Coercions.java

/*
 * 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.felix.scr.impl.helper;

import java.lang.reflect.Array;
import java.util.Collection;

import org.osgi.framework.Bundle;
import org.osgi.service.component.ComponentException;

/**
 * This implements the coercion table in RFC 190 5.6.3 
 *
 */
public class Coercions
{
    // Numbers are   AtomicInteger, AtomicLong, BigDecimal, BigInteger, Byte, Double, Float, Integer, Long, Short
    //annotation fields can be primitives, String, Class, enums, annotations, and arrays of the preceding types 
    //    input scalars
    //    String | Integer | Long | Float
    //    | Double | Byte | Short
    //| Character | Boolean
    private static final byte byte0 = 0;
    private static final char char0 = 0;
    private static final double double0 = 0;
    private static final float float0 = 0;
    private static final int int0 = 0;
    private static final long long0 = 0;
    private static final short short0 = 0;

    public static Object coerce(Class<?> type, Object raw, Bundle bundle)
    {
        if ( type == Byte.class || type == byte.class )
        {
            return coerceToByte( raw );
        }
        if ( type == Boolean.class || type == boolean.class )
        {
            return coerceToBoolean( raw );
        }
        if ( type == Character.class || type == char.class )
        {
            return coerceToChar( raw );
        }
        if ( type == Class.class )
        {
            return coerceToClass( raw, bundle );
        }
        if ( type == Double.class || type == double.class )
        {
            return coerceToDouble( raw );
        }
        if ( type.isEnum() )
        {
            Class clazz = type; //TODO is there a better way to do ? enum creation?
            return coerceToEnum( raw, clazz );
        }
        if ( type == Float.class || type == float.class )
        {
            return coerceToFloat( raw );
        }
        if ( type == Integer.class || type == int.class )
        {
            return coerceToInteger( raw );
        }
        if ( type == Long.class || type == long.class )
        {
            return coerceToLong( raw );
        }
        if ( type == Short.class || type == short.class )
        {
            return coerceToShort( raw );
        }
        if ( type == String.class )
        {
            return coerceToString( raw );
        }
        if ( raw != null )
        {
            raw = multipleToSingle( raw, null );
            if ( raw != null )
            {
                if ( type.isAssignableFrom( raw.getClass() ) )
                {
                    return raw;
                }
                throw new ComponentException( "unexpected output type " + type );
            }
        }
        return null;
    }

    public static byte coerceToByte(Object o)
    {
        o = multipleToSingle( o, byte0 );
        if ( o instanceof Byte )
        {
            return (Byte) o;
        }
        if ( o instanceof String )
        {
            try
            {
                return Byte.parseByte( (String) o );
            }
            catch ( NumberFormatException e )
            {
                throw new ComponentException( e );
            }
        }
        if ( o instanceof Boolean )
        {
            return (Boolean) o? 1: byte0;
        }
        if ( o instanceof Character )
        {
            return (byte) ( (Character) o ).charValue();
        }
        if ( o instanceof Number )
        {
            return ( (Number) o ).byteValue();
        }
        if ( o == null )
        {
            return 0;
        }
        throw new ComponentException( "Unrecognized input value: " + o + " of type: " + o.getClass() );
    }

    public static char coerceToChar(Object o)
    {
        o = multipleToSingle( o, byte0 );
        if ( o instanceof Character )
        {
            return (Character) o;
        }
        if ( o instanceof String )
        {
            if ( ( (String) o ).length() > 0 )
            {
                return ( (String) o ).charAt( 0 );
            }
            return char0;
        }
        if ( o instanceof Boolean )
        {
            return (Boolean) o? 1: char0;
        }
        if ( o instanceof Number )
        {
            return (char) ( (Number) o ).intValue();
        }
        if ( o == null )
        {
            return char0;
        }
        throw new ComponentException( "Unrecognized input value: " + o + " of type: " + o.getClass() );
    }

    public static double coerceToDouble(Object o)
    {
        o = multipleToSingle( o, double0 );
        if ( o instanceof Double )
        {
            return (Double) o;
        }
        if ( o instanceof String )
        {
            try
            {
                return Double.parseDouble( (String) o );
            }
            catch ( NumberFormatException e )
            {
                throw new ComponentException( e );
            }
        }
        if ( o instanceof Boolean )
        {
            return (Boolean) o? 1: 0;
        }
        if ( o instanceof Character )
        {
            return (double) ( (Character) o ).charValue();
        }
        if ( o instanceof Number )
        {
            return ( (Number) o ).doubleValue();
        }
        if ( o == null )
        {
            return 0;
        }
        throw new ComponentException( "Unrecognized input value: " + o + " of type: " + o.getClass() );
    }

    public static float coerceToFloat(Object o)
    {
        o = multipleToSingle( o, float0 );
        if ( o instanceof Float )
        {
            return (Float) o;
        }
        if ( o instanceof String )
        {
            try
            {
                return Float.parseFloat( (String) o );
            }
            catch ( NumberFormatException e )
            {
                throw new ComponentException( e );
            }
        }
        if ( o instanceof Boolean )
        {
            return (Boolean) o? 1: 0;
        }
        if ( o instanceof Character )
        {
            return (float) ( (Character) o ).charValue();
        }
        if ( o instanceof Number )
        {
            return ( (Number) o ).floatValue();
        }
        if ( o == null )
        {
            return 0;
        }
        throw new ComponentException( "Unrecognized input value: " + o + " of type: " + o.getClass() );
    }

