IntelliJ IDEA 2016.3 re-introduced the Grails view for Grails 3 applications. Grails 2 applications already were supported with a Grails view in IDEA. Using this view we get an overview of all the Grails artifacts like controller, services, views and more. We can easily navigate to the the class files we need. Now this view is also available for Grails 3 applications. To enable the view we must click on the view selector in the project view:
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In a previous post we learned how to create a class that extends RuleSource with methods that define rules on how to create and change objects in the Gradle model space. With the model configuration block in a build file we can also define creation rules for Rule based model configuration.
In the following build file we define a model block and define a creation rule for creating the object versionInfo of type VersionFile. Also we add a new task to the tasks object of type ModelMap<Task>:
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Rule based model configuration in Gradle allows us to have a graph of objects with dependencies that are resolved by Gradle. To make this work Gradle needs to know about the object in this model space. The model space is populated with objects of our own and with objects from Gradle. At time of writing this blog post we can not interact with the Gradle Project object in our rule based model configuration. It is not officially part of the model space. Probably in the future this might change and will the Project object managed by Gradle be part of the model space. Which means we can use then a Project object as input parameter for any rule methods we have. For now the official way to pass project information to the rule based model space is via the model configuration block in our build script. The model configuration block can be used to set properties on objects with values from our Project object.
In the following example we have VersionFile object that is part of the model space.
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Rule based model configuration gives Gradle more knowledge about the objects and their dependencies. This information can be used by Gradle to optimise the build process. We define rules on how we want Gradle to create objects and how we want to mutate objects in a class that extends RuleSource. We can also add rules to validate objects available in the Gradle model space. We use the @Validate annotation on methods that have validation logic. The first argument of the method is of the type of the object we want to validate. This type must be managed by Gradle.
In the following example we use the sample from a previous post. In this sample we have a VersionFile class that is managed by Gradle. The class has a version and outputFile property. The version must be set and must start with a v. The outputFile property is also required.
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Gradle 3.2 deprecates the << operator to add actions to a task. The << operator maps to the leftShift method of a task. This operator confuses a lot people that are new to Gradle. Because without the operator we are configuring a task instead of adding actions. I can tell from experience the mistake is easily made. If we use the << in our build script with Gradle 3.2 we get a warning on the console. The warning message already mentions a solution: use the doLast method to add actions.
In the following example build script we define the task deprecatedSample using the << operator. The other task newSample uses the doLast method to add an action:
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When we use Rule based model configuration in our Gradle project we can give Gradle rules on how to manage objects from the model space. These rules are defined in a class that extends RuleSource. When we want to set some default values for properties of a model object (in Gradle terms this is a subject) we can use the @Defaults annotation. Rules annotated with @Defaults are invoked right after the object is created and before any other methods that can mutate the state of the object.
The method, to set the default values, must have the type of the object as first parameter. Other parameters are considered input parameters and can be used to set a default value based on other model objects.
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Some time ago I went to a Meetup session “Death To Null” by Ties van de Ven from JDriven.
During the presentation it became clear that it wasn‘t so much about null checks and NullPointerExceptions but more about Immutability and how it can help keep your software free of bugs and NullPointerExceptions.
One of the statements that got me thinking was (something along the lines of): “Java chose the wrong default.
Instead of making everything explicitly final when we want an immutable variable, everything should be implicitly final unless the developer makes it explicitly mutable”.
Not knowing that much about the implementation of annotations I thought it would be fun to try to write an annotation which would do exactly that.
The first bump I encountered is that annotations cannot modify the programmers source code, or the classes generated from this source code; they can generate new sources or validate code.
This quickly turned my attention to project Lombok which does that already.
If you use project Lombok for the generation of getters and setters these never show up in your source code.
How can your IDE still hint at the existence of the getters and setters?
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We use the model task to see which objects are available in the Gradle model space. The model spaced is managed by Rule based model configuration. Objects can be defined as hidden by the object author(s). By default a hidden object is not shown in the model report. We must use the task option --showHidden to show also the hidden objects in the model report.
