driver-mapping/src/main/java/com/datastax/driver/mapping/ReflectionMapper.java

/*
 *      Copyright (C) 2012-2015 DataStax Inc.
 *
 *   Licensed 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 com.datastax.driver.mapping;

import java.beans.IntrospectionException;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.atomic.AtomicInteger;

import com.google.common.reflect.TypeToken;

import com.datastax.driver.core.ConsistencyLevel;

/**
 * An {@link EntityMapper} implementation that use reflection to read and write fields
 * of an entity.
 */
class ReflectionMapper<T> extends EntityMapper<T> {

    private static ReflectionFactory factory = new ReflectionFactory();

    private ReflectionMapper(Class<T> entityClass, String keyspace, String table, ConsistencyLevel writeConsistency, ConsistencyLevel readConsistency) {
        super(entityClass, keyspace, table, writeConsistency, readConsistency);
    }

    public static Factory factory() {
        return factory;
    }

    @Override
    public T newEntity() {
        try {
            return entityClass.newInstance();
        } catch (Exception e) {
            throw new RuntimeException("Can't create an instance of " + entityClass.getName());
        }
    }

    private static class LiteralMapper<T> extends ColumnMapper<T> {

        private final Method readMethod;
        private final Method writeMethod;

        private LiteralMapper(Field field, int position, PropertyDescriptor pd, AtomicInteger columnCounter) {
            super(field, position, columnCounter);
            this.readMethod = pd.getReadMethod();
            this.writeMethod = pd.getWriteMethod();
        }

        @Override
        public Object getValue(T entity) {
            try {
                return readMethod.invoke(entity);
            } catch (IllegalArgumentException e) {
                throw new IllegalArgumentException("Could not get field '" + fieldName + "'");
            } catch (Exception e) {
                throw new IllegalStateException("Unable to access getter for '" + fieldName + "' in " + entity.getClass().getName(), e);
            }
        }

        @Override
        public void setValue(Object entity, Object value) {
            try {
                writeMethod.invoke(entity, value);
            } catch (IllegalArgumentException e) {
                throw new IllegalArgumentException("Could not set field '" + fieldName + "' to value '" + value + "'");
            } catch (Exception e) {
                throw new IllegalStateException("Unable to access setter for '" + fieldName + "' in " + entity.getClass().getName(), e);
            }
        }
    }

    private static class EnumMapper<T> extends LiteralMapper<T> {

        private final EnumType enumType;
        private final Map<String, Object> fromString;

        private EnumMapper(Field field, int position, PropertyDescriptor pd, EnumType enumType, AtomicInteger columnCounter) {
            super(field, position, pd, columnCounter);
            this.enumType = enumType;

            if (enumType == EnumType.STRING) {
                fromString = new HashMap<String, Object>(fieldType.getRawType().getEnumConstants().length);
                for (Object constant : fieldType.getRawType().getEnumConstants())
                    fromString.put(constant.toString().toLowerCase(), constant);

            } else {
                fromString = null;
            }
        }

        @SuppressWarnings("rawtypes")
        @Override
        public Object getValue(T entity) {
            Object value = super.getValue(entity);
            switch (enumType) {
                case STRING:
                    return (value == null) ? null : value.toString();
                case ORDINAL:
                    return (value == null) ? null : ((Enum)value).ordinal();
            }
            throw new AssertionError();
        }

        @Override
        public void setValue(Object entity, Object value) {
            Object converted = null;
            switch (enumType) {
                case STRING:
                    converted = fromString.get(value.toString().toLowerCase());
                    break;
                case ORDINAL:
                    converted = fieldType.getRawType().getEnumConstants()[(Integer)value];
                    break;
            }
            super.setValue(entity, converted);
        }

        @Override
        public TypeToken<Object> getPivotType() {
            return enumType.pivotType;
        }
    }

    private static class ReflectionFactory implements Factory {

        public <T> EntityMapper<T> create(Class<T> entityClass, String keyspace, String table, ConsistencyLevel writeConsistency, ConsistencyLevel readConsistency) {
            return new ReflectionMapper<T>(entityClass, keyspace, table, writeConsistency, readConsistency);
        }

        @SuppressWarnings({ "unchecked", "rawtypes" })
        public <T> ColumnMapper<T> createColumnMapper(Class<T> entityClass, Field field, int position, MappingManager mappingManager, AtomicInteger columnCounter) {
            String fieldName = field.getName();
            try {
                PropertyDescriptor pd = new PropertyDescriptor(fieldName, field.getDeclaringClass());

                if (field.getType().isEnum()) {
                    return new EnumMapper<T>(field, position, pd, AnnotationParser.enumType(field), columnCounter);
                }

                for (Class<?> udt : TypeMappings.findUDTs(field.getGenericType()))
                    mappingManager.getUDTCodec(udt);

                return new LiteralMapper<T>(field, position, pd, columnCounter);

            } catch (IntrospectionException e) {
                throw new IllegalArgumentException("Cannot find matching getter and setter for field '" + fieldName + "'");
            }
        }
    }
}