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WSO2 Governance Registry generates notifications for events triggered by various operations performed on resources and collections stored in the repository. Notifications can be consumed in a variety of formats including E-mail. Read more about Notifications and also the API-Level Access provided for subscription operations. The contents of notification eE-mails can be customized by using an Axis2 Handler. WSO2 Governance Registry contains an Apache Axis2 based runtime as a part of the WSO2 Carbon Framework. We will be reusing the code of the Handler Sample in this example. This sample requires Apache Maven. See Installing Apache Maven for Governance Registry on Windows or Installing Apache Maven for Governance Registry on Linux.
This sample also includes two advanced use-cases which have been included at the bottom of this page.
Instructions
1. Navigate to GREG_HOME/
samples/handler/src
to find the source code of the Handler Sample.
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A successful run of Apache Maven will generate a report similar to the following:
4. Copy the GREG_HOME/
samples/handler/src/target/
org.wso2.carbon.registry.samples.handler-4.5.0.jar
into GREG_HOME/repository/components/dropins
.
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7. Start the server and observe the command prompt. See Starting Governance Registry Management Console on Windows or Starting Governance Registry Management Console on Linux.
8. Navigate to the / collection of the Resource Browser and add an E-mail subscription for Update events.
Click the "Subscribe" button to create the subscription. Read about Managing the Resources and Managing Breadcrumb to learn how to navigate to the / collection. And read more about Managing Subscriptions.
9. Click on the E-mail Address verification link that you will receive via E-mail.
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In this example, John Smith uses a Gmail account. |
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11. You should now receive a Notification E-mail which contains the following text:
Code Block |
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This message was intercepted by EmailTransformHandler |
See also Notifications and Managing Subscriptions.
Advanced Use-case 1
This sample can be improved to include a clickable link in the E-mail body, making it possible for users to easily navigate to the resources in which changes have been made. The following modification can be made to the code segment to achieve this:
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In this example, John Smith uses a Gmail account. Gmail automatically converts URLs into clickable links. This might not be the case if you are using a traditional E-mail client. In such situations, you might have to embed HTML syntax to convert your URL into a clickable link. |
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package org.wso2.carbon.registry.samples.notifications; import org.apache.axiom.om.OMElement; import org.apache.axiom.om.xpath.AXIOMXPath; import org.apache.axiom.soap.SOAPEnvelope; import org.apache.axis2.AxisFault; import org.apache.axis2.context.MessageContext; import org.apache.axis2.engine.Handler; import org.apache.axis2.handlers.AbstractHandler; import org.apache.axis2.transport.mail.MailConstants; import org.jaxen.JaxenException; import java.util.ArrayList; import java.util.Map; public class EmailTransformHandler extends AbstractHandler implements Handler { private String name; public String getName() { return name; } public InvocationResponse invoke(MessageContext msgContext) throws AxisFault { String address = msgContext.getTo().getAddress(); if (msgContext.getTo() != null && address.startsWith("mailto:")) { try { SOAPEnvelope envelope = msgContext.getEnvelope(); AXIOMXPath xPath = new AXIOMXPath("//ns:text"); xPath.addNamespace("ns", "http://ws.apache.org/commons/ns/payload"); OMElement element = (OMElement) ((ArrayList) xPath.evaluate(envelope)).get(0); fixPath(msgContext, element); element.setText(element.getText().replace("--", "This message was intercepted by " + "EmailTransformHandler\n--")); } catch (JaxenException e) { e.printStackTrace(); } } return InvocationResponse.CONTINUE; } private void fixPath(MessageContext msgContext, OMElement element) { String subject = ((Map<String, String>) msgContext.getOptions().getProperty( MessageContext.TRANSPORT_HEADERS)).get(MailConstants.MAIL_HEADER_SUBJECT); if (!subject.contains("Updated")) { return; } String path = element.getText(); path = path.substring(path.indexOf("path ") + "path ".length()); path = path.substring(0, path.indexOf(" was updated")); element.setText(element.getText().replace("path " + path, "path https://localhost:9443/" + "carbon/resources/resource.jsp?region=region3&item=resource_browser_menu&path=" + path + "&screenWidth=1600")); } public void revoke(MessageContext msgContext) { } public void setName(String name) { this.name = name; } } |
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In here, the link that we have used requires the user to sign-in to the management console to browse the resource. Such notifications are useful for approvals. However, there can be situations where those who approve do not need to sing-in to the management console. Such situations can be addressed by providing a clickable link that directs the user to a web service hosted on Governance Registry which does not require authentication. Learn more on how to add web services to Governance Registry by following the Endpoint Look-up Sample. Please be informed that this might introduce a security risk unless necessary precautions have been taken. As a precaution, for example, a token can be generated at the point of notifying the user, which will also appear on the URL within the E-mail. The web service logic can validate the presence of this token to prevent fraudulent access. |
Advanced Use-case 2
This sample can be improved to restrict which users will receive an E-mail notification. For example, it might be required to get an approval from a particular group of users before moving from one state to another. However, this E-mail might not make sense to be delivered to John Smith or Joe Bloggs. The following modification can be made to the code segment to restrict the recipients such that John Doe will receive this E-mail though John Smith or Joe Bloggs would not.
