Getting Started with Fax4J: Installation, Configuration, and Examples

Fax4J is a lightweight Java library that provides a unified API to send faxes through multiple back-end providers (modems, email-to-fax gateways, third-party fax services). This guide walks through installation, configuration, and practical examples so you can integrate faxing into Java applications quickly.

Prerequisites

Java 8+ runtime and JDK for development
Maven or Gradle for dependency management (examples use Maven)
An operational fax provider integration (local modem, SMTP-to-fax, or third‑party service) and relevant credentials

Installation

Maven

Add Fax4J and any provider-specific dependencies to your pom.xml. A minimal Fax4J dependency looks like:

xml
<dependency>
<groupId>net.sf.fax4j</groupId>
  <artifactId>fax4j</artifactId>
  <version>0.0.9</version>
</dependency>

(Also add provider-specific jars if required by your chosen connector.)

Gradle

Add to build.gradle:

groovy
implementation ‘net.sf.fax4j:fax4j:0.0.9’

Configuration overview

Fax4J uses a configuration properties file or programmatic properties to select a fax client (connector) and set provider parameters (SMTP server, modem port, API key, etc.). Key configuration areas:

Client type (e.g., SMTP, HTTP, modem)
Provider-specific connection settings (host, port, credentials)
Transfer settings (retries, timeouts)
Logging and tracing options

Create a properties file (fax4j.properties) on the classpath or supply a java.util.Properties object to the FaxClientFactory.

Example keys (varies by connector):

fax.client.impl – fully qualified class name of the fax client implementation
fax.smtp.host, fax.smtp.port, fax.smtp.username, fax.smtp.password
fax.modem.port, fax.modem.baudRate

Example 1 — Sending via SMTP-to-Fax gateway

This example demonstrates sending a PDF via an SMTP fax gateway (common when using a provider that accepts email-to-fax).

fax4j.properties (place on classpath):

Code
fax.client.impl=net.sf.fax4j.provider.email.EmailFaxClientImpl fax.smtp.host=smtp.example.com fax.smtp.port=587 fax.smtp.username=your_username fax.smtp.password=yourpassword fax.smtp.auth=true fax.smtp.starttls.enable=true

Java code:

java
import net.sf.fax4j.FaxClientFactory; import net.sf.fax4j.FaxException; import net.sf.fax4j.FaxJob; import net.sf.fax4j.FaxJobImpl; import net.sf.fax4j.FaxClient; import java.io.File; public class FaxExample { public static void main(String[] args) { try { FaxClient faxClient = FaxClientFactory.getFaxClient(null); FaxJob faxJob = new FaxJobImpl(); faxJob.setDocumentFile(new File(“document.pdf”)); faxJob.setRecipientAddress(”[email protected]”); // provider-specific addressing faxClient.send(faxJob); System.out.println(“Fax submitted.”); } catch (FaxException e) { e.printStackTrace(); } } }

Example 2 — Sending via HTTP/REST provider

For providers offering HTTP APIs, use an HTTP client implementation (either community-provided or write a thin adapter). Configuration keys will be provider specific.

Programmatic properties approach:

java
Properties props = new Properties(); props.put(“fax.client.impl”, “com.yourcompany.fax.HttpFaxClientImpl”); props.put(“fax.http.url”, “https://api.faxservice.example/send”); props.put(“fax.http.apikey”, “your_apikey”); FaxClient faxClient = FaxClientFactory.getFaxClient(props);

Then create and send a FaxJob as in Example 1. Implement a FaxClient that maps FaxJob fields to provider API parameters and handles responses.

Example 3 — Local modem (T.30) sending

Using a connected modem requires native drivers and correct serial-port settings.

Sample properties:

Code
fax.client.impl=net.sf.fax4j.provider.modem.ModemFaxClientImpl fax.modem.port=COM3 fax.modem.baudRate=115200

Modem setup and permissions vary by OS; ensure the JVM can access the serial port. Use FaxJob with recipient number only.

Handling Results and Callbacks

Fax4J supports asynchronous listeners and job status tracking through FaxJob attributes and event listeners. Attach a FaxJobListener to react to events like QUEUED, SENDING, SUCCESS, FAILURE.

Simple synchronous check:

java
FaxClient faxClient = FaxClientFactory.getFaxClient(null); String jobId = faxClient.send(faxJob); FaxJobStatus status = faxClient.getJobStatus(jobId);

Error Handling and Retries

Configure retry counts and intervals in properties or implement retry logic around send calls.

Log provider responses and device/modem logs to diagnose failures.

Common issues: wrong SMTP credentials, blocked ports, modem access permissions, incorrect recipient formatting.

Testing Tips

Use small test documents (one-page PDF) and confirm provider test numbers if available.

Run in a controlled environment for modem tests to avoid tying up phone lines.

Monitor provider dashboards or email notifications for delivery status.

Security Considerations

Store credentials securely (environment variables, vaults) rather than plain properties files.

Use TLS for SMTP/HTTP connections.

Sanitize document inputs if generating faxes from user content.

Useful Resources

Fax4J project page and Javadocs for API details

Your fax provider’s SMTP/HTTP API documentation

Serial port access guides for your OS when using modems

Example quick checklist

Install fax4j dependency

Choose and configure client (SMTP/HTTP/modem)

Provide credentials securely

Test with a small document

Implement logging and retries

That’s enough to get a basic Fax4J integration running. Adjust properties and client implementation depending on your chosen provider and environment.

Getting Started with Fax4J: Installation, Configuration, and Examples