# Excel Writer Extension
The **Excel Writer** is a built‑in **Custom Extension** provided by ONEWEB that allows **Microflows** and **Process Flows** to write structured data to **Microsoft Excel files**.\
Excel Writer complements the **Excel Reader** extension by enabling applications not only to read Excel data but also to **generate, export, and deliver Excel outputs** as part of backend logic or workflows.
This makes Excel Writer suitable for **reporting, data exchange, and batch output scenarios** commonly found in enterprise applications.
***
### Purpose of Excel Writer
The Excel Writer extension is designed to:
* Write structured data into Microsoft Excel files
* Generate Excel files as outputs of Microflows or Processes
* Support file‑based data export and reporting use cases
* Integrate backend systems with Excel‑based consumers
#### Typical Use Cases
* Exporting transaction data or reports to Excel
* Generating Excel files for downstream systems
* Producing downloadable Excel reports for end users
* Writing processed batch results into spreadsheets
Excel Writer enables ONEWEB applications to deliver results in a widely adopted, business‑friendly format.
***
### Installing the Excel Writer Extension
Before using Excel Writer, the extension must be **installed and enabled** for the application.
To install the extension:
* Follow the steps described in **Section 6.4.16 – Custom Extensions**
* Install and enable the **Excel Writer** extension in the application
Once installed:
* The Excel Writer node appears in the **diagram palette**
* It can be used like any standard activity node within Microflow or Process Designer
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### Configuring Excel Writer
After placing the Excel Writer node onto the canvas, users can configure **how and where data is written** to Excel files.
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#### File Destination Configuration
Excel Writer supports writing Excel files to multiple destinations:
* File System
* Network locations
* FTP
* SFTP
* FTPS
Users can:
* Specify directory and file details directly, or
* Retrieve destination information dynamically from a **Business Object**, similar to Excel Reader
Excel Writer also supports transforming Microflow data into the required Excel structure before writing.
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#### Writing Data to Excel Sheets
Excel Writer supports multiple data‑writing modes, configurable per worksheet:
* **Specific Field (Column‑level)**
* Writes values to selected columns only
* **Records (Row‑level)**
* Writes complete rows as records
These options provide fine‑grained control over how data appears in each Excel sheet.
***
#### Writing Multiple Sheets
Excel Writer supports generating **multiple worksheets** within a single Excel file.
With this capability:
* Different datasets can be mapped to different sheets
* Sheet names and mappings can be configured dynamically
* All sheets are written as part of a single execution
This makes Excel Writer well‑suited for **complex reporting** and **batch export** scenarios.
***
### Data Mapping
Excel Writer relies on **Business Objects** to define:
* Input data to be written
* Field‑to‑column mappings
* Record‑level data structures
Mapping is performed using the same **visual parameter mapping interface** as other Microflow activity nodes, ensuring consistency across integration and processing logic.
***
### Best Practices
To ensure reliable and maintainable Excel‑based integrations:
* Use Excel Writer primarily for **output and reporting**, not transactional updates
* Validate directory paths and permissions before writing files
* Avoid unintentionally overwriting critical or shared files
* Prefer environment variables for destination paths
* Combine Excel Writer with Database, Excel Reader, or Web Service nodes for end‑to‑end data flows
***
### Summary
The **Excel Writer Extension** enables ONEWEB applications to **generate and export data into Excel files** as part of Microflows or Process Flows.
With Excel Writer, developers can:
* Write structured data into Excel spreadsheets
* Generate multi‑sheet Excel files
* Output data to local or remote destinations
* Build Excel‑based reporting and batch export workflows
Excel Writer is a key component for implementing **file‑based output, reporting, and batch integration scenarios** in enterprise‑grade ONEWEB applications.
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