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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
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 * 2 along with this work; if not, write to the Free Software Foundation,
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package com.sun.tracing;

import java.util.HashSet;
import java.io.PrintStream;
import java.lang.reflect.Field;
import java.security.AccessController;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;
import sun.security.action.GetPropertyAction;

import sun.tracing.NullProviderFactory;
import sun.tracing.PrintStreamProviderFactory;
import sun.tracing.MultiplexProviderFactory;
import sun.tracing.dtrace.DTraceProviderFactory;


ProviderFactory is a factory class used to create instances of providers. To enable tracing in an application, this class must be used to create instances of the provider interfaces defined by users. The system-defined factory is obtained by using the getDefaultFactory() static method. The resulting instance can be used to create any number of providers. 
Since:1.7
/**
 * {@code ProviderFactory} is a factory class used to create instances of
 * providers.
 *
 * To enable tracing in an application, this class must be used to create
 * instances of the provider interfaces defined by users.
 * The system-defined factory is obtained by using the
 * {@code getDefaultFactory()} static method.  The resulting instance can be
 * used to create any number of providers.
 *
 * @since 1.7
 */
public abstract class ProviderFactory {

    protected ProviderFactory() {}

    
Creates an implementation of a Provider interface.

Params:
  • cls – the provider interface to be defined.
Throws:
Returns:an implementation of cls, whose methods, when called, will trigger tracepoints in the application.
/**
     * Creates an implementation of a Provider interface.
     *
     * @param cls the provider interface to be defined.
     * @return an implementation of {@code cls}, whose methods, when called,
     * will trigger tracepoints in the application.
     * @throws NullPointerException if cls is null
     * @throws IllegalArgumentException if the class definition contains
     * non-void methods
     */
    public abstract <T extends Provider> T createProvider(Class<T> cls);

    
Returns an implementation of a ProviderFactory which creates instances of Providers. The created Provider instances will be linked to all appropriate and enabled system-defined tracing mechanisms in the JDK. 
Returns:a ProviderFactory that is used to create Providers.
/**
     * Returns an implementation of a {@code ProviderFactory} which
     * creates instances of Providers.
     *
     * The created Provider instances will be linked to all appropriate
     * and enabled system-defined tracing mechanisms in the JDK.
     *
     * @return a {@code ProviderFactory} that is used to create Providers.
     */
    public static ProviderFactory getDefaultFactory() {
        HashSet<ProviderFactory> factories = new HashSet<ProviderFactory>();

        // Try to instantiate a DTraceProviderFactory
        String prop = AccessController.doPrivileged(
            new GetPropertyAction("com.sun.tracing.dtrace"));

        if ( (prop == null || !prop.equals("disable")) &&
             DTraceProviderFactory.isSupported() ) {
            factories.add(new DTraceProviderFactory());
        }

        // Try to instantiate an output stream factory
        prop = AccessController.doPrivileged(
            new GetPropertyAction("sun.tracing.stream"));
        if (prop != null) {
            for (String spec : prop.split(",")) {
                PrintStream ps = getPrintStreamFromSpec(spec);
                if (ps != null) {
                    factories.add(new PrintStreamProviderFactory(ps));
                }
            }
        }

        // See how many factories we instantiated, and return an appropriate
        // factory that encapsulates that.
        if (factories.size() == 0) {
            return new NullProviderFactory();
        } else if (factories.size() == 1) {
            return factories.toArray(new ProviderFactory[1])[0];
        } else {
            return new MultiplexProviderFactory(factories);
        }
    }

    private static PrintStream getPrintStreamFromSpec(final String spec) {
        try {
            // spec is in the form of <class>.<field>, where <class> is
            // a fully specified class name, and <field> is a static member
            // in that class.  The <field> must be a 'PrintStream' or subtype
            // in order to be used.
            final int fieldpos = spec.lastIndexOf('.');
            final Class<?> cls = Class.forName(spec.substring(0, fieldpos));

            Field f = AccessController.doPrivileged(new PrivilegedExceptionAction<Field>() {
                public Field run() throws NoSuchFieldException {
                    return cls.getField(spec.substring(fieldpos + 1));
                }
            });

            return (PrintStream)f.get(null);
        } catch (ClassNotFoundException e) {
            throw new AssertionError(e);
        } catch (IllegalAccessException e) {
            throw new AssertionError(e);
        } catch (PrivilegedActionException e) {
            throw new AssertionError(e);
        }
    }
}