/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.cassandra.cql3.functions;

import java.lang.management.ManagementFactory;
import java.lang.management.ThreadMXBean;
import java.net.InetAddress;
import java.net.URL;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Enumeration;
import java.util.HashSet;
import java.util.List;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

import com.google.common.base.Objects;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.datastax.driver.core.DataType;
import com.datastax.driver.core.TypeCodec;
import com.datastax.driver.core.UserType;
import org.apache.cassandra.config.Config;
import org.apache.cassandra.config.DatabaseDescriptor;
import org.apache.cassandra.config.Schema;
import org.apache.cassandra.cql3.ColumnIdentifier;
import org.apache.cassandra.db.marshal.AbstractType;
import org.apache.cassandra.exceptions.FunctionExecutionException;
import org.apache.cassandra.exceptions.InvalidRequestException;
import org.apache.cassandra.schema.Functions;
import org.apache.cassandra.schema.KeyspaceMetadata;
import org.apache.cassandra.service.ClientWarn;
import org.apache.cassandra.service.MigrationManager;
import org.apache.cassandra.tracing.Tracing;
import org.apache.cassandra.transport.ProtocolVersion;
import org.apache.cassandra.utils.ByteBufferUtil;
import org.apache.cassandra.utils.JVMStabilityInspector;

Base class for User Defined Functions.
/**
 * Base class for User Defined Functions.
 */
public abstract class UDFunction extends AbstractFunction implements ScalarFunction
{
    protected static final Logger logger = LoggerFactory.getLogger(UDFunction.class);

    static final ThreadMXBean threadMXBean = ManagementFactory.getThreadMXBean();

    protected final List<ColumnIdentifier> argNames;

    protected final String language;
    protected final String body;

    protected final TypeCodec<Object>[] argCodecs;
    protected final TypeCodec<Object> returnCodec;
    protected final boolean calledOnNullInput;

    protected final UDFContext udfContext;

    //
    // Access to classes is controlled via a whitelist and a blacklist.
    //
    // When a class is requested (both during compilation and runtime),
    // the whitelistedPatterns array is searched first, whether the
    // requested name matches one of the patterns. If not, nothing is
    // returned from the class-loader - meaning ClassNotFoundException
    // during runtime and "type could not resolved" during compilation.
    //
    // If a whitelisted pattern has been found, the blacklistedPatterns
    // array is searched for a match. If a match is found, class-loader
    // rejects access. Otherwise the class/resource can be loaded.
    //
    private static final String[] whitelistedPatterns =
    {
    "com/datastax/driver/core/",
    "com/google/common/reflect/TypeToken",
    "java/io/IOException.class",
    "java/io/Serializable.class",
    "java/lang/",
    "java/math/",
    "java/net/InetAddress.class",
    "java/net/Inet4Address.class",
    "java/net/Inet6Address.class",
    "java/net/UnknownHostException.class", // req'd by InetAddress
    "java/net/NetworkInterface.class", // req'd by InetAddress
    "java/net/SocketException.class", // req'd by InetAddress
    "java/nio/Buffer.class",
    "java/nio/ByteBuffer.class",
    "java/text/",
    "java/time/",
    "java/util/",
    "org/apache/cassandra/cql3/functions/JavaUDF.class",
    "org/apache/cassandra/cql3/functions/UDFContext.class",
    "org/apache/cassandra/exceptions/",
    "org/apache/cassandra/transport/ProtocolVersion.class"
    };
    // Only need to blacklist a pattern, if it would otherwise be allowed via whitelistedPatterns
    private static final String[] blacklistedPatterns =
    {
    "com/datastax/driver/core/Cluster.class",
    "com/datastax/driver/core/Metrics.class",
    "com/datastax/driver/core/NettyOptions.class",
    "com/datastax/driver/core/Session.class",
    "com/datastax/driver/core/Statement.class",
    "com/datastax/driver/core/TimestampGenerator.class", // indirectly covers ServerSideTimestampGenerator + ThreadLocalMonotonicTimestampGenerator
    "java/lang/Compiler.class",
    "java/lang/InheritableThreadLocal.class",
    "java/lang/Package.class",
    "java/lang/Process.class",
    "java/lang/ProcessBuilder.class",
    "java/lang/ProcessEnvironment.class",
    "java/lang/ProcessImpl.class",
    "java/lang/Runnable.class",
    "java/lang/Runtime.class",
    "java/lang/Shutdown.class",
    "java/lang/Thread.class",
    "java/lang/ThreadGroup.class",
    "java/lang/ThreadLocal.class",
    "java/lang/instrument/",
    "java/lang/invoke/",
    "java/lang/management/",
    "java/lang/ref/",
    "java/lang/reflect/",
    "java/util/ServiceLoader.class",
    "java/util/Timer.class",
    "java/util/concurrent/",
    "java/util/function/",
    "java/util/jar/",
    "java/util/logging/",
    "java/util/prefs/",
    "java/util/spi/",
    "java/util/stream/",
    "java/util/zip/",
    };

