tapestry/tapestry-framework/src/java/org/apache/tapestry/components/IfBean.java

// Copyright 2004, 2005 The Apache Software Foundation
//
// 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 org.apache.tapestry.components;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hivemind.ApplicationRuntimeException;
import org.apache.hivemind.HiveMind;
import org.apache.tapestry.*;
import org.apache.tapestry.engine.NullWriter;
import org.apache.tapestry.form.AbstractFormComponent;
import org.apache.tapestry.services.DataSqueezer;

/**
 * @author mb
 */
public abstract class IfBean extends AbstractFormComponent
{
    public static final Log _log = LogFactory.getLog(IfBean.class);
    
    public static final String IF_VALUE_ATTRIBUTE = "org.mb.tapestry.base.IfValue";
    
    private boolean _rendering = false;

    private boolean _conditionValue;
    
    public abstract IBinding getConditionValueBinding();

    public abstract boolean getCondition();

    public abstract boolean getVolatile();

    public abstract String getElement();
    
    public abstract boolean getRenderTag();
    
    public abstract IActionListener getListener();
    
    protected void renderComponent(IMarkupWriter writer, IRequestCycle cycle)
    {
        boolean cycleRewinding = cycle.isRewinding();
        
        // form may be null if component is not located in a form
        IForm form = (IForm)cycle.getAttribute(TapestryUtils.FORM_ATTRIBUTE);
        
        // If the cycle is rewinding, but not this particular form,
        // then do nothing (don't even render the body).
        
        if (cycleRewinding && form != null && !form.isRewinding())
            return;
        
        // get the condition. work with a hidden field if necessary
        
        _conditionValue = evaluateCondition(cycle, form, cycleRewinding);
        _rendering = true;
        
        if (!cycleRewinding && form != null && !NullWriter.class.isInstance(writer))
            form.setFormFieldUpdating(true);
        
        try
        {
            // call listener
            IActionListener listener = getListener();
            if (listener != null)
                listener.actionTriggered(this, cycle);
            
            // now render if condition is true
            if (_conditionValue)
            {
                String element = HiveMind.isNonBlank(getElement()) ? getElement() : getTemplateTagName();
                
                boolean render = !cycleRewinding && (getRenderTag() || HiveMind.isNonBlank(getElement()));
                
                if (render)
                {
                    writer.begin(element);

                    renderInformalParameters(writer, cycle);
                    renderIdAttribute(writer, cycle);
                }

                renderBody(writer, cycle);

                if (render)
                    writer.end(element);
            }
        }
        finally
        {
            _rendering = false;
        }

        cycle.setAttribute(IF_VALUE_ATTRIBUTE, new Boolean(_conditionValue));
    }

    /**
     * Overriden from {@link AbstractFormComponent} to handle cases where
     * we're not being wrapped by a {@link IForm} component.
     *
     * <p>This is basically a copy of the same method implemented in {@link AbstractComponent}.</p> 
     */
    protected void generateClientId()
    {
        String id = getSpecifiedId();

        if (id != null && getPage() != null && getPage().getRequestCycle() != null)
             setClientId(getPage().getRequestCycle().getUniqueId(TapestryUtils.convertTapestryIdToNMToken(id)));
    }

    protected boolean evaluateCondition(IRequestCycle cycle, IForm form, boolean cycleRewinding)
    {
        boolean condition;

        if (form == null || getVolatile())
        {
            condition = getCondition();
        }
        else
        {
            // we are in a form and we care -- load/store the condition in a hidden field
            
            String name = form.getElementId(this);
            
            if (!cycleRewinding)
            {
                condition = getCondition();
                writeValue(form, name, condition);
            }
            else
            {
                condition = readValue(cycle, name);
            }
        }
        
        // write condition value if parameter is bound
        
        IBinding conditionValueBinding = getConditionValueBinding();
        
        if (conditionValueBinding != null)
            conditionValueBinding.setObject(new Boolean(condition));

        return condition;
    }
    
    private void writeValue(IForm form, String name, boolean value)
    {
        String externalValue;

        Object booleanValue = new Boolean(value);
        try
        {
            externalValue = getDataSqueezer().squeeze(booleanValue);
        }
        catch (Exception ex)
        {
            throw new ApplicationRuntimeException(Tapestry.format("If.unable-to-convert-value",booleanValue), this, null, ex);
        }

        form.addHiddenValue(name, externalValue);
    }

    private boolean readValue(IRequestCycle cycle, String name)
    {
        String submittedValue = cycle.getParameter(name);
        
        _log.debug("readValue() with : " + name + " [" + submittedValue + "]");
        
        try
        {
            Object valueObject = getDataSqueezer().unsqueeze(submittedValue);
            if (!(valueObject instanceof Boolean))
                throw new ApplicationRuntimeException(Tapestry.format("If.invalid-condition-type", submittedValue));

            return ((Boolean) valueObject).booleanValue();
        }
        catch (Exception ex)
        {
            throw new ApplicationRuntimeException(Tapestry.format(
                    "If.unable-to-convert-string",
                    submittedValue), this, null, ex);
        }
    }

    public abstract DataSqueezer getDataSqueezer();

    public boolean isDisabled()
    {
        return false;
    }

    /**
     * Returns the value of the condition.
     * 
     * @return the condition value
     */
    public boolean getConditionValue()
    {
        if (!_rendering)
            throw Tapestry.createRenderOnlyPropertyException(this, "conditionValue");

        return _conditionValue;
    }

    // Do nothing in those methods, but make the JVM happy
    protected void renderFormComponent(IMarkupWriter writer, IRequestCycle cycle)
    {
    }

    protected void rewindFormComponent(IMarkupWriter writer, IRequestCycle cycle)
    {
    }

    /**
     * For component can not take focus.
     */
    protected boolean getCanTakeFocus()
    {
        return false;
    }
}