Ratpack

Ratpacked: Conditionally Map Or Flatmap A Promise

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Hubert Klein Ikkink

When we want to transform a Promise value we can use the map and flatMap methods. There are also variants to this methods that will only transform a value when a given predicate is true: mapIf and flatMapIf. We provide a predicate and function to the methods. If the predicate is true the function is invoked, otherwise the function is not invoked and the promised value is returned as is.

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Ratpacked: Override Registry Objects With Mocks In Integration Specifications

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Hubert Klein Ikkink

Testing a Ratpack application is not difficult. Ratpack has excellent support for writing unit and integration tests. When we create the fixture MainClassApplicationUnderTest we can override the method addImpositions to add mock objects to the application. We can add them using the ImpositionsSpec object. When the application starts with the test fixture the provided mock objects are used instead of the original objects. For a Groovy based Ratpack application we can do the same thing when we create the fixture GroovyRatpackMainApplicationUnderTest.

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Ratpacked: Combine Groovy DSL With RatpackServer Java Configuration

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Hubert Klein Ikkink

We have several options to define a Ratpack application. We can use a Java syntax to set up the bindings and handlers. Or we can use the very nice Groovy DSL. It turns out we can use both together as well. For example we can define the handlers with the Groovy DSL and the rest of the application definition is written in Java. To combine both we start with the Java configuration and use the bindings and handlers method of the Groovy.Script class to inject the files with the Groovy DSL.

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Ratpacked: Type Check And Static Compilation For Groovy DSL

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Hubert Klein Ikkink

One of the very nice features of Ratpack is the Groovy DSL to define our application. We get a nice DSL to set up the registry, to define handlers and more. Because of clever use of the @DelegateTo annotation we get good code completion in our IDE. We can also add static compilation of our Groovy DSL when we start our Ratpack application. With static compilation the script is type checked at compile time so we get earlier feedback on possible errors in the script. To configure static compilation we must invoke the app method of the Groovy.Script class with the argument true.

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Ratpacked: Implement Custom Rendering With Renderable Interface

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Hubert Klein Ikkink

Ratpack uses renderers to render output. We can create our own renderer by implementing the Renderer interface. The renderer class needs to implement a render method that has the object we want to render as argument. Alternatively we can add the logic to render a object to the class definition of that object. So instead of having a separate renderer class for a class, we add the render logic to the class itself. To achieve this we must implement the Renderable interface for our class. Ratpack provides a RenderableRenderer in the registry that knows how to render classes that implement the Renderable interface.

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Ratpacked: Implement A Custom Request Parser

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Hubert Klein Ikkink

Ratpack has parsers to parse a request with a JSON body or a HTML form. We simply use the parse method of Context and Ratpack will check if there is a compliant parser in the registry. If there is a parser for that type available then Ratpack will parse the request and return a Promise with the value. To write a new parser we need to implement the Parser interface. The easiest way to implement this interface is by writing a class that extends ParserSupport. Using the ParserSupport class we can also work with an options object that a user can pass on to the parse method of Context. If we don’t need options we can also extend the NoOptParserSupport class.

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Ratpacked: Using Spring Cloud Contract As Client

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Hubert Klein Ikkink

In a previous post we learned about Spring Cloud Contract. We saw how we can use contracts to implement the server side of the contract. But Spring Cloud Contract also creates a stub based on the contract. The stub server is implemented with Wiremock and Spring Boot. The server can match incoming requests with the contracts and send back the response as defined in the contract. Let’s write an application that is invoking HTTP requests on the server application we wrote before. In the tests that we write for this client application we use the stub that is generated by Spring Cloud Contract. We know the stub is following the contract of the actual server.

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Ratpacked: Using Spring Cloud Contract To Implement Server

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Hubert Klein Ikkink

Spring Cloud Contract is a project that allows to write a contract for a service using a Groovy DSL. In the contract we describe the expected requests and responses for the service. From this contract a stub is generated that can be used by a client application to test the code that invokes the service. Spring Cloud Contract also generates tests based on the contract for the service implementation. Let’s see how we can use the generated tests for the service implementation for a Ratpack application.

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Ratpacked: Creating Pairs From Promises

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Hubert Klein Ikkink

The Pair class in Ratpack is an easy way to create a growing data structure, passed on via Promise methods. A Pair object has a left and right part containing data. These parts can even be other Pair objects. Since Ratpack 1.4.0 the Promise class has methods to set the right or left part of a Pair: left, flatLeft, right and flatRight. The result of these methods is a Promise<Pair> object. The input can be Promise type or a Function that can use a previous Promise.

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Ratpacked: Create a Partial Response

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Hubert Klein Ikkink

Suppose we want to support partial JSON responses in our Ratpack application. The user must send a request parameter with a list of fields that need to be part of the response. In our code we must use the value of the request parameter and output only the given properties of an object. We implement this logic using a custom renderer in Ratpack. Inside the renderer we can get access to the request parameters of the original request.

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Ratpacked: Using Groovy Configuration Scripts As Configuration Source

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Hubert Klein Ikkink

Ratpack has a lot of options to add configuration data to our application. We can use for example YAML and JSON files, properties, environment variables and Java system properties. Groovy has the ConfigSlurper class to parse Groovy script with configuration data. It even supports an environments block to set configuration value for a specific environment. If we want to support Groovy scripts as configuration definition we write a class that implements the ratpack.config.ConfigSource interface.

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