    static boolean secureResource(String resource)
    {
        while (resource.startsWith("/"))
            resource = resource.substring(1);

        for (String white : whitelistedPatterns)
            if (resource.startsWith(white))
            {

                // resource is in whitelistedPatterns, let's see if it is not explicityl blacklisted
                for (String black : blacklistedPatterns)
                    if (resource.startsWith(black))
                    {
                        logger.trace("access denied: resource {}", resource);
                        return false;
                    }

                return true;
            }

        logger.trace("access denied: resource {}", resource);
        return false;
    }

    // setup the UDF class loader with no parent class loader so that we have full control about what class/resource UDF uses
    static final ClassLoader udfClassLoader = new UDFClassLoader();

    protected UDFunction(FunctionName name,
                         List<ColumnIdentifier> argNames,
                         List<AbstractType<?>> argTypes,
                         AbstractType<?> returnType,
                         boolean calledOnNullInput,
                         String language,
                         String body)
    {
        this(name, argNames, argTypes, UDHelper.driverTypes(argTypes), returnType,
             UDHelper.driverType(returnType), calledOnNullInput, language, body);
    }

    protected UDFunction(FunctionName name,
                         List<ColumnIdentifier> argNames,
                         List<AbstractType<?>> argTypes,
                         DataType[] argDataTypes,
                         AbstractType<?> returnType,
                         DataType returnDataType,
                         boolean calledOnNullInput,
                         String language,
                         String body)
    {
        super(name, argTypes, returnType);
        assert new HashSet<>(argNames).size() == argNames.size() : "duplicate argument names";
        this.argNames = argNames;
        this.language = language;
        this.body = body;
        this.argCodecs = UDHelper.codecsFor(argDataTypes);
        this.returnCodec = UDHelper.codecFor(returnDataType);
        this.calledOnNullInput = calledOnNullInput;
        KeyspaceMetadata keyspaceMetadata = Schema.instance.getKSMetaData(name.keyspace);
        this.udfContext = new UDFContextImpl(argNames, argCodecs, returnCodec,
                                             keyspaceMetadata);
    }

    public static UDFunction create(FunctionName name,
                                    List<ColumnIdentifier> argNames,
                                    List<AbstractType<?>> argTypes,
                                    AbstractType<?> returnType,
                                    boolean calledOnNullInput,
                                    String language,
                                    String body)
    {
        UDFunction.assertUdfsEnabled(language);

        switch (language)
        {
            case "java":
                return new JavaBasedUDFunction(name, argNames, argTypes, returnType, calledOnNullInput, body);
            default:
                return new ScriptBasedUDFunction(name, argNames, argTypes, returnType, calledOnNullInput, language, body);
        }
    }