$ gradle -q model --showHidden
------------------------------------------------------------
Root project
------------------------------------------------------------
+ buildDir
| Type: java.io.File
| Value: /Users/mrhaki/Projects/sample/build
| Creator: Project..buildDir()
+ extensionContainer
| Type: org.gradle.api.plugins.ExtensionContainer
| Creator: Project..extensionContainer()
+ fileOperations
| Type: org.gradle.api.internal.file.FileOperations
| Creator: DefaultProject.BasicServicesRules#fileOperations(ServiceRegistry)
+ instantiator
| Type: org.gradle.internal.reflect.Instantiator
| Creator: DefaultProject.BasicServicesRules#instantiator(ServiceRegistry)
+ nodeInitializerRegistry
| Type: org.gradle.model.internal.core.NodeInitializerRegistry
| Creator: DefaultProject.BasicServicesRules#nodeInitializerRegistry(ModelSchemaStore, StructBindingsStore)
+ projectIdentifier
| Type: org.gradle.api.internal.project.ProjectIdentifier
| Value: root project 'versionrule'
| Creator: Project..projectIdentifier()
+ proxyFactory
| Type: org.gradle.model.internal.manage.instance.ManagedProxyFactory
| Creator: DefaultProject.BasicServicesRules#proxyFactory(ServiceRegistry)
+ schemaStore
| Type: org.gradle.model.internal.manage.schema.ModelSchemaStore
| Creator: DefaultProject.BasicServicesRules#schemaStore(ServiceRegistry)
+ serviceRegistry
| Type: org.gradle.internal.service.ServiceRegistry
| Value: ProjectScopeServices
| Creator: Project..serviceRegistry()
+ sourceDirectorySetFactory
| Type: org.gradle.api.internal.file.SourceDirectorySetFactory
| Creator: DefaultProject.BasicServicesRules#sourceDirectorySetFactory(ServiceRegistry)
+ structBindingsStore
| Type: org.gradle.model.internal.manage.binding.StructBindingsStore
| Creator: DefaultProject.BasicServicesRules#structBindingsStore(ServiceRegistry)
+ taskFactory
| Type: org.gradle.api.internal.project.taskfactory.ITaskFactory
| Creator: DefaultProject.BasicServicesRules#taskFactory(ServiceRegistry)
+ tasks
| Type: org.gradle.model.ModelMap | Creator: Project..tasks()
| Rules:
⤷ VersionFileTaskRules#createVersionFileTask(ModelMap, VersionFile)
+ buildEnvironment
| Type: org.gradle.api.tasks.diagnostics.BuildEnvironmentReportTask
| Value: task ':buildEnvironment'
| Creator: tasks.addPlaceholderAction(buildEnvironment)
| Rules:
⤷ copyToTaskContainer
+ components
| Type: org.gradle.api.reporting.components.ComponentReport
| Value: task ':components'
| Creator: tasks.addPlaceholderAction(components)
| Rules:
⤷ copyToTaskContainer
+ dependencies
| Type: org.gradle.api.tasks.diagnostics.DependencyReportTask
| Value: task ':dependencies'
| Creator: tasks.addPlaceholderAction(dependencies)
| Rules:
⤷ copyToTaskContainer
+ dependencyInsight
| Type: org.gradle.api.tasks.diagnostics.DependencyInsightReportTask
| Value: task ':dependencyInsight'
| Creator: tasks.addPlaceholderAction(dependencyInsight)
| Rules:
⤷ HelpTasksPlugin.Rules#addDefaultDependenciesReportConfiguration(DependencyInsightReportTask, ServiceRegistry)
⤷ copyToTaskContainer
+ dependentComponents
| Type: org.gradle.api.reporting.dependents.DependentComponentsReport
| Value: task ':dependentComponents'
| Creator: tasks.addPlaceholderAction(dependentComponents)
| Rules:
⤷ copyToTaskContainer
+ generateVersionFile
| Type: mrhaki.gradle.VersionFileTask
| Value: task ':generateVersionFile'
| Creator: VersionFileTaskRules#createVersionFileTask(ModelMap, VersionFile) > create(generateVersionFile)
| Rules:
⤷ copyToTaskContainer
+ help
| Type: org.gradle.configuration.Help
| Value: task ':help'
| Creator: tasks.addPlaceholderAction(help)
| Rules:
⤷ copyToTaskContainer
+ init
| Type: org.gradle.buildinit.tasks.InitBuild
| Value: task ':init'
| Creator: tasks.addPlaceholderAction(init)
| Rules:
⤷ copyToTaskContainer
+ model
| Type: org.gradle.api.reporting.model.ModelReport
| Value: task ':model'
| Creator: tasks.addPlaceholderAction(model)
| Rules:
⤷ copyToTaskContainer
+ projects
| Type: org.gradle.api.tasks.diagnostics.ProjectReportTask
| Value: task ':projects'
| Creator: tasks.addPlaceholderAction(projects)
| Rules:
⤷ copyToTaskContainer
+ properties
| Type: org.gradle.api.tasks.diagnostics.PropertyReportTask
| Value: task ':properties'
| Creator: tasks.addPlaceholderAction(properties)
| Rules:
⤷ copyToTaskContainer
+ tasks
| Type: org.gradle.api.tasks.diagnostics.TaskReportTask
| Value: task ':tasks'
| Creator: tasks.addPlaceholderAction(tasks)
| Rules:
⤷ copyToTaskContainer
+ wrapper
| Type: org.gradle.api.tasks.wrapper.Wrapper
| Value: task ':wrapper'
| Creator: tasks.addPlaceholderAction(wrapper)
| Rules:
⤷ copyToTaskContainer
