ExceptionMapperFactory.java

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package org.glassfish.jersey.internal;

import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Proxy;
import java.lang.reflect.Type;
import java.lang.reflect.TypeVariable;
import java.util.Collection;
import java.util.LinkedHashSet;
import java.util.Set;
import java.util.SortedSet;
import java.util.TreeSet;
import java.util.logging.Level;
import java.util.logging.Logger;

import javax.ws.rs.ProcessingException;
import javax.ws.rs.ext.ExceptionMapper;

import org.glassfish.jersey.internal.inject.Bindings;
import org.glassfish.jersey.internal.inject.InjectionManager;
import org.glassfish.jersey.internal.inject.InstanceBinding;
import org.glassfish.jersey.internal.inject.Providers;
import org.glassfish.jersey.internal.inject.ServiceHolder;
import org.glassfish.jersey.internal.util.ReflectionHelper;
import org.glassfish.jersey.internal.util.collection.ClassTypePair;
import org.glassfish.jersey.internal.util.collection.LazyValue;
import org.glassfish.jersey.internal.util.collection.Value;
import org.glassfish.jersey.internal.util.collection.Values;
import org.glassfish.jersey.spi.ExceptionMappers;
import org.glassfish.jersey.spi.ExtendedExceptionMapper;

/**
 * {@link ExceptionMappers Exception mappers} implementation that aggregates
 * exception mappers and server as the main entry point for exception mapper
 * instance lookup.
 *
 * @author Paul Sandoz
 * @author Santiago Pericas-Geertsen (Santiago.PericasGeertsen at oracle.com)
 * @author Marek Potociar (marek.potociar at oracle.com)
 * @author Jakub Podlesak (jakub.podlesak at oracle.com)
 */
public class ExceptionMapperFactory implements ExceptionMappers {

    private static final Logger LOGGER = Logger.getLogger(ExceptionMapperFactory.class.getName());

    /**
     * Configurator which initializes and register {@link ExceptionMappers} instance into {@link InjectionManager} and
     * {@link BootstrapBag}.
     *
     * @author Petr Bouda (petr.bouda at oracle.com)
     */
    public static class ExceptionMappersConfigurator implements BootstrapConfigurator {

        private ExceptionMapperFactory exceptionMapperFactory;

        @Override
        public void init(InjectionManager injectionManager, BootstrapBag bootstrapBag) {
            exceptionMapperFactory = new ExceptionMapperFactory(injectionManager);
            InstanceBinding<ExceptionMapperFactory> binding =
                    Bindings.service(exceptionMapperFactory)
                            .to(ExceptionMappers.class);
            injectionManager.register(binding);
        }

        @Override
        public void postInit(InjectionManager injectionManager, BootstrapBag bootstrapBag) {
            bootstrapBag.setExceptionMappers(exceptionMapperFactory);
        }
    }

    private static class ExceptionMapperType {

        ServiceHolder<ExceptionMapper> mapper;
        Class<? extends Throwable> exceptionType;

        public ExceptionMapperType(final ServiceHolder<ExceptionMapper> mapper, final Class<? extends Throwable> exceptionType) {
            this.mapper = mapper;
            this.exceptionType = exceptionType;
        }
    }

    private final Value<Set<ExceptionMapperType>> exceptionMapperTypes;

    @Override
    @SuppressWarnings("unchecked")
    public <T extends Throwable> ExceptionMapper<T> findMapping(final T exceptionInstance) {
        return find((Class<T>) exceptionInstance.getClass(), exceptionInstance);
    }

    @Override
    public <T extends Throwable> ExceptionMapper<T> find(final Class<T> type) {
        return find(type, null);
    }

    @SuppressWarnings("unchecked")
    private <T extends Throwable> ExceptionMapper<T> find(final Class<T> type, final T exceptionInstance) {
        ExceptionMapper<T> mapper = null;
        int minDistance = Integer.MAX_VALUE;

        for (final ExceptionMapperType mapperType : exceptionMapperTypes.get()) {
            final int d = distance(type, mapperType.exceptionType);
            if (d >= 0 && d <= minDistance) {
                final ExceptionMapper<T> candidate = mapperType.mapper.getInstance();

                if (isPreferredCandidate(exceptionInstance, candidate, d == minDistance)) {
                    mapper = candidate;
                    minDistance = d;
                    if (d == 0) {
                        // slight optimization: if the distance is 0, it is already the best case, so we can exit
                        return mapper;
                    }
                }
            }
        }
        return mapper;
    }

    /**
     * Determines whether the currently considered candidate should be preferred over the previous one.
     *
     * @param exceptionInstance exception to be mapped.
     * @param candidate         mapper able to map given exception type.
     * @param sameDistance      flag indicating whether this and the previously considered candidate are in the same distance.
     * @param <T>               exception type.
     * @return {@code true} if the given candidate is preferred over the previous one with the same or lower distance,
     * {@code false} otherwise.
     */
    private <T extends Throwable> boolean isPreferredCandidate(final T exceptionInstance, final ExceptionMapper<T> candidate,
                                                               final boolean sameDistance) {
        if (exceptionInstance == null) {
            return true;
        }
        if (candidate instanceof ExtendedExceptionMapper) {
            return !sameDistance
                    && ((ExtendedExceptionMapper<T>) candidate).isMappable(exceptionInstance);
        } else {
            return !sameDistance;
        }
    }