    public static int coerceToInteger(Object o)
    {
        o = multipleToSingle( o, int0 );
        if ( o instanceof Integer )
        {
            return (Integer) o;
        }
        if ( o instanceof String )
        {
            try
            {
                return Integer.parseInt( (String) o );
            }
            catch ( NumberFormatException e )
            {
                throw new ComponentException( e );
            }
        }
        if ( o instanceof Boolean )
        {
            return (Boolean) o? 1: 0;
        }
        if ( o instanceof Character )
        {
            return (int) ( (Character) o ).charValue();
        }
        if ( o instanceof Number )
        {
            return ( (Number) o ).intValue();
        }
        if ( o == null )
        {
            return 0;
        }
        throw new ComponentException( "Unrecognized input value: " + o + " of type: " + o.getClass() );
    }

    public static long coerceToLong(Object o)
    {
        o = multipleToSingle( o, long0 );
        if ( o instanceof Long )
        {
            return (Long) o;
        }
        if ( o instanceof String )
        {
            try
            {
                return Long.parseLong( (String) o );
            }
            catch ( NumberFormatException e )
            {
                throw new ComponentException( e );
            }
        }
        if ( o instanceof Boolean )
        {
            return (Boolean) o? 1: 0;
        }
        if ( o instanceof Character )
        {
            return (long) ( (Character) o ).charValue();
        }
        if ( o instanceof Number )
        {
            return ( (Number) o ).longValue();
        }
        if ( o == null )
        {
            return 0;
        }
        throw new ComponentException( "Unrecognized input value: " + o + " of type: " + o.getClass() );
    }

    public static short coerceToShort(Object o)
    {
        o = multipleToSingle( o, short0 );
        if ( o instanceof Short )
        {
            return (Short) o;
        }
        if ( o instanceof String )
        {
            try
            {
                return Short.parseShort( (String) o );
            }
            catch ( NumberFormatException e )
            {
                throw new ComponentException( e );
            }
        }
        if ( o instanceof Boolean )
        {
            return (Boolean) o? 1: short0;
        }
        if ( o instanceof Character )
        {
            return (short) ( (Character) o ).charValue();
        }
        if ( o instanceof Number )
        {
            return ( (Number) o ).shortValue();
        }
        if ( o == null )
        {
            return 0;
        }
        throw new ComponentException( "Unrecognized input value: " + o + " of type: " + o.getClass() );
    }

    public static String coerceToString(Object o)
    {
        o = multipleToSingle( o, null );
        if ( o instanceof String )
        {
            return (String) o;
        }
        if ( o == null )
        {
            return null;
        }

        return o.toString();
    }

    public static boolean coerceToBoolean(Object o)
    {
        o = multipleToSingle( o, false );
        if ( o instanceof Boolean )
        {
            return (Boolean) o;
        }
        if ( o instanceof String )
        {
            try
            {
                return Boolean.parseBoolean( (String) o );
            }
            catch ( NumberFormatException e )
            {
                throw new ComponentException( e );
            }
        }
        if ( o instanceof Character )
        {
            return ( (Character) o ).charValue() != 0;
        }
        if ( o instanceof Number )
        {
            return ( (Number) o ).doubleValue() != 0D;
        }
        if ( o == null )
        {
            return false;
        }
        throw new ComponentException( "Unrecognized input value: " + o + " of type: " + o.getClass() );
    }

    public static Class<?> coerceToClass(Object o, Bundle b)
    {
        o = multipleToSingle( o, null );
        if ( o == null )
        {
            return null;
        }
        if ( o instanceof String )
        {
            try
            {
                return b.loadClass( (String) o );
            }
            catch ( ClassNotFoundException e )
            {
                throw new ComponentException( e );
            }
        }
        throw new ComponentException( "Unrecognized input value: " + o + " of type: " + o.getClass() );
    }

    public static <T extends Enum<T>> T coerceToEnum(Object o, Class<T> clazz)
    {
        o = multipleToSingle( o, null );
        if ( o instanceof String )
        {
            try
            {
                return Enum.valueOf( clazz, (String) o );
            }
            catch ( IllegalArgumentException e )
            {
                throw new ComponentException( e );
            }
        }
        if ( o == null )
        {
            return null;
        }
        throw new ComponentException( "Unrecognized input value: " + o + " of type: " + o.getClass() );
    }

    private static Object multipleToSingle(Object o, Object defaultValue)
    {
        if ( o instanceof Collection )
        {
            return firstCollectionElement( o, defaultValue );
        }
        if ( o != null && o.getClass().isArray() )
        {
            return firstArrayElement( o, defaultValue );
        }
        return o;
    }

    private static Object firstCollectionElement(Object raw, Object defaultValue)
    {
        if ( !( raw instanceof Collection ) )
        {
            throw new ComponentException( "Not a collection: " + raw );
        }
        Collection<?> c = (Collection<?>) raw;
        if ( c.isEmpty() )
        {
            return defaultValue;
        }
        return c.iterator().next();
    }

    private static Object firstArrayElement(Object o, Object defaultValue)
    {
        if ( o == null || !o.getClass().isArray() )
        {
            throw new ComponentException( "Not an array: " + o );
        }
        if ( Array.getLength( o ) == 0 )
        {
            return defaultValue;
        }
        return Array.get( o, 0 );
    }

}