SpringImplementationProcessor.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.tuscany.sca.implementation.spring.xml;

import static javax.xml.stream.XMLStreamConstants.END_ELEMENT;

import javax.xml.namespace.QName;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.XMLStreamReader;
import javax.xml.stream.XMLStreamWriter;

import org.apache.tuscany.sca.assembly.AssemblyFactory;
import org.apache.tuscany.sca.assembly.ComponentType;
import org.apache.tuscany.sca.assembly.xml.Constants;
import org.apache.tuscany.sca.assembly.xml.PolicySubjectProcessor;
import org.apache.tuscany.sca.contribution.processor.BaseStAXArtifactProcessor;
import org.apache.tuscany.sca.contribution.processor.ContributionReadException;
import org.apache.tuscany.sca.contribution.processor.ContributionResolveException;
import org.apache.tuscany.sca.contribution.processor.ContributionWriteException;
import org.apache.tuscany.sca.contribution.processor.ProcessorContext;
import org.apache.tuscany.sca.contribution.processor.StAXArtifactProcessor;
import org.apache.tuscany.sca.contribution.resolver.ModelResolver;
import org.apache.tuscany.sca.core.ExtensionPointRegistry;
import org.apache.tuscany.sca.core.FactoryExtensionPoint;
import org.apache.tuscany.sca.implementation.spring.SpringImplementation;
import org.apache.tuscany.sca.implementation.spring.introspect.SpringXMLComponentTypeLoader;
import org.apache.tuscany.sca.monitor.Monitor;
import org.apache.tuscany.sca.monitor.Problem;
import org.apache.tuscany.sca.monitor.Problem.Severity;

/**
 * SpringArtifactProcessor is responsible for processing the XML of an <implementation.spring.../>
 * element in an SCA SCDL file.
 *
 * @version $Rev$ $Date$
 */
public class SpringImplementationProcessor extends BaseStAXArtifactProcessor implements
    StAXArtifactProcessor<SpringImplementation> {

    private static final String LOCATION = "location";
    private static final String IMPLEMENTATION_SPRING = "implementation.spring";
    private static final QName IMPLEMENTATION_SPRING_QNAME = new QName(Constants.SCA11_NS, IMPLEMENTATION_SPRING);
    private static final String MSG_LOCATION_MISSING = "Reading implementation.spring - location attribute missing";

    private ExtensionPointRegistry registry;
    private AssemblyFactory assemblyFactory;
    private PolicySubjectProcessor policyProcessor;

    private FactoryExtensionPoint factories;

    public SpringImplementationProcessor(ExtensionPointRegistry registry) {
        this.registry = registry;
        this.factories = registry.getExtensionPoint(FactoryExtensionPoint.class);
        this.assemblyFactory = factories.getFactory(AssemblyFactory.class);
        this.policyProcessor = new PolicySubjectProcessor(registry);
    }

    /**
     * Report a exception.
     *
     * @param problems
     * @param message
     * @param model
     */
    private void error(Monitor monitor, String message, Object model, Exception ex) {
        if (monitor != null) {
            Problem problem =
                monitor.createProblem(this.getClass().getName(),
                                      "impl-spring-validation-messages",
                                      Severity.ERROR,
                                      model,
                                      message,
                                      ex);
            monitor.problem(problem);
        }
    }

    /**
     * Report a error.
     *
     * @param problems
     * @param message
     * @param model
     */
    private void error(Monitor monitor, String message, Object model, Object... messageParameters) {
        if (monitor != null) {
            Problem problem =
                monitor.createProblem(this.getClass().getName(),
                                      "impl-spring-validation-messages",
                                      Severity.ERROR,
                                      model,
                                      message,
                                      (Object[])messageParameters);
            monitor.problem(problem);
        }
    }

