Grails Development FAQ

Updated October 10, 2017

This is a growing list of frequently asked questions (FAQ) that I encounter teaching Groovy & Grails, with an eye toward Ellucian Banner XE Self-Service development. While many of these questions are Grails specific, a few pertain to the JetBrains IntelliJ Idea IDE that I use in class. Check back to see if the list has grown bigger:

1. Can I open multiple projects in the same window in IntelliJ?
2. Why doesn’t my Grails classrecompile and reload in the development server?
3. Changes to my controller and domain classes compile and work. So, why do I get random errors in the run window, often a NullPointerException, sometimes related to scaffolding?
4. I already have the browser open on the application page that I want, how do I stop IntelliJ from launching a new page for the application if I restart the development server?
5. Hibernate with the H2 database writes an awful lot of log messages to the Grails console!
6. If I use respond in the controller, where is the model data in the view?
7. Where is the model data? I can’t find it when I dump out the request in the GSP!
8. If I create a new domain instance from the params map, the id property is not set! And, the same thing happens if I try to copy the properties from one domain object to another. What is happening?
9. Do I need to convert a string id from the params map to an integer before using get?
10. How do I fix the Grails SDK? It changes every time someone checks in the project!
11. I change the Grails SDK, and now IntelliJ Idea says that Groovy is not configured!
12. null id in ... entry (don't flush the Session after an exception occurs)
13. Why does saving a new domain object flush database changes?
14. On a Mac I can't see ~/.sdkman to get to the Groovy or Grails SDKs?

Banner 9/Grails 2.5 Development Problems and Resolutions

Updated 3/29/2018

This is a page of random problems and solutions encountered using Grails 2.5 for Ellucian Banner XE (9) Self-Service development. As new problems are resolved, they will be added to this list ordered by the resolution date.

20180329 Grails cannot build SSB app

Grails cannot install the plugins needed to build an SSB application. The problem often is the repository configuration, see the blog post Grails Cannot Build Ellucian SSB Application.

20171005 module not found: org.codehaus.groovy#groovy-all;2.4.4

This is a grails 2.5.5 issue. Make sure that you are using Grails 2.5.0 for Banner development. Grails 2.5.5 was a bad release where projects are configured to use Groovy 2.4.4, but it shipped with Groovy 2.4.5.

20150910 JavaLaunchHelper has Multiple Definitions

This one shows up in Apple MacOS, but not in Windows. In Java 8 the class JavaLaunchHelper is implemented in both the JDK java command and in the libinstrument.dylib library. Since they both seem to be exactly the same, the message is just an annoyance that cannot be squelched.

20170902 Grails Throws a NullPointerException on Recompile & Reload

After a file is changed, such as a controller, Grails notices the change, recompiles, and reloads the file but throws an error similar to this: ERROR plugins.AbstractGrailsPluginManager  - Plugin [controllers:2.5.0] could not reload changes to file.

Update 2017-10-09: this problem has appeared for me on Linux as well. This problem has only appeared for me on Microsoft Windows systems: when a class is recompiled and reloaded, a NullPointerException is thrown, often by the AbstractGrailsPluginManager. The class is actually recompiled and reloaded, so it was not clear exactly what the problem was. Sometimes the error originates in the scaffolding system, even when the application does use scaffolding. There are plenty of comments around the Internet about disabling forked execution, but only one comment clarified why.

Banner, Eclipse, and Grails!

You can use Eclipse as a single IDE for developing both Banner Admin Pages and Self-Service extensions! It is also possible to use other IDEs for developing Self-Service extensions; NetBeans has excellent Groovy and Grails support. The focus in this post is on using Eclipse for both development environments.

Disclaimer and warning: this post may become outdated at any time, but currently the most up-to-date information from Ellucian is:

• Eclipse 4.6 (Neon) is the most current Eclipse IDE supported for developing Admin Pages. You must use an Eclipse-based IDE for developing Admin Pages, because the required plugins for development are only available for Eclipse. The plugins have been tested with Eclipse 4.4 (Mars), 4.5 (Luna), and (4.6) Neon.
• IntelliJ Idea Ultimate is the recommended IDE for developing Self-Service extensions. The current IntelliJ version 2017.2.3 still supports the Groovy and Grails versions being shipped with Banner.
• Other IDEs with Groovy and Grails support may be used for Self-Service development. Support for extending Banner and using Grails will be provided, but do not count on any support for using the IDE with Groovy and Grails.
• Banner 9 ships with Grails 2.5, which depends on and includes Groovy 2.4.