4.7. Generating Default JDO Metadata
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## 4.7. Generating Default JDO Metadata

Kodo JDO now includes a preview release of our upcoming metadata tool. The metadata tool uses reflection to generate default JDO metadata for your persistent classes. It cannot fill in information that is not available from the class definition itself, such as the element type of collections or the primary key fields of a class using application identity. It does, however, provide a good starting point from which to build up your metadata.

The metadata tool recognizes JDO's extensive system of defaults, so fields that are persistent by default will not be included in the generated XML document. The only exception to this rule is for collection and map fields: the tool adds these fields to the metadata and sets their `element-type`, `key-type`, and `value-type` attributes to `Object` as a reminder to you to provide this information.

The metadata tool can be run via the included `rd-metadatatool` script, or through its Java class, `com.solarmetric.rd.kodo.meta.JDOMetaDataTool`. In addition to the standard configuration flags accepted by all Kodo JDO tools, the reverse mapping tool recognizes the following command line flags:

- -file <metadata file>: The name of the metadata file to generate. If this argument is not supplied, the tool will print the generated metadata to stdout.

Each additional argument to the tool should be the class name, .class file, or .java file of a class to generate metadata for. Each class must be compiled.

Standard usage example:

    rd-metadatatool -properties myprops.properties -file mypackage/mypackage.jdo
    mypackage/*.java

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