Introduction

To avoid unnecessary regeneration (which may be very time-consuming), the plugin checks, if the generated code is still up-to-date (copared to the source schemas and other files). If everything is up-to-date then code generation will be skipped. However, you can use the forceRegenerate=true to force regeneration every time. This is explicitly not recommended.

The up-to-date check algorithm

The up-to-date check algorithm is as follows:

• Gather the URIs of the "source" resources:
  • The pom.xml file of the project.
  • The resolved URIs of the catalog files and resources.
  • The resolved URIs of the schema files and resources.
  • The resolved URIs of the binding files and resources.
  • URIs of the additionally configured otherDepends/otherDependsIncludes/otherDependsExcludes files.
• Gather the URIs of the "target" resources:
  • Scan the generateDirectory for files which match the produces pattern, and collect their URIs.
• Find out the latest timestamp of the "source" resources (timestamp of the resource update) and earliest timestamp of the "target" resources (timestamp of the generation).
• If timestamp of the update is later than the timestamp of the generation, or if some of the timestamps is unknown, regenerate.
• Otherwise - that is, if both update and generation timestamps are known and update was not later that generation, do not regenerate.

Configuration

The regeneration is controlled by the following configuration elements:

• forceRegenerate - If true, no up-to-date check is performed and the XJC always re-generates the sources. Otherwise schemas will only be recompiled if anything has changed (this is the default behavior). Setting forceRegenerate to true is not recommended.
• Configured catalogs, schemas and bindings.
• otherDepends - other files to check for updates. Deprecated, use otherDependsIncludes/otherDependsExcludes instead.
• otherDependsIncludes/otherDependsExcludes - patterns of other files to check for updates.
• produces - patterns of of files produced by this plugin. Default value is **/*.*, **/*.java, **/bgm.ser, **/jaxb.properties.

Finding out last modification timestamps for URIs

To perform the up-to-date-check, the plugin has to find out the last modification timestamp for each of the source URIs. These source URIs may be files, but also other URIs. The plugin supports the following URI schemes:

• file (a normal file) - last modification of the target file.
• jar (a resource inside a JAR file) - last modification of the JAR file. It is assumed that if the JAR file was changed then the resource inside it was changed as well.
• http or https (Web resources) - last modification is taked from the Last-Modified HTTP header. However, this is not reliable. Compiling schemas directly from Web resources is strongly discouraged anyway.

If the last modification timestamp could not be found out for some reason (for instance, the Web server does not return the header), it is assumed to be unknown and will consequently force regenration.

Up-to-date check for Maven artifact resources

You may note that the maven scheme used in Maven artifact resources is not listed. This is because all the URIs are resolved prior to the check. So the Maven artifact resource URI will either be resolved into a jar URI or a file URI, both of which are supported.

So this up-to-date check also works with Maven artifact resources. If you use a schema from the Maven artifact then the plugin will check that artifact/resource for actuality.

Limitations

This up-to-date-check only works for resources directly configured in the plugin condiguration. If your schema a.xsd import some other schema b.xsd and that schema is not configured in the plugin configuration, it will not be considered during the up-to-date check. You may use otherDependsIncludes and otherDependsExcludes to configure additional resources to check.