Each instance of TransformService supports a specific
* transform or canonicalization algorithm and XML mechanism type. To create a
* TransformService, call one of the static
* {@link #getInstance getInstance} methods, passing in the algorithm URI and
* XML mechanism type desired, for example:
*
*
* TransformService ts = TransformService.getInstance(Transform.XPATH2, "DOM");
* TransformService implementations are registered and loaded
* using the {@link java.security.Provider} mechanism. Each
* TransformService service provider implementation should include
* a MechanismType service attribute that identifies the XML
* mechanism type that it supports. If the attribute is not specified,
* "DOM" is assumed. For example, a service provider that supports the
* XPath Filter 2 Transform and DOM mechanism would be specified in the
* Provider subclass as:
*
* put("TransformService." + Transform.XPATH2,
* "org.example.XPath2TransformService");
* put("TransformService." + Transform.XPATH2 + " MechanismType", "DOM");
*
* TransformService implementations that support the DOM
* mechanism type must abide by the DOM interoperability requirements defined
* in the
* DOM
* Mechanism Requirements section of the API overview. See the
* Service
* Providers section of the API overview for a list of standard mechanism
* types.
*
* Once a TransformService has been created, it can be used
* to process Transform or CanonicalizationMethod
* objects. If the Transform or CanonicalizationMethod
* exists in XML form (for example, when validating an existing
* XMLSignature), the {@link #init(XMLStructure, XMLCryptoContext)}
* method must be first called to initialize the transform and provide document
* context (even if there are no parameters). Alternatively, if the
* Transform or CanonicalizationMethod is being
* created from scratch, the {@link #init(TransformParameterSpec)} method
* is called to initialize the transform with parameters and the
* {@link #marshalParams marshalParams} method is called to marshal the
* parameters to XML and provide the transform with document context. Finally,
* the {@link #transform transform} method is called to perform the
* transformation.
*
* Concurrent Access *
The static methods of this class are guaranteed to be thread-safe. * Multiple threads may concurrently invoke the static methods defined in this * class with no ill effects. * *
However, this is not true for the non-static methods defined by this
* class. Unless otherwise documented by a specific provider, threads that
* need to access a single TransformService instance
* concurrently should synchronize amongst themselves and provide the
* necessary locking. Multiple threads each manipulating a different
* TransformService instance need not synchronize.
*
* @author Sean Mullan
* @author JSR 105 Expert Group
*/
public abstract class TransformService implements Transform {
private String algorithm;
private String mechanism;
private Provider provider;
/**
* Default constructor, for invocation by subclasses.
*/
protected TransformService() {}
/**
* Returns a TransformService that supports the specified
* algorithm URI (ex: {@link Transform#XPATH2}) and mechanism type
* (ex: DOM).
*
*
This method uses the standard JCA provider lookup mechanism to
* locate and instantiate a TransformService implementation
* of the desired algorithm and MechanismType service
* attribute. It traverses the list of registered security
* Providers, starting with the most preferred
* Provider. A new TransformService object
* from the first Provider that supports the specified
* algorithm and mechanism type is returned.
*
*
Note that the list of registered providers may be retrieved via
* the {@link Security#getProviders() Security.getProviders()} method.
*
* @param algorithm the URI of the algorithm
* @param mechanismType the type of the XML processing mechanism and
* representation
* @return a new TransformService
* @throws NullPointerException if algorithm or
* mechanismType is null
* @throws NoSuchAlgorithmException if no Provider supports a
* TransformService implementation for the specified
* algorithm and mechanism type
* @see Provider
*/
public static TransformService getInstance
(String algorithm, String mechanismType)
throws NoSuchAlgorithmException {
if (mechanismType == null || algorithm == null) {
throw new NullPointerException();
}
return findInstance(algorithm, mechanismType, null);
}
/**
* Returns a TransformService that supports the specified
* algorithm URI (ex: {@link Transform#XPATH2}) and mechanism type
* (ex: DOM) as supplied by the specified provider. Note that the specified
* Provider object does not have to be registered in the
* provider list.
*
* @param algorithm the URI of the algorithm
* @param mechanismType the type of the XML processing mechanism and
* representation
* @param provider the Provider object
* @return a new TransformService
* @throws NullPointerException if provider,
* algorithm, or mechanismType is
* null
* @throws NoSuchAlgorithmException if a TransformService
* implementation for the specified algorithm and mechanism type is not
* available from the specified Provider object
* @see Provider
*/
public static TransformService getInstance
(String algorithm, String mechanismType, Provider provider)
throws NoSuchAlgorithmException {
if (mechanismType == null || algorithm == null || provider == null) {
throw new NullPointerException();
}
return findInstance(algorithm, mechanismType, provider);
}
/**
* Returns a TransformService that supports the specified
* algorithm URI (ex: {@link Transform#XPATH2}) and mechanism type
* (ex: DOM) as supplied by the specified provider. The specified provider
* must be registered in the security provider list.
