jakarta.xml.bind.JAXBContext Maven / Gradle / Ivy
/*
* Copyright (c) 2003, 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 jakarta.xml.bind;
import org.w3c.dom.Node;
import java.io.IOException;
import java.util.Collections;
import java.util.Map;
/**
* The {@code JAXBContext} class provides the client's entry point to the
* Jakarta XML Binding API. It provides an abstraction for managing the XML/Java binding
* information necessary to implement the Jakarta XML Binding binding framework operations:
* unmarshal, marshal and validate.
*
* A client application normally obtains new instances of this class using
* one of these two styles for newInstance methods, although there are other
* specialized forms of the method available:
*
*
* - {@link #newInstance(String, ClassLoader) JAXBContext.newInstance( "com.acme.foo:com.acme.bar" )}
* The JAXBContext instance is initialized from a list of colon
* separated Java package names. Each java package contains
* Jakarta XML Binding mapped classes, schema-derived classes and/or user annotated
* classes. Additionally, the java package may contain Jakarta XML Binding package annotations
* that must be processed. (see JLS, Section 7.4.1 "Named Packages").
*
* - {@link #newInstance(Class...) JAXBContext.newInstance( com.acme.foo.Foo.class )}
* The JAXBContext instance is initialized with class(es)
* passed as parameter(s) and classes that are statically reachable from
* these class(es). See {@link #newInstance(Class...)} for details.
*
*
*
*
* The provider must call the
* {@link DatatypeConverter#setDatatypeConverter(DatatypeConverterInterface)
* DatatypeConverter.setDatatypeConverter} api prior to any client
* invocations of the marshal and unmarshal methods. This is necessary to
* configure the datatype converter that will be used during these operations.
*
*
*
Unmarshalling
*
* The {@link Unmarshaller} class provides the client application the ability
* to convert XML data into a tree of Java content objects.
* The unmarshal method allows for
* any global XML element declared in the schema to be unmarshalled as
* the root of an instance document.
* Additionally, the unmarshal method allows for an unrecognized root element that
* has an xsi:type attribute's value that references a type definition declared in
* the schema to be unmarshalled as the root of an instance document.
* The {@code JAXBContext} object
* allows the merging of global elements and type definitions across a set of schemas (listed
* in the {@code contextPath}). Since each schema in the schema set can belong
* to distinct namespaces, the unification of schemas to an unmarshalling
* context must be namespace independent. This means that a client
* application is able to unmarshal XML documents that are instances of
* any of the schemas listed in the {@code contextPath}. For example:
*
*
* JAXBContext jc = JAXBContext.newInstance( "com.acme.foo:com.acme.bar" );
* Unmarshaller u = jc.createUnmarshaller();
* FooObject fooObj = (FooObject)u.unmarshal( new File( "foo.xml" ) ); // ok
* BarObject barObj = (BarObject)u.unmarshal( new File( "bar.xml" ) ); // ok
* BazObject bazObj = (BazObject)u.unmarshal( new File( "baz.xml" ) ); // error, "com.acme.baz" not in contextPath
*
*
*
* The client application may also generate Java content trees explicitly rather
* than unmarshalling existing XML data. For all Jakarta XML Binding-annotated value classes,
* an application can create content using constructors.
* For schema-derived interface/implementation classes and for the
* creation of elements that are not bound to a Jakarta XML Binding-annotated
* class, an application needs to have access and knowledge about each of
* the schema derived {@code ObjectFactory} classes that exist in each of
* java packages contained in the {@code contextPath}. For each schema
* derived java class, there is a static factory method that produces objects
* of that type. For example,
* assume that after compiling a schema, you have a package {@code com.acme.foo}
* that contains a schema derived interface named {@code PurchaseOrder}. In
* order to create objects of that type, the client application would use the
* factory method like this:
*
*
* com.acme.foo.PurchaseOrder po =
* com.acme.foo.ObjectFactory.createPurchaseOrder();
*
*
*
* Once the client application has an instance of the the schema derived object,
* it can use the mutator methods to set content on it.
*
*
* For more information on the generated {@code ObjectFactory} classes, see
* Section 4.2 Java Package of the specification.
