PicoContainer example source code file (ConstantParameter.java)

This example PicoContainer source code file (ConstantParameter.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - PicoContainer tags/keywords

class, class, componentadapter, componentadapter, constantparameter, field, io, nosuchfieldexception, object, object, parameter, parametername, parametername, picocompositionexception, reflection, serializable

The PicoContainer ConstantParameter.java source code

/*****************************************************************************
 * Copyright (c) PicoContainer Organization. All rights reserved.            *
 * ------------------------------------------------------------------------- *
 * The software in this package is published under the terms of the BSD      *
 * style license a copy of which has been included with this distribution in *
 * the LICENSE.txt file.                                                     *
 *                                                                           *
 * Idea by Rachel Davies, Original code by Jon Tirsen                        *
 *****************************************************************************/

package org.picocontainer.parameters;

import org.picocontainer.ComponentAdapter;
import org.picocontainer.Parameter;
import org.picocontainer.PicoContainer;
import org.picocontainer.PicoException;
import org.picocontainer.PicoCompositionException;
import org.picocontainer.PicoVisitor;
import org.picocontainer.ParameterName;

import java.io.Serializable;
import java.lang.reflect.Field;


/**
 * A ConstantParameter should be used to pass in "constant" arguments to constructors. This
 * includes {@link String}s,{@link Integer}s or any other object that is not registered in
 * the container.
 *
 * @author Jon Tirsén
 * @author Aslak Hellesøy
 * @author Jörg Schaible
 * @author Thomas Heller
 * @version $Revision: 3516 $
 */
public class ConstantParameter
        implements Parameter, Serializable {

    private final Object value;

    public ConstantParameter(Object value) {
        this.value = value;
    }

    public Object resolveInstance(PicoContainer container, ComponentAdapter adapter, Class expectedType, ParameterName expectedParameterName) {
        return value;
    }

    public boolean isResolvable(PicoContainer container, ComponentAdapter adapter, Class expectedType, ParameterName expectedParameterName) {
        try {
            verify(container, adapter, expectedType, expectedParameterName);
            return true;
        } catch(final PicoCompositionException e) {
            return false;
        }
    }

    /**
     * {@inheritDoc}
     *
     * @see org.picocontainer.Parameter#verify(org.picocontainer.PicoContainer,org.picocontainer.ComponentAdapter,Class,org.picocontainer.ParameterName)
     */
    public void verify(PicoContainer container, ComponentAdapter adapter, Class expectedType, ParameterName expectedParameterName) throws PicoException {
        if (!checkPrimitive(expectedType) && !expectedType.isInstance(value)) {
            throw new PicoCompositionException(expectedType.getClass().getName() + " is not assignable from " +
                                                 (value != null ? value.getClass().getName() : "null"));
        }
    }

    /**
     * Visit the current {@link Parameter}.
     *
     * @see org.picocontainer.Parameter#accept(org.picocontainer.PicoVisitor)
     */
    public void accept(final PicoVisitor visitor) {
        visitor.visitParameter(this);
    }

    private boolean checkPrimitive(Class expectedType) {
        try {
            if (expectedType.isPrimitive()) {
                final Field field = value.getClass().getField("TYPE");
                final Class type = (Class) field.get(value);
                return expectedType.isAssignableFrom(type);
            }
        } catch (NoSuchFieldException e) {
            //ignore
        } catch (IllegalAccessException e) {
            //ignore
        }
        return false;
    }

}