+ typeConverter
| Type: org.gradle.internal.typeconversion.TypeConverter
| Creator: DefaultProject.BasicServicesRules#typeConverter(ServiceRegistry)
+ versionFile
| Type: mrhaki.gradle.VersionFile
| Creator: VersionFileTaskRules#versionFile(VersionFile)
| Rules:
⤷ versionFile { ... } @ build.gradle line 8, column 5
+ outputFile
| Type: java.io.File
| Value: /Users/mrhaki/Projects/sample/build/version.txt
| Creator: VersionFileTaskRules#versionFile(VersionFile)
+ version
| Type: java.lang.String
| Value: 1.0.1.RELEASE
| Creator: VersionFileTaskRules#versionFile(VersionFile)
$
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The Gradle model task shows the objects in the model space of Gradle. The output shows the object hierarchy. By default a full report is shown, with a lot of information. We can customize the output format with the --format task argument. The default value is full, but we can also use the value short. With the value short a lot less information is shown.
Let's see the output of the model task for a sample project:
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When playing around in Polymer, we encounter iron signals. Besides normal javascript events, this gives us a lot of options for dealing with events. Lets try it all out! We can catch events using the on-event attribute:
1
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In general a REST service serves JSON document formats.
In Spring Boot it is even the standard without having to configure anything.
Over HTTP we have the ability to send a Content-Type as header to instruct the server to return a certain document format (Mime type).
Besides handling JSON, XML is another common document format.
But what if we want to serve or read a YAML document format? This tutorial provides the required steps to be able to handle objects in YAML format.
To be able to send a YAML Content-Type with the header, and to be able to serialize and deserialize with the existing ObjectMappers of Jackson.
This tutorial will use Spring Boot, Jackson and a YAML dataformat extension library for Jackson.
First we need to add the YAML Jackson extension to our Gradle build file.
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Gradle has an incubating feature Rule based model configuration.
This is a new way to configure Gradle projects where Gradle has more control of the configuration and the dependencies between configuration objects.
This allows Gradle to resolve configuration values before they are used, because Gradle knows there is a dependency.
With this new model we don't need any lazy evaluation "tricks" we had to use.
For example there was an internal convention mapping mechanism for tasks to assign values to a task configuration after the task was already created.
Also the project.afterEvalute is a mechanism to have late binding for task properties.
With the new rule based model Gradle can do without these options, we can rely on Gradle resolving all dependent configuration values when we create a task.
In Gradle we already know about the "project space" where the Project object is the root of the object graph.
For example repositories are part of the project space. Gradle can get some useful information from the project space, but it is mostly a graph of objects that Gradle only partially can reason about.
Then we have the "model space".
This is part of a project and we can use it in our build script with the model configuration block.
The model space is separate from the project space and contains objects that are managed by Gradle.
Gradle knows dependencies between the objects and how to create and change them.
This helps Gradle to optimise build logic.
To help Gradle we must define rules to work with objects in the model space.
Each rule is like a recipe for Gradle on how to work with the model.
Gradle can build a graph of models and know about dependencies between models.
This way Gradle guarantees that model objects are completely configured before being used.
For example if a rule needs a VersionFile model configuration object then Gradle makes sure that the VersionFile is created and all properties are set.
So we don't need any lazy or late binding anymore, because the properties will be set (Gradle makes sure) when we want to use them.
The rules are defined a class that extends RuleSource.
Such a class is stateless and only contains methods to work with the model objects.
Gradle has some specific annotations that can be used on methods to indicate what a method should do.
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