jdk/src/share/classes/com/sun/jmx/mbeanserver/Introspector.java

/*
 * Copyright 1999-2007 Sun Microsystems, Inc.  All Rights Reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Sun designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Sun in the LICENSE file that accompanied this code.
 *
 * This code 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 General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
 */

package com.sun.jmx.mbeanserver;

import java.lang.annotation.Annotation;
import java.lang.reflect.AnnotatedElement;
import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.lang.reflect.UndeclaredThrowableException;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;

import javax.management.Descriptor;
import javax.management.DescriptorKey;
import javax.management.DynamicMBean;
import javax.management.ImmutableDescriptor;
import javax.management.MBeanInfo;
import javax.management.NotCompliantMBeanException;

import com.sun.jmx.mbeanserver.Util;

/**
 * This class contains the methods for performing all the tests needed to verify
 * that a class represents a JMX compliant MBean.
 *
 * @since 1.5
 */
public class Introspector {


     /*
     * ------------------------------------------
     *  PRIVATE CONSTRUCTORS
     * ------------------------------------------
     */

    // private constructor defined to "hide" the default public constructor
    private Introspector() {

        // ------------------------------
        // ------------------------------

    }

    /*
     * ------------------------------------------
     *  PUBLIC METHODS
     * ------------------------------------------
     */

    /**
     * Tell whether a MBean of the given class is a Dynamic MBean.
     * This method does nothing more than returning
     * <pre>
     * javax.management.DynamicMBean.class.isAssignableFrom(c)
     * </pre>
     * This method does not check for any JMX MBean compliance:
     * <ul><li>If <code>true</code> is returned, then instances of
     *     <code>c</code> are DynamicMBean.</li>
     *     <li>If <code>false</code> is returned, then no further
     *     assumption can be made on instances of <code>c</code>.
     *     In particular, instances of <code>c</code> may, or may not
     *     be JMX standard MBeans.</li>
     * </ul>
     * @param c The class of the MBean under examination.
     * @return <code>true</code> if instances of <code>c</code> are
     *         Dynamic MBeans, <code>false</code> otherwise.
     *
     **/
    public static final boolean isDynamic(final Class c) {
        // Check if the MBean implements the DynamicMBean interface
        return javax.management.DynamicMBean.class.isAssignableFrom(c);
    }

    /**
     * Basic method for testing that a MBean of a given class can be
     * instantiated by the MBean server.<p>
     * This method checks that:
     * <ul><li>The given class is a concrete class.</li>
     *     <li>The given class exposes at least one public constructor.</li>
     * </ul>
     * If these conditions are not met, throws a NotCompliantMBeanException.
     * @param c The class of the MBean we want to create.
     * @exception NotCompliantMBeanException if the MBean class makes it
     *            impossible to instantiate the MBean from within the
     *            MBeanServer.
     *
     **/
    public static void testCreation(Class c)
        throws NotCompliantMBeanException {
        // Check if the class is a concrete class
        final int mods = c.getModifiers();
        if (Modifier.isAbstract(mods) || Modifier.isInterface(mods)) {
            throw new NotCompliantMBeanException("MBean class must be concrete");
        }

        // Check if the MBean has a public constructor
        final Constructor[] consList = c.getConstructors();
        if (consList.length == 0) {
            throw new NotCompliantMBeanException("MBean class must have public constructor");
        }
    }

    public static void checkCompliance(Class mbeanClass)
        throws NotCompliantMBeanException {
        // Is DynamicMBean?
        //
        if (DynamicMBean.class.isAssignableFrom(mbeanClass))
            return;
        // Is Standard MBean?
        //
        final Exception mbeanException;
        try {
            getStandardMBeanInterface(mbeanClass);
            return;
        } catch (NotCompliantMBeanException e) {
            mbeanException = e;
        }
        // Is MXBean?
        //
        final Exception mxbeanException;
        try {
            getMXBeanInterface(mbeanClass);
            return;
        } catch (NotCompliantMBeanException e) {
            mxbeanException = e;
        }
        final String msg =
            "MBean class " + mbeanClass.getName() + " does not implement " +
            "DynamicMBean, neither follows the Standard MBean conventions (" +
            mbeanException.toString() + ") nor the MXBean conventions (" +
            mxbeanException.toString() + ")";
        throw new NotCompliantMBeanException(msg);
    }