    
It can happen that a function has been declared (is listed in the scheam) but cannot
be loaded (maybe only on some nodes). This is the case for instance if the class defining
the class is not on the classpath for some of the node, or after a restart. In that case,
we create a "fake" function so that:
 1) the broken function can be dropped easily if that is what people want to do.
 2) we return a meaningful error message if the function is executed (something more precise
    than saying that the function doesn't exist)
/**
     * It can happen that a function has been declared (is listed in the scheam) but cannot
     * be loaded (maybe only on some nodes). This is the case for instance if the class defining
     * the class is not on the classpath for some of the node, or after a restart. In that case,
     * we create a "fake" function so that:
     *  1) the broken function can be dropped easily if that is what people want to do.
     *  2) we return a meaningful error message if the function is executed (something more precise
     *     than saying that the function doesn't exist)
     */
    public static UDFunction createBrokenFunction(FunctionName name,
                                                  List<ColumnIdentifier> argNames,
                                                  List<AbstractType<?>> argTypes,
                                                  AbstractType<?> returnType,
                                                  boolean calledOnNullInput,
                                                  String language,
                                                  String body,
                                                  InvalidRequestException reason)
    {
        return new UDFunction(name, argNames, argTypes, returnType, calledOnNullInput, language, body)
        {
            protected ExecutorService executor()
            {
                return Executors.newSingleThreadExecutor();
            }

            protected Object executeAggregateUserDefined(ProtocolVersion protocolVersion, Object firstParam, List<ByteBuffer> parameters)
            {
                throw broken();
            }

            public ByteBuffer executeUserDefined(ProtocolVersion protocolVersion, List<ByteBuffer> parameters)
            {
                throw broken();
            }

            private InvalidRequestException broken()
            {
                return new InvalidRequestException(String.format("Function '%s' exists but hasn't been loaded successfully "
                                                                 + "for the following reason: %s. Please see the server log for details",
                                                                 this,
                                                                 reason.getMessage()));
            }
        };
    }

    public final ByteBuffer execute(ProtocolVersion protocolVersion, List<ByteBuffer> parameters)
    {
        assertUdfsEnabled(language);

        if (!isCallableWrtNullable(parameters))
            return null;

        long tStart = System.nanoTime();
        parameters = makeEmptyParametersNull(parameters);

        try
        {
            // Using async UDF execution is expensive (adds about 100us overhead per invocation on a Core-i7 MBPr).
            ByteBuffer result = DatabaseDescriptor.enableUserDefinedFunctionsThreads()
                                ? executeAsync(protocolVersion, parameters)
                                : executeUserDefined(protocolVersion, parameters);

            Tracing.trace("Executed UDF {} in {}\u03bcs", name(), (System.nanoTime() - tStart) / 1000);
            return result;
        }
        catch (InvalidRequestException e)
        {
            throw e;
        }
        catch (Throwable t)
        {
            logger.trace("Invocation of user-defined function '{}' failed", this, t);
            if (t instanceof VirtualMachineError)
                throw (VirtualMachineError) t;
            throw FunctionExecutionException.create(this, t);
        }
    }

    
Like ScalarFunction.execute(ProtocolVersion, List<ByteBuffer>) but the first parameter is already in non-serialized form. Remaining parameters (2nd paramters and all others) are in parameters. This is used to prevent superfluous (de)serialization of the state of aggregates. Means: scalar functions of aggregates are called using this variant. /**
     * Like {@link ScalarFunction#execute(ProtocolVersion, List)} but the first parameter is already in non-serialized form.
     * Remaining parameters (2nd paramters and all others) are in {@code parameters}.
     * This is used to prevent superfluous (de)serialization of the state of aggregates.
     * Means: scalar functions of aggregates are called using this variant.
     */
    public final Object executeForAggregate(ProtocolVersion protocolVersion, Object firstParam, List<ByteBuffer> parameters)
    {
        assertUdfsEnabled(language);

        if (!calledOnNullInput && firstParam == null || !isCallableWrtNullable(parameters))
            return null;

        long tStart = System.nanoTime();
        parameters = makeEmptyParametersNull(parameters);

        try
        {
            // Using async UDF execution is expensive (adds about 100us overhead per invocation on a Core-i7 MBPr).
            Object result = DatabaseDescriptor.enableUserDefinedFunctionsThreads()
                                ? executeAggregateAsync(protocolVersion, firstParam, parameters)
                                : executeAggregateUserDefined(protocolVersion, firstParam, parameters);
            Tracing.trace("Executed UDF {} in {}\u03bcs", name(), (System.nanoTime() - tStart) / 1000);
            return result;
        }
        catch (InvalidRequestException e)
        {
            throw e;
        }
        catch (Throwable t)
        {
            logger.debug("Invocation of user-defined function '{}' failed", this, t);
            if (t instanceof VirtualMachineError)
                throw (VirtualMachineError) t;
            throw FunctionExecutionException.create(this, t);
        }
    }

