Changes for page Multipart form-data

Last modified by Erik Bakker on 2024/06/17 11:39

From 9.2 to 9.1 From 20.1 to 19.1

From version 19.1

edited by Erik Bakker
on 2022/08/05 14:33

Change comment: There is no comment for this version

To version 9.2

edited by Erik Bakker
on 2022/07/26 13:04

Change comment: Update document after refactoring.

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--Multipart form-data
++expert-securing-data-traffic-api-gw-security-external-idp

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  {{container}}{{container layoutStyle="columns"}}(((
--Sometimes when you call an external REST endpoint, they require you to send meta information and one or more "attachments" in one call to the REST endpoint. To make this possible, you need to send the information with the contentType called multipart/form-data. In this microlearning, we will discuss how you can configure a valid message within the eMagiz platform that allows you to send out messages with this contentType and have them accepted by the endpoint in question.
++In most cases, you will transform XML messages to other XML messages, or you will transform JSON or EDI messages in another of these formats. However, sometimes you want to perform an image transformation. With this image transformation, you can convert images in specific formats to another format (i.e., png). This can come in handy when you want to standardize the image format before using it further downstream in your business application(s).
  Should you have any questions, please get in touch with [[academy@emagiz.com>>mailto:academy@emagiz.com]].
@@ -9,78 +9,55 @@
  == 2. Key concepts ==
--This microlearning focuses on configuring a multipart/form-data message within eMagiz to ensure it is sent correctly to an endpoint.
++This microlearning focuses on performing image transformations in eMagiz.
--Key aspects are:
++By image transformation, we mean transforming the raw data that represents an image into another image format.
--* Defining the boundary that separates the parts of the message
--* Defining the content types of each part of the message
--* Construction of the complete message according to the specification
++* Read the help text of the component to understand which formats are supported
++* Ensure the input image is supplied in the correct format
++* Ensure you wrap the output image in something if you want to do additional transformations on the data further downstream
--== 3. Multipart form-data ==
++== 3. Image Transformation ==
--Sometimes when you call an external REST endpoint, they require you to send meta information and one or more "attachments" in one call to the REST endpoint. To make this possible, you need to send the information with the contentType called multipart/form-data. In this microlearning, we will discuss how you can configure a valid message within the eMagiz platform that allows you to send out messages with this contentType and have them accepted by the endpoint in question.
++In most cases, you will transform XML messages to other XML messages, or you will transform JSON or EDI messages in another of these formats. However, sometimes you want to perform an image transformation. With this image transformation, you can convert images in specific formats to another format (i.e., png). This can come in handy when you want to standardize the image format before using it further downstream in your business application(s).
--Key aspects are:
++Before we dive into the specifics of how to configure this, let us first consider the following:
--* Defining the boundary that separates the parts of the message
--* Defining the content types of each part of the message
--* Construction of the complete message according to the specification
++* Read the help text of the component to understand which formats are supported
++* Ensure the input image is supplied in the correct format
++* Ensure you wrap the output image in something if you want to do additional transformations on the data further downstream
--To actually construct the message there a several steps needed to make it work. Luckily, most of the steps needed have to do with concepts we have already discussed in previous microlearnings. As you can imagine based on what mulipart/form-data entails we need a way to both store the meta information and the file(s) we want to send to the external party. To do so it is advisable to put the metadata in one (or multiple) header(s) and use the file content as payload. This you can achieve with a header enricher and standard transformer.
++{{warning}} This microlearning focuses on the image transformer component. Ensuring that the input is valid and the output fits the remainder of the process is highly dependent on the use case and will therefore not be discussed in this microlearning{{/warning}}
--Once the file content is your payload you need to make sure that the data is "raw" in nature. So when you have a base64 encoded string you should decode the string before sending it to the endpoint.
++When turning to the Create phase of eMagiz, we need to open the flow and enter "Start Editing" mode to add the necessary component. For example, in the left panel, you can search for "Image." This will yield the following result.
--On top of that we need to define the contentType header as follows.
++[[image:Main.Images.Microlearning.WebHome@expert-create-your-transformations-image-transformation-image-transformation-component.png]]