    public static DynamicMBean makeDynamicMBean(Object mbean)
        throws NotCompliantMBeanException {
        if (mbean instanceof DynamicMBean)
            return (DynamicMBean) mbean;
        final Class mbeanClass = mbean.getClass();
        Class<?> c = null;
        try {
            c = getStandardMBeanInterface(mbeanClass);
        } catch (NotCompliantMBeanException e) {
            // Ignore exception - we need to check whether
            // mbean is an MXBean first.
        }
        if (c != null)
            return new StandardMBeanSupport(mbean, Util.<Class<Object>>cast(c));

        try {
            c = getMXBeanInterface(mbeanClass);
        } catch (NotCompliantMBeanException e) {
            // Ignore exception - we cannot decide whether mbean was supposed
            // to be an MBean or an MXBean. We will call checkCompliance()
            // to generate the appropriate exception.
        }
        if (c != null)
            return new MXBeanSupport(mbean, Util.<Class<Object>>cast(c));
        checkCompliance(mbeanClass);
        throw new NotCompliantMBeanException("Not compliant"); // not reached
    }

    /**
     * Basic method for testing if a given class is a JMX compliant MBean.
     *
     * @param baseClass The class to be tested
     *
     * @return <code>null</code> if the MBean is a DynamicMBean,
     *         the computed {@link javax.management.MBeanInfo} otherwise.
     * @exception NotCompliantMBeanException The specified class is not a
     *            JMX compliant MBean
     */
    public static MBeanInfo testCompliance(Class baseClass)
        throws NotCompliantMBeanException {

        // ------------------------------
        // ------------------------------

        // Check if the MBean implements the MBean or the Dynamic
        // MBean interface
        if (isDynamic(baseClass))
            return null;

        return testCompliance(baseClass, null);
    }

    public static void testComplianceMXBeanInterface(Class interfaceClass)
            throws NotCompliantMBeanException {
        MXBeanIntrospector.getInstance().getAnalyzer(interfaceClass);
    }

    /**
     * Basic method for testing if a given class is a JMX compliant
     * Standard MBean.  This method is only called by the legacy code
     * in com.sun.management.jmx.
     *
     * @param baseClass The class to be tested.
     *
     * @param mbeanInterface the MBean interface that the class implements,
     * or null if the interface must be determined by introspection.
     *
     * @return the computed {@link javax.management.MBeanInfo}.
     * @exception NotCompliantMBeanException The specified class is not a
     *            JMX compliant Standard MBean
     */
    public static synchronized MBeanInfo
            testCompliance(final Class<?> baseClass,
                           Class<?> mbeanInterface)
            throws NotCompliantMBeanException {
        if (mbeanInterface == null)
            mbeanInterface = getStandardMBeanInterface(baseClass);
        MBeanIntrospector<?> introspector = StandardMBeanIntrospector.getInstance();
        return getClassMBeanInfo(introspector, baseClass, mbeanInterface);
    }

    private static <M> MBeanInfo
            getClassMBeanInfo(MBeanIntrospector<M> introspector,
                              Class<?> baseClass, Class<?> mbeanInterface)
    throws NotCompliantMBeanException {
        PerInterface<M> perInterface = introspector.getPerInterface(mbeanInterface);
        return introspector.getClassMBeanInfo(baseClass, perInterface);
    }

