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Last modified by Erik Bakker on 2024/08/26 12:38
From version 29.1
edited by Erik Bakker
on 2022/06/10 13:22
Change comment: There is no comment for this version
To version 28.1
edited by Erik Bakker
on 2022/06/10 13:12
Change comment: There is no comment for this version

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1 -Processing a File per Line
1 +Header line
Content
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1 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.
2 +In this microlearning, we will learn how you can define a header line in which you specify the naming of the various columns. Some external systems require a header line when you supply them with data via a flat file that is placed somewhere.
3 3  
4 4  Should you have any questions, please contact [[academy@emagiz.com>>mailto:academy@emagiz.com]].
5 5  
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12 12  
13 13  == 2. Key concepts ==
14 14  
15 -This microlearning centers around learning how to process an incoming file per line.
15 +This microlearning centers around learning how to place a header line on a flat-file output.
16 16  
17 -By processing per line, we mean: Splitting up the input into discernable pieces that each will become a unique message
17 +By header line we mean: A line in the output that defines the naming of the various columns
18 18  
19 -* Easy way of reading a file line by line and sending it to eMagiz (Low on memory)
20 -* Ability to process each line based on distinctive logic that is relevant on line level
21 -* Can be used for flat file as well as XML input files
19 +Some external parties require that the first line in the flat file output (i.e. CSV) is filled with column names (i.e. headers). In eMagiz, we call this line a header line.
22 22  
23 -== 3. Processing a File per Line ==
21 +== 3. Header line ==
24 24  
25 -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.
23 +In this microlearning, we will learn how you can define a header line in which you specify the naming of the various columns. Some external systems require a header line when you supply them with data via a flat file that is placed somewhere. The header line is the first line in the flat file output. Within this line, the various column names are specified for clarity.
26 26  
27 -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.
25 +To add such a header line in eMagiz you need to navigate to the Create phase of eMagiz and open the exit flow in which you want to drop the file to a certain location. Within the context of this flow, we need to add functionality that will ensure that a header line is written to the output before any functional lines are added. To do so first enter "Start Editing" mode on flow level. After you have done so please add a file outbound channel adapter to the flow including an input channel. We will use this component to write our header line to the flat file output.
28 28  
29 -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.
27 +Ensure that the directory to which you reference is the same as in your functional file outbound channel adapter.
30 30  
31 -[[image:Main.Images.Microlearning.WebHome@novice-file-based-connectivity-processing-a-file-per-line--file-item-reader-directory.png]]
29 +[[image:Main.Images.Microlearning.WebHome@novice-file-based-connectivity-header-line--file-outbound-channel-header-line.png]]
32 32  
33 -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.
31 +Now it is time to turn our attention to the Advanced tab. For the Mode select Ignore. Select this option to ensure that the header line is only written down once when there is no output created yet and not somewhere in the middle, in the end, or every time. Furthermore, select the option Append New Line to ensure that the remainder of the information is not appended to the same line.
34 34  
35 -=== 3.1 Item reader Type ===
33 +[[image:Main.Images.Microlearning.WebHome@novice-file-based-connectivity-header-line--file-outbound-channel-header-line-advanced.png]]
36 36  
37 -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 +After you have done so we need to add a standard transformer that defines the various column names to be written to the flat file output. To do so add the standard transformer component to the canvas including an input channel. After you have done so define the relevant SpEL expression. In this case, we advise using a property value that represents a string of column names. The value of the property should be something as follows:
38 38  
39 -[[image:Main.Images.Microlearning.WebHome@novice-file-based-connectivity-processing-a-file-per-line--item-reader-type-options.png]]
37 +'Header1;Header2;Header3;Header4'
40 40  
41 -Based on your choice the exact configuration will differ.
39 +Do note that the separator, in this case, needs to match the requirements of the external system. At the flow configuration level, the standard transformer should look as follows.
42 42  
43 -==== 3.1.1 Stax Event Item Reader ====
41 +[[image:Main.Images.Microlearning.WebHome@novice-file-based-connectivity-header-line--define-columns-names.png]]
44 44  
45 -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.
43 +Our last step is to ensure that this piece of logic is tied to the main flow and is executed before writing the functional line(s) to the output file. To make that happen we need to add a wiretap to the flow. With the help of this functionality, you can define which part of the logic takes precedence over another part of the logic. To do so double click on the channel on which you want to place a wiretap, select the option wiretap and select the correct wiretap channel. After you have done this the result should be something as follows:
46 46  
47 -[[image:Main.Images.Microlearning.WebHome@novice-file-based-connectivity-processing-a-file-per-line--stax-event-item-reader-config.png]]
45 +[[image:Main.Images.Microlearning.WebHome@novice-file-based-connectivity-header-line--wiretap-result.png]]
48 48  
49 -==== 3.1.2 Flat File Item Reader ====
47 +With these couple of steps, you have now successfully added logic to your flow that will ensure that a header line is added before any functional line(s) are written to the output file.
50 50  
51 -For the Flat File item reader, there are some more choices and configurations to be made. There are three options you can choose from:
52 -- Pass through line mapper
53 -- Default line mapper
54 -- Pattern matching composite line mapper
55 -
56 -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).
57 -
58 -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.
59 -
60 -For the remainder of this microlearning, we will assume that the option pass through line mapper is chosen.
61 -
62 -[[image:Main.Images.Microlearning.WebHome@novice-file-based-connectivity-processing-a-file-per-line--flat-file-item-reader-passthrough.png]]
63 -
64 -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.
65 -
66 -[[image:Main.Images.Microlearning.WebHome@novice-file-based-connectivity-processing-a-file-per-line--flat-file-item-reader-passthrough-advanced.png]]
67 -
68 -=== 3.2 Poller ===
69 -
70 -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:
71 -
72 -- Fixed Delay Trigger
73 -- Fixed Rate Trigger
74 -- Cron Trigger
75 -
76 -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.
77 -
78 -[[image:Main.Images.Microlearning.WebHome@novice-file-based-connectivity-processing-a-file-per-line--poller-config.png]]
79 -
80 -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.
81 -
82 82  == 4. Assignment ==
83 83  
84 -Configure an entry in which you define the component and configuration needed to process a file on a per-line basis.
51 +Configure an exit in which you define and write a header line to a flat-file output before adding functional lines.
85 85  This assignment can be completed with the help of the (Academy) project that you have created/used in the previous assignment.
86 86  
87 87  == 5. Key takeaways ==
88 88  
89 -* Easy way of reading a file line by line and sending it to eMagiz (Low on memory)
90 -* Ability to process each line based on distinctive logic that is relevant on line level
91 -* Can be used for flat file as well as XML input files
92 -* Try to avoid complex transformations within the entry
56 +* The header line contains the names of the columns of the flat file output
57 +* Use the Ignore mode to ensure the header line is created once
58 +* Use the wiretap to ensure the header line is created first
93 93  
94 94  == 6. Suggested Additional Readings ==
95 95  
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99 99  
100 100  This video demonstrates how you could have handled the assignment and gives you some context on what you have just learned.
101 101  
102 -{{video attachment="novice-file-based-connectivity-processing-a-file-per-line.mp4" reference="Main.Videos.Microlearning.WebHome"/}}
68 +{{video attachment="novice-file-based-connectivity-header-line.mp4" reference="Main.Videos.Microlearning.WebHome"/}}
103 103  
104 104  )))((({{toc/}}))){{/container}}{{/container}}