*
*
* The provider must generate a class in each
* package that contains all of the necessary object factory methods for that
* package named ObjectFactory as well as the static
* {@code newInstance( javaContentInterface )} method
*
*
Marshalling
*
* The {@link Marshaller} class provides the client application the ability
* to convert a Java content tree back into XML data. There is no difference
* between marshalling a content tree that is created manually using the factory
* methods and marshalling a content tree that is the result an {@code unmarshal}
* operation. Clients can marshal a java content tree back to XML data
* to a {@code java.io.OutputStream} or a {@code java.io.Writer}. The
* marshalling process can alternatively produce SAX2 event streams to a
* registered {@code ContentHandler} or produce a DOM Node object.
* Client applications have control over the output encoding as well as
* whether or not to marshal the XML data as a complete document or
* as a fragment.
*
*
* Here is a simple example that unmarshals an XML document and then marshals
* it back out:
*
*
* JAXBContext jc = JAXBContext.newInstance( "com.acme.foo" );
*
* // unmarshal from foo.xml
* Unmarshaller u = jc.createUnmarshaller();
* FooObject fooObj = (FooObject)u.unmarshal( new File( "foo.xml" ) );
*
* // marshal to System.out
* Marshaller m = jc.createMarshaller();
* m.marshal( fooObj, System.out );
*
*
*
* Validation
*
* In Jakarta XML Binding, the {@link Unmarshaller} has included convenience methods that expose
* the JAXP {@link javax.xml.validation} framework. Please refer to the
* {@link Unmarshaller#setSchema(javax.xml.validation.Schema)} API for more
* information.
*
*
*
Jakarta XML Binding Runtime Framework Compatibility
*
* The following JAXB 1.0 restriction only applies to binding schema to
* interfaces/implementation classes.
* Since this binding does not require a common runtime system, a Jakarta XML Binding
* client application must not attempt to mix runtime objects ({@code JAXBContext,
* Marshaller}, etc. ) from different providers. This does not
* mean that the client application isn't portable, it simply means that a
* client has to use a runtime system provided by the same provider that was
* used to compile the schema.
*
*
*
Discovery of Jakarta XML Binding implementation
*
* To create an instance of {@link JAXBContext}, one of {@code JAXBContext.newInstance(...)} methods is invoked. After
* JAX-B implementation is discovered, call is delegated to appropriate provider's method {@code createContext(...)}
* passing parameters from the original call.
*
* JAX-B implementation discovery happens each time {@code JAXBContext.newInstance} is invoked. If there is no user
* specific configuration provided, default JAX-B provider must be returned.
*
* Implementation discovery consists of following steps:
*
*
*
* -
* If the system property {@link #JAXB_CONTEXT_FACTORY} exists, then its value is assumed to be the provider
* factory class. This phase of the look up enables per-JVM override of the Jakarta XML Binding implementation.
*
*
-
* Provider of {@link jakarta.xml.bind.JAXBContextFactory} is loaded using the service-provider loading
* facilities, defined by the {@link java.util.ServiceLoader} class, to attempt
* to locate and load an implementation of the service using the {@linkplain
* java.util.ServiceLoader#load(java.lang.Class) default loading mechanism}: the service-provider loading facility
* will use the {@linkplain java.lang.Thread#getContextClassLoader() current thread's context class loader}
* to attempt to load the context factory. If the context class loader is null, the
* {@linkplain ClassLoader#getSystemClassLoader() system class loader} will be used.
*
* In case of {@link java.util.ServiceConfigurationError service
* configuration error} a {@link jakarta.xml.bind.JAXBException} will be thrown.
*
* -
* Finally, if all the steps above fail, then the rest of the look up is unspecified. That said,
* the recommended behavior is to simply look for some hard-coded platform default Jakarta XML Binding implementation.
* This phase of the look up is so that the environment can have its own Jakarta XML Binding implementation as the last resort.
*
*
*
* Once the provider factory class is discovered, context creation is delegated to one of its
* {@code createContext(...)} methods.
