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Oracle TopLink Developer's Guide 10g Release 3 (10.1.3) B13593-01 |
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# Descriptor Query Manager Queries

Each `Descriptor` owns an instance of `DescriptorQueryManager` that you can use for the following:

- Configuring Named Queries

- Configuring Default Query Implementations

- Configuring Additional Join Expressions

## Configuring Named Queries

The `DescriptorQueryManager` provides API for storing and retrieving frequently used queries by name.

For more information, see "Named Queries".

## Configuring Default Query Implementations

The `DescriptorQueryManager` of each `Descriptor` lets you customize the query implementation that TopLink uses for the following data source operations:

- insert object

- update object

- read object

- read all objects

- delete object

For example, if you need to insert an object using a stored procedure, you can override the default `SQLCall` used by the `DescriptorQueryManager` insert object query.

Whenever you execute a query on a given `Class`, TopLink consults the `DescriptorQueryManager` to determine how to perform the given data source operation.

You can use this capability for a variety of purposes such as to extend TopLink behavior, access nonrelational data, or use stored procedures or customized SQL calls.

WARNING: Allowing an unverified SQL string to be passed into methods makes your application vulnerable to SQL injection attacks.

For information and examples on customizing these default query implementations, see:

- "Configuring Custom SQL Queries for Basic Persistence Operations"

- "Configuring Custom EIS Interactions for Basic Persistence Operations"

## Configuring Additional Join Expressions

You can configure the DescriptorQueryManager to automatically append an expression to every query it performs on a class. For example, you can add an expression that filters the data source for the valid instances of a given class.

For more information, see "Appending Additional Join Expressions".