# Interface RetrievalMethod

All Superinterfaces:
  `URIReference, XMLStructure`

public interface RetrievalMethod extends URIReference, XMLStructure
A representation of the XML `RetrievalMethod` element as defined in the W3C Recommendation for XML-Signature Syntax and Processing. A `RetrievalMethod` object is used to convey a reference to `KeyInfo` information that is stored at another location. The XML schema definition is defined as:

      <element name="RetrievalMethod" type="ds:RetrievalMethodType"/>
      <complexType name="RetrievalMethodType">
        <sequence>
          <element name="Transforms" type="ds:TransformsType" minOccurs="0"/>
        </sequence>
        <attribute name="URI" type="anyURI"/>
        <attribute name="Type" type="anyURI" use="optional"/>
      </complexType>

A `RetrievalMethod` instance may be created by invoking one of the `newRetrievalMethod` methods of the `KeyInfoFactory` class, and passing it the URI identifying the location of the KeyInfo, an optional type URI identifying the type of KeyInfo, and an optional list of `Transform`s; for example:

      KeyInfoFactory factory = KeyInfoFactory.getInstance("DOM");
      RetrievalMethod rm = factory.newRetrievalMethod
         ("#KeyValue-1", KeyValue.DSA_TYPE, Collections.singletonList(Transform.BASE64));

Since:
  1.6
See Also:
  - `KeyInfoFactory.newRetrievalMethod(String)`
  - `KeyInfoFactory.newRetrievalMethod(String, String, List)`

- ## Method Summary

  Modifier and Type
  Method
  Description
  `Data`
  `dereference(XMLCryptoContext context)`
  Dereferences the `KeyInfo` information referenced by this `RetrievalMethod` and applies the specified `Transform`s.
  `List<Transform>`
  `getTransforms()`
  Returns an `unmodifiable list` of `Transform`s of this `RetrievalMethod`.
  `String`
  `getURI()`
  Returns the URI of the referenced `KeyInfo` information.

  ### Methods declared in interface URIReference

  `getType`
  Modifier and Type
  Method
  Description
  `String`
  `getType()`
  Returns the type of data referenced by this URI.

  ### Methods declared in interface XMLStructure

  `isFeatureSupported`
  Modifier and Type
  Method
  Description
  `boolean`
  `isFeatureSupported(String feature)`
  Indicates whether a specified feature is supported.

- ## Method Details

  - ### getTransforms

    List<Transform> getTransforms()
    Returns an `unmodifiable list` of `Transform`s of this `RetrievalMethod`.
    Returns:
      an unmodifiable list of `Transform` objects (may be empty but never `null`).

  - ### getURI

    String getURI()
    Returns the URI of the referenced `KeyInfo` information.
    Specified by:
      `getURI` in interface `URIReference`
    Returns:
      the URI of the referenced `KeyInfo` information in RFC 2396 format (never `null`)

  - ### dereference

    Data dereference(XMLCryptoContext context) throws URIReferenceException
    Dereferences the `KeyInfo` information referenced by this `RetrievalMethod` and applies the specified `Transform`s.
    Parameters:
      `context` - an `XMLCryptoContext` that may contain additional useful information for dereferencing the URI. The context's `baseURI` and `dereferencer` parameters (if specified) are used to resolve and dereference this `RetrievalMethod`
    Returns:
      a `Data` object representing the raw contents of the `KeyInfo` information referenced by this `RetrievalMethod`. It is the caller's responsibility to convert the returned data to an appropriate `KeyInfo` object.
    Throws:
      `NullPointerException` - if `context` is `null`
      `URIReferenceException` - if there is an error while dereferencing