    /**
     * Create new exception mapper factory initialized with {@link InjectionManager injection manager}
     * instance that will be used to look up all providers implementing {@link ExceptionMapper} interface.
     *
     * @param injectionManager injection manager.
     */
    public ExceptionMapperFactory(InjectionManager injectionManager) {
        exceptionMapperTypes = createLazyExceptionMappers(injectionManager);
    }

    /**
     * Returns {@link LazyValue} of exception mappers that delays their creation to the first use. The exception mappers won't be
     * created during bootstrap but at the time of the first call.
     *
     * @param injectionManager injection manager that may not be fully populated at the time of a function call therefore the
     *                         result is wrapped to lazy value.
     * @return lazy value of exception mappers.
     */
    private LazyValue<Set<ExceptionMapperType>> createLazyExceptionMappers(InjectionManager injectionManager) {
        return Values.lazy((Value<Set<ExceptionMapperType>>) () -> {
            Collection<ServiceHolder<ExceptionMapper>> mapperHandles =
                    Providers.getAllServiceHolders(injectionManager, ExceptionMapper.class);

            Set<ExceptionMapperType> exceptionMapperTypes = new LinkedHashSet<>();
            for (ServiceHolder<ExceptionMapper> mapperHandle: mapperHandles) {
                ExceptionMapper mapper = mapperHandle.getInstance();

                if (Proxy.isProxyClass(mapper.getClass())) {
                    SortedSet<Class<? extends ExceptionMapper>> mapperTypes =
                            new TreeSet<>((o1, o2) -> o1.isAssignableFrom(o2) ? -1 : 1);

                    Set<Type> contracts = mapperHandle.getContractTypes();
                    for (final Type contract : contracts) {
                        if (contract instanceof Class
                                && ExceptionMapper.class.isAssignableFrom((Class<?>) contract)
                                && contract != ExceptionMapper.class) {
                            //noinspection unchecked
                            mapperTypes.add((Class<? extends ExceptionMapper>) contract);
                        }
                    }

                    if (!mapperTypes.isEmpty()) {
                        final Class<? extends Throwable> c = getExceptionType(mapperTypes.first());
                        if (c != null) {
                            exceptionMapperTypes.add(new ExceptionMapperType(mapperHandle, c));
                        }
                    }
                } else {
                    final Class<? extends Throwable> c = getExceptionType(mapper.getClass());
                    if (c != null) {
                        exceptionMapperTypes.add(new ExceptionMapperType(mapperHandle, c));
                    }
                }
            }
            return exceptionMapperTypes;
        });
    }

    private int distance(Class<?> c, final Class<?> emtc) {
        int distance = 0;
        if (!emtc.isAssignableFrom(c)) {
            return -1;
        }

        while (c != emtc) {
            c = c.getSuperclass();
            distance++;
        }

        return distance;
    }

    @SuppressWarnings("unchecked")
    private Class<? extends Throwable> getExceptionType(final Class<? extends ExceptionMapper> c) {
        final Class<?> t = getType(c);
        if (Throwable.class.isAssignableFrom(t)) {
            return (Class<? extends Throwable>) t;
        }

        if (LOGGER.isLoggable(Level.WARNING)) {
            LOGGER.warning(LocalizationMessages.EXCEPTION_MAPPER_SUPPORTED_TYPE_UNKNOWN(c.getName()));
        }

        return null;
    }

    /**
     * Get exception type for given exception mapper class.
     *
     * @param clazz class to get exception type for.
     * @return exception type for given class.
     */
    private Class getType(final Class<? extends ExceptionMapper> clazz) {
        Class clazzHolder = clazz;

        while (clazzHolder != Object.class) {
            final Class type = getTypeFromInterface(clazzHolder, clazz);
            if (type != null) {
                return type;
            }

            clazzHolder = clazzHolder.getSuperclass();
        }

        throw new ProcessingException(LocalizationMessages.ERROR_FINDING_EXCEPTION_MAPPER_TYPE(clazz));
    }

    /**
     * Iterate through interface hierarchy of {@code clazz} and get exception type for given class.
     *
     * @param clazz class to inspect.
     * @return exception type for given class or {@code null} if the class doesn't implement {@code ExceptionMapper}.
     */
    private Class getTypeFromInterface(Class<?> clazz, final Class<? extends ExceptionMapper> original) {
        final Type[] types = clazz.getGenericInterfaces();

        for (final Type type : types) {
            if (type instanceof ParameterizedType) {
                final ParameterizedType pt = (ParameterizedType) type;
                if (pt.getRawType() == ExceptionMapper.class
                        || pt.getRawType() == ExtendedExceptionMapper.class) {
                    return getResolvedType(pt.getActualTypeArguments()[0], original, clazz);
                }
            } else if (type instanceof Class<?>) {
                clazz = (Class<?>) type;

                if (ExceptionMapper.class.isAssignableFrom(clazz)) {
                    return getTypeFromInterface(clazz, original);
                }
            }
        }

        return null;
    }

    private Class getResolvedType(final Type t, final Class c, final Class dc) {
        if (t instanceof Class) {
            return (Class) t;
        } else if (t instanceof TypeVariable) {
            final ClassTypePair ct = ReflectionHelper.resolveTypeVariable(c, dc, (TypeVariable) t);
            if (ct != null) {
                return ct.rawClass();
            } else {
                return null;
            }
        } else if (t instanceof ParameterizedType) {
            final ParameterizedType pt = (ParameterizedType) t;
            return (Class) pt.getRawType();
        } else {
            return null;
        }
    }
}