = true	// Bind the checkbox
	}

def create = { create() }
def create()
	{
	 def instance = service.newinstance()
	 instance.properties = params
	 render('view': 'crud', 'model': ['instance': instance, 'edit': true, 'mode': Constants.CREATE, 'instancename': instancename])
	}

def save = { save() }
def save()
	{
	def instance = service.save(params)
	if (instance.hasErrors())
		{
		 // redisplay the 'crud.gsp' view until the user corrects the validation issues
		 render('view': 'crud', 'model': ['instance': instance, 'edit': true, 'mode': Constants.CREATE, 'instancename': instancename])
		}
	else
		{
		 flash.message = "$instancename '${instance.toMessage()}' created"
		 redirect('action': 'list', 'id': instance?.id)	// The id passed in the URL is used to highlight the instance in the list
		}
	}

def formactions = { formactions() }
def formactions()
	{
	 // we use only one view for 'show', 'create' and 'update': the 'crud.gsp' view
	 // We come here from 'crud.gsp': captures all the button actions: 'save', 'delete', 'cancel'
	 // the action to perform is in params.operation, since it is the name of the buttons
	 // we cannot use the buttons name 'action' since it's used by Grails
	 // params: [id:4, operation:save, description:outdoors, name:t-shirt, action:formactions, defaultuniform:on, controller:uniform]
//	 println(">>>> InstanceController formactions params: $params")
	 // this method is called from 'crud.gsp' with the different actions: 'save', 'delete', 'cancel'

	 def instance = service.getById(params.id)
	 if (params.operation == 'cancel')
		{
		 if ((params.mode == Constants.EDIT) && params.id)
			{
			 redirect('action': 'show', 'id': params.id)
			 return
			}
		 // redirect 'cancel' to the list view by default
		 redirect('action': 'list', 'id': instance?.id)	// The id passed in the URL is used to highlight the instance in the list
		 return
		}

	 if (params.operation == 'save')
		{
		 if (params.id)	// if it's an existing instance to save
			{
			 update()
			}
		 else
			{
			 save()	// new instance to save
			}
		 return
		}

	 if (params.operation == 'edit') { edit() ; return }
	 if (params.operation == 'delete') { delete() ; return }

	 // We should never get here...
	}
}

in /controllers/StreettypeController.groovy

class StreettypeController extends InstanceController {

def streettypeService	// injected by Grails

// the delete, save and update actions only accept POST requests
static allowedMethods = ['delete': 'POST', 'save': 'POST', 'update': 'POST']

def setup()
	{
	 service = streettypeService
	 instancename = 'Street Type'	// for display
	}
}

in /views/Streettype/crud.gsp

<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/>
        <meta name="layout" content="main" />
		<!-- Streettype/crud.gsp -->
        <title>${instancename} Details</title>
    </head>
    <body>
        <div class="nav">
            <span class="menuButton"><a class="home" href="${createLinkTo(dir:'')}">Home</a></span>
            <span class="menuButton"><g:link class="list" action="list">${instancename} List</g:link></span>
            <span class="menuButton"><g:link class="create" action="create">New ${instancename}</g:link></span>
        </div>
        <div class="body">
            <h1>${title}</h1>

            <g:if test="${flash.message}">
            <div class="message">${flash.message}</div>
            </g:if>
            <g:hasErrors bean="${instance}">
            <div class="errors">
                <g:renderErrors bean="${instance}" as="list" />
            </div>
            </g:hasErrors>
			<%-- the 'formactions' closure is called in 'InstanceController' --%>
            <g:form action="formactions" method="post" >
                <div class="dialog">
                    <table>
                        <tbody>
                            <tr class="prop">
                                <td valign="top" class="name">
									<g:if test="${edit}">
										<label for="name">name</label>
									</g:if>
									<g:else>
										name
									</g:else>
                                </td>
                                <td valign="top" class="value ${hasErrors('bean': instance, field: 'name', 'errors')}">
									<g:if test="${edit}">
										<input type="text" maxlength="50" id="name" name="name" value="${fieldValue('bean': instance, 'field': 'name')}"/>
									</g:if>
									<g:else>
										${instance?.name}
									</g:else>
                                </td>
                            </tr>
                        </tbody>
                    </table>
                </div>
				<%-- Used in InstanceController/formactions --%>
                <input type="hidden" name="id" value="${instance?.id}" />
                <input type="hidden" name="mode" value="${mode}" />
                <div class="buttons">
					<g:if test="${edit}">
						<span class='button'><input class='save'  type='submit' name='operation' value='save'/></span>
					</g:if>
					<g:else>
						<span class='button'><input class='edit'  type='submit' name='operation' value='edit'/></span>
					</g:else>
					<g:if test="${mode != Constants.CREATE}">	<%-- Show the 'delete button only in 'show' or 'edit'. Not when creating a new instance --%>
						<span class='button'><input class='delete'  type='submit' name='operation' value='delete' onclick="return confirm('Delete, are you sure?');"/></span>
					</g:if>
						<span class='button'><input class='cancel' type='submit' name='operation' value='cancel'/></span>
                </div>
			</g:form>
        </div>
    </body>
</html>

in /views/Streettype/list.gsp

<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/>
        <meta name="layout" content="main" />
		<!-- Streettype/list.gsp -->
        <title>${instancename} List</title>
    </head>
    <body>
        <div class="nav">
            <span class="menuButton"><a class="home" href="${createLinkTo(dir:'')}">Home</a></span>
            <span class="menuButton"><g:link class="create" action="create">New ${instancename}</g:link></span>
        </div>
        <div class="body">
            <h1>${instancename} List</h1>
            <g:if test="${flash.message}">
            <div class="message">${flash.message}</div>
            </g:if>
            <div class="list">
                <table>
                    <thead>
                        <tr>
                   	        <th>name</th>
                        </tr>
                    </thead>
                    <tbody>
                    <g:each in="${instancelist}" status="i" var="instance">
					  <%-- need a css class 'selected' to highlight the line like this: "tr.selected { background-color: #FFFFA0;	/* lightyellow; */ }" --%>
                        <tr class="${(i % 2) == 0 ? 'odd' : 'even'}${(instance.id == selectedid) ? ' selected' : ''}">
                            <td class='streettype-name'><g:link action="show" id="${instance.id}">${instance.name}</g:link></td>
                        </tr>
                    </g:each>
                    </tbody>
                </table>
            </div>
<%--
			<div class="paginateButtons">
                <g:paginate total="${instancetotal}" />
            </div>
--%>
		</div>
    </body>
</html>

in main.css add

tr.selected {
	background-color: #FFFFA0;	/* lightyellow; */
}