org.metawidget.inspector.impl.BaseXmlInspector Maven / Gradle / Ivy
// Metawidget
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
package org.metawidget.inspector.impl;
import static org.metawidget.inspector.InspectionResultConstants.*;
import java.io.InputStream;
import java.util.Map;
import org.metawidget.config.iface.ResourceResolver;
import org.metawidget.inspector.iface.DomInspector;
import org.metawidget.inspector.iface.InspectorException;
import org.metawidget.inspector.impl.propertystyle.Property;
import org.metawidget.inspector.impl.propertystyle.PropertyStyle;
import org.metawidget.inspector.impl.propertystyle.ValueAndDeclaredType;
import org.metawidget.util.ArrayUtils;
import org.metawidget.util.ClassUtils;
import org.metawidget.util.LogUtils;
import org.metawidget.util.LogUtils.Log;
import org.metawidget.util.XmlUtils;
import org.metawidget.util.simple.StringUtils;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
/**
* Convenience implementation for Inspectors that inspect XML files.
*
* Handles taking a 'flat' XML file (eg. only one <entity> node deep) and
* traversing nested paths, such as foo/bar, from...
*
*
* <entity type="foo">
* <property name="myBar" type="bar">
* </entity>
*
*
* ...to top level...
*
*
* <entity type="bar">
*
*
* ...and constructing...
*
* <entity name="myBar" type="bar">
*
* ...as output.
*
*
Schema Validation
*
* This class does not support schema validation - it is not that useful in practice for two
* reasons. First, Inspectors like HibernateInspector cannot use it because they can be
* pointed at different kinds of files (eg. hibernate.cfg.xml or hibernate-mapping.hbm.xml). Second,
* Inspectors that are intended for Android environments (eg. XmlInspector) cannot use
* it because Android's Dalvik preprocessor balks at the unsupported schema classes (even if they're
* wrapped in a ClassNotFoundException).
*
*
Mixing XML and Object-based Inspectors
*
* Several pieces of functionality apply to mixing XML-based Inspectors (e.g.
* XmlInspector) and Object-based Inspectors (e.g.
* PropertyTypeInspector) in the same application (i.e. via
* CompositeInspector).
*
* First, you may encounter a problem whereby the Object-based Inspectors will always
* stop at null or recursive references, whereas the XML Inspectors (which
* have no knowledge of Object values) will continue. This can lead to the
* WidgetBuilders constructing a UI for a null Object, which may upset
* some WidgetProcessors (e.g. BeansBindingProcessor). To resolve this,
* you can set BaseXmlInspectorConfig.setRestrictAgainstObject, whereby the XML-based
* Inspector will do a check for null or recursive references, and not
* return any XML.
*
* In addition, setting restrictAgainstObject allows the XML Inspector to
* traverse child relationships and infer their types using the Object. This saves having to
* explicitly specify those types and relationships in the XML.
*
* Second, by default you need to explicitly specify any inheritance relationships between types in
* the XML, because the XML has no knowledge of your Java classes. This includes the names of any
* proxied classes. If this becomes laborious, you can set
* BaseXmlInspectorConfig.setInferInheritanceHierarchy to infer the relationships
* automatically from your Java classes. If you are using setRestrictAgainstObject,
* setInferInheritanceHierarchy is implied.
*
* Third, it is important the properties defined by the XML and the ones defined by the Java classes
* stay in sync. To enforce this, you can set
* BaseXmlInspectorConfig.setValidateAgainstClasses.
*
* @author Richard Kennard
*/
public abstract class BaseXmlInspector
implements DomInspector {
//
// Protected members
//
protected Log mLog = LogUtils.getLog( getClass() );
//
// Private members
//
/**
* Shared DOM to store this Inspector's source XML.
*
* This member is private because, as pointed out here: "There's no
* requirement that a DOM be thread safe, so applications need to make sure that threads are
* properly synchronized for concurrent access to [a shared] DOM. This is true even if you're
* just invoking read operations".