    /*
     * Read the XML and parse out the attributes.
     *
     * <implementation.spring.../> has a single required attribute:
     * "location" - which is the target URI of of an archive file or a directory that contains the Spring
     * application context files.
     * If the resource identified by the location attribute is an archive file, then the file
     * META-INF/MANIFEST.MF is read from the archive.
     * If the location URI identifies a directory, then META-INF/MANIFEST.MF must exist
     * underneath that directory.
     * If the manifest file contains a header "Spring-Context" of the format:
     *    Spring-Context ::= path ( ';' path )*
     *
     * Where path is a relative path with respect to the location URI, then the set of paths
     * specified in the header identify the context configuration files.
     * If there is no MANIFEST.MF file or no Spring-Context header within that file,
     * then the default behaviour is to build an application context using all the *.xml files
     * in the META-INF/spring directory.
     */
    public SpringImplementation read(XMLStreamReader reader, ProcessorContext context)
        throws ContributionReadException, XMLStreamException {

        // Create the Spring implementation
        SpringImplementation springImplementation = null;

        // Read the location attribute for the spring implementation
        String springLocation = getURIString(reader, LOCATION);
        if (springLocation != null) {
            springImplementation = new SpringImplementation();
            springImplementation.setLocation(springLocation);
            springImplementation.setUnresolved(true);
            processComponentType(springImplementation);
        } else {
            error(context.getMonitor(), "LocationAttributeMissing", reader);
            //throw new ContributionReadException(MSG_LOCATION_MISSING);
        }

        // Read policies
        policyProcessor.readPolicies(springImplementation, reader);

        // Skip to end element
        while (reader.hasNext()) {
            if (reader.next() == END_ELEMENT && IMPLEMENTATION_SPRING_QNAME.equals(reader.getName())) {
                break;
            }
        } // end while

        return springImplementation;
    } // end read

    /*
     * Handles the component type for the Spring implementation
     * @param springImplementation - a Spring implementation.  The component type information
     * is created for this implementation
     *
     */
    private void processComponentType(SpringImplementation springImplementation) {

        // Create a ComponentType and mark it unresolved
        ComponentType componentType = assemblyFactory.createComponentType();
        componentType.setUnresolved(true);
        springImplementation.setComponentType(componentType);
    } // end processComponentType

    /*
     * Write out the XML representation of the Spring implementation
     * <implementation.spring location="..." />
     */
    public void write(SpringImplementation springImplementation, XMLStreamWriter writer, ProcessorContext context)
        throws ContributionWriteException, XMLStreamException {

        // Write <implementation.spring>
        writer.writeStartElement(Constants.SCA11_NS, IMPLEMENTATION_SPRING);
        policyProcessor.writePolicyAttributes(springImplementation, writer);

        if (springImplementation.getLocation() != null) {
            writer.writeAttribute(LOCATION, springImplementation.getLocation());
        }

        writer.writeEndElement();

    } // end write

    /**
     * Resolves the Spring implementation - loads the Spring application-context XML and
     * derives the spring implementation componentType from it
     */
    public void resolve(SpringImplementation springImplementation, ModelResolver resolver, ProcessorContext context)
        throws ContributionResolveException {

        if (springImplementation == null)
            return;

        Monitor monitor = context.getMonitor();
        /* Load the Spring component type by reading the Spring application context */
        SpringXMLComponentTypeLoader springLoader = new SpringXMLComponentTypeLoader(registry);
        try {
            // Load the Spring Implementation information from its application context file...
            springLoader.load(springImplementation, resolver, context);
        } catch (ContributionReadException e) {
            ContributionResolveException ce = new ContributionResolveException(e);
            error(monitor, "ContributionResolveException", resolver, ce);
            throw ce;
        }

        ComponentType ct = springImplementation.getComponentType();
        if (ct.isUnresolved()) {
            // If the introspection fails to resolve, try to find a side file...
            ComponentType componentType = resolver.resolveModel(ComponentType.class, ct, context);
            if (componentType.isUnresolved()) {
                error(monitor, "UnableToResolveComponentType", resolver);
                //throw new ContributionResolveException("SpringArtifactProcessor: unable to resolve componentType for Spring component");
            } else {
                springImplementation.setComponentType(componentType);
                springImplementation.setUnresolved(false);
            }

        } // end if

    } // end method resolve

    public QName getArtifactType() {
        return IMPLEMENTATION_SPRING_QNAME;
    }

    public Class<SpringImplementation> getModelType() {
        return SpringImplementation.class;
    }

} // end class SpringArtifactProcessor