    public static void assertUdfsEnabled(String language)
    {
        if (!DatabaseDescriptor.enableUserDefinedFunctions())
            throw new InvalidRequestException("User-defined functions are disabled in cassandra.yaml - set enable_user_defined_functions=true to enable");
        if (!"java".equalsIgnoreCase(language) && !DatabaseDescriptor.enableScriptedUserDefinedFunctions())
            throw new InvalidRequestException("Scripted user-defined functions are disabled in cassandra.yaml - set enable_scripted_user_defined_functions=true to enable if you are aware of the security risks");
    }

    static void initializeThread()
    {
        // Get the TypeCodec stuff in Java Driver initialized.
        // This is to get the classes loaded outside of the restricted sandbox's security context of a UDF.
        TypeCodec.inet().format(InetAddress.getLoopbackAddress());
        TypeCodec.ascii().format("");
    }

    private static final class ThreadIdAndCpuTime extends CompletableFuture<Object>
    {
        long threadId;
        long cpuTime;

        ThreadIdAndCpuTime()
        {
            // Looks weird?
            // This call "just" links this class to java.lang.management - otherwise UDFs (script UDFs) might fail due to
            //      java.security.AccessControlException: access denied: ("java.lang.RuntimePermission" "accessClassInPackage.java.lang.management")
            // because class loading would be deferred until setup() is executed - but setup() is called with
            // limited privileges.
            threadMXBean.getCurrentThreadCpuTime();
        }

        void setup()
        {
            this.threadId = Thread.currentThread().getId();
            this.cpuTime = threadMXBean.getCurrentThreadCpuTime();
            complete(null);
        }
    }

    private ByteBuffer executeAsync(ProtocolVersion protocolVersion, List<ByteBuffer> parameters)
    {
        ThreadIdAndCpuTime threadIdAndCpuTime = new ThreadIdAndCpuTime();

        return async(threadIdAndCpuTime, () -> {
            threadIdAndCpuTime.setup();
            return executeUserDefined(protocolVersion, parameters);
        });
    }

    
Like executeAsync(ProtocolVersion, List<ByteBuffer>) but the first parameter is already in non-serialized form. Remaining parameters (2nd paramters and all others) are in parameters. This is used to prevent superfluous (de)serialization of the state of aggregates. Means: scalar functions of aggregates are called using this variant. /**
     * Like {@link #executeAsync(int, List)} but the first parameter is already in non-serialized form.
     * Remaining parameters (2nd paramters and all others) are in {@code parameters}.
     * This is used to prevent superfluous (de)serialization of the state of aggregates.
     * Means: scalar functions of aggregates are called using this variant.
     */
    private Object executeAggregateAsync(ProtocolVersion protocolVersion, Object firstParam, List<ByteBuffer> parameters)
    {
        ThreadIdAndCpuTime threadIdAndCpuTime = new ThreadIdAndCpuTime();

        return async(threadIdAndCpuTime, () -> {
            threadIdAndCpuTime.setup();
            return executeAggregateUserDefined(protocolVersion, firstParam, parameters);
        });
    }

    private <T> T async(ThreadIdAndCpuTime threadIdAndCpuTime, Callable<T> callable)
    {
        Future<T> future = executor().submit(callable);

        try
        {
            if (DatabaseDescriptor.getUserDefinedFunctionWarnTimeout() > 0)
                try
                {
                    return future.get(DatabaseDescriptor.getUserDefinedFunctionWarnTimeout(), TimeUnit.MILLISECONDS);
                }
                catch (TimeoutException e)
                {

                    // log and emit a warning that UDF execution took long
                    String warn = String.format("User defined function %s ran longer than %dms", this, DatabaseDescriptor.getUserDefinedFunctionWarnTimeout());
                    logger.warn(warn);
                    ClientWarn.instance.warn(warn);
                }

