org.metawidget.inspector.jsp.JspAnnotationInspector Maven / Gradle / Ivy

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// 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.jsp;

import static org.metawidget.inspector.jsp.JspInspectionResultConstants.*;

import java.util.Map;
import java.util.regex.Pattern;

import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.el.ExpressionEvaluator;
import javax.servlet.jsp.el.VariableResolver;

import org.metawidget.inspector.iface.InspectorException;
import org.metawidget.inspector.impl.BaseObjectInspector;
import org.metawidget.inspector.impl.BaseObjectInspectorConfig;
import org.metawidget.inspector.impl.Trait;
import org.metawidget.inspector.impl.propertystyle.Property;
import org.metawidget.util.CollectionUtils;
import org.metawidget.util.InspectorUtils;
import org.metawidget.util.ThreadUtils;

/**
 * Inspects annotations defined by Metawidget's JSP support (declared in this same package).
 *
 * @author Richard Kennard
 */

public class JspAnnotationInspector
	extends BaseObjectInspector {

	//
	// Private member
	//

	private static final ThreadLocal	LOCAL_PAGE_CONTEXT	= ThreadUtils.newThreadLocal();

	//
	// Public statics
	//

	/**
	 * Sets the PageContext to use for this Inspection.
	 * 
	 * Unfortunately, JSP lacks a standardized mechanism to retrieve the PageContext
	 * (or the HttpServletRequest) statically. Many containers work around this using
	 * ThreadLocal-variables, but this is implementation specific.
	 * 
	 * Clients wishing to use UiJspAttribute or UiJspAttributes must call
	 * this static method before each inspection to inject the PageContext.
	 * org.metawidget.jsp.tagext.MetawidgetTag does this automatically.
	 */

	public static void setThreadLocalPageContext( PageContext pageContext ) {

		LOCAL_PAGE_CONTEXT.set( pageContext );
	}

	//
	// Constructor
	//

	public JspAnnotationInspector() {

		this( new BaseObjectInspectorConfig() );
	}

	public JspAnnotationInspector( BaseObjectInspectorConfig config ) {

		super( config );
	}

	//
	// Protected methods
	//

	@Override
	protected Map inspectTrait( Trait trait )
		throws Exception {

		// UiJspAttributes/UiJspAttribute

		UiJspAttributes jspAttributes = trait.getAnnotation( UiJspAttributes.class );
		UiJspAttribute jspAttribute = trait.getAnnotation( UiJspAttribute.class );

		if ( jspAttributes == null && jspAttribute == null ) {
			return null;
		}

		Map attributes = CollectionUtils.newHashMap();
		PageContext pageContext = LOCAL_PAGE_CONTEXT.get();

		if ( pageContext == null ) {
			throw InspectorException.newException( "ThreadLocalPageContext not set" );
		}

		ExpressionEvaluator expressionEvaluator;

		try {
			expressionEvaluator = pageContext.getExpressionEvaluator();
		} catch ( Exception e ) {
			throw InspectorException.newException( "ExpressionEvaluator requires JSP 2.0" );
		}

		VariableResolver variableResolver = pageContext.getVariableResolver();

		// UiJspAttribute

		if ( jspAttribute != null ) {
			putJspAttribute( expressionEvaluator, variableResolver, attributes, jspAttribute );
		}

		// UiJspAttributes

		if ( jspAttributes != null ) {
			for ( UiJspAttribute nestedJspAttribute : jspAttributes.value() ) {
				putJspAttribute( expressionEvaluator, variableResolver, attributes, nestedJspAttribute );
			}
		}

		return attributes;
	}

	@Override
	protected Map inspectProperty( Property property )
		throws Exception {

		Map attributes = CollectionUtils.newHashMap();

		// UiJspLookup

		UiJspLookup jspLookup = property.getAnnotation( UiJspLookup.class );

		if ( jspLookup != null ) {
			attributes.put( JSP_LOOKUP, jspLookup.value() );
		}

		return attributes;
	}

	protected void putJspAttribute( ExpressionEvaluator expressionEvaluator, VariableResolver variableResolver, Map attributes, UiJspAttribute jspAttribute )
		throws Exception {

		String expression = jspAttribute.expression();

		if ( !isExpression( expression ) ) {
			throw InspectorException.newException( "Expression '" + expression + "' is not of the form ${...}" );
		}

		Object value = expressionEvaluator.evaluate( expression, Object.class, variableResolver, null );

		if ( value == null ) {
			return;
		}

		for ( String attributeName : jspAttribute.name() ) {
			InspectorUtils.putAttributeValue( attributes, attributeName, value );
		}
	}

	//
	// Private methods
	//

	private static final Pattern	PATTERN_BINDING	= Pattern.compile( "^\\$\\{(.*)\\}$" );

	private boolean isExpression( String binding ) {

		return PATTERN_BINDING.matcher( binding ).matches();
	}
}