*
* @implNote
* Within the last step, if Glassfish AS environment detected, its specific service loader is used to find factory class.
*
* @author
- Ryan Shoemaker, Sun Microsystems, Inc.
* - Kohsuke Kawaguchi, Sun Microsystems, Inc.
* - Joe Fialli, Sun Microsystems, Inc.
*
* @see Marshaller
* @see Unmarshaller
* @see S 7.4.1 "Named Packages"
* in Java Language Specification
*
* @since 1.6, JAXB 1.0
*/
public abstract class JAXBContext {
/**
* The name of the property that contains the name of the class capable
* of creating new {@code JAXBContext} objects.
*/
public static final String JAXB_CONTEXT_FACTORY = "jakarta.xml.bind.JAXBContextFactory";
protected JAXBContext() {
}
/**
* Create a new instance of a {@code JAXBContext} class.
*
*
* This is a convenience method to invoke the
* {@link #newInstance(String,ClassLoader)} method with
* the context class loader of the current thread.
*
* @param contextPath the context path
*
* @return the new instance of a {@code JAXBContext} class
*
* @throws JAXBException if an error was encountered while creating the
* {@code JAXBContext} such as
*
* - failure to locate either ObjectFactory.class or jaxb.index in the packages
* - an ambiguity among global elements contained in the contextPath
* - failure to locate a value for the context factory provider property
* - mixing schema derived packages from different providers on the same contextPath
* - packages are not open to {@code jakarta.xml.bind} module
*
*/
public static JAXBContext newInstance( String contextPath )
throws JAXBException {
//return newInstance( contextPath, JAXBContext.class.getClassLoader() );
return newInstance( contextPath, getContextClassLoader());
}
/**
* Create a new instance of a {@code JAXBContext} class.
*
*
* The client application must supply a context path which is a list of
* colon (':', \u005Cu003A) separated java package names that contain
* schema-derived classes and/or fully qualified Jakarta XML Binding-annotated classes.
* Schema-derived
* code is registered with the JAXBContext by the
* ObjectFactory.class generated per package.
* Alternatively than being listed in the context path, programmer
* annotated Jakarta XML Binding mapped classes can be listed in a
* {@code jaxb.index} resource file, format described below.
* Note that a java package can contain both schema-derived classes and
* user annotated Jakarta XML Binding classes. Additionally, the java package may
* contain Jakarta XML Binding package annotations that must be processed. (see JLS,
* Section 7.4.1 "Named Packages").
*
*
*
* Every package listed on the contextPath must meet one or both of the
* following conditions otherwise a {@code JAXBException} will be thrown:
*
*
* - it must contain ObjectFactory.class
* - it must contain jaxb.index
*
*
*
* Format for jaxb.index
*
* The file contains a newline-separated list of class names.
* Space and tab characters, as well as blank
* lines, are ignored. The comment character
* is '#' (0x23); on each line all characters following the first comment
* character are ignored. The file must be encoded in UTF-8. Classes that
* are reachable, as defined in {@link #newInstance(Class...)}, from the
* listed classes are also registered with JAXBContext.
*
* Constraints on class name occuring in a {@code jaxb.index} file are:
*
* - Must not end with ".class".
* - Class names are resolved relative to package containing
* {@code jaxb.index} file. Only classes occuring directly in package
* containing {@code jaxb.index} file are allowed.
* - Fully qualified class names are not allowed.
* A qualified class name,relative to current package,
* is only allowed to specify a nested or inner class.
*
*
*
* If there are any global XML element name collisions across the various
* packages listed on the {@code contextPath}, a {@code JAXBException}
* will be thrown.
*
*
* Mixing generated interface/impl bindings from multiple Jakarta XML Binding Providers
* in the same context path may result in a {@code JAXBException}
* being thrown.
*
*
* The steps involved in discovering the Jakarta XML Binding implementation is discussed in the class javadoc.
*
* @param contextPath
* List of java package names that contain schema
* derived class and/or java to schema (Jakarta XML Binding-annotated)
* mapped classes.
* Packages in {@code contextPath} that are in named modules must be
* {@code open} to at least the {@code jakarta.xml.bind} module.
