Plugin Extensions

Understanding iDempiere’s plugin extension point system

Overview

iDempiere uses Eclipse’s plugin extension framework to provide extensibility throughout the system. Extension points allow plugins to contribute functionality without modifying core code.

Extension Point Architecture

Extension points are defined in the plugin.xml file of the org.adempiere.base bundle. Each extension point has:

• ID: Unique identifier for the extension point
• Name: Human-readable name
• Schema: XML schema defining the structure (.exsd files)

Core Extension Points

iDempiere provides several key extension points defined in org.adempiere.base/plugin.xml:

Business Logic Extensions

• org.adempiere.base.IColumnCallout: Column callout implementations
• org.adempiere.base.Process: Business process implementations
• org.adempiere.base.ModelValidator: Model event listeners

Integration Extensions

• org.compiere.model.PaymentProcessor: Payment gateway integrations
• org.adempiere.model.ITaxProvider: Tax calculation services
• org.adempiere.model.IShipmentProcessor: Shipping carrier integrations
• org.adempiere.model.IAddressValidation: Address validation services

Data Exchange Extensions

• org.adempiere.base.IGridTabExporter: Grid data export formats
• org.adempiere.base.IGridTabImporter: Grid data import formats

Extension Point Definition

From org.adempiere.base/plugin.xml:

<extension-point 
    id="org.adempiere.base.Process" 
    name="Process" 
    schema="schema/org.adempiere.base.Process.exsd"/>

<extension-point 
    id="org.compiere.model.PaymentProcessor" 
    name="Payment Processor" 
    schema="schema/org.compiere.model.PaymentProcessor.exsd"/>

<extension-point 
    id="org.adempiere.model.ITaxProvider" 
    name="Tax Provider" 
    schema="schema/org.adempiere.model.ITaxProvider.exsd"/>

<extension-point 
    id="org.adempiere.model.IShipmentProcessor" 
    name="Shipment Processor" 
    schema="schema/org.adempiere.model.IShipmentProcessor.exsd"/>

Creating an Extension

1. Define Extension in plugin.xml

In your plugin’s plugin.xml file:

<extension
    id="com.example.MyProcess"
    name="My Custom Process"
    point="org.adempiere.base.Process">
    <process
        class="com.example.MyProcess"
        priority="0">
    </process>
</extension>

2. Extension Attributes

Required Attributes:

• id: Unique identifier for your extension
• point: The extension point ID you’re extending
• class: Fully qualified class name of your implementation

Optional Attributes:

• name: Human-readable name
• priority: Numeric priority (higher values = higher priority, default: 0)

3. Priority System

When multiple extensions exist for the same extension point:

• Higher priority values are selected first
• Extensions with equal priority are selected in load order
• Default priority is 0

<!-- This extension will be preferred over default implementations -->
<extension
    id="com.example.CustomTaxProvider"
    name="Custom Tax Provider"
    point="org.adempiere.model.ITaxProvider">
    <provider
        class="com.example.CustomTaxProvider"
        priority="10">
    </provider>
</extension>

Built-in Extensions

iDempiere includes several built-in extensions in plugin.xml:

Grid Data Exporters

<extension
    id="org.adempiere.impexp.GridTabXlsExporter"
    name="Grid data excel exporter"
    point="org.adempiere.base.IGridTabExporter">
    <exporter
        class="org.adempiere.impexp.GridTabExcelExporter"
        priority="0">
    </exporter>
</extension>

<extension
    id="org.adempiere.impexp.GridTabXLSXExporter"
    name="Grid data excel exporter"
    point="org.adempiere.base.IGridTabExporter">
    <exporter
        class="org.adempiere.impexp.GridTabXLSXExporter"
        priority="0">
    </exporter>
</extension>

<extension
    id="org.adempiere.impexp.GridTabCSVExporter"
    name="Grid data CSV exporter"
    point="org.adempiere.base.IGridTabExporter">
    <exporter
        class="org.adempiere.impexp.GridTabCSVExporter"
        priority="0">
    </exporter>
</extension>

<extension
    id="org.adempiere.impexp.GridTabSQLInsertExporter"
    name="Export data as SQL insert statement"
    point="org.adempiere.base.IGridTabExporter">
    <exporter
        class="org.adempiere.impexp.GridTabSQLInsertExporter"
        priority="0">
    </exporter>
</extension>

Standard Tax Provider

<extension
    id="org.compiere.model.StandardTaxProvider"
    name="Standard Tax Provider"
    point="org.adempiere.model.ITaxProvider">
    <provider
        class="org.compiere.model.StandardTaxProvider"
        priority="0">
    </provider>
</extension>

Extension Discovery

iDempiere discovers extensions through:

1. OSGi Bundle Scanning: Reads plugin.xml from all active bundles
2. Extension Registry: Eclipse extension registry manages all extensions
3. Factory Pattern: Core classes use factories to instantiate extensions

Example: Core Class Integration

From org.compiere.model.PaymentProcessor:

public static PaymentProcessor create(MBankAccountProcessor mbap, 
                                       PaymentInterface mp) {
    return Core.getPaymentProcessor(mbap, mp);
}

The Core class uses the extension registry to find and instantiate the appropriate implementation based on configuration.

Database Configuration

Many extensions are configured through database tables:

• C_PaymentProcessor.PayProcessorClass: Payment processor class name
• C_TaxProvider.TaxProviderClass: Tax provider class name
• X_ShippingProcessor.ShippingProcessorClass: Shipment processor class name

These fields store the fully qualified class name that matches an extension’s class attribute.

Best Practices

Extension Design

1. Single Responsibility: Each extension should have one clear purpose
2. Loose Coupling: Depend on interfaces, not implementations
3. Error Handling: Handle errors gracefully and provide meaningful messages
4. Logging: Use iDempiere’s logging framework for debugging

Priority Management

1. Use Default Priority (0): For most extensions
2. Higher Priority (10+): Only for replacements of default implementations
3. Document Priority: Explain why non-zero priority is needed

Testing

1. Unit Tests: Test extension logic independently
2. Integration Tests: Test within iDempiere environment
3. Priority Testing: Test behavior with multiple implementations

Plugin Structure

A typical plugin bundle structure:

com.example.plugin/
├── META-INF/
│   └── MANIFEST.MF          # OSGi bundle manifest
├── plugin.xml               # Extension declarations
├── schema/
│   └── *.exsd              # Custom extension point schemas
└── src/
    └── com/example/
        └── MyExtension.java # Implementation classes

Related Topics

• Payment Processors: Payment gateway integration
• Tax Providers: Tax calculation integration
• Shipment Processors: Shipping carrier integration
• Model Validators: Database event handling
• Callouts: UI field event handling