.. _tuto-hookcustomizations-events:

Using Events
############

From GeoNetwork 3.0.x on, there are a number of events you can listen to on your Java code.

Enabling Event Listeners
========================

To enable this on your Maven project, you have to add the event dependencies. Edit the file :file:`custom/pom.xml` and add the dependencies tag:


.. code:: xml

   <dependencies>
      <dependency>
        <groupId>${project.groupId}</groupId>
        <artifactId>events</artifactId>
        <version>${project.version}</version>
      </dependency>
      <dependency>
        <groupId>${project.groupId}</groupId>
        <artifactId>core</artifactId>
        <version>${project.version}</version>
      </dependency>
   </dependencies>


Then create the file custom/src/main/resources/config-spring-geonetwork.xml to tell Spring to load your custom beans adding the following content:

.. code:: xml

     <?xml version="1.0" encoding="UTF-8"?>
     <beans xmlns="http://www.springframework.org/schema/beans"
            xmlns:util="http://www.springframework.org/schema/util"
            xmlns:context="http://www.springframework.org/schema/context"
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xsi:schemaLocation=
               "http://www.springframework.org/schema/beans 
                http://www.springframework.org/schema/beans/spring-beans.xsd
                http://www.springframework.org/schema/util
                http://www.springframework.org/schema/util/spring-util.xsd
                http://www.springframework.org/schema/context
                http://www.springframework.org/schema/context/spring-context-3.2.xsd">
       <bean class="org.fao.geonet.events.listeners.MyCustomListener" ></bean>
     </beans>

This file should contain a list of all the classes that listen to events inside GeoNetwork scope.

Simple Example
==============

We can add a simple example listener like this one, which will print a string every time a metadata gets removed.

.. code:: java

   package org.fao.geonet.events.listeners;

   import org.fao.geonet.domain.*;

   import org.fao.geonet.events.md.MetadataRemove;

   import org.springframework.context.ApplicationListener;

   import org.springframework.stereotype.Component;

   @Component
   public class MyCustomListener implements ApplicationListener<MetadataRemove> { 
      @Override
      public void onApplicationEvent(MetadataRemove event) {
         System.out.println("REMOVED");
      }
   }


For example, we can call an external REST API that gets triggered every time a Metadata gets removed or updated.


GeoNetwork API
==============

There is also a new API you can use to interact with GeoNetwork from an external script. See more on :ref:`api-guide`.