* @param classLoader
* This class loader will be used to locate the implementation
* classes.
*
* @return a new instance of a {@code JAXBContext}
* @throws JAXBException if an error was encountered while creating the
* {@code JAXBContext} such as
*
* - failure to locate either ObjectFactory.class or jaxb.index in the packages
* - an ambiguity among global elements contained in the contextPath
* - failure to locate a value for the context factory provider property
* - mixing schema derived packages from different providers on the same contextPath
* - packages are not open to {@code jakarta.xml.bind} module
*
*/
public static JAXBContext newInstance( String contextPath, ClassLoader classLoader ) throws JAXBException {
return newInstance(contextPath,classLoader,Collections.emptyMap());
}
/**
* Create a new instance of a {@code JAXBContext} class.
*
*
* This is mostly the same as {@link JAXBContext#newInstance(String, ClassLoader)},
* but this version allows you to pass in provider-specific properties to configure
* the instantiation of {@link JAXBContext}.
*
*
* The interpretation of properties is up to implementations. Implementations must
* throw {@code JAXBException} if it finds properties that it doesn't understand.
*
* @param contextPath
* List of java package names that contain schema
* derived class and/or java to schema (Jakarta XML Binding-annotated)
* mapped classes.
* Packages in {@code contextPath} that are in named modules must be
* {@code open} to at least the {@code jakarta.xml.bind} module.
* @param classLoader
* This class loader will be used to locate the implementation classes.
* @param properties
* provider-specific properties. Can be null, which means the same thing as passing
* in an empty map.
*
* @return a new instance of a {@code JAXBContext}
* @throws JAXBException if an error was encountered while creating the
* {@code JAXBContext} such as
*
* - failure to locate either ObjectFactory.class or jaxb.index in the packages
* - an ambiguity among global elements contained in the contextPath
* - failure to locate a value for the context factory provider property
* - mixing schema derived packages from different providers on the same contextPath
* - packages are not open to {@code jakarta.xml.bind} module
*
* @since 1.6, JAXB 2.0
*/
public static JAXBContext newInstance( String contextPath,
ClassLoader classLoader,
Map properties ) throws JAXBException {
return ContextFinder.find(
/* The default property name according to the Jakarta XML Binding spec */
JAXB_CONTEXT_FACTORY,
/* the context path supplied by the client app */
contextPath,
/* class loader to be used */
classLoader,
properties );
}
// TODO: resurrect this once we introduce external annotations
// /**
// * Create a new instance of a {@code JAXBContext} class.
// *
// *
// * The client application must supply a list of classes that the new
// * context object needs to recognize.
// *
// * Not only the new context will recognize all the classes specified,
// * but it will also recognize any classes that are directly/indirectly
// * referenced statically from the specified classes.
// *
// * For example, in the following Java code, if you do
// * {@code newInstance(Foo.class)}, the newly created {@link JAXBContext}
// * will recognize both {@code Foo} and {@code Bar}, but not {@code Zot}:
// *
// * class Foo {
// * Bar b;
// * }
// * class Bar { int x; }
// * class Zot extends Bar { int y; }
// *
// *
// * Therefore, a typical client application only needs to specify the
// * top-level classes, but it needs to be careful.
// *
// * TODO: if we are to define other mechanisms, refer to them.
// *
// * @param externalBindings
// * list of external binding files. Can be null or empty if none is used.
// * when specified, those files determine how the classes are bound.
// *
// * @param classesToBeBound
// * list of java classes to be recognized by the new {@link JAXBContext}.
// * Can be empty, in which case a {@link JAXBContext} that only knows about
// * spec-defined classes will be returned.
// *
// * @return
// * A new instance of a {@code JAXBContext}.
// *
// * @throws JAXBException
// * if an error was encountered while creating the
// * {@code JAXBContext}, such as (but not limited to):
// *
// * - No Jakarta XML Binding implementation was discovered
// *
- Classes use Jakarta XML Binding annotations incorrectly
// *
- Classes have colliding annotations (i.e., two classes with the same type name)
// *
- Specified external bindings are incorrect
// *
- The Jakarta XML Binding implementation was unable to locate
// * provider-specific out-of-band information (such as additional
// * files generated at the development time.)
