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FactoryFinder.javaAPI DocGlassfish v2 API5961Wed Sep 06 11:36:26 BST 2006javax.el

FactoryFinder

public class FactoryFinder extends Object

Fields Summary
Constructors Summary
Methods Summary
static java.lang.Objectfind(java.lang.String factoryId, java.lang.String fallbackClassName, java.util.Properties properties)
Finds the implementation Class object for the given factory name, or if that fails, finds the Class object for the given fallback class name. The arguments supplied must be used in order. If using the first argument is successful, the second one will not be used.

This method is package private so that this code can be shared.

return
the Class object of the specified message factory; may not be null
param
factoryId the name of the factory to find, which is a system property
param
fallbackClassName the implementation class name, which is to be used only if nothing else is found; null to indicate that there is no fallback class name
exception
ELException if there is an error

        ClassLoader classLoader;
        try {
            classLoader = Thread.currentThread().getContextClassLoader();
        } catch (Exception x) {
            throw new ELException(x.toString(), x);
        }

        String serviceId = "META-INF/services/" + factoryId;
        // try to find services in CLASSPATH
        try {
            InputStream is=null;
            if (classLoader == null) {
                is=ClassLoader.getSystemResourceAsStream(serviceId);
            } else {
                is=classLoader.getResourceAsStream(serviceId);
            }
        
            if( is!=null ) {
                BufferedReader rd =
                    new BufferedReader(new InputStreamReader(is, "UTF-8"));
        
                String factoryClassName = rd.readLine();
                rd.close();

                if (factoryClassName != null &&
                    ! "".equals(factoryClassName)) {
                    return newInstance(factoryClassName, classLoader, properties);
                }
            }
        } catch( Exception ex ) {
        }
        

        // try to read from $java.home/lib/el.properties
        try {
            String javah=System.getProperty( "java.home" );
            String configFile = javah + File.separator +
                "lib" + File.separator + "el.properties";
            File f=new File( configFile );
            if( f.exists()) {
                Properties props=new Properties();
                props.load( new FileInputStream(f));
                String factoryClassName = props.getProperty(factoryId);
                return newInstance(factoryClassName, classLoader, properties);
            }
        } catch(Exception ex ) {
        }


        // Use the system property
        try {
            String systemProp =
                System.getProperty( factoryId );
            if( systemProp!=null) {
                return newInstance(systemProp, classLoader, properties);
            }
        } catch (SecurityException se) {
        }

        if (fallbackClassName == null) {
            throw new ELException(
                "Provider for " + factoryId + " cannot be found", null);
        }

        return newInstance(fallbackClassName, classLoader, properties);
private static java.lang.ObjectnewInstance(java.lang.String className, java.lang.ClassLoader classLoader, java.util.Properties properties)
Creates an instance of the specified class using the specified ClassLoader object.

exception
ELException if the given class could not be found or could not be instantiated

        try {
            Class spiClass;
            if (classLoader == null) {
                spiClass = Class.forName(className);
            } else {
                spiClass = classLoader.loadClass(className);
            }
            if (properties != null) {
                Constructor constr = null;
                try {
                    constr = spiClass.getConstructor(Properties.class);
                } catch (Exception ex) {
                }
                if (constr != null) {
                    return constr.newInstance(properties);
                }
            }
            return spiClass.newInstance();
        } catch (ClassNotFoundException x) {
            throw new ELException(
                "Provider " + className + " not found", x);
        } catch (Exception x) {
            throw new ELException(
                "Provider " + className + " could not be instantiated: " + x,
                x);
        }