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package org.glassfish.enterprise.iiop.util;

import java.lang.reflect.Method;
import java.util.Iterator;
import java.util.Map;
import java.util.ArrayList;
import java.util.HashMap;
import org.glassfish.external.statistics.Stats;
import org.glassfish.external.statistics.Statistic;

/** Provides for generic implementation of any Stats interface. This class facilitates
 * composition over inheritance for all the classes that implement their
 * specific Stats interfaces. None of them has to implement the methods defined
 * by the {@link javax.management.j2ee.statistics.Stats} interface. This class
 * implements the same interface and does that job. All that implementing classes
 * have to do is implement the specific accessing methods in their Stats interfaces
 * and delegate the rest to this class.  This class invokes all these methods in
 * implementing class through introspection. 
 * @author Kedar Mhaswade
 * @since S1AS8.0
 * @version $Version$
 */
public class GenericStatsImpl implements Stats {
    
    private final Class     statsInterface;
    private final Object    statsProvider;
    /** A map with binding of a String XXX to a method with name getXXX */
    private final Map       getters;
    
    /**
     */
    public GenericStatsImpl(String statsInterfaceName, Object statsProvider) 
    throws ClassNotFoundException {
        this(statsInterfaceName, GenericStatsImpl.class.getClassLoader(), statsProvider);
    }
    
    /**
     */
    public GenericStatsImpl(String statsInterfaceName, ClassLoader loader, 
    Object statsProvider) throws ClassNotFoundException {
        this(Class.forName(statsInterfaceName, true, loader), statsProvider);
    }
    
    /** Constructs a new instance of this class for a given interface and its implementation.
     * It is mandatory that following contract is satisfied to call this satisfactorily:
     * 
    *
  • None of the parameters are null.
  • *
  • Given statsProvider implements the given statsInterface.
  • *
  • Given statsInterface has to extend the @{link Stats} interface.
  • *
* Note that it is expected (though not mandatory) to have a getXXX method that * does not return an instance of {@link Statistic} interface. * @throws NullPointerException if any of the given parameters are null * @throws IllegalArgumentException if the contract is not satisfied by given parameters */ public GenericStatsImpl(Class statsInterface, Object statsProvider) { if (!implementsInterface(statsInterface, statsProvider) || ! extendsStatsInterface(statsInterface)) { throw new IllegalArgumentException("Contract violation: invalid interface-implementation pair"); } this.statsProvider = statsProvider; this.statsInterface = statsInterface; this.getters = new HashMap(); populateGetterMap(); } public Statistic getStatistic(String statisticName) { final Method getter = (Method) getters.get(statisticName); assert (getter != null) : ("Getter not initialized properly: " + statisticName); Object result = null; try { result = getter.invoke(statsProvider); } catch(Exception e) { final RuntimeException oe = new IllegalStateException(); oe.initCause(e); throw oe; } return ( (Statistic)result ); } public String[] getStatisticNames() { /* The return array is fixed at the construction time */ final String[] names = new String[getters.size()]; return ( (String[])getters.keySet().toArray(names) ); //TODOOOOOOO } public Statistic[] getStatistics() { return ( getStatisticsOneByOne() ); //invokes sequentially } private Statistic[] getStatisticsOneByOne() { final Iterator iter = getters.keySet().iterator(); final Statistic[] stats = new Statistic[getters.keySet().size()]; int i = 0; while (iter.hasNext()) { final String sn = (String) iter.next(); stats[i++] = this.getStatistic(sn); } assert (stats.length == i); return ( stats ); } private boolean implementsInterface(Class c, Object o) { boolean impls = false; final Class[] interfaces = o.getClass().getInterfaces(); for (int i = 0 ; i < interfaces.length ; i++) { if (interfaces[i].equals(c)){ impls = true; break; } } return ( impls ); } private boolean extendsStatsInterface(Class i) { final Class statInterface = org.glassfish.external.statistics.Stats.class; return ( statInterface.isAssignableFrom(i) ); } private void populateGetterMap() { // Fix for Bugs 5045435, 6172088 //final Method[] apis = statsInterface.getDeclaredMethods(); //all of these should be PUBLIC. final Method[] m = statsInterface.getMethods(); // exclude methods that belong to the javax.management.j2ee.Stats final Method[] apis = filterStatsMethods(m); final Method[] methods = getGetters(apis); final String[] names = methods2Statistics(methods); assert (names.length == methods.length) : ("Statistic names array is not having same length as that of array of getters"); int i; for (i = 0 ; i < names.length ; i++) { getters.put(names[i], methods[i]); } assert (getters.size() == i) : ("Getters map is incorrect, names.length = " + names.length + " methods.length = " + methods.length); } private Method[] getGetters(Method[] all) { final ArrayList l = new ArrayList(); for (int i = 0 ; i < all.length ; i++) { final Method am = all[i]; if (isValidGetter(am)) { l.add(am); } } final Method[] m = new Method[l.size()]; return ( (Method[])l.toArray(m) ); } private boolean isValidGetter(Method m) { final boolean startsWithGet = m.getName().startsWith("get"); final boolean hasNoParams = m.getParameterTypes().length == 0; final boolean returnsStatistic = Statistic.class.isAssignableFrom(m.getReturnType()); return ( startsWithGet && hasNoParams && returnsStatistic ); } private String[] methods2Statistics(Method[] methods) { final String[] names = new String[methods.length]; for (int i = 0 ; i < methods.length ; i++) { final String m = methods[i].getName(); final int s = "get".length(); names[i] = m.substring(s); } return ( names ); } private boolean isStatsInterfaceMethod(String name) { final Method[] methods = org.glassfish.external.statistics.Stats.class.getMethods(); boolean isInterfaceMethod = false; for (int i = 0 ; i < methods.length ; i++) { if (methods[i].getName().equals(name)) { isInterfaceMethod = true; break; } } return ( isInterfaceMethod ); } private Method[] filterStatsMethods(Method[] m) { ArrayList methodList = new ArrayList(); for(int i = 0; i < m.length; i++) { if(! isStatsInterfaceMethod(m[i].getName())) methodList.add(m[i]); } final Method[] methods = new Method[methodList.size()]; return (Method[])methodList.toArray(methods); } }




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