api/src/main/java/javax/faces/component/_ValueBindingToValueExpression.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 javax.faces.component;

import javax.el.ELContext;
import javax.el.ELException;
import javax.el.PropertyNotFoundException;
import javax.el.PropertyNotWritableException;
import javax.el.ValueExpression;
import javax.faces.context.FacesContext;
import javax.faces.el.EvaluationException;
import javax.faces.el.ValueBinding;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * Wraps a ValueBinding inside a ValueExpression. Also allows access to the original ValueBinding object.
 * 
 * Although ValueExpression implements Serializable, this class implements StateHolder instead.
 * 
 * ATTENTION: If you make changes to this class, treat {@link _ValueBindingToValueExpression} accordingly.
 * 
 * @author Stan Silvert
 * @see javax.faces.component._ValueBindingToValueExpression
 */
@SuppressWarnings("deprecation")
class _ValueBindingToValueExpression extends ValueExpression implements StateHolder
{
    private static final long serialVersionUID = 8071429285360496554L;

    private static final Log logger = LogFactory.getLog(_ValueBindingToValueExpression.class);

    private ValueBinding _valueBinding;

    private boolean _transient;

    /**
     * No-arg constructor used during restoreState
     */
    protected _ValueBindingToValueExpression()
    {
    }

    private ValueBinding getNotNullValueBinding()
    {
        if (_valueBinding == null)
        {
            throw new IllegalStateException("value binding is null");
        }
        return _valueBinding;
    }

    /** Creates a new instance of ValueBindingToValueExpression */
    public _ValueBindingToValueExpression(ValueBinding valueBinding)
    {
        if (valueBinding == null)
        {
            throw new IllegalArgumentException("value binding must not be null");
        }
        this._valueBinding = valueBinding;
    }

    public ValueBinding getValueBinding()
    {
        return _valueBinding;
    }

    @Override
    public boolean isReadOnly(final ELContext context) throws NullPointerException, PropertyNotFoundException,
            ELException
    {
        return invoke(new Invoker<Boolean>()
        {
            public Boolean invoke()
            {
                return getNotNullValueBinding().isReadOnly(getFacesContext(context));
            }
        });
    }

    @Override
    public Object getValue(final ELContext context) throws NullPointerException, PropertyNotFoundException, ELException
    {
        return invoke(new Invoker<Object>()
        {
            public Object invoke()
            {
                return getNotNullValueBinding().getValue(getFacesContext(context));
            }
        });
    }

    @Override
    public Class<?> getType(final ELContext context) throws NullPointerException, PropertyNotFoundException,
            ELException
    {
        return invoke(new Invoker<Class<?>>()
        {
            public Class<?> invoke()
            {
                return getNotNullValueBinding().getType(getFacesContext(context));
            }
        });
    }

    @Override
    public void setValue(final ELContext context, final Object value) throws NullPointerException,
            PropertyNotFoundException, PropertyNotWritableException, ELException
    {
        invoke(new Invoker<Object>()
        {
            public Object invoke()
            {
                getNotNullValueBinding().setValue(getFacesContext(context), value);
                return null;
            }
        });
    }

    @Override
    public int hashCode()
    {
        final int PRIME = 31;
        int result = 1;
        result = PRIME * result + (_transient ? 1231 : 1237);
        result = PRIME * result + ((_valueBinding == null) ? 0 : _valueBinding.hashCode());
        return result;
    }

    @Override
    public boolean equals(Object obj)
    {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        final _ValueBindingToValueExpression other = (_ValueBindingToValueExpression) obj;
        if (_transient != other._transient)
            return false;
        if (_valueBinding == null)
        {
            if (other._valueBinding != null)
                return false;
        }
        else if (!_valueBinding.equals(other._valueBinding))
            return false;
        return true;
    }

    @Override
    public boolean isLiteralText()
    {
        return false;
    }

    @Override
    public String getExpressionString()
    {
        return getNotNullValueBinding().getExpressionString();
    }

    @Override
    public Class<?> getExpectedType()
    {
        if (_valueBinding != null)
        {
            try
            {
                Object value = getNotNullValueBinding().getValue(FacesContext.getCurrentInstance());
                if (value != null)
                {
                    return value.getClass();
                }
            }
            catch (Throwable e)
            {
                logger.warn("Could not determine expected type for '" + _valueBinding.getExpressionString() + "': "
                        + e.getMessage(), e);
            }
        }
        return null;
    }

    public void restoreState(FacesContext context, Object state)
    {
        if (state instanceof ValueBinding)
        {
            _valueBinding = (ValueBinding) state;
        }
        else if (state != null)
        {
            Object[] stateArray = (Object[]) state;
            _valueBinding = (ValueBinding) _ClassUtils.newInstance((String) stateArray[0], ValueBinding.class);
            ((StateHolder) _valueBinding).restoreState(context, stateArray[1]);
        }
    }

    public Object saveState(FacesContext context)
    {
        if (!_transient)
        {
            if (_valueBinding instanceof StateHolder)
            {
                Object[] state = new Object[2];
                state[0] = _valueBinding.getClass().getName();
                state[1] = ((StateHolder) _valueBinding).saveState(context);
                return state;
            }
            return _valueBinding;
        }
        return null;
    }

    public void setTransient(boolean newTransientValue)
    {
        _transient = newTransientValue;
    }

    public boolean isTransient()
    {
        return _transient;
    }

    private FacesContext getFacesContext(ELContext context)
    {
        if (context == null)
        {
            throw new IllegalArgumentException("el context must not be null.");
        }
        FacesContext facesContext = (FacesContext) context.getContext(FacesContext.class);
        if (context == null)
        {
            throw new IllegalStateException("faces context not available in el context.");
        }
        return facesContext;
    }

    private <T> T invoke(Invoker<T> invoker)
    {
        try
        {
            return invoker.invoke();
        }
        catch (javax.faces.el.PropertyNotFoundException e)
        {
            throw new PropertyNotFoundException(e.getMessage(), e);
        }
        catch (EvaluationException e)
        {
            throw new ELException(e.getMessage(), e);
        }
    }

    private interface Invoker<T>
    {
        T invoke();
    }
}