How to Add Server Side Hooks

Overview

Hooks provide an easy mechanism to extend functionality from external module. It basically consists on a lightweight mechanism (build using WELD) that allows to inject dependencies from third party modules.

There are two roles for hooks:

• Base module that provides the standard functionality and defines some point in its flow that can be extended by external modules
• External modules that provide extra functionality to the base one. Logic for this extra functionality is executed in the point the base module defines for this purpose.

How to define a server side hook in the base module

Base module needs to define which are the points other modules can extend through hooks. This is done with the following code:

step 1:

Define the abstract class for the new hook:

 
package org.openbravo.retail.posterminal;
 
public abstract class MyNewHook {
  
  public abstract void exec(Object param1, Object param2)
      throws Exception;
}
 

step 2:

Define a function to call to every classes which are registered in the defined hooks.

 
  private void executeHooks(Instance<? extends Object> hooks, Object param1, Object param2) throws Exception {
    for (Iterator<? extends Object> procIter = hooks.iterator(); procIter.hasNext();) {
      Object proc = procIter.next();
      ((MyNewHook) proc).exec(param1, param2);
    }
  }

step 3:

Execute hooks in the desired point of your module.

 
  @Inject
  @Any
  private Instance<MyNewHook> myNewHook;
  //your code
  executeHooks(myNewHook, myParam, null);

When this code is reached, all the hooks defined by external modules for this hookName will be sequentially executed.

How to provide logic in external modules

When there is a base module that defines a hook as mentioned in the previous section, external modules can provide logic to be executed at that point creating a new class in following manner:

 
package org.openbravo.retail.posterminal;
 
import javax.enterprise.context.ApplicationScoped;
 
@ApplicationScoped
public class MyNewHookExtension extends MyNewHook {
 
  @Override
  public void exec(Object param1, Object param2) throws Exception {
    // Business Logic
  }
}

Server Side Hooks in Web POS

This document list of server side hooks available in Web POS.