KeyView 24.1

# Access Metadata Fields

This section explains how to process metadata fields using the KeyView API.

## Standardized Fields

When KeyView understands the meaning of a metadata field in a document, it outputs that data in a standardized field. For a `MetadataElement` that represents a standardized field:

- `isStandard()` returns `true`.

- `getStandardKey()` returns the standardized field key, which indicates the meaning of the field. For a full list of the standardized metadata fields, refer to the documentation for the `MetadataKey` enum in the JavaDocs.

- `getKey()` returns a string that is uniquely determined by the standard field key. If you are handling the value of a standardized field based on its standardized name, you can ignore this value. It is provided so that standardized fields can optionally be handled in the same way as non-standardized fields.

Each standardized field is guaranteed to occur at most once in the metadata output. For example, the metadata output will contain zero or one `MetadataElement` objects with the standardized name `TITLE`.

## Non-standardized fields

Non-standardized fields include user created fields, or fields that are specific to that type of document. KeyView handles these in the following way:

- `isStandard()` returns `false`.
- `getStandardKey()` returns `OTHER` to signify that it is a non-standardized field.
- `getKey()` returns a string representation of a field's key. If a field key exists in the document, that value is returned. Otherwise, KeyView generates a value to describe the field.

## Field Values

To obtain a field value as a string, you can call the method `getValueAsString()` on a `MetadataElement` object.

However, you might prefer to process metadata field values as appropriate types through a visitor pattern. To do this, write a class that inherits from the `MetadataVisitor` class and handles each of the possible metadata types. Then, pass your class to the `accept()` method of a `MetadataList` or `MetadataElement` object.

For example code that demonstrates how to do this, see the `FilterTest` sample program.

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Version 24.1 | Last updated December 2023

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Product: IDOL KeyView 24.1

Topic Title: Access Metadata Fields