Since Grails 2.3 all ${} expression output is automatically escaped on GSPs. This is very useful, because user input is now escaped and any HTML or JavaScript in the input value is escaped and not interpreted by the browser as HTML or JavaScript. This is done so our Grails application is protected from Cross Site Scripting (XSS) attacks.
But sometimes we do want to output unescaped HTML content in the web browser. For example we generate the value ourselves and we know the value is safe and cannot be misused for XSS attacks. In Grails 2.3 we can use a new raw() method in our GSPs, tag libraries or controllers. The method will leave the content unchanged and return the unescaped value to be displayed. Alternatively we can use encodeAsRaw() on the content we want to leave unescaped. Finally the encodeAs tag accepts Raw or None as values for the attribute codec and will return the unescaped value.
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Since Grails 2.3 it is very easy to define RESTful URL mappings for a controller. We can use the resources and resource attribute and use a controller name as the value. Grails will then automatically create a couple of URL mappings. Suppose we use the following mapping in grails-app/conf/UrlMappings.groovy: "/api/users"(resources: 'user'), then the following mappings are automatically created:
"/api/users/create"(controller: 'user', action: 'create', method: 'GET')
"/api/users/(*)/edit"(controller: 'user', action: 'edit', method: 'GET')
"/api/users(.(*))?"(controller: 'user', action: 'save', method: 'POST')
"/api/users(.(*))?"(controller: 'user', action: 'index', method: 'GET')
"/api/users/(*)(.(*))?"(controller: 'user', action: 'delete', method: 'DELETE')
"/api/users/(*)(.(*))?"(controller: 'user', action: 'update', method: 'PUT')
"/api/users/(*)(.(*))?"(controller: 'user', action: 'show', method: 'GET')
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In a Grails application we can organize our controllers into packages, but if we use the same name for multiple controllers, placed in different packages, then Grails cannot resolve the correct controller name. Grails ignores the package name when finding a controller by name. But with namespace support since Grails 2.3 we can have controllers with the same name, but we can use a namespace property to distinguish between the different controllers.
We can add a new static property to a controller class with the name namespace. The value of this property defines the namespace. We can then write new URL mappings in the grails-app/conf/UrlMappings.groovy file and use the namespace value as a mapping attribute.
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Grails has a built-in URL constraint to check if a String value is a valid URL. We can use the constraint in our code to check for example that the user input http://www.mrhaki.com is valid and http://www.invalid.url is not. The basic URL validation checks the value according to standards RFC1034 and RFC1123. If want to allow other domain names, for example server names found in our internal network, we can add an extra parameter to the URL constraint. We can pass a regular expressions or a list of regular expressions for patterns that we want to allow to pass the validation. This way we can add IP addresses, domain names and even port values that are all considered valid. The regular expression is matched against the so called authority part of the URL. The authority part is a hostname, colon (:) and port number.
In the following sample code we define a simple command object with a String property address. In the constraints block we use the URL constraint. We assign a list of regular expression String values to the URL constraint. Each of the given expressions are valid authorities, we want the validation to be valid. Instead of a list of values we can also assign one value if needed. If we don't want to add extra valid authorities we can simple use the parameter true.
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In Grails we can define properties for services, controller, taglibs, Spring components and other components in the Spring application context through configuration. This is called property overriding in Spring terminology. This feature is very useful to define or override property values on components in the application context. We can define the property values in a beans{} block in Config.groovy. We can also load external configuration files, like property files and define property values in those.
With property overriding we don't have to look for property values via an injected GrailsApplication object and the config property of GrailsApplication. The code using the property value is now much cleaner and easier to test.
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When we mock or stub methods we can use the method arguments passed to the method in the response for the mocked or stubbed method. We must write a closure after the rightShift operator (>>) and the closure arguments will resemble the arguments of the mocked or stubbed method. Alternatively we can use a single non-typed argument in the closure and this will contains the method argument list.
Let's create a specification where we use this feature. In the following sample we use a mock for the AgeService used in the class under test. The method allowedMaxTime() is invoked by the class under test and basically should return the maximum hour of the day a show can be broadcasted. In our specification we use the name of the show to return different values during the test.
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In a previous blog post we learned how we can unit test a template or view independently. But what if we want to unit test a controller that uses the render() method and a template with the template key instead of a view? Normally the view and model are stored in the modelAndView property of the response. We can even use shortcuts in our test code like view and model to check the result. But a render() method invocation with a template key will simply execute the template (also in test code) and the result is put in the response. With the text property of the response we can check the result.
In the following sample controller we use the header template and pass a username model property to render output.
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Since Grails 2 we can render binary output with the render() method and the file attribute. The file attribute can be assigned a byte[], File, InputStream or String value. Grails will try to determine the content type for files, but we can also use the contentType attribute to set the content type.
In the following controller we find an image in our application using grailsResourceLocator. Then we use the render() method and the file and contenType attributes to render the image in a browser:
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Grails uses Spring and we can piggyback on the Spring support for resource loading to find for examples files in the classpath of our application. We can use the Spring org.springframework.core.io.Resource or org.springframework.core.io.ResourceLoader interface to find resources in our application.
And since Grails 2.0 we can also use the org.codehaus.groovy.grails.core.io.ResourceLocator interface. In our code we can use the grailsResourceLocator service which implements the ResourceLocator interface. We must inject the grailsResourceLocator service into our code and we use the method findResourceForURI(String) to find a resource. The advantage of the grailsResourceLocator service is that it knows about a Grails application. For example resources in plugins can also be accessed.
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Spock has some great features to write specifications or tests that are short and compact. One of them is the old() method. The old() method can only be used in a then: block. With this method we get the value a statement had before the when: block is executed.
Let's see this with a simple example. In the following specification we create a StringBuilder with an initial value. In the then: block we use the same initial value for the assertion:
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There is really no excuse to not write unit tests in Grails. The support for writing tests is excellent, also for testing code that has to deal with the locale set in a user's request. For example we could have a controller or taglib that needs to access the locale. In a unit test we can invoke the addPreferredLocale() method on the mocked request object and assign a locale. The code under test uses the custom locale we set via this method.
In the following controller we create a NumberFormat object based on the locale in the request.
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Grails adds a couple of methods and properties to our controller classes automatically. One of the methods is the header() method. With this method we can set a response header with a name and value. The methods accepts two arguments: the first argument is the header name and the second argument is the header value.
In the following controller we invoke the header() method to set the header X-Powered-By with the Grails and Groovy version.
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