A quick journey through Grails searchable plugin

Grails searchable plugin is a great Compass based tool to implement search in Grails. As a part of my server inventory app, I used it to implement Ajax based search where search results update as you type. The relevant part of my domain model looks like this:

class BaseDomain {
    Date dateCreated
    Date lastUpdated
    Boolean active = true
}

class Host extends BaseDomain {
    String ipAddress
    String hostName
    Site site
}

class Site extends BaseDomain {
    String name
    String description
}

Objective: user searches for matching hosts by either IP address, host name, site name, as well as filter by active/inactive field.


Defining searchable fields.

class Host extends BaseDomain {
    static searchable = {
        only: ["ipAddress", "hostName", "site", "active"]
        ipAddress boost: 2.0
        hostName boost: 2.0 
        site component: true
    }

    String ipAddress
    String hostName
    Site site
}

class Site extends BaseDomain {
    static searchable = { 
        only: ["name", "active"]
    }

    String name
    String description
}

"ipAddress" and "hostName" get a boost over "active" and Site.name. Site is defined as searchable component, meaning if a match is found on a site name, the Host that has a Site whose name matched the query is returned in the search result.


Working the query

User submitted query string should be a wildcard match on Host.ipAddress and Host.hostName fields, so if we have following data:

ip address	127.0.0.1
host name	localhost
active	true
site name	yahoo

queries like '127.0' or '0.0.1', 'local', 'calho' , 'yahoo', should all produce the above Host object as a match. Since there is only one search field, there is no way to know if what a user submitted is an ip address, a host name, or a site, therefore, all fields need to be checked. So, if a user submits "127.0", the query string for search should look like this:

ipAddress:*127.0* OR hostName:*127.0*

Since Site is a component, its matches are to be handled separately inside the search closure:

def wildcardQuery = "*" + params.query + "*"
def searchQuery = "ipAddress:" + wildcardQuery + " OR hostName:" + wildcardQuery 
return Host.search({
    must {
        queryString(searchQuery)
        wildcard('$/Host/site/name', wildcardQuery)
    }
}, params)

Then we add search for only active Hosts unless 'inactive' flag is set:

return Host.search({
    must {
        queryString(searchQuery)
        wildcard('$/Host/site/name', wildcardQuery)
    }
    if (!params.inactive) {
        must(term('$/Host/active', "true"))
    }
}, params) 

Now, let's add sort to the query. Technically, nothing needs to be added to the above snippet as long as there is a params.sort in the request. It works fine for fields like "ipAddress" and "hostName". However, if sorting by Site.name or 'active', actual "sort" request parameter must contain '$/Host/site/name' and '$/Host/active', which is not very convenient. It is more practical to have "site" and "active" as the value for params.sort, clone params into a separate map, and then overwrite sort param with the right value. This is how entire search closure looks:

def search = { 
    def searchParams = [:]
    params.each {
        searchParams."$it.key" = it.value
    }

    switch (params.sort) {
        case "site" :
            searchParams.sort = '$/Host/site/name'
            break
        case "active" :
            searchParams.sort = '$/Host/active'
    }

    def wildcardQuery = "*" + searchParams.query + "*"
    def searchQuery = "ipAddress:" + wildcardQuery + " OR hostName:" + wildcardQuery 
    return Host.search({
        must {
            queryString(searchQuery)
            wildcard('$/Host/site/name', wildcardQuery)
        }
        if (!params.inactive) {
            must(term('$/Host/active', "true"))
        }
    }, searchParams)
}

Reverse sort dropdown values in a GSP page

In a GSP page in a Grails application, it is easy to sort values in a dropdown in ascending order. Just pass a closure to sort() call with the name of the attribute to sort by.

${i.name}

It is just as easy to sort in descending order. Just provide a sort closure with 2 parameters and return 1 or -1 as in a Comparator.compare() method.

${i.name}

... or see Tom's post below.

Using your application classes inside Grails Gant script

So you have a Grails application, and want to script some cool things on top of it, like calling your RESTful service, using dynamic finders on domain classes, or adding new records using Hibernate. No surprise, there are some caveats that await for you on the way. Let's see what they are:

1. Loading your application context

This is an obvious first step, and this is what Grails expects you to do:

includeTargets << grailsScript("_GrailsBootstrap")   
target(main: "My Gant script") {       
    depends(configureProxy, packageApp, classpath, loadApp, configureApp, compile)       
    ...  
}   
setDefaultTarget("main")   

Yep, all these parts of depends() clause are needed, although "compile" part is needed only if domain objects are directly used, i.e., MyDomainClass.findByAttr().