--[[image:Main.Images.Microlearning.WebHome@expert-data-handling-multipart-form-data--content-type-header-config.png]]
++After dragging the component onto the canvas, you must define the channels first.
--After you have set the stage you can use a standard transformer component to build your message in the correct manner. To build it correctly you need to take the following into account:
++[[image:Main.Images.Microlearning.WebHome@expert-create-your-transformations-image-transformation-image-transformation-component-help.png]]
--* Each part of the message needs to be seperated by a boundary
--* The message needs to start with a boundary and finish with a boundary
--* Line breaks are needed to differentiate between the boundary and the text content
--* No line break is needed when the content is not text based
++Secondly, we must select the desired image format we want to transform. Finally, the field indicates all valid values you can choose. Please note that 'PNG' is the default selection.
--Given all this you can write the following SpEL expression that will yield a desirable output:
++[[image:Main.Images.Microlearning.WebHome@expert-create-your-transformations-image-transformation-image-transformation-component-image-options.png]]
--{{code}}test{{/code}}
++Once you have done this, the component configuration is finished, and you can transform your input image to a desired output image format.
--Most users would think that communication via queues to connect two separate eMagiz models is a bright idea. However, this is something that we do not encourage. We discourage this for several practical and technical reasons alike.
--
--When looking at the practical side of things getting it configured correctly is time-consuming and an error-prone action (as is evident by the question). Furthermore, it can lead to unexpected situations where you make a typo to listen to a queue on which no messages are provided. This queue will, however, be registered on the JMS level (when you activate the flow in question with the custom configuration), which can lead to confusing queue statistics and even more troublesome false-positive alerting based on missing queue metrics or missing consumers.
--
--On top of that, when you allow one model to write and read from queues registered in another model, maintaining both models will become very complex. This holds for the ones working on the project at the moment but also for those working on it at a later stage and does that need to provide (incidental) support on the environments.
--
--Another practical reason for not wanting this is that we do not actively support this use case from eMagiz. This means that when we update our technical infrastructure, we will not consider this scenario. This could lead to additional work in the future and reduced stability of your solution.
--
--From the technical point of view, the consequence of this construction is that both models need to know each other certificates and credentials, which are not considered secure. On top of that, because you, theoretically, can exchange data from any queue to any queue, you could create a situation in which updates in one model trigger changes in the other model (i.e., when using the same data model) that are unexpected (and frankly unwanted).
--
--We advise using functionality that makes it explicit that both models function independently of each other. From eMagiz, we consider two valid alternatives for this:
--- Using a web service as a communication layer between the two models. This web service can be REST or SOAP and has been implemented before
--- Using the Event Streaming functionality of eMagiz to write and read from topics.
--
--Both alternatives have the benefit that the security can be tight and explicit (i.e., only model A can write/post data to model B). Furthermore, managing the solution becomes much easier as it uses the standard functionality within the platform. Therefore, we have no plans to support this approach in the product.
--
  == 4. Assignment ==
--Consider what your criteria are when communicating between models and compare them to our criteria.
--This assignment can be completed with the help of the (Academy) project you created/used in the previous assignment.
++Check whether the solution we discussed today can be found within your project.
++This assignment can be completed within the (Academy) project you created/used in the previous assignment.
  == 5. Key takeaways ==
--* Consider the following when communication between two models
--** Security
--** Loose coupling
--** Maintainability
--** Clarity
++* Read the help text of the component to understand which formats are supported
++* Ensure the input image is supplied in the correct format
++* Ensure you wrap the output image in something if you want to do additional transformations on the data further downstream
  == 6. Suggested Additional Readings ==
--If you are interested in this topic please read the helptexts in the platform and read the following link:
++If you are interested in this topic and want more information, please read the help text provided by eMagiz.
--* https://www.sobyte.net/post/2021-12/learn-about-http-multipart-form-data/
--
  == 7. Silent demonstration video ==
  As this is more of theoretical microlearning, there is no video accompanying the microlearning.)))((({{toc/}}))){{/container}}{{/container}}

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