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Last modified by Erik Bakker on 2024/09/05 14:00
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1 -Communication between models
1 +expert-create-your-transformations-xpath-expert
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1 -en
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1 1  {{container}}{{container layoutStyle="columns"}}(((
2 -In this microlearning, we'll explore the best practices for communication between two eMagiz models. Effective communication is crucial, and it's important to prioritize security, loose coupling, maintainability, and clarity. We'll discuss why using queues for inter-model communication is generally discouraged and why alternatives like web services and Event Streaming are preferred. By focusing on these key considerations, you'll be better equipped to design robust and maintainable integration solutions within eMagiz.
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 communication between two eMagiz models. When communicating to any external party (from the view of a specific model), you should always consider the following:
16 +This microlearning focuses on very complex XPath operations.
13 13  
14 -* Security
15 -* Loose coupling
16 -* Maintainability
17 -* Clarity
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.
18 18  
19 -== 3. Communication between models ==
20 +Some of the very complex XPath options are:
20 20  
21 -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.
22 +* matches
23 +* replace
24 +* tokenize
22 22  
23 -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.
26 +== 3. XPath Expert ==
24 24  
25 -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.
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.
26 26  
27 -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.
30 +Some of the very complex XPath options are:
28 28  
29 -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).
32 +* matches
33 +* replace
34 +* tokenize
30 30  
31 -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:
32 -- 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
33 -- Using the Event Streaming functionality of eMagiz to write and read from topics.
36 +=== 3.1 matches ===
34 34  
35 -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.
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.
36 36  
37 -== 4. Key takeaways ==
40 +matches(OrderID,'^\d{7}$')
38 38  
39 -* Consider the following when communication between two models
40 -** Security
41 -** Loose coupling
42 -** Maintainability
43 -** Clarity
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.
44 44  
45 -== 5. Suggested Additional Readings ==
44 +=== 3.2 replace ===
46 46  
47 -* [[Fundamentals (Navigation)>>doc:Main.eMagiz Academy.Fundamentals.WebHome||target="blank"]]
48 -** [[eMagiz Security Guide (Explanation)>>doc:Main.eMagiz Academy.Fundamentals.fundamental-emagiz-security-guide||target="blank"]]
49 -** [[Multi-Model Explained (Explanation)>>doc:Main.eMagiz Academy.Fundamentals.fundamental-emagiz-multi-model-explained.WebHome||target="blank"]]
50 -** [[Multi-Model Best Practice (Explanation)>>doc:Main.eMagiz Academy.Fundamentals.fundamental-emagiz-multi-model-best-practice.WebHome||target="blank"]]
51 -* [[Communication between models (Search Result)>>url:https://docs.emagiz.com/bin/view/Main/Search?sort=score&sortOrder=desc&highlight=true&facet=true&r=1&f_space_facet=0%2FMain.&f_type=DOCUMENT&f_locale=en&f_locale=&f_locale=en&text=communication+between+models||target="blank"]]
52 -)))((({{toc/}}))){{/container}}{{/container}}
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.
47 +
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.
49 +
50 +replace(OrderID,'\D','')
51 +
52 +With a given input string of 12C34A567, the returned result will be 1234567.
53 +
54 +=== 3.3 tokenize ===
55 +
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.
57 +
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.
59 +
60 +tokenize(AddressID,',')
61 +
62 +The given input detailed above will result in the following output: street housenumber housenumberaddition.
63 +
64 +== 4. Assignment ==
65 +
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.
68 +
69 +== 5. Key takeaways ==
70 +
71 +Some of the very complex XPath options are:
72 +
73 +* matches
74 +* replace
75 +* tokenize
76 +
77 +== 6. Suggested Additional Readings ==
78 +
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:
80 +
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
84 +
85 +== 7. Silent demonstration video ==
86 +
87 +As this is more of theoretical microlearning, there is no video accompanying the microlearning.)))((({{toc/}}))){{/container}}{{/container}}