*/
private Element mRoot;
private final PropertyStyle mRestrictAgainstObject;
private final boolean mInferInheritanceHierarchy;
//
// Constructor
//
/**
* Config-based constructor.
*
* All BaseXmlInspector inspectors must be configurable, to allow specifying an XML file.
*/
protected BaseXmlInspector( BaseXmlInspectorConfig config ) {
try {
// Look up the XML file
InputStream[] files = config.getInputStreams();
if ( files != null && files.length > 0 ) {
mRoot = getDocumentElement( config.getResourceResolver(), config.getInputStreams() );
}
if ( mRoot == null ) {
throw InspectorException.newException( "No XML input file specified" );
}
// Debug
if ( mLog.isTraceEnabled() ) {
mLog.trace( XmlUtils.documentToString( mRoot.getOwnerDocument(), false ) );
}
// restrictAgainstObject
mRestrictAgainstObject = config.getRestrictAgainstObject();
// inferInheritanceHierarchy
mInferInheritanceHierarchy = config.isInferInheritanceHierarchy();
if ( mRestrictAgainstObject != null && mInferInheritanceHierarchy ) {
throw InspectorException.newException( "When using restrictAgainstObject, inferInheritanceHierarchy is implied" );
}
// validateAgainstClasses
PropertyStyle validateAgainstClasses = config.getValidateAgainstClasses();
if ( validateAgainstClasses != null ) {
String topLevelTypeAttribute = getTopLevelTypeAttribute();
String extendsAttribute = getExtendsAttribute();
String nameAttribute = getNameAttribute();
String typeAttribute = getTypeAttribute();
// For each entity...
Element entity = XmlUtils.getChildWithAttribute( mRoot, topLevelTypeAttribute );
while ( entity != null ) {
// ...the maps to a Java class...
String topLevelType = entity.getAttribute( topLevelTypeAttribute );
Class actualClass = ClassUtils.niceForName( topLevelType );
if ( actualClass != null ) {
// ...check its extends...
String extendz = entity.getAttribute( extendsAttribute );
Class actualSuperclass = actualClass.getSuperclass();
if ( !"".equals( extendz ) && !extendz.equals( actualSuperclass.getName() ) ) {
throw InspectorException.newException( actualClass + " extends " + actualSuperclass + ", not '" + extendz + "'" );
}
// ...then for each property...
Map actualProperties = validateAgainstClasses.getProperties( topLevelType );
Element property = XmlUtils.getChildWithAttribute( entity, nameAttribute );
while ( property != null ) {
// ...check it exists
String propertyName = property.getAttribute( nameAttribute );
Property actualProperty = actualProperties.get( propertyName );
if ( actualProperty == null ) {
throw InspectorException.newException( actualClass + " does not define a property '" + propertyName + "'" );
}
String propertyType = property.getAttribute( typeAttribute );
String actualType = actualProperty.getType();
if ( !"".equals( propertyType ) && !propertyType.equals( actualType ) ) {
throw InspectorException.newException( actualClass + " defines property '" + propertyName + "' to be " + actualType + ", not '" + propertyType + "'" );
}
property = XmlUtils.getSiblingWithAttribute( property, nameAttribute );
}
}
entity = XmlUtils.getSiblingWithAttribute( entity, topLevelTypeAttribute );
}
}
} catch ( Exception e ) {
throw InspectorException.newException( e );
}
}
//
// Public methods
//
/**
* Inspect the given Object according to the given path, and return the result as a String
* conforming to inspection-result-1.0.xsd.
*
* This method is marked final because most Metawidget implementations will call
* inspectAsDom directly instead.
