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1		- XPath Advanced
	1	+Multipart form-data

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1	1	{{container}}{{container layoutStyle="columns"}}(((
2		-Within the crash course, we already explained XPath conceptually. In that same microlearning, we also 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](crashcourse-platform-create-transformation-xpath-basic.md). In the intermediate microlearning on this subject, we built upon that knowledge. Please check out this [microlearning](intermediate-create-your-transformations-xpath-intermediate.md) if you need a refresher on that. In this microlearning, we will build upon that knowledge and look at some concrete, practical examples that could be useful in your project.
	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.
3	3
4	4	Should you have any questions, please get in touch with [[academy@emagiz.com>>mailto:academy@emagiz.com]].
5	5
6		-* Last update: October 25th, 2021
7		-* Required reading time: 6 minutes
8		-
9	9	== 1. Prerequisites ==
10	10
11		-* Advanced knowledge of the eMagiz platform
12		-* [[XPath Basic>>doc:Main.eMagiz Academy.Microlearnings.Crash Course.Crash Course Platform.crashcourse-platform-create-transformation-xpath-basic.WebHome||target="blank"]]
13		-* [[XPath Intermediate>>doc:Main.eMagiz Academy.Microlearnings.Intermediate Level.Create your transformations.intermediate-create-your-transformations-xpath-intermediate.WebHome||target="blank"]]
	8	+* Expert knowledge of the eMagiz platform
14	14
15		-
16	16	== 2. Key concepts ==
17	17
18		-This microlearning focuses on more complex XPath operations.
	12	+This microlearning focuses on configuring a multipart/form-data message within eMagiz to ensure it is sent correctly to an endpoint.
19	19
20		-With XPath Advanced, we mean learning that XPath options are complex but could benefit you in your daily work.
	14	+Key aspects are:
21	21
22		-Some of the more complex XPath options are:
	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
23	23
24		-* dateTime calculation
25		-* Filter list
26		-* XPath on JSON
27		-* SpEL notation for XPath
	20	+== 3. Multipart form-data ==
28	28
	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.
29	29
	24	+Key aspects are:
30	30
31		-== 3. XPath Advanced ==
	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
32	32
33		-Within the crash course, we already explained XPath conceptually. In that same microlearning, we also 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 this microlearning, we will build upon that knowledge and look at some concrete, practical examples that could be useful in your project.
	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.
34	34
35		-Some of the more complex XPath options are:
	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	36
37		-* dateTime calculation
38		-* Filter list
39		-* XPath on JSON
40		-* SpEL notation for XPath
	34	+On top of that we need to define the contentType header as follows.
41	41
42		-=== 3.1 dateTime calculation ===
	36	+[[image:Main.Images.Microlearning.WebHome@expert-data-handling-multipart-form-data--content-type-header-config.png]]
43	43
44		-Sometimes we see that a dateTime calculation is needed within a transformation to determine a specific action. As these calculations are not natively supported within the eMagiz platform, you need to use XPath's functionality to calculate the new valid date (or dateTime).
	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:
45	45
46		-The XPath standard offers several functions to calculate with dateTime values. The two most used options are dayTimeDuration and yearMonthDuration. With the help of the dayTimeDuration, you can add, subtract, multiple, or divide seconds, minutes, hours, and days regarding the original value. The yearMonthDuration works similarly but then for months and years. An example of such an XPath is: <xsl:value-of xmlns:xs="http://www.w3.org/2001/XMLSchema" select="CDM:StartDate + xs:dayTimeDuration('P1D') * xs:yearMonthDuration('P1M')"/>. In this example, XPath adds one day and subtracts one month from the input date. Note that making this work requires the additional namespace to be defined. Therefore you need a custom snippet within your transformation or a custom transformation to make this work. Furthermore, note that the P1D and P1M could also be filled with the help of parameters to make them dynamic in nature.
	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
47	47
48		-Some examples that we saw during the years:
	45	+Given all this you can write the following SpEL expression that will yield a desirable output:
49	49
50		-* https://my.emagiz.com/p/question/172825635700358186
51		-* https://my.emagiz.com/p/question/172825635700352588
	47	+{{code}}test{{/code}}
52	52
53		-=== 3.2 Filter list ===
	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.
54	54
55		-Sometimes you have a large message which contains a certain list within it. However, logic dictates that you can only send the message if at least one entry in the list for which attribute A is filled and attribute B equals type C. To make that happen in XPath, we first need to navigate to the list within the message. As we previously learned, there are two options to do so. One is to use // to navigate to the entity somewhere in the tree directly. The other is to start at the root and walk the tree from there. In this example, we use the latter. That results in the following XPath example: /root/list[attributeB = 'type C']/attributeA !=''. With this XPath, you filter the list on the specified check and subsequently check whether one of those entries that remains has an attributeA which is filled in.
	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.
56	56
57		-=== 3.3 XPath on JSON ===
	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.
58	58
59		-With the release of build number .50, we expanded our offering on JSON messages to resemble much of the functionality we previously offered for XML messages. As a result, you can use XPath expressions on JSON messages within the following components (related to XPath):
	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.
60	60
61		-* XPath header enricher
62		-* XPath transformer
63		-* XPath router
	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).
64	64
65		-To activate the functionality, simply link the JSON source factory support object to one of these components to achieve the desired result. For more information, check out: https://emagiz.github.io/docs/release-notes/build50.
	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.
66	66
67		-=== 3.4 SpEL notation for XPath ===
	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.
68	68
69		-Sometimes you want to perform an XPath operation but store the header via a standard message header enricher component. As a result, you need a valid SpEL expression to help you in this cause. To do so, you need to know the correct notation for an XPath expression when using the SpEL language. An example of the correct notation is: #xpath(payload,'/root/entity/attribute')
70		-
71	71	== 4. Assignment ==
72	72
73		-Check out which of the XPaths we have discussed today can be found within your project.
74		-This assignment can be completed within the (Academy) project you created/used in the previous assignment.
	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.
75	75
76	76	== 5. Key takeaways ==
77	77
78		-Some of the more complex XPath options are:
	72	+* Consider the following when communication between two models
	73	+** Security
	74	+** Loose coupling
	75	+** Maintainability
	76	+** Clarity
79	79
80		-* dateTime calculation
81		-* Filter list
82		-* XPath on JSON
83		-* SpEL notation for XPath
84		-
85	85	== 6. Suggested Additional Readings ==
86	86
87		-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 link:
	80	+If you are interested in this topic please read the helptexts in the platform and read the following link:
88	88
89		-* https://www.w3schools.com/xml/xpath_intro.asp
	82	+* https://www.sobyte.net/post/2021-12/learn-about-http-multipart-form-data/
90	90
91	91	== 7. Silent demonstration video ==
92	92