13.8. Delegating Translators

You can create a delegating translator by extending the org.teiid.translator.BaseDelegatingExecutionFactory class.

Once your classes are packaged as a custom translator, you will be able to wire another translator instance into your delegating translator at runtime in order to intercept all of the calls to the delegate. This base class does not provide any functionality on its own, other than delegation.

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Table 13.2. Execution Properties
Name	Description	Default
delegateName	Translator instance name to delegate to.

As an example, consider if you are currently using "oracle" translator in your VDB and you need to intercept the calls going through this translator.

You first write a custom delegating translator:

@Translator(name="interceptor", description="interceptor")
public class InterceptorExecutionFactory extends org.teiid.translator.BaseDelegatingExecutionFactory{
    @Override
    public void getMetadata(MetadataFactory metadataFactory, C conn) throws TranslatorException {
        // do intercepting code here..

        // If you need to call the original delegate, do not call if do not need to.
        // but if you did not call the delegate fulfill the method contract
        super.getMetadata(metadataFactory, conn);

        // do more intercepting code here..
    }
}

@Translator(name="interceptor", description="interceptor")
public class InterceptorExecutionFactory extends org.teiid.translator.BaseDelegatingExecutionFactory{
    @Override
    public void getMetadata(MetadataFactory metadataFactory, C conn) throws TranslatorException {
        // do intercepting code here..

        // If you need to call the original delegate, do not call if do not need to.
        // but if you did not call the delegate fulfill the method contract
        super.getMetadata(metadataFactory, conn);

        // do more intercepting code here..
    }
}

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Then you deploy this translator.

Then modify your -vdb.xml or .vdb file:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<vdb name="myvdb" version="1">

    <model name="mymodel">
        <source name="source" translator-name="oracle-interceptor" connection-jndi-name="java:oracle-ds"/>
    </model>

    <!-- the below it is called translator overriding, where you can set different properties -->
    <translator name="oracle-interceptor" type="interceptor" />
        <property name="delegateName" value="oracle" />
   </translator>
</vdb>

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<vdb name="myvdb" version="1">

    <model name="mymodel">
        <source name="source" translator-name="oracle-interceptor" connection-jndi-name="java:oracle-ds"/>
    </model>

    <!-- the below it is called translator overriding, where you can set different properties -->
    <translator name="oracle-interceptor" type="interceptor" />
        <property name="delegateName" value="oracle" />
   </translator>
</vdb>

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We have defined a "translator" called "oracle-interceptor", which is based on the custom translator "interceptor" from above, and supplied the translator it required to delegate to "oracle" as its delegateName. Then, we used this override translator "oracle-interceptor" in the VDB. Now any calls going into this VDB model's translator will be intercepted by your code to do whatever you need to do.

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13.8. Delegating Translators

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