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1		-expert-create-your-transformations-xpath-expert
	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 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.
	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
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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"]]
12	12
13		-
14	14	== 2. Key concepts ==
15	15
16		-This microlearning focuses on very 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.
17	17
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.
	14	+Key aspects are:
19	19
20		-Some of the very 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
21	21
22		-* matches
23		-* replace
24		-* tokenize
	20	+== 3. Multipart form-data ==
25	25
26		-== 3. XPath Expert ==
	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.
27	27
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.
	24	+Key aspects are:
29	29
30		-Some of the very complex XPath options are:
	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
31	31
32		-* matches
33		-* replace
34		-* tokenize
	30	+{{info}}
	31	+The following criteria apply when utilizing the boundary functionality within the multipart/form-data construction:
	32	+* The value of the Boundary must begin with a double horizontal bar –, this is called a leading hyphen
	33	+* The value of the Boundary must not contain more than 70 characters in addition to the leading hyphen.
	34	+* The value of the Boundary must not contain characters that are disabled by the HTTP protocol or the URL, such as the colon: etc.
	35	+* A boundary within the request body must always be preceeded by a CRLF line. This means that when the request body **ends** with a CRLF line an **additional** CRLF line is needed **before** the boundary doubling the CRLF lines in that part of the request body.{{/info}}
35	35
36		-=== 3.1 matches ===
	37	+=== 3.1 Prepare the message ===
37	37
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.
	39	+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.
39	39
40		-matches(OrderID,'^\d{7}$')
	41	+Once the file content is your payload, you must ensure that the data is "raw." So when you have a base64 encoded string, you should decode it before sending it to the endpoint.
41	41
42		-As a result, you will get a true or false back which you can then use as a filter or within an if-then-else construction.
	43	+On top of that, we need to define the contentType header.
43	43
44		-=== 3.2 replace ===
	45	+[[image:Main.Images.Microlearning.WebHome@expert-data-handling-multipart-form-data--content-type-header-config.png]]
45	45
46		-The replace function has many similarities with the matches function. It builds on the premise of the matches function, but instead of returning a true or false, you can state with what you want to replace the matched string. In other words, this function returns a string produced from the input string by replacing any substrings that match a given regular expression with a supplied replacement string.
	47	+=== 3.2 Construct the message ===
47	47
48		-When we apply this to our earlier example, we can state that when the OrderID contains any non-digit, we will replace this value with nothing. This will lead to the following XPath expression.
	49	+After you have set the stage, you can use a standard transformer component to build your message correctly. To create it correctly, you need to take the following into account:
49	49
50		-replace(OrderID,'\D','')
	51	+* Each part of the message needs to be separated by a boundary
	52	+* The message needs to start with a boundary and finish with a boundary
	53	+* Line breaks are needed to differentiate between the boundary and the text content
	54	+* No line break is needed when the content is not text-based
51	51
52		-With a given input string of 12C34A567, the returned result will be 1234567.
	56	+Given all this, you can write the following SpEL expression that will yield a desirable output:
53	53
54		-=== 3.3 tokenize ===
	58	+{{code}}'${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}}
55	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.
	60	+Putting this in a standard transformation gives you the following solution in the flow.
57	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.
	62	+[[image:Main.Images.Microlearning.WebHome@expert-data-handling-multipart-form-data--standard-transformer-config.png]]
59	59
60		-tokenize(AddressID,',')
	64	+=== 3.3 Calling the endpoint ===
61	61
62		-The given input detailed above will result in the following output: street housenumber housenumberaddition.
	66	+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.
63	63
64		-== 4. Assignment ==
	68	+== 4. Key takeaways ==
65	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.
	70	+* Make sure to define the boundary that separates the parts of the message
	71	+* Make sure to define the content types of each part of the message
	72	+* Make sure to define the content type that matches the specification for multipart/form-data
	73	+* Construct the complete message according to the specification
68	68
69		-== 5. Key takeaways ==
	75	+== 5. Suggested Additional Readings ==
70	70
71		-Some of the very complex XPath options are:
	77	+If you are interested in this topic, please read the help texts on the platform and read the following link:
72	72
73		-* matches
74		-* replace
75		-* tokenize
	79	+* [[Multipart form-data explained>>https://www.sobyte.net/post/2021-12/learn-about-http-multipart-form-data/||target="blank"]]
76	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}}
	81	+)))((({{toc/}}))){{/container}}{{/container}}