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package org.wso2.carbon.registry.samples.notifications; import org.apache.axiom.om.OMElement; import org.apache.axiom.om.xpath.AXIOMXPath; import org.apache.axiom.soap.SOAPEnvelope; import org.apache.axis2.AxisFault; import org.apache.axis2.context.MessageContext; import org.apache.axis2.engine.Handler; import org.apache.axis2.handlers.AbstractHandler; import org.apache.axis2.transport.mail.MailConstants; import org.jaxen.JaxenException; import java.util.ArrayList; import java.util.Arrays; import java.util.Map; public class EmailTransformHandler extends AbstractHandler implements Handler { private String[] blacklist = {"john@smith.com", "joe@bloggs.co.uk"}; private String name; public String getName() { return name; } public InvocationResponse invoke(MessageContext msgContext) throws AxisFault { String address = msgContext.getTo().getAddress(); if (msgContext.getTo() != null && address.startsWith("mailto:")) { try { SOAPEnvelope envelope = msgContext.getEnvelope(); AXIOMXPath xPath = new AXIOMXPath("//ns:text"); xPath.addNamespace("ns", "http://ws.apache.org/commons/ns/payload"); OMElement element = (OMElement) ((ArrayList) xPath.evaluate(envelope)).get(0); if (restrict(msgContext, address, element)) { return InvocationResponse.ABORT; } element.setText(element.getText().replace("--", "This message was intercepted by " + "EmailTransformHandler |
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\n--"));
} catch (JaxenException e) {
e.printStackTrace();
}
}
return InvocationResponse.CONTINUE;
}
private boolean restrict(MessageContext msgContext, String address, OMElement element) {
final String checkItem = "Smoke Test Passed";
final String state = "Testing";
String subject = ((Map<String, String>) msgContext.getOptions().getProperty(
MessageContext.TRANSPORT_HEADERS)).get(MailConstants.MAIL_HEADER_SUBJECT);
return (subject.contains("CheckListItemChecked") && element.getText().contains(
"CheckList item '" + checkItem + "' of LifeCycle State '" + state + "' was") &&
Arrays.binarySearch(blacklist, address.substring("mailto:".length())) >= 0);
}
public void revoke(MessageContext msgContext) {
}
public void setName(String name) {
this.name = name;
}
} |
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In this example we have used the default We have also assumed that the For this to work, each user on Governance Registry should fill out their User Profile. |
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In here, we have enumerated a list of E-mail addresses that would be treated as blacklisted. However, in a real-world scenario it might be cumbersome to hard-code all E-mail addresses. In such situations the User Management APIs of Governance Registry can be used. The |
An Axis2 Handler must implement the org.apache.axis2.engine.Handler
interface and can optionally extend the org.apache.axis2.handlers.AbstractHandler
class. Read more about Axis2 Handlers to get a better understanding of their uses.
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