*/
public final String inspect( Object toInspect, String type, String... names ) {
Element element = inspectAsDom( toInspect, type, names );
if ( element == null ) {
return null;
}
return XmlUtils.nodeToString( element, false );
}
public Element inspectAsDom( Object toInspect, String type, String... names ) {
// If no type, return nothing
if ( type == null ) {
return null;
}
try {
Document document;
Element entity;
ValueAndDeclaredType valueAndDeclaredType;
Map parentAttributes = null;
// "There's no requirement that a DOM be thread safe, so applications need to make sure
// that threads are properly synchronized for concurrent access to [a shared] DOM. This
// is true even if you're just invoking read operations"
//
// https://issues.apache.org/jira/browse/XERCESJ-727
synchronized ( mRoot ) {
// If the path has a parent...
if ( names != null && names.length > 0 ) {
// ...inspect its property for useful attributes...
Element propertyInParent = (Element) traverse( toInspect, type, true, names ).getValue();
if ( propertyInParent != null ) {
parentAttributes = inspectProperty( propertyInParent );
}
}
// ...otherwise, just start at the end point
valueAndDeclaredType = traverse( toInspect, type, false, names );
if ( valueAndDeclaredType.getValue() == null ) {
if ( parentAttributes == null || parentAttributes.isEmpty() ) {
return null;
}
document = XmlUtils.newDocument();
entity = document.createElementNS( NAMESPACE, ENTITY );
} else {
// Inspect traits
document = XmlUtils.newDocument();
entity = document.createElementNS( NAMESPACE, ENTITY );
inspectTraits( (Element) valueAndDeclaredType.getValue(), entity );
// Nothing of consequence to return?
if ( !entity.hasChildNodes() ) {
return null;
}
}
}
Element root = document.createElementNS( NAMESPACE, ROOT );
root.setAttribute( VERSION, "1.0" );
document.appendChild( root );
root.appendChild( entity );
// Add parent attributes (if any)
XmlUtils.setMapAsAttributes( entity, parentAttributes );
// Use the declared type so as to align with other Inspectors
entity.setAttribute( TYPE, valueAndDeclaredType.getDeclaredType() );
// Return the root
return root;
} catch ( Exception e ) {
throw InspectorException.newException( e );
}
}
//
// Protected methods
//
/**
* Parse the given InputStreams into a single DOM Document, and return its root.
*
* @param resolver
* helper in case getDocumentElement needs to resolve references defined
* in the InputStream.
*/
protected Element getDocumentElement( ResourceResolver resolver, InputStream... files )
throws Exception {
Document documentMaster = null;
for ( InputStream file : files ) {
Document documentParsed = XmlUtils.parse( file );
if ( !documentParsed.hasChildNodes() ) {
continue;
}
preprocessDocument( documentParsed );
if ( documentMaster == null || !documentMaster.hasChildNodes() ) {
documentMaster = documentParsed;
continue;
}
XmlUtils.combineElements( documentMaster.getDocumentElement(), documentParsed.getDocumentElement(), getTopLevelTypeAttribute(), getNameAttribute() );
}
if ( documentMaster == null ) {
return null;
}
return documentMaster.getDocumentElement();
}
/**
* Hook for subclasses to preprocess the document after the Inspector is initialized.
*
* For example, HibernateInspector preprocesses the class names in Hibernate
* mapping files to make them fully qualified.
*
* @param document
* DOM of XML being processed
*/
protected void preprocessDocument( Document document ) {
// Do nothing by default
}
/**
* Inspect the toInspect for properties and actions.
*
* This method can be overridden by clients wishing to modify the inspection process. Most
* clients will find it easier to override one of the sub-methods, such as
* inspectTrait or inspectProperty.
*/
protected void inspectTraits( Element toInspect, Element toAddTo ) {
if ( toInspect == null ) {
return;
}
Document document = toAddTo.getOwnerDocument();
// Do 'extends' attribute first
String extendsAttribute = getExtendsAttribute();
if ( extendsAttribute != null ) {
if ( toInspect.hasAttribute( extendsAttribute ) ) {
inspectTraits( (Element) traverse( null, toInspect.getAttribute( extendsAttribute ), false ).getValue(), toAddTo );
}
}
// Next, for each child...
Element element = document.createElementNS( NAMESPACE, ENTITY );
Element trait = XmlUtils.getFirstChildElement( toInspect );
while ( trait != null ) {
// ...inspect its attributes...
