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1		-Multipart form-data
	1	+expert-create-your-transformations-xpath-expert

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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	+Within the crash course, we already explained XPath conceptually. In that same microlearning, we looked at some more uncomplicated cases of using XPath within your transformation. If you need to brush up on that knowledge, please check out this [[microlearning>>doc:Main.eMagiz Academy.Microlearnings.Crash Course.Crash Course Platform.crashcourse-platform-create-transformation-xpath-basic.WebHome||target="blank"]]. In the intermediate microlearning on this subject, we built upon that knowledge. Please check out this [[microlearning>>doc:Main.eMagiz Academy.Microlearnings.Intermediate Level.Create your transformations.intermediate-create-your-transformations-xpath-intermediate.WebHome||target="blank"]] if you need a refresher on that. In the [[microlearning>>doc:Main.eMagiz Academy.Microlearnings.Advanced Level.Create your transformations.advanced-create-your-transformations-xpath-advanced.WebHome||target="blank"]] that followed, we built upon that knowledge and looked at some concrete, practical examples that could be useful in your project. In this microlearning, we will wrap the concept of XPath by looking at three complex XPath alternatives that are sometimes needed when dealing with messages in eMagiz.
3	3
4	4	Should you have any questions, please get in touch with [[academy@emagiz.com>>mailto:academy@emagiz.com]].
5	5
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6	6	== 1. Prerequisites ==
7	7
8	8	* Expert knowledge of the eMagiz platform
	9	+* [[XPath Basic>>doc:Main.eMagiz Academy.Microlearnings.Crash Course.Crash Course Platform.crashcourse-platform-create-transformation-xpath-basic.WebHome||target="blank"]]
	10	+* [[XPath Intermediate>>doc:Main.eMagiz Academy.Microlearnings.Intermediate Level.Create your transformations.intermediate-create-your-transformations-xpath-intermediate.WebHome||target="blank"]]
	11	+* [[XPath Advanced>>doc:Main.eMagiz Academy.Microlearnings.Advanced Level.Create your transformations.advanced-create-your-transformations-xpath-advanced.WebHome||target="blank"]]
9	9
	13	+
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.
	16	+This microlearning focuses on very complex XPath operations.
13	13
14		-Key aspects are:
	18	+With XPath Expert, we mean learning that XPath options are sometimes very complex but could benefit you in specific cases in your daily work.
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
	20	+Some of the very complex XPath options are:
19	19
20		-== 3. Multipart form-data ==
	22	+* matches
	23	+* replace
	24	+* tokenize
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.
	26	+== 3. XPath Expert ==
23	23
24		-Key aspects are:
	28	+Within the crash course, we already explained XPath conceptually. In that same microlearning, we looked at some more uncomplicated cases of using XPath within your transformation. If you need to brush up on that knowledge, please check out this [[microlearning>>doc:Main.eMagiz Academy.Microlearnings.Crash Course.Crash Course Platform.crashcourse-platform-create-transformation-xpath-basic.WebHome||target="blank"]]. In the intermediate microlearning on this subject, we built upon that knowledge. Please check out this [[microlearning>>doc:Main.eMagiz Academy.Microlearnings.Intermediate Level.Create your transformations.intermediate-create-your-transformations-xpath-intermediate.WebHome||target="blank"]] if you need a refresher on that. In the [[microlearning>>doc:Main.eMagiz Academy.Microlearnings.Advanced Level.Create your transformations.advanced-create-your-transformations-xpath-advanced.WebHome||target="blank"]] that followed, we built upon that knowledge and looked at some concrete, practical examples that could be useful in your project. In this microlearning, we will wrap the concept of XPath by looking at three complex XPath alternatives that are sometimes needed when dealing with messages in eMagiz.
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
	30	+Some of the very complex XPath options are:
29	29
30		-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.
	32	+* matches
	33	+* replace
	34	+* tokenize
31	31
32		-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.