            // retry with difference of warn-timeout to fail-timeout
            return future.get(DatabaseDescriptor.getUserDefinedFunctionFailTimeout() - DatabaseDescriptor.getUserDefinedFunctionWarnTimeout(), TimeUnit.MILLISECONDS);
        }
        catch (InterruptedException e)
        {
            Thread.currentThread().interrupt();
            throw new RuntimeException(e);
        }
        catch (ExecutionException e)
        {
            Throwable c = e.getCause();
            if (c instanceof RuntimeException)
                throw (RuntimeException) c;
            throw new RuntimeException(c);
        }
        catch (TimeoutException e)
        {
            // retry a last time with the difference of UDF-fail-timeout to consumed CPU time (just in case execution hit a badly timed GC)
            try
            {
                //The threadIdAndCpuTime shouldn't take a long time to be set so this should return immediately
                threadIdAndCpuTime.get(1, TimeUnit.SECONDS);

                long cpuTimeMillis = threadMXBean.getThreadCpuTime(threadIdAndCpuTime.threadId) - threadIdAndCpuTime.cpuTime;
                cpuTimeMillis /= 1000000L;

                return future.get(Math.max(DatabaseDescriptor.getUserDefinedFunctionFailTimeout() - cpuTimeMillis, 0L),
                                  TimeUnit.MILLISECONDS);
            }
            catch (InterruptedException e1)
            {
                Thread.currentThread().interrupt();
                throw new RuntimeException(e);
            }
            catch (ExecutionException e1)
            {
                Throwable c = e.getCause();
                if (c instanceof RuntimeException)
                    throw (RuntimeException) c;
                throw new RuntimeException(c);
            }
            catch (TimeoutException e1)
            {
                TimeoutException cause = new TimeoutException(String.format("User defined function %s ran longer than %dms%s",
                                                                            this,
                                                                            DatabaseDescriptor.getUserDefinedFunctionFailTimeout(),
                                                                            DatabaseDescriptor.getUserFunctionTimeoutPolicy() == Config.UserFunctionTimeoutPolicy.ignore
                                                                            ? "" : " - will stop Cassandra VM"));
                FunctionExecutionException fe = FunctionExecutionException.create(this, cause);
                JVMStabilityInspector.userFunctionTimeout(cause);
                throw fe;
            }
        }
    }

    private List<ByteBuffer> makeEmptyParametersNull(List<ByteBuffer> parameters)
    {
        List<ByteBuffer> r = new ArrayList<>(parameters.size());
        for (int i = 0; i < parameters.size(); i++)
        {
            ByteBuffer param = parameters.get(i);
            r.add(UDHelper.isNullOrEmpty(argTypes.get(i), param)
                  ? null : param);
        }
        return r;
    }

    protected abstract ExecutorService executor();

    public boolean isCallableWrtNullable(List<ByteBuffer> parameters)
    {
        if (!calledOnNullInput)
            for (int i = 0; i < parameters.size(); i++)
                if (UDHelper.isNullOrEmpty(argTypes.get(i), parameters.get(i)))
                    return false;
        return true;
    }

    protected abstract ByteBuffer executeUserDefined(ProtocolVersion protocolVersion, List<ByteBuffer> parameters);

    protected abstract Object executeAggregateUserDefined(ProtocolVersion protocolVersion, Object firstParam, List<ByteBuffer> parameters);

    public boolean isAggregate()
    {
        return false;
    }

    public boolean isNative()
    {
        return false;
    }

    public boolean isCalledOnNullInput()
    {
        return calledOnNullInput;
    }

    public List<ColumnIdentifier> argNames()
    {
        return argNames;
    }

    public String body()
    {
        return body;
    }

    public String language()
    {
        return language;
    }

    
Used by UDF implementations (both Java code generated by JavaBasedUDFunction and script executor ScriptBasedUDFunction) to convert the C* serialized representation to the Java object representation. 
Params:
protocolVersion – the native protocol version used for serialization
argIndex –        index of the UDF input argument/**
     * Used by UDF implementations (both Java code generated by {@link JavaBasedUDFunction}
     * and script executor {@link ScriptBasedUDFunction}) to convert the C*
     * serialized representation to the Java object representation.
     *
     * @param protocolVersion the native protocol version used for serialization
     * @param argIndex        index of the UDF input argument
     */
    protected Object compose(ProtocolVersion protocolVersion, int argIndex, ByteBuffer value)
    {
        return compose(argCodecs, protocolVersion, argIndex, value);
    }

