Changes for page Multipart form-data

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

From 13.2 to 14.1

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edited by Erik Bakker
on 2022/07/28 10:28

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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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--Communication between models
++Multipart form-data

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

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  {{container}}{{container layoutStyle="columns"}}(((
--In a low-code platform like eMagiz, you want to prevent using custom scripting as much as possible. However, sometimes in practice, you encounter situations that cannot be realized with the standard toolbox provided within the platform. As a result, we offer the option to use a Groovy script in these situations to achieve the desired solution. In this microlearning, we will look at where you can use a Groovy script and discuss the key considerations when implementing a Groovy script within your model.
++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]].
@@ -9,72 +9,73 @@
  == 2. Key concepts ==
--This microlearning focuses on groovy scripts. A groovy script is a piece of code written in the groovy language that allows you to extend the platform's functionality beyond the mere use of the components supplied via the flow designer.
++This microlearning focuses on configuring a multipart/form-data message within eMagiz to ensure it is sent correctly to an endpoint.
--* Groovy scripts should be viewed as an extension that can be used in fringe cases, not as a standard best practice
--* When a groovy script becomes so complex that you are programming, you should consider alternatives to the solution
--* Groovy scripts can be used in a filter, transformation, and as part of a standard executor
--* Groovy scripts should be well documented as they are though to read for most of our community members
--* There is no guarantee from eMagiz that Groovy scripts within models keep working in newer versions of the platform
++Key aspects are:
--== 3. Groovy script ==
++* 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
--In a low-code platform like eMagiz, you want to prevent using custom scripting as much as possible. However, sometimes in practice, you encounter situations that cannot be realized with the standard toolbox provided within the platform. As a result, we offer the option to use a Groovy script in these situations to achieve the desired solution. In this microlearning, we will look at where you can use a Groovy script and discuss the key considerations when implementing a Groovy script within your model.
++== 3. Multipart form-data ==
--=== 3.1 Implementation in Create ===
++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.
--To implement a groovy script in Create, you first need to consider what your Groovy script should do. Then, within the flow designer, there are five components available that can handle a Groovy script.
--
--* In case you want the Groovy script to filter out messages, you should implement the Groovy script in a "standard filter" component.
--* If you want your Groovy script to always transform your message from a certain format into another format, you should consider using a "standard transformer" component.
--* The "standard service activator" is your friend if you need an optional output. So, for example, when you want to do some transformation and check whether a message can continue, you can use the "standard service activator" and have an optional output.
--* When you want to split your message based on a Groovy script, you should use the "standard splitter."
--* If you want to route messages based on a Groovy script, you should use the "standard router."
++Key aspects are:
--{{warning}}Note that in practice, we mainly see use cases for the "standard service activator" and the "standard transformation." {{/warning}}
++* 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
--[[image:Main.Images.Microlearning.WebHome@expert-data-handling-groovy-script-available-components.png]]
++{{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}}
--Regardless of the component you choose, you always need to select the "Groovy script" option and reference the Groovy resource available on the flow level you want to use within the component.
++=== 3.1 Prepare the message ===
--[[image:Main.Images.Microlearning.WebHome@expert-data-handling-groovy-script-groovy-configuration.png]]
++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.
--{{info}}As you can see in the help text when selecting the "resource" attribute, you need to make sure that the Groovy script is uploaded within the context of your flow.{{/info}}
++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.
--After you have the component in such a way that the correct Groovy script is called, you are done with the component's configuration and can test the flow using flow testing.
++On top of that, we need to define the contentType header.
--=== 3.2 Key considerations ===
++[[image:Main.Images.Microlearning.WebHome@expert-data-handling-multipart-form-data--content-type-header-config.png]]
--* To make some groovy scripts work, you need to upload (third-party) Java libraries that are not packaged on default by eMagiz
--* To make some groovy scripts work, you need to reference Java libraries via a standard header enricher or as a dummy variable
--* The store consists of several groovy scripts that might be of use to you
--* Groovy scripts should be viewed as an extension that can be used in fringe cases, not as a standard best practice
--* When a groovy script becomes so complex that you are programming, you should consider alternatives to the solution
--* Groovy scripts can be used in a filter, transformation, and as part of a standard executor
--* Groovy scripts should be well documented as they are though to read for most of our community members
--* There is no guarantee from eMagiz that Groovy scripts within models keep working in newer versions of the platform
++=== 3.2 Construct the message ===
--== 4. Assignment ==
++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:
--Try to implement a component that references a Groovy script and see whether the flow can be tested.
--This assignment can be completed with the help of the (Academy) project you created/used in the previous assignment.
++* 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
--== 5. Key takeaways ==
++Given all this, you can write the following SpEL expression that will yield a desirable output:
--* To make some groovy scripts work, you need to upload (third-party) Java libraries that are not packaged on default by eMagiz
--* To make some groovy scripts work, you need to reference Java libraries via a standard header enricher or as a dummy variable
--* The store consists of several groovy scripts that might be of use to you
--* Groovy scripts should be viewed as an extension that can be used in fringe cases, not as a standard best practice
--* When a groovy script becomes so complex that you are programming, you should consider alternatives to the solution
--* Groovy scripts can be used in a filter, transformation, and as part of a standard executor
--* Groovy scripts should be well documented as they are though to read for most of our community members
--* There is no guarantee from eMagiz that Groovy scripts within models keep working in newer versions of the platform
++{{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}}
--== 6. Suggested Additional Readings ==
++Putting this in a standard transformation gives you the following solution in the flow.
--If you are interested in this topic and want more information, please read the help text provided by eMagiz and read the following link:
--* https://www.tutorialspoint.com/groovy/index.htm
++[[image:Main.Images.Microlearning.WebHome@expert-data-handling-multipart-form-data--standard-transformer-config.png]]
--== 7. Silent demonstration video ==
++=== 3.3 Calling the endpoint ===
--As this is more of theoretical microlearning, there is no video accompanying the microlearning.)))((({{toc/}}))){{/container}}{{/container}}
++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.
++
++== 4. Key takeaways ==
++
++* 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
++
++== 5. Suggested Additional Readings ==
++
++If you are interested in this topic, please read the help texts on the platform and read the following link:
++
++* [[Multipart form-data explained>>https://www.sobyte.net/post/2021-12/learn-about-http-multipart-form-data/||target="blank"]]
++
++)))((({{toc/}}))){{/container}}{{/container}}

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