Changes for page Multipart form-data

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1		-Multipart form-data
	1	+Communication between models

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1	1	{{container}}{{container layoutStyle="columns"}}(((
2		-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.
	2	+When your integration landscape grows through time, you might decide to split functional business processes into multiple eMagiz models. In those cases, the question of connecting these models easily, stable, and securely could arise. This microlearning will focus on that question and provide an answer based on our vision and best practices when dealing with the platform.
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4	4	Should you have any questions, please get in touch with [[academy@emagiz.com>>mailto:academy@emagiz.com]].
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9	9
10	10	== 2. Key concepts ==
11	11
12		-This microlearning focuses on configuring a multipart/form-data message within eMagiz to ensure it is sent correctly to an endpoint.
	12	+This microlearning focuses on communication between two eMagiz models. When communicating to any external party (from the view of a certain model) you should always consider the following:
13	13
14		-Key aspects are:
	14	+* Security
	15	+* Loose coupling
	16	+* Maintainability
	17	+* Clarity
15	15
16		-* Defining the boundary that separates the parts of the message
17		-* Defining the content types of each part of the message
18		-* Construction of the complete message according to the specification
	19	+== 3. Communication between models ==
19	19
20		-== 3. Multipart form-data ==
	21	+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.
21	21
22		-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.
	23	+Most users would think that communication via queues to connect two separate eMagiz models is a smart idea. However, this is something that we do not encourage. We discourage this for several practical and technical reasons alike.
23	23
24		-Key aspects are:
	25	+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 in which 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.
25	25
26		-* Defining the boundary that separates the parts of the message
27		-* Defining the content types of each part of the message
28		-* Construction of the complete message according to the specification
	27	+On top of that because you basically allow one model to write and read from queues registered in another model maintaining both models will become very confusing 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.
29	29
30		-=== 3.1 Prepare the message ===
	29	+Another practical reason for not wanting this is that we do not actively support this use case from eMagiz. This means that when we do updates to our technical infrastructure we will not take this scenario into account. This could lead to additional work on your part in the future and reduced stability of your solution.
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32		-To construct the message, several steps are needed to make it work. Luckily, most of the steps necessary have to do with concepts we have already discussed in previous microlearnings. As you can imagine, based on what multipart/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. For example, put the metadata in one (or multiple) header(s) and use the file content as a payload. This you can achieve with a header enricher and standard transformer.
	31	+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).
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34		-Once the file content is your payload, you must ensure that the data is "raw." So when you have a base64 encoded string, you should decode it before sending it to the endpoint.
	33	+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:
	34	+- Using a web service as a layer of communication between the two models. This web service can be REST or SOAP and has been implemented before
	35	+- Using the Event Streaming functionality of eMagiz to write and read from topics.
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36		-On top of that, we need to define the contentType header.
	37	+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 a lot easier as it makes use of the standard functionality within the platform. We have no plans to support this approach in the product.
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38		-[[image:Main.Images.Microlearning.WebHome@expert-data-handling-multipart-form-data--content-type-header-config.png]]
39		-
40		-=== 3.2 Construct the message ===
41		-
42		-After you have set the stage, you can use a standard transformer component to build your message correctly. To create it correctly, you need to take the following into account:
43		-
44		-* Each part of the message needs to be separated by a boundary
45		-* The message needs to start with a boundary and finish with a boundary
46		-* Line breaks are needed to differentiate between the boundary and the text content
47		-* No line break is needed when the content is not text-based
48		-
49		-Given all this, you can write the following SpEL expression that will yield a desirable output:
50		-
51		-{{code}}'${multi-part-form-data.data-handling.boundary}' + headers.metaInfo + T(com.emagiz.util.Newline).CRLF.characters + '${multi-part-form-data.data-handling.boundary}' + T(com.emagiz.util.Newline).CRLF.characters + 'Content-Disposition: form-data; name="file"; filename="' + headers.filename + '"' + T(com.emagiz.util.Newline).CRLF.characters + 'Content-Type: application/pdf' + T(com.emagiz.util.Newline).CRLF.characters + T(com.emagiz.util.Newline).CRLF.characters + payload + '${multi-part-form-data.data-handling.boundary}'{{/code}}
52		-
53		-Putting this in a standard transformation gives you the following solution in the flow.
54		-
55		-[[image:Main.Images.Microlearning.WebHome@expert-data-handling-multipart-form-data--standard-transformer-config.png]]
56		-
57		-=== 3.3 Calling the endpoint ===
58		-
59		-Now that we have constructed our message correctly, the last thing to do is call the endpoint in question. Since we have prepared our message and accurately defined our contentType calling the endpoint does not require any additional configurations compared to what you are already used to when dealing with REST endpoints.
60		-
61	61	== 4. Assignment ==
62	62
63		-Try to see whether you can construct the flow so that it outputs a valid multipart/form-data message.
	41	+Consider what your criteria are when communicate between models and compare them to our criteria.
64	64	This assignment can be completed with the help of the (Academy) project you created/used in the previous assignment.
65	65
66	66	== 5. Key takeaways ==
67	67
68		-* Make sure to define the boundary that separates the parts of the message
69		-* Make sure to define the content types of each part of the message
70		-* Make sure to define the content type that matches the specification for multipart/form-data
71		-* Construct the complete message according to the specification
	46	+* Consider the following when communication between two models
	47	+** Security
	48	+** Loose coupling
	49	+** Maintainability
	50	+** Clarity
72	72
73	73	== 6. Suggested Additional Readings ==
74	74
75		-If you are interested in this topic, please read the help texts on the platform and read the following link:
	54	+If you are interested in this topic and want more information, please consult us at [[productmanagement@emagiz.com>>mailto:productmanagement@emagiz.com]]
76	76
77		-* https://www.sobyte.net/post/2021-12/learn-about-http-multipart-form-data/
78		-
79	79	== 7. Silent demonstration video ==
80	80
81	81	As this is more of theoretical microlearning, there is no video accompanying the microlearning.)))((({{toc/}}))){{/container}}{{/container}}