    /**
     * Get the MBean interface implemented by a JMX Standard
     * MBean class. This method is only called by the legacy
     * code in "com.sun.management.jmx".
     *
     * @param baseClass The class to be tested.
     *
     * @return The MBean interface implemented by the MBean.
     *         Return <code>null</code> if the MBean is a DynamicMBean,
     *         or if no MBean interface is found.
     */
    public static Class getMBeanInterface(Class baseClass) {
        // Check if the given class implements the MBean interface
        // or the Dynamic MBean interface
        if (isDynamic(baseClass)) return null;
        try {
            return getStandardMBeanInterface(baseClass);
        } catch (NotCompliantMBeanException e) {
            return null;
        }
    }

    /**
     * Get the MBean interface implemented by a JMX Standard MBean class.
     *
     * @param baseClass The class to be tested.
     *
     * @return The MBean interface implemented by the Standard MBean.
     *
     * @throws NotCompliantMBeanException The specified class is
     * not a JMX compliant Standard MBean.
     */
    public static Class getStandardMBeanInterface(Class baseClass)
        throws NotCompliantMBeanException {
        Class current = baseClass;
        Class mbeanInterface = null;
        while (current != null) {
            mbeanInterface =
                findMBeanInterface(current, current.getName());
            if (mbeanInterface != null) break;
            current = current.getSuperclass();
        }
        if (mbeanInterface != null) {
            return mbeanInterface;
        } else {
            final String msg =
                "Class " + baseClass.getName() +
                " is not a JMX compliant Standard MBean";
            throw new NotCompliantMBeanException(msg);
        }
    }

    /**
     * Get the MXBean interface implemented by a JMX MXBean class.
     *
     * @param baseClass The class to be tested.
     *
     * @return The MXBean interface implemented by the MXBean.
     *
     * @throws NotCompliantMBeanException The specified class is
     * not a JMX compliant MXBean.
     */
    public static Class getMXBeanInterface(Class baseClass)
        throws NotCompliantMBeanException {
        try {
            return MXBeanSupport.findMXBeanInterface(baseClass);
        } catch (Exception e) {
            throw throwException(baseClass,e);
        }
    }

    /*
     * ------------------------------------------
     *  PRIVATE METHODS
     * ------------------------------------------
     */


    /**
     * Try to find the MBean interface corresponding to the class aName
     * - i.e. <i>aName</i>MBean, from within aClass and its superclasses.
     **/
    private static Class findMBeanInterface(Class aClass, String aName) {
        Class current = aClass;
        while (current != null) {
            final Class[] interfaces = current.getInterfaces();
            final int len = interfaces.length;
            for (int i=0;i<len;i++)  {
                final Class inter =
                    implementsMBean(interfaces[i], aName);
                if (inter != null) return inter;
            }
            current = current.getSuperclass();
        }
        return null;
    }

    public static Descriptor descriptorForElement(final AnnotatedElement elmt) {
        if (elmt == null)
            return ImmutableDescriptor.EMPTY_DESCRIPTOR;
        final Annotation[] annots = elmt.getAnnotations();
        return descriptorForAnnotations(annots);
    }

    public static Descriptor descriptorForAnnotations(Annotation[] annots) {
        if (annots.length == 0)
            return ImmutableDescriptor.EMPTY_DESCRIPTOR;
        Map<String, Object> descriptorMap = new HashMap<String, Object>();
        for (Annotation a : annots) {
            Class<? extends Annotation> c = a.annotationType();
            Method[] elements = c.getMethods();
            for (Method element : elements) {
                DescriptorKey key = element.getAnnotation(DescriptorKey.class);
                if (key != null) {
                    String name = key.value();
                    Object value;
                    try {
                        value = element.invoke(a);
                    } catch (RuntimeException e) {
                        // we don't expect this - except for possibly
                        // security exceptions?
                        // RuntimeExceptions shouldn't be "UndeclaredThrowable".
                        // anyway...
                        //
                        throw e;
                    } catch (Exception e) {
                        // we don't expect this
                        throw new UndeclaredThrowableException(e);
                    }
                    value = annotationToField(value);
                    Object oldValue = descriptorMap.put(name, value);
                    if (oldValue != null && !equals(oldValue, value)) {
                        final String msg =
                            "Inconsistent values for descriptor field " + name +
                            " from annotations: " + value + " :: " + oldValue;
                        throw new IllegalArgumentException(msg);
                    }
                }
            }
        }

