com.sun.xml.bind.api.ClassResolver Maven / Gradle / Ivy
/*
* Copyright (c) 1997, 2021 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 com.sun.xml.bind.api;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.Unmarshaller;
import javax.xml.bind.ValidationEventHandler;
import javax.xml.bind.annotation.XmlAnyElement;
import com.sun.istack.NotNull;
import com.sun.istack.Nullable;
/**
* Dynamically locates classes to represent elements discovered during the unmarshalling.
*
*
* THIS INTERFACE IS SUBJECT TO CHANGE WITHOUT NOTICE.
*
*
Background
*
* {@link JAXBContext#newInstance(Class...)} requires that application informs JAXB
* about all the classes that it may see in the instance document. While this allows
* JAXB to take time to optimize the unmarshalling, it is sometimes inconvenient
* for applications.
*
*
* This is where {@link ClassResolver} comes to resucue.
*
*
* A {@link ClassResolver} instance can be specified on {@link Unmarshaller} via
* {@link Unmarshaller#setProperty(String, Object)} as follows:
*
*
* unmarshaller.setProperty( ClassResolver.class.getName(), new MyClassResolverImpl() );
*
*
*
* When an {@link Unmarshaller} encounters (i) an unknown root element or (ii) unknown
* elements where unmarshaller is trying to unmarshal into {@link XmlAnyElement} with
* {@code lax=true}, unmarshaller calls {@link #resolveElementName(String, String)}
* method to see if the application may be able to supply a class that corresponds
* to that class.
*
*
* When a {@link Class} is returned, a new {@link JAXBContext} is created with
* all the classes known to it so far, plus a new class returned. This operation
* may fail (for example because of some conflicting annotations.) This failure
* is handled just like {@link Exception}s thrown from
* {@link ClassResolver#resolveElementName(String, String)}.
*
* @author Kohsuke Kawaguchi
* @since 2.1
*/
public abstract class ClassResolver {
/**
* JAXB calls this method when it sees an unknown element.
*
*
* See the class javadoc for details.
*
* @param nsUri
* Namespace URI of the unknown element. Can be empty but never null.
* @param localName
* Local name of the unknown element. Never be empty nor null.
*
* @return
* If a non-null class is returned, it will be used to unmarshal this element.
* If null is returned, the resolution is assumed to be failed, and
* the unmarshaller will behave as if there was no {@link ClassResolver}
* to begin with (that is, to report it to {@link ValidationEventHandler},
* then move on.)
*
* @throws Exception
* Throwing any {@link RuntimeException} causes the unmarshaller to stop
* immediately. The exception will be propagated up the call stack.
* Throwing any other checked {@link Exception} results in the error
* reproted to {@link ValidationEventHandler} (just like any other error
* during the unmarshalling.)
*/
public abstract @Nullable Class resolveElementName(@NotNull String nsUri, @NotNull String localName) throws Exception;
}