Element inspectedTrait = inspectTrait( document, trait );
if ( inspectedTrait != null ) {
element.appendChild( inspectedTrait );
}
trait = XmlUtils.getNextSiblingElement( trait );
}
// ...and combine them all. Note the element may already exist from the superclass,
// and its attributes will get overridden by the subclass
XmlUtils.combineElements( toAddTo, element, NAME, NAME );
}
/**
* Inspect the given Element and return a Map of attributes if it is a trait.
*
* It is this method's responsibility to decide whether the given Element does, in fact, qualify
* as a 'trait' - based on its own rules.
*
* @param toInspect
* DOM element to inspect
*/
protected Element inspectTrait( Document toAddTo, Element toInspect ) {
// Properties
Map propertyAttributes = inspectProperty( toInspect );
if ( propertyAttributes != null && !propertyAttributes.isEmpty() ) {
Element child = toAddTo.createElementNS( NAMESPACE, PROPERTY );
XmlUtils.setMapAsAttributes( child, propertyAttributes );
return child;
}
// Actions
Map actionAttributes = inspectAction( toInspect );
if ( actionAttributes != null && !actionAttributes.isEmpty() ) {
// Sanity check
if ( propertyAttributes != null ) {
throw InspectorException.newException( "Ambigious match: " + toInspect.getNodeName() + " matches as both a property and an action" );
}
Element child = toAddTo.createElementNS( NAMESPACE, ACTION );
XmlUtils.setMapAsAttributes( child, actionAttributes );
return child;
}
return null;
}
/**
* Inspect the given Element and return a Map of attributes if it is a property.
*
* It is this method's responsibility to decide whether the given Element does, in fact, qualify
* as a 'property' - based on its own rules. Does nothing by default.
*
* @param toInspect
* DOM element to inspect
* @return a Map of the property's attributes, or null if this Element is not a property
*/
protected Map inspectProperty( Element toInspect ) {
return null;
}
/**
* Inspect the given Element and return a Map of attributes if it is an action.
*
* It is this method's responsibility to decide whether the given Element does, in fact, qualify
* as an 'action' - based on its own rules. Does nothing by default.
*
* @param toInspect
* DOM element to inspect
* @return a Map of the property's attributes, or null if this Element is not an action
*/
protected Map inspectAction( Element toInspect ) {
return null;
}
/**
* @return the Element (may be null) and its declared type (not actual type). Never null.
* If the declared type within the ValueAndDeclaredType is null, inspection will be
* aborted
*/
protected ValueAndDeclaredType traverse( Object toTraverse, String type, boolean onlyToParent, String... names ) {
// If given a non-null Object, use it to restrictAgainstObject
String typeToInspect = type;
String[] namesToInspect = names;
Object traverseAgainstObject = null;
String declaredType = null;
if ( toTraverse != null && mRestrictAgainstObject != null ) {
ValueAndDeclaredType valueAndDeclaredType = mRestrictAgainstObject.traverse( toTraverse, typeToInspect, onlyToParent, namesToInspect );
traverseAgainstObject = valueAndDeclaredType.getValue();
if ( valueAndDeclaredType.getDeclaredType() != null ) {
declaredType = valueAndDeclaredType.getDeclaredType();
}
if ( traverseAgainstObject == null ) {
return new ValueAndDeclaredType( null, declaredType );
}
if ( onlyToParent ) {
namesToInspect = new String[] { namesToInspect[namesToInspect.length - 1] };
} else {
namesToInspect = null;
}
typeToInspect = traverseAgainstObject.getClass().getName();
}
if ( declaredType == null ) {
declaredType = typeToInspect;
}
// Validate type
String topLevelTypeAttribute = getTopLevelTypeAttribute();
Element entityElement = XmlUtils.getChildWithAttributeValue( mRoot, topLevelTypeAttribute, typeToInspect );
if ( entityElement == null ) {
if ( traverseAgainstObject == null && !mInferInheritanceHierarchy ) {
