Metamodel classes are a not-so-well known feature of the JPA 2.0 standard. They allow you to write typesafe criteria queries using metamodel attributes instead of plain old strings to reference entity fields. (See this tutorial for some more background.)
Metamodel classes are generated by an annotation processor during the build process, but this is not enabled by default. OpenJPA logs a runtime warning when you build a criteria query and the metamodel classes cannot be found. So even if you don't use the metamodel, you may want to generate it just to get rid of this warning.
This article explains how to generate the metamodel both in Maven batch builds and in the Eclipse workspace.
Showing posts with label m2e. Show all posts
Showing posts with label m2e. Show all posts
15 April 2012
Multi-Instance Deployment from Eclipse to Tomcat
Problem
- You are developing a web application for Tomcat in Eclipse.
- You want to deploy multiple instances of the same application with different configurations directly from your workspace.
- Of course, you don't want to duplicate any projects in your workspace.
Solution
This scenario can be solved quite easily with the vanilla Apache Tomcat adapter of Eclipse WTP. There is no need for any additional Eclipse plugins.
29 August 2011
Eclipse Maven Integration Extensions
For me, the most important new feature in Eclipse 3.7.0 (Indigo) is the improved Maven Integration, formerly developed by Sonatype under the name of m2eclipse, now an official Eclipse subproject under the name of m2e.
m2eclipse and Eclipse sometimes used to have different opinions on what was going on in the workspace, and so we had to go through series of refresh/update dependencies/update configuration/rebuild voodoo (or "m2eclipse dance" as some called it) to get projects in a good state. (Quote from the m2e Wiki).
m2e has a different approach. First of all, it complains when detecting a Maven plugin in one of your POMs that it cannot handle out of the box. m2e flags your POM with an error marker that will not go away until you tell m2e what do to about the unknown plugin. The easy way out is a Quick Fix to ignore the plugin, which means you'll have to run the corresponding Maven goal manually when you need it.
However, when the Maven plugin in question generates source code or post-processes byte code, this is usually not sufficient - ideally, Eclipse and m2e should pick up the required build steps from your POM automatically.
This issue is addressed by m2e extensions, which provide the missing link between Eclipse project builders and Maven plugins. An m2e extension for a given Maven plugin not only invokes the required mojos but also informs Eclipse about new source or binary folders created by the mojos, so that Eclipse and Maven can stay in sync.
My projects use a number of Maven plugins that are not supported by m2e out of the box, e.g. for JAXB and OpenJPA, so I started creating some custom extensions for these plugins, based on a GitHub fork of the official m2e extensions from Sonatype.
See the wiki page at GitHub for more details. The GitHub project also contains an Eclipse update site (aka p2 repository) for installing the plugins. Time permitting, I'll try to make these extensions available via the Eclipse marketplace.
For any fixes, additions or new extensions, feel free to send my pull requests.
m2eclipse and Eclipse sometimes used to have different opinions on what was going on in the workspace, and so we had to go through series of refresh/update dependencies/update configuration/rebuild voodoo (or "m2eclipse dance" as some called it) to get projects in a good state. (Quote from the m2e Wiki).
m2e has a different approach. First of all, it complains when detecting a Maven plugin in one of your POMs that it cannot handle out of the box. m2e flags your POM with an error marker that will not go away until you tell m2e what do to about the unknown plugin. The easy way out is a Quick Fix to ignore the plugin, which means you'll have to run the corresponding Maven goal manually when you need it.
However, when the Maven plugin in question generates source code or post-processes byte code, this is usually not sufficient - ideally, Eclipse and m2e should pick up the required build steps from your POM automatically.
This issue is addressed by m2e extensions, which provide the missing link between Eclipse project builders and Maven plugins. An m2e extension for a given Maven plugin not only invokes the required mojos but also informs Eclipse about new source or binary folders created by the mojos, so that Eclipse and Maven can stay in sync.
My projects use a number of Maven plugins that are not supported by m2e out of the box, e.g. for JAXB and OpenJPA, so I started creating some custom extensions for these plugins, based on a GitHub fork of the official m2e extensions from Sonatype.
See the wiki page at GitHub for more details. The GitHub project also contains an Eclipse update site (aka p2 repository) for installing the plugins. Time permitting, I'll try to make these extensions available via the Eclipse marketplace.
For any fixes, additions or new extensions, feel free to send my pull requests.
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