This project contains a Google AppEngine project that :
- has a servlet implementing the PayPal IPN "protocol" (Instant Payment Notification)
- persists all IPN messages (and parses them partially)
- uses postback validation
- a minimal Vaadin application to browse the stored IPN messages
Keep in mind that the PayPal sandbox can be pretty slow. So you might get timeouts on validation messaages (GAE has a set 10s max timeout)
Feel free to fork this project and improve it. I'd love to see some cooperation on taming the PayPal beast :)
You have to replace the application and version in war/src/main/webapp/WEB-INF/appengine-web.xml with your own before deploying.
in .m2/settings.xml:
<settings>
<profiles>
<profile>
<id>gae-config</id>
<properties>
<gae.home>C:\Java\lib\appengine-java-sdk-1.5.4</gae.home>
</properties>
</profile>
</profiles>
<activeProfiles>
<activeProfile>gae-config</activeProfile>
</activeProfiles>
</settings>
mvn clean installcd warmvn gae:run
In our web.xml, make sure you register the IPNContextListener, else you won't be able to persist the messages to the datastore.
<listener>
<listener-class>com.streamhead.gae.paypal.ipn.IPNContextListener</listener-class>
</listener>
Add in web.xml
<context-param>
<param-name>payPalEnvironment</param-name>
<param-value>SANDBOX</param-value>
</context-param>
Possible values: SANDBOX, LIVE
In your WEB-INF directory, create a queue.xml file to configure the task queue that will handle validation. Example:
<?xml version="1.0" encoding="UTF-8"?>
<queue-entries>
<queue>
<name>paypal</name>
<rate>1/s</rate>
<bucket-size>10</bucket-size>
<max-concurrent-requests>10</max-concurrent-requests>
<retry-parameters>
<task-retry-limit>10</task-retry-limit>
<task-age-limit>1d</task-age-limit>
<min-backoff-seconds>10</min-backoff-seconds>
<max-backoff-seconds>600</max-backoff-seconds>
<max-doublings>2</max-doublings>
</retry-parameters>
</queue>
</queue-entries>
To process PayPal IPN messages, the task queue is used. This allows for easy and configurable retries. To properly process IPN messages you will need three servlets. Two are part of this packages, one you will need to implement yourself.
The IPNServlet stores incoming IPN messages as is and forwards them to the IPNValidationServlet through a task queue.
<servlet>
<servlet-name>IPNServlet</servlet-name>
<servlet-class>com.streamhead.gae.paypal.ipn.IPNServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>IPNServlet</servlet-name>
<url-pattern>/ipn</url-pattern>
</servlet-mapping>
The IPNValidationServlet tries to validate the message. The number and frequency of retries is configured in the queue. After successful validation, the servlet starts the processing task.
<servlet>
<servlet-name>IPNValidationServlet</servlet-name>
<servlet-class>com.streamhead.gae.paypal.ipn.IPNValidationServlet</servlet-class>
<init-param>
<description>Task to launch after validation</description>
<param-name>processingTask</param-name>
<param-value>/ipn/process</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>IPNValidationServlet</servlet-name>
<url-pattern>/ipn/validate</url-pattern>
</servlet-mapping>
The processing servlet should be implemented by you. To get you started, this project contains a dummy servlet.
<servlet>
<servlet-name>IPNProcessingServlet</servlet-name>
<servlet-class>com.streamhead.gae.paypal.ipn.IPNProcessingServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>IPNProcessingServlet</servlet-name>
<url-pattern>/ipn/process</url-pattern>
</servlet-mapping>
The current snapshot is hosted on Sonatype's snapshot repository, so if you just want to use the project add this to your pom.xml:
<repositories>
<repository>
<id>sonatype-snapshots</id>
<name>Sonatype Open Source snapshot repository (for POW and MailJimp)</name>
<url>https://oss.sonatype.org/content/groups/public/</url>
</repository>
</repositories>
<dependencies>
<dependency>
<groupId>com.pow.paypal</groupId>
<artifactId>pow-paypal-core</artifactId>
<version>0.0.1-SNAPSHOT</version>
</dependency>
</dependencies>
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