return new ValueAndDeclaredType( null, declaredType );
}
// If using mRestrictAgainstObject or mInferInheritanceHierarchy, attempt to match
// superclasses by checking against the Java class heirarchy
Class actualClass;
if ( traverseAgainstObject != null ) {
actualClass = traverseAgainstObject.getClass();
} else {
actualClass = ClassUtils.niceForName( typeToInspect );
if ( actualClass == null ) {
return new ValueAndDeclaredType( null, typeToInspect );
}
}
while ( entityElement == null && ( actualClass = actualClass.getSuperclass() ) != null ) {
entityElement = XmlUtils.getChildWithAttributeValue( mRoot, topLevelTypeAttribute, actualClass.getName() );
}
if ( entityElement == null ) {
return new ValueAndDeclaredType( null, declaredType );
}
}
if ( namesToInspect == null ) {
return new ValueAndDeclaredType( entityElement, declaredType );
}
int length = namesToInspect.length;
if ( length == 0 ) {
return new ValueAndDeclaredType( entityElement, declaredType );
}
// Traverse names
String extendsAttribute = getExtendsAttribute();
String nameAttribute = getNameAttribute();
String typeAttribute = getTypeAttribute();
for ( int loop = 0; loop < length; loop++ ) {
String name = namesToInspect[loop];
Element property = XmlUtils.getChildWithAttributeValue( entityElement, nameAttribute, name );
if ( property == null ) {
// XML structure may not support 'extends'
if ( extendsAttribute == null ) {
return new ValueAndDeclaredType( null, null );
}
// Property may be defined in an 'extends'
while ( true ) {
if ( !entityElement.hasAttribute( extendsAttribute ) ) {
return new ValueAndDeclaredType( null, null );
}
String childExtends = entityElement.getAttribute( extendsAttribute );
entityElement = XmlUtils.getChildWithAttributeValue( mRoot, topLevelTypeAttribute, childExtends );
if ( entityElement == null ) {
return new ValueAndDeclaredType( null, null );
}
property = XmlUtils.getChildWithAttributeValue( entityElement, nameAttribute, name );
if ( property != null ) {
break;
}
}
// This check is unnecessary. However it stops a 'potential null pointer access'
// warning in Eclipse!
if ( property == null ) {
throw new NullPointerException( "property" );
}
}
if ( onlyToParent && loop >= ( length - 1 ) ) {
return new ValueAndDeclaredType( property, property.getAttribute( typeAttribute ) );
}
if ( !property.hasAttribute( typeAttribute ) ) {
throw InspectorException.newException( "Property " + name + " in entity " + entityElement.getAttribute( typeAttribute ) + " has no @" + typeAttribute + " attribute in the XML, so cannot navigate to " + type + ArrayUtils.toString( namesToInspect, StringUtils.SEPARATOR_FORWARD_SLASH, true, false ) );
}
declaredType = property.getAttribute( typeAttribute );
entityElement = XmlUtils.getChildWithAttributeValue( mRoot, topLevelTypeAttribute, declaredType );
if ( entityElement == null ) {
break;
}
}
return new ValueAndDeclaredType( entityElement, declaredType );
}
/**
* The attribute on top-level elements that uniquely identifies them.
*/
protected String getTopLevelTypeAttribute() {
return TYPE;
}
/**
* The attribute on child elements that uniquely identifies them.
*/
protected String getNameAttribute() {
return NAME;
}
/**
* The attribute on child elements that identifies another top-level element.
*
* This is necessary for path traversal. If an XML format does not specify a way to traverse
* from a child to another top-level element, the Inspector cannot find information along paths
* (eg. foo/bar/baz). There is a way around this but, on balance, we
* decided against it (see http://blog.kennardconsulting.com/2008/01/ask-your-father.html).
*/
protected String getTypeAttribute() {
return TYPE;
}
/**
* The attribute on top-level elements that identifies a superclass relationship (if any).
*/
protected String getExtendsAttribute() {
return null;
}
}