// *
// *
// * @throws IllegalArgumentException
// * if the parameter contains {@code null} (i.e., {@code newInstance(null);})
// *
// * @since JAXB 2.0
// */
// public static JAXBContext newInstance( Source[] externalBindings, Class... classesToBeBound )
// throws JAXBException {
//
// // empty class list is not an error, because the context will still include
// // spec-specified classes like String and Integer.
// // if(classesToBeBound.length==0)
// // throw new IllegalArgumentException();
//
// // but it is an error to have nulls in it.
// for( int i=classesToBeBound.length-1; i>=0; i-- )
// if(classesToBeBound[i]==null)
// throw new IllegalArgumentException();
//
// return ContextFinder.find(externalBindings,classesToBeBound);
// }
/**
* Create a new instance of a {@code JAXBContext} class.
*
*
* The client application must supply a list of classes that the new
* context object needs to recognize.
*
* Not only the new context will recognize all the classes specified,
* but it will also recognize any classes that are directly/indirectly
* referenced statically from the specified classes. Subclasses of
* referenced classes nor {@code @XmlTransient} referenced classes
* are not registered with JAXBContext.
*
* For example, in the following Java code, if you do
* {@code newInstance(Foo.class)}, the newly created {@link JAXBContext}
* will recognize both {@code Foo} and {@code Bar}, but not {@code Zot} or {@code FooBar}:
*
* class Foo {
* @XmlTransient FooBar c;
* Bar b;
* }
* class Bar { int x; }
* class Zot extends Bar { int y; }
* class FooBar { }
*
*
* Therefore, a typical client application only needs to specify the
* top-level classes, but it needs to be careful.
*
*
* Note that for each java package registered with JAXBContext,
* when the optional package annotations exist, they must be processed.
* (see JLS, Section 7.4.1 "Named Packages").
*
*
* The steps involved in discovering the Jakarta XML Binding implementation is discussed in the class javadoc.
*
* @param classesToBeBound
* List of java classes to be recognized by the new {@link JAXBContext}.
* Classes in {@code classesToBeBound} that are in named modules must be in a package
* that is {@code open} to at least the {@code jakarta.xml.bind} module.
* Can be empty, in which case a {@link JAXBContext} that only knows about
* spec-defined classes will be returned.
*
* @return
* A new instance of a {@code JAXBContext}.
*
* @throws JAXBException
* if an error was encountered while creating the
* {@code JAXBContext}, such as (but not limited to):
*
* - No Jakarta XML Binding implementation was discovered
*
- Classes use Jakarta XML Binding annotations incorrectly
*
- Classes have colliding annotations (i.e., two classes with the same type name)
*
- The Jakarta XML Binding implementation was unable to locate
* provider-specific out-of-band information (such as additional
* files generated at the development time.)
*
- {@code classesToBeBound} are not open to {@code jakarta.xml.bind} module
*
*
* @throws IllegalArgumentException
* if the parameter contains {@code null} (i.e., {@code newInstance(null);})
*
* @since 1.6, JAXB 2.0
*/
public static JAXBContext newInstance( Class ... classesToBeBound )
throws JAXBException {
return newInstance(classesToBeBound,Collections.emptyMap());
}
/**
* Create a new instance of a {@code JAXBContext} class.
*
*
* An overloading of {@link JAXBContext#newInstance(Class...)}
* to configure 'properties' for this instantiation of {@link JAXBContext}.
*
*
* The interpretation of properties is up to implementations. Implementations must
* throw {@code JAXBException} if it finds properties that it doesn't understand.
*
* @param classesToBeBound
* List of java classes to be recognized by the new {@link JAXBContext}.
* Classes in {@code classesToBeBound} that are in named modules must be in a package
* that is {@code open} to at least the {@code jakarta.xml.bind} module.
* Can be empty, in which case a {@link JAXBContext} that only knows about
* spec-defined classes will be returned.
* @param properties
* provider-specific properties. Can be null, which means the same thing as passing
* in an empty map.
