001/*****************************************************************************
002 * Copyright (c) PicoContainer Organization. All rights reserved.            *
003 * ------------------------------------------------------------------------- *
004 * The software in this package is published under the terms of the BSD      *
005 * style license a copy of which has been included with this distribution in *
006 * the LICENSE.txt file.                                                     *
007 *                                                                           *
008 * Idea by Rachel Davies, Original code by Jon Tirsen                        *
009 *****************************************************************************/
010
011package org.picocontainer.parameters;
012
013import org.picocontainer.ComponentAdapter;
014import org.picocontainer.Parameter;
015import org.picocontainer.PicoContainer;
016import org.picocontainer.PicoException;
017import org.picocontainer.PicoCompositionException;
018import org.picocontainer.PicoVisitor;
019import org.picocontainer.NameBinding;
020
021import java.io.Serializable;
022import java.lang.reflect.Field;
023import java.lang.reflect.ParameterizedType;
024import java.lang.reflect.Type;
025import java.lang.annotation.Annotation;
026
027
028/**
029 * A ConstantParameter should be used to pass in "constant" arguments to constructors. This
030 * includes {@link String}s,{@link Integer}s or any other object that is not registered in
031 * the container.
032 *
033 * @author Jon Tirsén
034 * @author Aslak Hellesøy
035 * @author Jörg Schaible
036 * @author Thomas Heller
037 */
038@SuppressWarnings("serial")
039public class ConstantParameter extends AbstractParameter implements Parameter, Serializable {
040
041    private final Object value;
042    
043
044    public ConstantParameter(Object value) {
045        this.value = value;
046    }
047
048    public Resolver resolve(PicoContainer container, ComponentAdapter<?> forAdapter,
049                            ComponentAdapter<?> injecteeAdapter, final Type expectedType, NameBinding expectedNameBinding,
050                            boolean useNames, Annotation binding) {
051        if (expectedType instanceof Class) {
052            return new Parameter.ValueResolver(isAssignable((Class) expectedType), value, null);
053        } else if (expectedType instanceof ParameterizedType) {
054                return new Parameter.ValueResolver(isAssignable(((ParameterizedType)expectedType).getRawType()), value, null);
055        }
056        return new Parameter.ValueResolver(true, value, null);
057    }
058
059    /**
060     * {@inheritDoc}
061     *
062     * @see Parameter#verify(org.picocontainer.PicoContainer,org.picocontainer.ComponentAdapter,java.lang.reflect.Type,org.picocontainer.NameBinding,boolean,java.lang.annotation.Annotation)
063     */
064    public void verify(PicoContainer container, ComponentAdapter<?> adapter,
065                       Type expectedType, NameBinding expectedNameBinding,
066                       boolean useNames, Annotation binding) throws PicoException {
067        if (!isAssignable(expectedType)) {
068            throw new PicoCompositionException(
069                expectedType + " is not assignable from " +
070                        (value != null ? value.getClass().getName() : "null"));
071        }
072    }
073
074    protected boolean isAssignable(Type expectedType) {
075        boolean isAssignable;
076        if (expectedType instanceof Class) {
077            Class expectedClass = (Class) expectedType;
078            if (checkPrimitive(expectedClass) || expectedClass.isInstance(value)) {
079                return true;
080            }
081        }
082        return false;
083    }
084
085    /**
086     * Visit the current {@link Parameter}.
087     *
088     * @see org.picocontainer.Parameter#accept(org.picocontainer.PicoVisitor)
089     */
090    public void accept(final PicoVisitor visitor) {
091        visitor.visitParameter(this);
092    }
093
094    private boolean checkPrimitive(Class expectedType) {
095        try {
096            if (expectedType.isPrimitive()) {
097                final Field field = value.getClass().getField("TYPE");
098                final Class type = (Class) field.get(value);
099                return expectedType.isAssignableFrom(type);
100            }
101        } catch (NoSuchFieldException e) {
102            //ignore
103        } catch (IllegalAccessException e) {
104            //ignore
105        }
106        return false;
107    }
108
109}