org.glassfish.jaxb.runtime.marshaller.NamespacePrefixMapper Maven / Gradle / Ivy
/*
* Copyright (c) 1997, 2022 Oracle and/or its affiliates. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Distribution License v. 1.0, which is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
package org.glassfish.jaxb.runtime.marshaller;
import jakarta.xml.bind.JAXBContext;
import org.w3c.dom.Node;
import javax.xml.stream.XMLEventWriter;
import javax.xml.stream.XMLStreamWriter;
import javax.xml.transform.dom.DOMResult;
import java.io.OutputStream;
// be careful about changing this class. this class is supposed to be
// extended by users and therefore we are not allowed to break
// those user code.
//
// this means:
// - don't add any abstract method
// - don't change any existing method signature
// - don't remove any existing method.
/**
* Implemented by the user application to determine URI {@code ->} prefix
* mapping.
*
* This is considered as an interface, though it's implemented
* as an abstract class to make it easy to add new methods in
* a future.
*
* @author
* Kohsuke Kawaguchi ([email protected])
*/
public abstract class NamespacePrefixMapper {
private static final String[] EMPTY_STRING = new String[0];
/**
* Default constructor.
*/
protected NamespacePrefixMapper() {}
/**
* Returns a preferred prefix for the given namespace URI.
*
* This method is intended to be overrided by a derived class.
*
*
* As noted in the return value portion of the javadoc, there
* are several cases where the preference cannot be honored.
* Specifically, as of JAXB RI 2.0 and onward:
*
*
* -
* If the prefix returned is already in use as one of the in-scope
* namespace bindings. This is partly necessary for correctness
* (so that we don't unexpectedly change the meaning of QNames
* bound to {@link String}), partly to simplify the marshaller.
*
-
* If the prefix returned is "" yet the current {@link JAXBContext}
* includes classes that use the empty namespace URI. This allows
* the JAXB RI to reserve the "" prefix for the empty namespace URI,
* which is the only possible prefix for the URI.
* This restriction is also to simplify the marshaller.
*
*
* @param namespaceUri
* The namespace URI for which the prefix needs to be found.
* Never be null. "" is used to denote the default namespace.
* @param suggestion
* When the content tree has a suggestion for the prefix
* to the given namespaceUri, that suggestion is passed as a
* parameter. Typicall this value comes from the QName.getPrefix
* to show the preference of the content tree. This parameter
* may be null, and this parameter may represent an already
* occupied prefix.
* @param requirePrefix
* If this method is expected to return non-empty prefix.
* When this flag is true, it means that the given namespace URI
* cannot be set as the default namespace.
*
* @return
* null if there's no prefered prefix for the namespace URI.
* In this case, the system will generate a prefix for you.
*
* Otherwise the system will try to use the returned prefix,
* but generally there's no guarantee if the prefix will be
* actually used or not.
*
* return "" to map this namespace URI to the default namespace.
* Again, there's no guarantee that this preference will be
* honored.
*
* If this method returns "" when requirePrefix=true, the return
* value will be ignored and the system will generate one.
*
* @since JAXB 1.0.1
*/
public abstract String getPreferredPrefix(String namespaceUri, String suggestion, boolean requirePrefix);
/**
* Returns a list of namespace URIs that should be declared
* at the root element.
*
*
* By default, the JAXB RI 1.0.x produces namespace declarations only when
* they are necessary, only at where they are used. Because of this
* lack of look-ahead, sometimes the marshaller produces a lot of
* namespace declarations that look redundant to human eyes. For example,
*
{@code
*
*
* ...
* ...
* ...
* ...
*
* }
*
*
* The JAXB RI 2.x mostly doesn't exhibit this behavior any more,
* as it declares all statically known namespace URIs (those URIs
* that are used as element/attribute names in JAXB annotations),
* but it may still declare additional namespaces in the middle of
* a document, for example when (i) a QName as an attribute/element value
* requires a new namespace URI, or (ii) DOM nodes as a portion of an object
* tree requires a new namespace URI.
*
*
* If you know in advance that you are going to use a certain set of
* namespace URIs, you can override this method and have the marshaller
* declare those namespace URIs at the root element.
*
*
* For example, by returning new String[]{"urn:foo"},
* the marshaller will produce:
*
{@code
*
*
* ...
* ...
* ...
* ...
*
* }
*
* To control prefixes assigned to those namespace URIs, use the
* {@link #getPreferredPrefix(String, String, boolean)} method.
*
* @return
* A list of namespace URIs as an array of {@link String}s.
* This method can return a length-zero array but not null.
* None of the array component can be null. To represent
* the empty namespace, use the empty string "".
*
* @since
* JAXB RI 1.0.2
*/
public String[] getPreDeclaredNamespaceUris() {
return EMPTY_STRING;
}
/**
* Similar to {@link #getPreDeclaredNamespaceUris()} but allows the
* (prefix,nsUri) pairs to be returned.
*
*
* With {@link #getPreDeclaredNamespaceUris()}, applications who wish to control
* the prefixes as well as the namespaces needed to implement both
* {@link #getPreDeclaredNamespaceUris()} and {@link #getPreferredPrefix(String, String, boolean)}.
*
*
* This version eliminates the needs by returning an array of pairs.
*
* @return
* always return a non-null (but possibly empty) array. The array stores
* data like (prefix1,nsUri1,prefix2,nsUri2,...) Use an empty string to represent
* the empty namespace URI and the default prefix. Null is not allowed as a value
* in the array.
*
* @since
* JAXB RI 2.0 beta
*/
public String[] getPreDeclaredNamespaceUris2() {
return EMPTY_STRING;
}
/**
* Returns a list of (prefix,namespace URI) pairs that represents
* namespace bindings available on ancestor elements (that need not be repeated
* by the JAXB RI.)
*
*
* Sometimes JAXB is used to marshal an XML document, which will be
* used as a subtree of a bigger document. When this happens, it's nice
* for a JAXB marshaller to be able to use in-scope namespace bindings
* of the larger document and avoid declaring redundant namespace URIs.
*
*
* This is automatically done when you are marshalling to {@link XMLStreamWriter},
* {@link XMLEventWriter}, {@link DOMResult}, or {@link Node}, because
* those output format allows us to inspect what's currently available
* as in-scope namespace binding. However, with other output format,
* such as {@link OutputStream}, the JAXB RI cannot do this automatically.
* That's when this method comes into play.
*
*
* Namespace bindings returned by this method will be used by the JAXB RI,
* but will not be re-declared. They are assumed to be available when you insert
* this subtree into a bigger document.
*
*
* It is NOT OK to return the same binding, or give
* the receiver a conflicting binding information.
* It's a responsibility of the caller to make sure that this doesn't happen
* even if the ancestor elements look like:
*
{@code
*
*
*
* ... JAXB marshalling into here.
*
*
*
* }
*
* @return
* always return a non-null (but possibly empty) array. The array stores
* data like (prefix1,nsUri1,prefix2,nsUri2,...) Use an empty string to represent
* the empty namespace URI and the default prefix. Null is not allowed as a value
* in the array.
*
* @since JAXB RI 2.0 beta
*/
public String[] getContextualNamespaceDecls() {
return EMPTY_STRING;
}
}