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1 -Processing a File per Line
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1 -XWiki.ebakker
1 +XWiki.marijn
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1 -{{container}}{{container layoutStyle="columns"}}(((
2 -In some cases, you want to treat each unique part of your input file as its message instead of processing the complete file as its message. In this microlearning, we will learn how you can process a (large) file on a per-line basis.
1 +{{html wiki="true"}}
2 +<div class="ez-academy">
3 + <div class="ez-academy_body">
3 3  
4 -Should you have any questions, please contact [[academy@emagiz.com>>mailto:academy@emagiz.com]].
5 +<div class="doc">
5 5  
6 -== 1. Prerequisites ==
7 7  
8 -* Basic knowledge of the eMagiz platform
9 9  
10 -== 2. Key concepts ==
9 += Annotations =
11 11  
12 -This microlearning centers around learning how to process an incoming file per line.
11 +In this microlearning, we will focus on using annotations to clarify your thought process. In the annotation, you either describe a best practice everyone should follow when they change that flow (i.e. within the asynchronous routing), describe how the (more complex) parts of the flow work or describe (parts of) of your message definitions (i.e. CDM, API Gateway Data model, system message, etc.). This will help yourself and others every time changes are needed.
13 13  
14 -By processing per line, we mean: Splitting up the input into discernable pieces that each will become a unique message
13 +Should you have any questions, please contact academy@emagiz.com.
15 15  
16 -* Easy way of reading a file line by line and sending it to eMagiz (Low on memory)
17 -* Ability to process each line based on distinctive logic that is relevant on line level
18 -* Can be used for flat file as well as XML input files
15 +* Last update: May 9th, 2021
16 +* Required reading time: 5 minutes
19 19  
20 -== 3. Processing a File per Line ==
18 +== 1. Prerequisites ==
21 21  
22 -In some cases, you want to treat each unique part of your input file as its message instead of processing the complete file as its message. In this microlearning, we will learn how you can process a (large) file on a per-line basis.
20 +* Basic knowledge of the eMagiz platform
23 23  
24 -To make this work in eMagiz you need to navigate to the Create phase of eMagiz and open the entry flow in which you want to retrieve the file to a certain location. Within the context of this flow, we need to add functionality that will ensure that each line is read and processed separately and will become its unique message. To do so first enter "Start Editing" mode on flow level. After you have done so please add a file item reader message source to the flow. We will use this component to read and process our input file on a per-line basis.
22 +== 2. Key concepts ==
25 25  
26 -The first step would be to define the directory from which we read our messages. As always reference to the directory with the help of a property.
24 +This microlearning centers around using annotations.
25 +With annotations, we mean: A piece of text to explain something to yourself and others
27 27  
28 -[[image:Main.Images.Microlearning.WebHome@novice-file-based-connectivity-processing-a-file-per-line--file-item-reader-directory.png]]
27 +Annotations can be used for:
29 29  
30 -Secondly, just as when reading the file as a whole ensure that you use a filter to retrieve only the correct files from the directory.
29 +* Describing a best practice everyone should follow
30 +* Describing (more complex) parts of the flow
31 +* Describe (parts of) your message definitions
31 31  
32 -=== 3.1 Item reader Type ===
33 33  
34 -Now it is time to select our Item reader Type. As the help text of the eMagiz component suggest there are two choices with this component. The first (and most frequently used) option is the Flat file item reader. With this option, you can read each line within the flat file input file and output is at a separate message. The second option is called the Stax event item reader. With this option, you can read your input XML and output messages on a per-record basis.
35 35  
36 -[[image:Main.Images.Microlearning.WebHome@novice-file-based-connectivity-processing-a-file-per-line--item-reader-type-options.png]]
35 +== 3. Annotations ==
37 37  
38 -Based on your choice the exact configuration will differ.
37 +In this microlearning, we will focus on using annotations on the flow level to clarify our thought process. In the annotation, you either describe a best practice everyone should follow when they change that flow (i.e. within the asynchronous routing) or describe how the (more complex) parts of the flow work. This will help yourself and others every time changes are needed within the flow.
39 39  
40 -==== 3.1.1 Stax Event Item Reader ====
39 +Annotations can be used for:
41 41  
42 -For the Stax event item reader, you need to define the name of the element on which you want to split the XML and define whether you want to throw an error in case no such element exists in the input file (By (de)selecting the option Strict). The default setting of eMagiz is advisable for this option.
41 +* Describing a best practice everyone should follow
42 +* Describing (more complex) parts of the flow
43 +* Describe (parts of) your message definitions
43 43  
44 -[[image:Main.Images.Microlearning.WebHome@novice-file-based-connectivity-processing-a-file-per-line--stax-event-item-reader-config.png]]
45 +To clarify the use cases let us take a look at how annotations can be added within the eMagiz platform. In our first example, we will take a look at asynchronous routing. In many eMagiz projects, a best practice is followed on how to add something to the asynchronous routing (or change something within the asynchronous routing). Because the best practice contains multiple steps it makes sense to use the annotation functionality of eMagiz to define all these steps and register them at the place you need them (i.e. the asynchronous routing). Having done so will result in something like this:
45 45  
46 -==== 3.1.2 Flat File Item Reader ====
47 +<p align="center">[[image:novice-devops-perspectives-annotations--annotation-best-practice-async-routing.png||]]</p>
47 47  
48 -For the Flat File item reader, there are some more choices and configurations to be made. There are three options you can choose from:
49 -- Pass through line mapper
50 -- Default line mapper
51 -- Pattern matching composite line mapper
49 +The second example is about using annotations on the flow level to describe parts of the flow. In this example, we will use the annotation to describe that we use a filter to determine which messages are picked up from a local directory and how we filter. That way anyway opening the flow has to merely read the annotation to get the context. Having done so will result in something like this:
52 52  
53 -Each of these options has some advantages and disadvantages. Adhering to the best practices of eMagiz (i.e. no transformation in the entry) the best option would be to use the pass-through line mapper. As the name suggests this option does nothing except give a string back to the flow on a per line basis. However, choosing this option means that the actual transformation from that string to XML needs to happen later in the process (most likely in the onramp) with the help of a flat-file to XML transformer (more on that component in a later course).