*
* @return
* A new instance of a {@code JAXBContext}.
*
* @throws JAXBException
* if an error was encountered while creating the
* {@code JAXBContext}, such as (but not limited to):
*
* - No Jakarta XML Binding implementation was discovered
*
- Classes use Jakarta XML Binding annotations incorrectly
*
- Classes have colliding annotations (i.e., two classes with the same type name)
*
- The Jakarta XML Binding implementation was unable to locate
* provider-specific out-of-band information (such as additional
* files generated at the development time.)
*
- {@code classesToBeBound} are not open to {@code jakarta.xml.bind} module
*
*
* @throws IllegalArgumentException
* if the parameter contains {@code null} (i.e., {@code newInstance(null,someMap);})
*
* @since 1.6, JAXB 2.0
*/
public static JAXBContext newInstance( Class[] classesToBeBound, Map properties )
throws JAXBException {
if (classesToBeBound == null) {
throw new IllegalArgumentException();
}
// but it is an error to have nulls in it.
for (int i = classesToBeBound.length - 1; i >= 0; i--) {
if (classesToBeBound[i] == null) {
throw new IllegalArgumentException();
}
}
return ContextFinder.find(classesToBeBound,properties);
}
/**
* Create an {@code Unmarshaller} object that can be used to convert XML
* data into a java content tree.
*
* @return an {@code Unmarshaller} object
*
* @throws JAXBException if an error was encountered while creating the
* {@code Unmarshaller} object
*/
public abstract Unmarshaller createUnmarshaller() throws JAXBException;
/**
* Create a {@code Marshaller} object that can be used to convert a
* java content tree into XML data.
*
* @return a {@code Marshaller} object
*
* @throws JAXBException if an error was encountered while creating the
* {@code Marshaller} object
*/
public abstract Marshaller createMarshaller() throws JAXBException;
/**
* Creates a {@code Binder} object that can be used for
* associative/in-place unmarshalling/marshalling.
*
* @param domType select the DOM API to use by passing in its DOM Node class
*
* @param the DOM API type
*
* @return always a new valid {@code Binder} object.
*
* @throws UnsupportedOperationException
* if DOM API corresponding to {@code domType} is not supported by
* the implementation.
*
* @since 1.6, JAXB 2.0
*/
public Binder createBinder(Class domType) {
// to make JAXB 1.0 implementations work, this method must not be
// abstract
throw new UnsupportedOperationException();
}
/**
* Creates a {@code Binder} for W3C DOM.
*
* @return always a new valid {@code Binder} object.
*
* @since 1.6, JAXB 2.0
*/
public Binder createBinder() {
return createBinder(Node.class);
}
/**
* Creates a {@code JAXBIntrospector} object that can be used to
* introspect Jakarta XML Binding objects.
*
* @return
* always return a non-null valid {@code JAXBIntrospector} object.
*
* @throws UnsupportedOperationException
* Calling this method on JAXB 1.0 implementations will throw
* an UnsupportedOperationException.
*
* @since 1.6, JAXB 2.0
*/
public JAXBIntrospector createJAXBIntrospector() {
// to make JAXB 1.0 implementations work, this method must not be
// abstract
throw new UnsupportedOperationException();
}
/**
* Generates the schema documents for this context.
*
* @param outputResolver
* this object controls the output to which schemas
* will be sent.
*
* @throws IOException
* if {@link SchemaOutputResolver} throws an {@link IOException}.
*
* @throws UnsupportedOperationException
* Calling this method on JAXB 1.0 implementations will throw
* an UnsupportedOperationException.
*
* @since 1.6, JAXB 2.0
*/
public void generateSchema(SchemaOutputResolver outputResolver) throws IOException {
// to make JAXB 1.0 implementations work, this method must not be
// abstract
throw new UnsupportedOperationException();
}
private static ClassLoader getContextClassLoader() {
if (System.getSecurityManager() == null) {
return Thread.currentThread().getContextClassLoader();
} else {
return java.security.AccessController.doPrivileged(
(java.security.PrivilegedAction) ()
-> Thread.currentThread().getContextClassLoader());
}
}
}