	36	+=== 3.1 matches ===
33	33
34		-On top of that we need to define the contentType header as follows.
	38	+Sometimes, you want to determine whether a specific value within your payload matches a pattern. In those cases, you can use the XPath function called matches. The function will return true if the supplied string matches a given regular expression. So, for example, if you want to check whether your OrderID contains exactly seven digits and nothing else, the following XPath expression will work for your use case.
35	35
36		-[[image:Main.Images.Microlearning.WebHome@expert-data-handling-multipart-form-data--content-type-header-config.png]]
	40	+matches(OrderID,'^\d{7}$')
37	37
38		-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:
	42	+As a result, you will get a true or false back which you can then use as a filter or within an if-then-else construction.
39	39
40		-* Each part of the message needs to be seperated by a boundary
41		-* The message needs to start with a boundary and finish with a boundary
42		-* Line breaks are needed to differentiate between the boundary and the text content
43		-* No line break is needed when the content is not text based
	44	+=== 3.2 replace ===
44	44
45		-Given all this you can write the following SpEL expression that will yield a desirable output:
	46	+The replace function has many similarities with the matches function. It builds on the premise of the matches function, but instead of returning a true or false, you can state with what you want to replace the matched string. In other words, this function returns a string produced from the input string by replacing any substrings that match a given regular expression with a supplied replacement string.
46	46
47		-{{code}}test{{/code}}
	48	+When we apply this to our earlier example, we can state that when the OrderID contains any non-digit, we will replace this value with nothing. This will lead to the following XPath expression.
48	48
49		-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.
	50	+replace(OrderID,'\D','')
50	50
51		-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.
	52	+With a given input string of 12C34A567, the returned result will be 1234567.
52	52
53		-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.
	54	+=== 3.3 tokenize ===
54	54
55		-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.
	56	+The tokenize function can split a string into multiple entries for you. This is particularly useful when you want to match an input string to a list of possible values that are valid for that string. For example, the function returns a sequence of strings constructed by splitting the input wherever a separator is found; the separator is any substring that matches a given regular expression.
56	56
57		-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).
	58	+So, for example, when the input string for AddressID is "street,housenumber,housenumberaddition" and you want to tokenize this with the help of the separator, you could use, in this example, the comma between the values as the separator. This will lead to the following XPath expression.
58	58
59		-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:
60		-- 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
61		-- Using the Event Streaming functionality of eMagiz to write and read from topics.
	60	+tokenize(AddressID,',')
62	62
63		-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.
	62	+The given input detailed above will result in the following output: street housenumber housenumberaddition.
64	64
65	65	== 4. Assignment ==
66	66
67		-Consider what your criteria are when communicating between models and compare them to our criteria.
68		-This assignment can be completed with the help of the (Academy) project you created/used in the previous assignment.
	66	+Check out which of the XPaths we have discussed today can be found within your project.
	67	+This assignment can be completed within the (Academy) project you created/used in the previous assignment.
69	69
70	70	== 5. Key takeaways ==
71	71
72		-* Consider the following when communication between two models
73		-** Security
74		-** Loose coupling
75		-** Maintainability
76		-** Clarity
	71	+Some of the very complex XPath options are:
77	77
	73	+* matches
	74	+* replace
	75	+* tokenize
	76	+
78	78	== 6. Suggested Additional Readings ==
79	79
80		-If you are interested in this topic please read the helptexts in the platform and read the following link:
	79	+If you are interested in this topic and want more information on it, please read the help text provided by eMagiz and read more information on the following links:
81	81
82		-* https://www.sobyte.net/post/2021-12/learn-about-http-multipart-form-data/
	81	+* http://www.xsltfunctions.com/xsl/fn_matches.html
	82	+* http://www.xsltfunctions.com/xsl/fn_replace.html
	83	+* http://www.xsltfunctions.com/xsl/fn_tokenize.html
83	83
84	84	== 7. Silent demonstration video ==
85	85