51 +<p align="center">[[image:novice-devops-perspectives-annotations--describe-parts-of-flow.png||]]</p>
54 54  
55 -The other two options transform the input line into an XML output. So you win one step in the process. However, no standard eMagiz error handling is advisable when you start transforming data within the entry. So in case, something goes wrong to analyze the error will become more difficult. Furthermore, another potential disadvantage is that when one line fails the processing of the rest of the file also halts.
53 +The third example does not take place on the flow level but the message definition level. Therefore instead of going to Create, we go to Design. In Design when you navigate to the CDM, API Gateway Data model, Event Streaming Data model, message definitions, etc. you have the option to add annotations to the canvas. In this example, we want to make clear to all that make changes that a certain part of our CDM is used by a lot of integrations within eMagiz and therefore everyone should be careful and think twice before adjusting anything related to that part. Having done so will result in something like this:
56 56  
57 -For the remainder of this microlearning, we will assume that the option pass through line mapper is chosen.
55 +<p align="center">[[image:novice-devops-perspectives-annotations--describe-crucial-part-of-cdm.png||]]</p>
58 58  
59 -[[image:Main.Images.Microlearning.WebHome@novice-file-based-connectivity-processing-a-file-per-line--flat-file-item-reader-passthrough.png]]
57 +Now that we saw some examples let us turn our attention to the how. How can I add an annotation and how can I link it. Adding the annotation is simple. You drag the annotation icon from the left context menu onto the canvas. As a result, an empty annotation will be shown on the canvas. By double-clicking on it you can type whatever you want. Note that you need to be in "Start Editing" mode to change anything, including annotations.
60 60  
61 -As you can see on the Basic level we are done. However, it is always good to check out the settings on the Advanced tab, especially in this case, to see if there are additional configuration options that could benefit us. The setting of most interest, in this case, is the Lines to Skip setting (default setting is 0). With this setting, you can define whether or not you want to process the header line(s) that exists within your input file. The remainder of the settings is (in most cases) good the way eMagiz has set them up.
59 +<p align="center">[[image:novice-devops-perspectives-annotations--annotation-icon-context-menu.png||]]</p>
62 62  
63 -[[image:Main.Images.Microlearning.WebHome@novice-file-based-connectivity-processing-a-file-per-line--flat-file-item-reader-passthrough-advanced.png]]
61 +When you are satisfied with what you have written down you can press the Save button. After you have done so you can rescale the annotation to ensure that the complete text is visible. To link the annotation to a component (on flow level) or an entity (on message definition level) you hover over the annotation until your mouse indicator changes to a + icon, execute a right-click and drag from the annotation to the component in question.
64 64  
65 -=== 3.2 Poller ===
63 +Now you know what annotations are good for and how you can add them within the eMagiz platform.
66 66  
67 -Now that we have selected and configured the item reader type it becomes time to fill in the last part of the configuration, the poller. For polling eMagiz offers three options:
65 +===== Practice =====
68 68  
69 -- Fixed Delay Trigger
70 -- Fixed Rate Trigger
71 -- Cron Trigger
72 -
73 -Of these options, the cron trigger is used most frequently in eMagiz. The reason being is that you can define this option via a property that you can alter without having to alter the flow version in Create.
74 -
75 -[[image:Main.Images.Microlearning.WebHome@novice-file-based-connectivity-processing-a-file-per-line--poller-config.png]]
76 -
77 -After finishing all these configuration steps we can press Save to save our work and ensure that we can process the input file on a per-line basis.
78 -
79 79  == 4. Assignment ==
80 80  
81 -Configure an entry in which you define the component and configuration needed to process a file on a per-line basis.
69 +Add annotation on the flow level that describes how (a part of) a flow works.
82 82  This assignment can be completed with the help of the (Academy) project that you have created/used in the previous assignment.
83 83  
84 84  == 5. Key takeaways ==
85 85  
86 -* Easy way of reading a file line by line and sending it to eMagiz (Low on memory)
87 -* Ability to process each line based on distinctive logic that is relevant on line level
88 -* Can be used for flat file as well as XML input files
89 -* Try to avoid complex transformations within the entry
74 +* Annotations can be used for:
75 + * Describing a best practice everyone should follow
76 + * Describing (more complex) parts of the flow
77 + * Describe (parts of) your message definitions
78 +* You can add annotations by dragging and dropping the annotation icon on the canvas.
90 90  
80 +
81 +
91 91  == 6. Suggested Additional Readings ==
92 92  
93 93  There are no suggested additional readings on this topic
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96 96  
97 97  This video demonstrates how you could have handled the assignment and gives you some context on what you have just learned.
98 98  
99 -{{video attachment="novice-file-based-connectivity-processing-a-file-per-line.mp4" reference="Main.Videos.Microlearning.WebHome"/}}
90 +<iframe width="1280" height="720" src="../../vid/microlearning/novice-devops-perspectives-annotations.mp4" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
100 100  
101 -)))((({{toc/}}))){{/container}}{{/container}}
92 +</div>
93 +
94 +</div>
95 +</div>
96 +
97 +{{/html}}
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