*
*
Note that the list of registered providers may be retrieved via
* the {@link Security#getProviders() Security.getProviders()} method.
*
* @param algorithm the URI of the algorithm
* @param mechanismType the type of the XML processing mechanism and
* representation
* @param provider the string name of the provider
* @return a new TransformService
* @throws NoSuchProviderException if the specified provider is not
* registered in the security provider list
* @throws NullPointerException if provider,
* mechanismType, or algorithm is
* null
* @throws NoSuchAlgorithmException if a TransformService
* implementation for the specified algorithm and mechanism type is not
* available from the specified provider
* @see Provider
*/
public static TransformService getInstance
(String algorithm, String mechanismType, String provider)
throws NoSuchAlgorithmException, NoSuchProviderException {
if (mechanismType == null || algorithm == null || provider == null) {
throw new NullPointerException();
}
Provider prov = Security.getProvider(provider);
if (prov == null) {
throw new NoSuchProviderException("cannot find provider named "
+ provider);
}
return findInstance(algorithm, mechanismType, prov);
}
private static TransformService findInstance(String algorithm,
String mechanismType, Provider provider)
throws NoSuchAlgorithmException {
Object[] objs = (Object[]) XMLDSigSecurity.getImpl
(algorithm, new MechanismMapEntry(algorithm, mechanismType),
"TransformService", provider);
TransformService spi = (TransformService) objs[0];
spi.mechanism = mechanismType;
spi.algorithm = algorithm;
spi.provider = (Provider) objs[1];
return spi;
}
private static class MechanismMapEntry implements Map.Entry {
private final String mechanism;
private final String key;
MechanismMapEntry(String algorithm, String mechanism) {
this.mechanism = mechanism;
this.key = "TransformService." + algorithm + " MechanismType";
}
public boolean equals(Object o) {
if (!(o instanceof Map.Entry)) {
return false;
}
Map.Entry e = (Map.Entry) o;
return (getKey()==null ?
e.getKey()==null : getKey().equals(e.getKey())) &&
(getValue()==null ?
e.getValue()==null : getValue().equals(e.getValue()));
}
public Object getKey() {
return key;
}
public Object getValue() {
return mechanism;
}
public Object setValue(Object value) {
throw new UnsupportedOperationException();
}
public int hashCode() {
return (getKey()==null ? 0 : getKey().hashCode()) ^
(getValue()==null ? 0 : getValue().hashCode());
}
}
/**
* Returns the mechanism type supported by this TransformService.
*
* @return the mechanism type
*/
public final String getMechanismType() {
return mechanism;
}
/**
* Returns the URI of the algorithm supported by this
* TransformService.
*
* @return the algorithm URI
*/
public final String getAlgorithm() {
return algorithm;
}
/**
* Returns the provider of this TransformService.
*
* @return the provider
*/
public final Provider getProvider() {
return provider;
}
/**
* Initializes this TransformService with the specified
* parameters.
*
*
If the parameters exist in XML form, the
* {@link #init(XMLStructure, XMLCryptoContext)} method should be used to
* initialize the TransformService.
*
* @param params the algorithm parameters (may be null if
* not required or optional)
* @throws InvalidAlgorithmParameterException if the specified parameters
* are invalid for this algorithm
*/
public abstract void init(TransformParameterSpec params)
throws InvalidAlgorithmParameterException;
/**
* Marshals the algorithm-specific parameters. If there are no parameters
* to be marshalled, this method returns without throwing an exception.
*
* @param parent a mechanism-specific structure containing the parent
* node that the marshalled parameters should be appended to
* @param context the XMLCryptoContext containing
* additional context (may be null if not applicable)
* @throws ClassCastException if the type of parent or
* context is not compatible with this
* TransformService
* @throws NullPointerException if parent is null
* @throws MarshalException if the parameters cannot be marshalled
*/
public abstract void marshalParams
(XMLStructure parent, XMLCryptoContext context)
throws MarshalException;
/**
* Initializes this TransformService with the specified
* parameters and document context.
*
* @param parent a mechanism-specific structure containing the parent
* structure
* @param context the XMLCryptoContext containing
* additional context (may be null if not applicable)
* @throws ClassCastException if the type of parent or
* context is not compatible with this
* TransformService
* @throws NullPointerException if parent is null
* @throws InvalidAlgorithmParameterException if the specified parameters
* are invalid for this algorithm
*/
public abstract void init(XMLStructure parent, XMLCryptoContext context)
throws InvalidAlgorithmParameterException;
}