Changes for page Multipart form-data

Last modified by Erik Bakker on 2024/06/17 11:39

From 5.2 to 6.1

From version 6.1

edited by Erik Bakker
on 2022/07/26 08:31

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To version 23.2

edited by Erik Bakker
on 2024/06/17 11:39

Change comment: Update document after refactoring.

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

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--WebHome
++Main.eMagiz Academy.Microlearnings.Legacy Functionality.WebHome

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  {{container}}{{container layoutStyle="columns"}}(((
--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.
++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.
  Should you have any questions, please get in touch with [[academy@emagiz.com>>mailto:academy@emagiz.com]].
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  == 1. Prerequisites ==
  * Expert knowledge of the eMagiz platform
--* [[XPath Basic>>doc:Main.eMagiz Academy.Microlearnings.Crash Course.Crash Course Platform.crashcourse-platform-create-transformation-xpath-basic.WebHome||target="blank"]]
--* [[XPath Intermediate>>doc:Main.eMagiz Academy.Microlearnings.Intermediate Level.Create your transformations.intermediate-create-your-transformations-xpath-intermediate.WebHome||target="blank"]]
--* [[XPath Advanced>>doc:Main.eMagiz Academy.Microlearnings.Advanced Level.Create your transformations.advanced-create-your-transformations-xpath-advanced.WebHome||target="blank"]]
--
  == 2. Key concepts ==
--This microlearning focuses on more complex XPath operations.
++This microlearning focuses on configuring a multipart/form-data message within eMagiz to ensure it is sent correctly to an endpoint.
--With XPath Advanced, we mean learning that XPath options are complex but could benefit you in your daily work.
++Key aspects are:
--Some of the more complex XPath options are:
++* Defining the boundary that separates the parts of the message
++* Defining the content types of each part of the message
++* Construction of the complete message according to the specification
--* dateTime calculation
--* Filter list
--* XPath on JSON
--* SpEL notation for XPath
++== 3. Multipart form-data ==
++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.
++Key aspects are:
--== 3. XPath Advanced ==
++* Defining the boundary that separates the parts of the message
++* Defining the content types of each part of the message
++* Construction of the complete message according to the specification
--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.
++{{info}}
++The following criteria apply when utilizing the boundary functionality within the multipart/form-data construction:
++* The value of the Boundary must begin with a double horizontal bar –, this is called a leading hyphen
++* The value of the Boundary must not contain more than 70 characters in addition to the leading hyphen.
++* The value of the Boundary must not contain characters that are disabled by the HTTP protocol or the URL, such as the colon: etc.
++* 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}}
--Some of the more complex XPath options are:
++=== 3.1 Prepare the message ===
--* dateTime calculation
--* Filter list
--* XPath on JSON
--* SpEL notation for XPath
++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.
--=== 3.1 dateTime calculation ===
++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.
--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).
++On top of that, we need to define the contentType header.
--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.
++[[image:Main.Images.Microlearning.WebHome@expert-data-handling-multipart-form-data--content-type-header-config.png]]
--Some examples that we saw during the years:
++=== 3.2 Construct the message ===
--* https://my.emagiz.com/p/question/172825635700358186
--* https://my.emagiz.com/p/question/172825635700352588
++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:
--=== 3.2 Filter list ===
++* Each part of the message needs to be separated by a boundary
++* The message needs to start with a boundary and finish with a boundary
++* Line breaks are needed to differentiate between the boundary and the text content
++* No line break is needed when the content is not text-based
--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.
++Given all this, you can write the following SpEL expression that will yield a desirable output:
--=== 3.3 XPath on JSON ===
++{{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}}
--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):
++Putting this in a standard transformation gives you the following solution in the flow.
--* XPath header enricher
--* XPath transformer
--* XPath router
++[[image:Main.Images.Microlearning.WebHome@expert-data-handling-multipart-form-data--standard-transformer-config.png]]
--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.
++=== 3.3 Calling the endpoint ===
--=== 3.4 SpEL notation for XPath ===
++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.
--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')
++== 4. Key takeaways ==
--== 4. Assignment ==
++* Make sure to define the boundary that separates the parts of the message
++* Make sure to define the content types of each part of the message
++* Make sure to define the content type that matches the specification for multipart/form-data
++* Construct the complete message according to the specification
--Check out which of the XPaths we have discussed today can be found within your project.
--This assignment can be completed within the (Academy) project you created/used in the previous assignment.
++== 5. Suggested Additional Readings ==
--== 5. Key takeaways ==
++If you are interested in this topic, please read the help texts on the platform and read the following link:
--Some of the more complex XPath options are:
++* [[Multipart form-data explained>>https://www.sobyte.net/post/2021-12/learn-about-http-multipart-form-data/||target="blank"]]
--* dateTime calculation
--* Filter list
--* XPath on JSON
--* SpEL notation for XPath
--
--== 6. Suggested Additional Readings ==
--
--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:
--
--* https://www.w3schools.com/xml/xpath_intro.asp
--
--== 7. Silent demonstration video ==
--
--As this is more of theoretical microlearning, there is no video accompanying the microlearning.)))((({{toc/}}))){{/container}}{{/container}}
++)))((({{toc/}}))){{/container}}{{/container}}

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