Extending the delegator translator

You can create a delegating translator by extending the org.teiid.translator.BaseDelegatingExecutionFactory. After your classes are packaged as a custom translator, you can 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. You can hard code capabilities into the translator instead of defining them as part of the DDL configuration. You can also override methods to provide alternate behavior.

Table 1. Execution properties

Name

Description

Default

delegateName

Translator instance name to delegate to.

n/a

cachePattern

Regex pattern of queries that should be cached using the translator caching API.

n/a

cacheTtl

Time to live in milliseconds for queries matching the cache pattern.

n/a

For example, if you use the oracle translator in your virtual database, and you want to intercept calls that go through the translator, you could write a custom delegating translator, as in the following example:

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

        // do more intercepting code here..
    }
}

You could then deploy this translator in the Teiid Spring Boot engine. Then in your DDL file, define an interceptor translator as in the following example:

CREATE DATABASE myvdb VERSION '1';
USE DATABASE myvdb VERSION '1';
CREATE FOREIGN DATA WRAPPER "oracle-interceptor" TYPE interceptor OPTIONS (delegateName 'oracle');
CREATE SERVER source FOREIGN DATA WRAPPER "oracle-interceptor" OPTIONS ("resource-name" 'java:oracle-ds');
CREATE SCHEMA mymodel SERVER source;
SET SCHEMA mymodel;
IMPORT FROM SERVER source INTO mymodel;

We have defined a "translator" override called oracle-interceptor, which is based on the custom translator "interceptor" from above, and supplied the translator it needs to delegate to "oracle" as its delegateName. Then, we used this override translator oracle-interceptor in the VDB. Future calls going into this VDB model’s translator are intercepted by your code to do whatever you want to do.

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