    protected static Object compose(TypeCodec<Object>[] codecs, ProtocolVersion protocolVersion, int argIndex, ByteBuffer value)
    {
        return value == null ? null : UDHelper.deserialize(codecs[argIndex], protocolVersion, value);
    }

    
Used by UDF implementations (both Java code generated by JavaBasedUDFunction and script executor ScriptBasedUDFunction) to convert the Java object representation for the return value to the C* serialized representation. 
Params:
protocolVersion – the native protocol version used for serialization/**
     * Used by UDF implementations (both Java code generated by {@link JavaBasedUDFunction}
     * and script executor {@link ScriptBasedUDFunction}) to convert the Java
     * object representation for the return value to the C* serialized representation.
     *
     * @param protocolVersion the native protocol version used for serialization
     */
    protected ByteBuffer decompose(ProtocolVersion protocolVersion, Object value)
    {
        return decompose(returnCodec, protocolVersion, value);
    }

    protected static ByteBuffer decompose(TypeCodec<Object> codec, ProtocolVersion protocolVersion, Object value)
    {
        return value == null ? null : UDHelper.serialize(codec, protocolVersion, value);
    }

    @Override
    public boolean equals(Object o)
    {
        if (!(o instanceof UDFunction))
            return false;

        UDFunction that = (UDFunction)o;
        return Objects.equal(name, that.name)
            && Objects.equal(argNames, that.argNames)
            && Functions.typesMatch(argTypes, that.argTypes)
            && Functions.typesMatch(returnType, that.returnType)
            && Objects.equal(language, that.language)
            && Objects.equal(body, that.body);
    }

    @Override
    public int hashCode()
    {
        return Objects.hashCode(name, Functions.typeHashCode(argTypes), Functions.typeHashCode(returnType), returnType, language, body);
    }

    public void userTypeUpdated(String ksName, String typeName)
    {
        boolean updated = false;

        for (int i = 0; i < argCodecs.length; i++)
        {
            DataType dataType = argCodecs[i].getCqlType();
            if (dataType instanceof UserType)
            {
                UserType userType = (UserType) dataType;
                if (userType.getKeyspace().equals(ksName) && userType.getTypeName().equals(typeName))
                {
                    KeyspaceMetadata ksm = Schema.instance.getKSMetaData(ksName);
                    assert ksm != null;

                    org.apache.cassandra.db.marshal.UserType ut = ksm.types.get(ByteBufferUtil.bytes(typeName)).get();

                    DataType newUserType = UDHelper.driverType(ut);
                    argCodecs[i] = UDHelper.codecFor(newUserType);

                    argTypes.set(i, ut);

                    updated = true;
                }
            }
        }

        if (updated)
            MigrationManager.announceNewFunction(this, true);
    }

    private static class UDFClassLoader extends ClassLoader
    {
        // insecureClassLoader is the C* class loader
        static final ClassLoader insecureClassLoader = Thread.currentThread().getContextClassLoader();

        public URL getResource(String name)
        {
            if (!secureResource(name))
                return null;
            return insecureClassLoader.getResource(name);
        }

        protected URL findResource(String name)
        {
            return getResource(name);
        }

        public Enumeration<URL> getResources(String name)
        {
            return Collections.emptyEnumeration();
        }

        protected Class<?> findClass(String name) throws ClassNotFoundException
        {
            if (!secureResource(name.replace('.', '/') + ".class"))
                throw new ClassNotFoundException(name);
            return insecureClassLoader.loadClass(name);
        }

        public Class<?> loadClass(String name) throws ClassNotFoundException
        {
            if (!secureResource(name.replace('.', '/') + ".class"))
                throw new ClassNotFoundException(name);
            return super.loadClass(name);
        }
    }
}