2. Setting target environment

Two ways to do that. Standard grails way:

grails prod my-script    - for environments pre-defined in Grails, such as 'dev' or 'prod'
grails -Dgrails.env=stage my-script     - for custom environments

or place this at the beginning of your script:

scriptEnv = "envName"
and then simply run
grails my-script

3. Accessing your application classes and calling methods on them

The following example shows how to call a service method in your Gant script.

def serviceClass = grailsApp.getClassForName("com.killerapp.AwesomeService")
def serviceClassMethod = serviceClass.metaClass.getMetaMethod("blazingMethod")
def service = appCtx.getBean("awesomeService")
serviceClassMethod.invoke(service, [arg1, arg2] as Object[])

As seen in the example, there are 2 implicit variables that the script provides: "grailsApp" and "appCtx". First one is an instance of org.codehaus.groovy.grails.commons.GrailsApplication, and the second one is an instance of org.springframework.context.ApplicationContext. To call a service method, both are needed: grailsApp helps retrieve an instance of MetaMethod wrapper of the method you want to call. However, MetaMethod has to be called on a specific instance, which is Spring context singleton that Grails application creates when it initializes. appCtx helps retrieve that singleton. 
However, this is not enough. Your service method has to be defined as an actual method, like this:

void blazingMethod(arg1, arg2) {
      ...
}

, NOT a closure:

def blazingMethod { arg1, arg2 ->
      ...
}

That is because groovy closures are compiled into non-anonymous inner classes, not regular Java methods. Therefore, accessing closures by name will not work.


4. Running queries

To run dynamic finders, nothing extra needs to be done:

MyDomainClass.findByName("someName")

To run updates, an instance of org.springframework.orm.hibernate3.HibernateTemplate is needed. It can be obtained using appCtx:

def sessionFactory = appCtx.getBean("sessionFactory")
def template = new HibernateTemplate(sessionFactory)
def newRecord = new MyDomainClass(name: "someName")
template.saveOrUpdate(newRecord)

HibernateTemplate can also be used for queries, like this:

def domainClass = grailsApp.getClassForName("com.killerapp.MyDomainClass")
def allRecords = template.loadAll(domainClass) 

5. Cleaning script cache

As of Grails 1.3.4, using depends(compile) with accessing domain classes in a Gant script generates the following error simply running a script once, then making a change and re-running it:

java.lang.NoClassDefFoundError: com.killerapp.MyDomainClass

This is because scriptCache needs to be cleaned. Simply delete ~/.grails/1.3.4/projects/killerApp/scriptCache/ directory, and rerun the script.

Grails UrlMappings - mutually exclusive patterns

Let's say, I have URL patterns that are mutually exclusive and have to map to 2 different controllers. For instance, if I have an enum Vals with the following values: ROCK, PAPER, SCISSORS, and I want URLs like

/root/group/rock (or ROCK)

/root/group/paper (or PAPER) 

/root/group/scissors (or SCISSORS) to map to YouWinController

and

/root/group/(everything-else-but-ROCK|rock|PAPER|paper|SCISSORS|scissors) to map to YouLoseController

Both URL patterns are very similar, because each one consists of 3 strings separated by '/'. We can start by defining some constraints, but at the same time we have to define the exclusive pattern first. In this case, exclusive pattern is the one mapping to YouLoseController.

class UrlMappings {
    static mappings = {
        "/root/group/$loseParam"(controller: "youLose", action: "/loseAction")
        "/root/group/$winParam"(controller: "youWin", action: "/winAction") {
            constraints {
                  // get all string values from the enum
                  def list = stringList(Vals) 
                  // make sure lowercase values are also included
                  list.addAll(list*.toLowerCase()) 
                  $winParam(inList: list)
            }
        }
    }
}

Criteria queries don't work properly with Grails Enums

Looks like Grails (as of version 1.3.1) still didn't fix all the issues with Enums.

I'm using a criteria query like this:

c = MyDomainClass.createCriteria()
def list = c.list {
    and {
        classAttr {
            eq ("attr1", param1)
        }
        eq ("enumAttr", param2)
    }
} 

In this case, MyDomainClass.enumAttr represents an enum. It looks something like this:

enum CountryEnum {
    AUSTRIA("austria")
    BRAZIL("brazil")
    CANADA("canada")

    String name

    CountryEnum(String name) {
        this.name = name
    }
}

Grails, quite wisely, stores 'AUSTRIA', 'BRAZIL', and 'CANADA' in the DB.
However, the above criteria query generates the following error:

java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Enum

There a little section about Enums in Grails 1.1 release notes, which mentions that the value attribute should now be named 'id'. However switching 'name' to 'id' in my CountryEnum simply got rid of the exception, but the 'list' was still empty after the query completed. Extracting SQL from Hibernate debug output produced valid results, which means the problem lies somewhere in the Hibernate layer. Also DB values became 'austria', 'brazil', and 'canada', which are the values of 'id'.

Dynamic finders seem to handle Enums pretty well, but evidently the problem still exists when using Criteria or HQL.

Grails: using Groovy MarkupBuilder to render properly indented XML

When using Grails, the easiest way to render XML is to use 

 render obj as XML

command. However, that returns the entire XML on one line.

If you want XML to look pretty, you can use groovy.xml.MarkupBuilder

def showXml = {
    def writer = new StringWriter() 
    new MarkupBuilder(writer).root {
        child1 {
            child2('someValue')
        }       
    }

    render(text: writer.toString(), contentType: "text/xml")
}

This will produce a neat output where each tag is on a new line and properly indented.