Beagle Framework

This section explains how to create a backend without using frameworks such as Spring or Micronaut. You will find the tools to create a BFF for your project.

It’s important to mention:

• Beagle was created to be independent, you don’t need a specific backend structure.
• starters of the initial configuration already does all the processes described on this page and automatically add the configuration below:

Follow the next steps to configure your BFF manually:

Step 1: Add dependencies

<dependency>
	<groupId>br.com.zup.beagle</groupId>
	<artifactId>framework</artifactId>
	<version>${beagle_version}</version>
</dependency>

Step 2: Configure the Jackson’s ObjectMapper

It is necessary to set up Jackson’s ObjectMapper for Beagle. To do this, follow the instructions:

• Register BeagleModule in your ObjectMapper:

val mapper = // however your ObjectMapper is initialized
mapper.registerModule(BeagleModule)

Step 3: Configure the platform’s specification mechanism

You have to configure a filter if you want the element’s platform filter to work. You should register a filter that verifies your BFF’s response and filters the sent elements according to the specified platform on your customized beagle-platform header.

The BeaglePlatformUtil class was created to provide some tools to make the configuration easier to be used in your filter. See below:

An example of a Spring interceptor:

class BeaglePlatformInterceptor(private val objectMapper: ObjectMapper) : HandlerInterceptor {

    override fun preHandle(request: HttpServletRequest, response: HttpServletResponse, handler: Any): Boolean {
        request.setAttribute(
            BeaglePlatformUtil.BEAGLE_PLATFORM_HEADER,
            request.getHeader(BeaglePlatformUtil.BEAGLE_PLATFORM_HEADER)
        )
        return true
    }

    override fun postHandle(
        request: HttpServletRequest,
        response: HttpServletResponse,
        handler: Any,
        modelAndView: ModelAndView?
    ) {
        val responseWrapper = (response as ContentCachingResponseWrapper)
        val jsonTree = this.objectMapper.readTree(responseWrapper.contentAsByteArray)
        BeaglePlatformUtil.treatBeaglePlatform(
            request.getHeader(BeaglePlatformUtil.BEAGLE_PLATFORM_HEADER),
            jsonTree
        )
        val jsonData = jsonTree.toPrettyString()
        responseWrapper.resetBuffer()
        responseWrapper.outputStream.write(jsonData.toByteArray())
        responseWrapper.setContentLength(jsonData.length)
    }
}

In the example above, preHandle passed the information from the platform and the request was made as an attribute so that it can be accessed by the BFF later. This will make the platform’s identification easier. There is also a postHandle that filters the elements according to the targeted platform in your BFF’s response.

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