        if (descriptorMap.isEmpty())
            return ImmutableDescriptor.EMPTY_DESCRIPTOR;
        else
            return new ImmutableDescriptor(descriptorMap);
    }

    /**
     * Throws a NotCompliantMBeanException or a SecurityException.
     * @param notCompliant the class which was under examination
     * @param cause the raeson why NotCompliantMBeanException should
     *        be thrown.
     * @return nothing - this method always throw an exception.
     *         The return type makes it possible to write
     *         <pre> throw throwException(clazz,cause); </pre>
     * @throws SecurityException - if cause is a SecurityException
     * @throws NotCompliantMBeanException otherwise.
     **/
    static NotCompliantMBeanException throwException(Class<?> notCompliant,
            Throwable cause)
            throws NotCompliantMBeanException, SecurityException {
        if (cause instanceof SecurityException)
            throw (SecurityException) cause;
        if (cause instanceof NotCompliantMBeanException)
            throw (NotCompliantMBeanException)cause;
        final String classname =
                (notCompliant==null)?"null class":notCompliant.getName();
        final String reason =
                (cause==null)?"Not compliant":cause.getMessage();
        final NotCompliantMBeanException res =
                new NotCompliantMBeanException(classname+": "+reason);
        res.initCause(cause);
        throw res;
    }

    // Convert a value from an annotation element to a descriptor field value
    // E.g. with @interface Foo {class value()} an annotation @Foo(String.class)
    // will produce a Descriptor field value "java.lang.String"
    private static Object annotationToField(Object x) {
        // An annotation element cannot have a null value but never mind
        if (x == null)
            return null;
        if (x instanceof Number || x instanceof String ||
                x instanceof Character || x instanceof Boolean ||
                x instanceof String[])
            return x;
        // Remaining possibilities: array of primitive (e.g. int[]),
        // enum, class, array of enum or class.
        Class<?> c = x.getClass();
        if (c.isArray()) {
            if (c.getComponentType().isPrimitive())
                return x;
            Object[] xx = (Object[]) x;
            String[] ss = new String[xx.length];
            for (int i = 0; i < xx.length; i++)
                ss[i] = (String) annotationToField(xx[i]);
            return ss;
        }
        if (x instanceof Class)
            return ((Class<?>) x).getName();
        if (x instanceof Enum)
            return ((Enum) x).name();
        // The only other possibility is that the value is another
        // annotation, or that the language has evolved since this code
        // was written.  We don't allow for either of those currently.
        throw new IllegalArgumentException("Illegal type for annotation " +
                "element: " + x.getClass().getName());
    }

    // This must be consistent with the check for duplicate field values in
    // ImmutableDescriptor.union.  But we don't expect to be called very
    // often so this inefficient check should be enough.
    private static boolean equals(Object x, Object y) {
        return Arrays.deepEquals(new Object[] {x}, new Object[] {y});
    }

    /**
     * Returns the XXMBean interface or null if no such interface exists
     *
     * @param c The interface to be tested
     * @param clName The name of the class implementing this interface
     */
    private static Class implementsMBean(Class c, String clName) {
        String clMBeanName = clName + "MBean";
        if (c.getName().equals(clMBeanName)) {
            return c;
        }
        Class[] interfaces = c.getInterfaces();
        for (int i = 0;i < interfaces.length; i++) {
            if (interfaces[i].getName().equals(clMBeanName))
                return interfaces[i];
        }

        return null;
    }
}