org.activequant.util.spring.ServiceLocator.java Source code

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Here is the source code for org.activequant.util.spring.ServiceLocator.java

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package org.activequant.util.spring;

import java.io.File;

import org.springframework.beans.factory.access.BeanFactoryReference;
import org.springframework.context.ApplicationContext;
import org.springframework.context.access.ContextBeanFactoryReference;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.context.support.FileSystemXmlApplicationContext;

/**
 * Locates and provides all available application services.<br>
 * <br>
 * <b>History:</b><br>
 *  - [25.02.2007] Created (Erik Nijkamp)<br>
 *  - [25.10.2007] Added classpath/filesystem switch (Erik Nijkamp)<br>
 *
 *  @author Erik Nijkamp
 *  
 */
public class ServiceLocator {

    /**
    * The default bean reference factory location.
    */
    private static final String DEFAULT_BEAN_REFERENCE_LOCATION = "factory.xml";

    /**
     * The default bean reference factory ID.
     */
    private static final String DEFAULT_BEAN_REFERENCE_ID = "beanRefFactory";

    /**
     * The bean factory reference instance.
     */
    private BeanFactoryReference beanFactoryReference;

    /**
     * The bean factory reference location.
     */
    private String beanFactoryReferenceLocation;

    /**
     * The bean factory reference id.
     */
    private String beanRefFactoryReferenceId;

    /**
      * The shared instance of this ServiceLocator.
      */
    protected static ServiceLocator instance = new ServiceLocator();

    protected ServiceLocator() {
        // shouldn't be instantiated
    }

    /**
     * Gets the shared instance of this Class
     *
     * @return the shared service locator instance.
     */
    public static final ServiceLocator instance() {
        return instance;
    }

    /**
     * Gets the shared instance of this Class
     *
     * @return the shared service locator instance.
     */
    public static final ServiceLocator instance(final String beanFactoryReferenceLocation) {
        instance.init(beanFactoryReferenceLocation);
        return instance;
    }

    /**
     * Initializes the Spring application context from
     * the given <code>beanFactoryReferenceLocation</code>.  If <code>null</code>
     * is specified for the <code>beanFactoryReferenceLocation</code>
     * then the default application context will be used.
     *
     * @param beanFactoryReferenceLocation the location of the beanRefFactory reference.
     */
    public synchronized void init(final String beanFactoryReferenceLocation,
            final String beanRefFactoryReferenceId) {
        this.beanFactoryReferenceLocation = beanFactoryReferenceLocation;
        this.beanRefFactoryReferenceId = beanRefFactoryReferenceId;
        this.beanFactoryReference = null;
    }

    /**
    * Initializes the Spring application context from the given
    * <code>beanFactoryReferenceLocation</code>. If <code>null</code> is
    * specified for the <code>beanFactoryReferenceLocation</code> then the
    * default application context will be used.
    * 
    * @param beanFactoryReferenceLocation
    *            the location of the beanRefFactory reference.
    */
    public synchronized void init(final String beanFactoryReferenceLocation) {
        this.beanFactoryReferenceLocation = beanFactoryReferenceLocation;
        this.beanFactoryReference = null;
    }

    /**
    * Shuts down the ServiceLocator and releases any used resources.
    */
    public synchronized void shutdown() {
        if (this.beanFactoryReference != null) {
            this.beanFactoryReference.release();
            this.beanFactoryReference = null;
        }
    }

    /**
     * Gets the Spring ApplicationContext.
     */
    public synchronized ApplicationContext getContext() {
        if (this.beanFactoryReference == null) {
            // init defaults
            if (this.beanFactoryReferenceLocation == null) {
                this.beanFactoryReferenceLocation = DEFAULT_BEAN_REFERENCE_LOCATION;
            }
            if (this.beanRefFactoryReferenceId == null) {
                this.beanRefFactoryReferenceId = DEFAULT_BEAN_REFERENCE_ID;
            }
            // init context
            ApplicationContext context = resolveApplicationContext(beanFactoryReferenceLocation);

            // detect factory
            if (context.containsBean(DEFAULT_BEAN_REFERENCE_ID)) {
                // use bean factory (factory bean defined)
                beanFactoryReference = new ContextBeanFactoryReference(
                        (ApplicationContext) context.getBean(DEFAULT_BEAN_REFERENCE_ID));
            } else {
                // use context directly (no factory bean defined)
                beanFactoryReference = new ContextBeanFactoryReference(context);
            }
        }
        return (ApplicationContext) this.beanFactoryReference.getFactory();
    }

    private ApplicationContext resolveApplicationContext(String path) {
        // filesystem
        if (new File(path).exists()) {
            return new FileSystemXmlApplicationContext(path);
        }

        // classpath
        if (ServiceLocator.class.getClassLoader().getResource(path) != null) {
            return new ClassPathXmlApplicationContext(path);
        }

        // error
        throw new IllegalArgumentException("Cannot locate spring context file '" + path + "'");
    }

    /**
     * Gets an instance of the given service.
     */
    @SuppressWarnings("unchecked")
    public final <T> T getServiceByName(String serviceName) {
        return (T) getContext().getBean(serviceName);
    }

    /**
     * Gets an instance of the given service.
     */
    @SuppressWarnings("unchecked")
    public final <T> T getService(Class<T> clazz) {
        return (T) getContext().getBeansOfType(clazz).values().iterator().next();
    }
}