Traditionally the metadata for a Virtual Database is built by Teiid Designer and supplied to Teiid engine through a VDB archive file. This VDB file contains the metadata files called INDEX files, that are then read by a specific instance of _MetadataRepository_ by name _INDEX_. |
If above provided [metadata facilities|Metadata Repositories] are not sufficient then a developer can extend the _MetadataRepository_ class provided in the _org.teiid.api_ package to plug-in their own metadata facilities into the Teiid engine. For example, a user can write a metadata facility that is based on reading data from a database or a JCR repository. See [Setting up the build environment] to start development. For Example: |
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In the Dynamic VDB scenario, the built-in metadata repositories are: h3. _NATIVE_ This is only applicable on source models (and is also the default), when used the metadata for the model is retrieved from the source database itself. {code:XML|title=Sample vdb.xml file} <vdb name="{vdb-name}" version="1"> <model name="{model-name}" type="PHYSICAL"> <source name="AccountsDB" translator-name="oracle" connection-jndi-name="java:/oracleDS"/> <metadata type="NATIVE"></metadata> </model> </vdb> {code} h3. _DDL_ {code:XML|title=Sample vdb.xml file} <vdb name="{vdb-name}" version="1"> <model name="{model-name}" type="PHYSICAL"> <source name="AccountsDB" translator-name="oracle" connection-jndi-name="java:/oracleDS"/> <metadata type="DDL"> **DDL Here** </metadata> </model> </vdb> {code} This is applicable to both source and view models. See [DDL Metadata] for more information on how to use this feature. h3. _DDL-FILE_ {code:XML|title=Sample vdb.xml file} <vdb name="{vdb-name}" version="1"> <model name="{model-name}" type="PHYSICAL"> <source name="AccountsDB" translator-name="oracle" connection-jndi-name="java:/oracleDS"/> <metadata type="DDL-FILE">/accounts.ddl</metadata> </model> </vdb> {code} This is applicable to both source and view models in zip VDB deployments. See [DDL Metadata] for more information on how to use this feature. {tip:title=Chaining more than single repository} When defining the metadata import type for a model, user can define comma separated list of importers, such that all the repository instances defined by import types are consulted in the order they have configured to gather the metadata for the given model. For example: {code:XML|title=Sample vdb.xml file} <vdb name="{vdb-name}" version="1"> <model name="{model-name}" type="PHYSICAL"> <source name="AccountsDB" translator-name="oracle" connection-jndi-name="java:/oracleDS"/> <metadata type="NATIVE,DDL"> **DDL Here** </metadata> </model> </vdb> {code} For the above model, _NATIVE_ importer is first used, then DDL importer used to add additional metadata to _NATIVE_ imported metadata. {tip} h3. _Custom_ If above provided metadata facilities are not sufficient for user's needs then user can extend the _MetadataRepository_ class provided in the _org.teiid.api_ package to plug-in their own metadata facilities into Teiid engine. For example, a user can write a metadata facility that is based on reading data from a database or a JCR repository. See [Setting up the build environment] to start development. For Example: |
{code:JAVA|title=Sample Java Code} package com.something; |
... |
If above provided metadata facilities are not sufficient then a developer can extend the MetadataRepository class provided in the org.teiid.api package to plug-in their own metadata facilities into the Teiid engine. For example, a user can write a metadata facility that is based on reading data from a database or a JCR repository. See Setting up the build environment to start development. For Example:
package com.something; public class CustomMetadataRepository extends MetadataRepository { @Override public void loadMetadata(MetadataFactory factory, ExecutionFactory executionFactory, Object connectionFactory) throws TranslatorException { /* Provide implementation and fill the details in factory */ ... } }
Then build a JAR archive with above implementation class and create file named org.teiid.metadata.MetadataRepository in META-INF/services directory with contents
com.something.CustomMetadataRepository
Now that the JAR file has been built, this needs to be deployed in the JBoss AS as module under <jboss-as>/modules directory. Follow the below steps to create a module.
<?xml version="1.0" encoding="UTF-8"?> <module xmlns="urn:jboss:module:1.0" name="com.something"> <resources> <resource-root path="something.jar" /> </resources> <dependencies> <module name="javax.api"/> <module name="javax.resource.api"/> <module name="org.jboss.teiid.common-core"/> <module name="org.jboss.teiid.teiid-api" /> </dependencies> </module>
The below XML fragment shows how to configure the VDB with the custom metadata repository created
<vdb name="{vdb-name}" version="1"> <model name="{model-name}" type="PHYSICAL"> <source name="AccountsDB" translator-name="oracle" connection-jndi-name="java:/oracleDS"/> <metadata type="{metadata-repo-module}"></metadata> </model> </vdb>
Now when this VDB gets deployed, it will call the CustomMetadataRepository instance for metadata of the model. Using this you can define metadata for single model or for the whole VDB pragmatically. Be careful about holding state and synchronization in your repository instance.