Changes for page Multipart form-data

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

From 13.2 to 13.1 From 19.1 to 18.1

From version 18.1

edited by Erik Bakker
on 2022/08/05 14:24

Change comment: There is no comment for this version

To version 13.2

edited by Erik Bakker
on 2022/07/28 10:28

Change comment: Update document after refactoring.

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--Multipart form-data
++expert-data-handling-communication-between-models

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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 a low-code platform like eMagiz, you want to prevent using custom scripting as much as possible. However, sometimes in practice, you encounter situations that cannot be realized with the standard toolbox provided within the platform. As a result, we offer the option to use a Groovy script in these situations to achieve the desired solution. In this microlearning, we will look at where you can use a Groovy script and discuss the key considerations when implementing a Groovy script within your model.
  Should you have any questions, please get in touch with [[academy@emagiz.com>>mailto:academy@emagiz.com]].
@@ -9,65 +9,72 @@
  == 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 groovy scripts. A groovy script is a piece of code written in the groovy language that allows you to extend the platform's functionality beyond the mere use of the components supplied via the flow designer.
--Key aspects are:
++* Groovy scripts should be viewed as an extension that can be used in fringe cases, not as a standard best practice
++* When a groovy script becomes so complex that you are programming, you should consider alternatives to the solution
++* Groovy scripts can be used in a filter, transformation, and as part of a standard executor
++* Groovy scripts should be well documented as they are though to read for most of our community members
++* There is no guarantee from eMagiz that Groovy scripts within models keep working in newer versions of the platform
--* 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
++== 3. Groovy script ==
--== 3. Multipart form-data ==
++In a low-code platform like eMagiz, you want to prevent using custom scripting as much as possible. However, sometimes in practice, you encounter situations that cannot be realized with the standard toolbox provided within the platform. As a result, we offer the option to use a Groovy script in these situations to achieve the desired solution. In this microlearning, we will look at where you can use a Groovy script and discuss the key considerations when implementing a Groovy script within your model.
--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.
++=== 3.1 Implementation in Create ===
--Key aspects are:
++To implement a groovy script in Create, you first need to consider what your Groovy script should do. Then, within the flow designer, there are five components available that can handle a Groovy script.
++
++* In case you want the Groovy script to filter out messages, you should implement the Groovy script in a "standard filter" component.
++* If you want your Groovy script to always transform your message from a certain format into another format, you should consider using a "standard transformer" component.
++* The "standard service activator" is your friend if you need an optional output. So, for example, when you want to do some transformation and check whether a message can continue, you can use the "standard service activator" and have an optional output.
++* When you want to split your message based on a Groovy script, you should use the "standard splitter."
++* If you want to route messages based on a Groovy script, you should use the "standard router."
--* 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
++{{warning}}Note that in practice, we mainly see use cases for the "standard service activator" and the "standard transformation." {{/warning}}
--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.
++[[image:Main.Images.Microlearning.WebHome@expert-data-handling-groovy-script-available-components.png]]
--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.
++Regardless of the component you choose, you always need to select the "Groovy script" option and reference the Groovy resource available on the flow level you want to use within the component.
--On top of that we need to define the contentType header as follows.
++[[image:Main.Images.Microlearning.WebHome@expert-data-handling-groovy-script-groovy-configuration.png]]
--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.
++{{info}}As you can see in the help text when selecting the "resource" attribute, you need to make sure that the Groovy script is uploaded within the context of your flow.{{/info}}
--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.
++After you have the component in such a way that the correct Groovy script is called, you are done with the component's configuration and can test the flow using flow testing.
--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.
++=== 3.2 Key considerations ===
--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.
++* To make some groovy scripts work, you need to upload (third-party) Java libraries that are not packaged on default by eMagiz
++* To make some groovy scripts work, you need to reference Java libraries via a standard header enricher or as a dummy variable
++* The store consists of several groovy scripts that might be of use to you
++* Groovy scripts should be viewed as an extension that can be used in fringe cases, not as a standard best practice
++* When a groovy script becomes so complex that you are programming, you should consider alternatives to the solution
++* Groovy scripts can be used in a filter, transformation, and as part of a standard executor
++* Groovy scripts should be well documented as they are though to read for most of our community members
++* There is no guarantee from eMagiz that Groovy scripts within models keep working in newer versions of the platform
--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.
++Try to implement a component that references a Groovy script and see whether the flow can be tested.
  This assignment can be completed with the help of 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
++* To make some groovy scripts work, you need to upload (third-party) Java libraries that are not packaged on default by eMagiz
++* To make some groovy scripts work, you need to reference Java libraries via a standard header enricher or as a dummy variable
++* The store consists of several groovy scripts that might be of use to you
++* Groovy scripts should be viewed as an extension that can be used in fringe cases, not as a standard best practice
++* When a groovy script becomes so complex that you are programming, you should consider alternatives to the solution
++* Groovy scripts can be used in a filter, transformation, and as part of a standard executor
++* Groovy scripts should be well documented as they are though to read for most of our community members
++* There is no guarantee from eMagiz that Groovy scripts within models keep working in newer versions of the platform
  == 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 and read the following link:
++* https://www.tutorialspoint.com/groovy/index.htm
--* 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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