Learning Objectives

After completing this lesson, you’ll be able to:

Add multiple readers and writers to your workspace.
Update readers and writers.
Set reader and writer parameters.

Reading and Writing Workflows

By default, the Generate Workspace dialog creates a workspace with a single reader and a single writer. However, this does not mean the workspace is forever limited to this. Additionally, FME can read/write data using:

Multiple readers, multiple writers, or both
FeatureReader and/or FeatureWriter transformers
Integration transformers such as the DropboxConnector, Email, HTTPCaller, etc

Multiple Readers and Writers

An FME workspace is not limited to any particular number of readers or writers; readers and writers can be added to a workspace at any time, any number of formats can be used, and there does not need to be an equal number of readers and writers.

For example, the Navigator window shows this workspace contains two readers and three writers, of different data types and formats!

It's important to note that readers and writers don’t appear as objects on the Workbench canvas. Their feature types do, but readers and writers don't.
Instead, they are represented by entries in the Navigator window, as in the above screenshot.

Adding Readers and Writers

Additional readers or writers are added to a translation using the Quick Add menu:

...Or by selecting Readers > Add Reader (Writers > Add Writer) from the menu bar:

This action opens a dialog, similar to the Generate Workspace dialog, in which the parameters for the new reader or writer can be defined:

Add Writer dialog

You can add as many readers and writers as you require in this way.

A reader can also be added by dragging a dataset from a filesystem explorer and dropping it onto the Workbench canvas.

Removing a Reader or Writer

If a reader or writer is no longer required, then it can be removed very simply using options on the menu bar:

Alternatively, it's possible to right-click a reader/writer in the Navigator window and choose the Delete option.

Updating a Reader or Writer

Readers and writers can be updated so that older workspaces have the speed and functionality available in a newer version of FME. You can update a reader/writer by right-clicking the reader/writer in the Navigator window and choosing the Update option:

For readers, this tool provides the option to either update the reader or to also update the list of feature types being read. This way the workspace can be updated if the source data changes. Another way to update feature types is Reader > Update Feature Types on the menu bar.

Reader Parameters

As we know, a workspace contains a reader to read a dataset, and each feature type in that dataset is shown in the workspace canvas:

To control how that reader operates requires the use of reader parameters.

Finding Reader Parameters

Reader parameters can be located - and set - by clicking Parameters in the Generate Workspace or Add Reader dialogs:

They can also be found in the Navigator window in Workbench:

Because parameters refer to specific components and characteristics of the related format, readers of different formats have a different set of control parameters.

Setting Reader Parameters

To edit a parameter in the Navigator window, double-click on any of the parameters. Doing so opens up a dialog where the parameter’s value may be set:

Reader parameters control all feature types in the dataset. Think of it like brewing a pot of coffee. The strength control on the coffee machine affects all the cups that are poured.

Because some reader parameters affect how feature types are generated (e.g. how do you want to slice a JSON or XML file?), they can only be set when you add the reader. If you set them incorrectly or want to change them, you have to delete the reader and add it again.

This behavior does not exist in writer parameters.

Writer Parameters

Like readers, we know a workspace contains a writer to write a dataset, and each feature type to be written is shown in the workspace canvas:

To control how that writer operates requires the use of writer parameters.

Finding Writer Parameters

Writer parameters can be located - and set - by clicking Parameters when a new workspace is being generated:

They too can also be found in the Navigator window in Workbench:

Because parameters refer to specific components and characteristics of the related format, writers of different formats have a different set of control parameters.

Setting Writer Parameters

To edit a parameter in the Navigator window, double-click on any of the parameters. Doing so opens up a dialog where the parameter’s value may be set:

Like readers, writer parameters control all feature types in the dataset. For example, in the above screenshot, all feature types will be version 3.1.1.
But each reader and writer feature type does have its own settings (in the same way that each cup of coffee can be adjusted with cream and sugar). Learn more in the documentation.

Cross-Operating System Compatibility

One important consideration in overall workspace design is cross-OS compatibility. Generally, FME is designed so your workspaces will run on any of our supported operating systems. However, there are a few best practices to keep in mind that could save you from problems in the future. These include:

File paths
- Because operating systems use different rules for file path construction, we recommend using the Directory and File Pathnames reader and FME user parameters to handle file paths wherever possible. Hardcoding paths is a sure-fire way to cause cross-OS compatibility issues
Special characters
- It's best practice to at a minimum, avoid using non-printable characters (including ASCII control characters) and \/:*?"<>|, null, and / in your file and folder names. For more advice, see this thread.
Case insensitivity
- Databases you are using, including those used in conjunction with FME Server, might have different case expectations. For example. some databases allow myObject and myobject while others will reject these fields as a duplicate violation. Assuming case insensitivity is the safest method.