/*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The ASF licenses this file to You under the Apache License, Version 2.0
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* (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.gitblit.wicket.freemarker;
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import java.io.IOException;
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import java.io.StringWriter;
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import java.util.Map;
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import org.apache.wicket.MarkupContainer;
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import org.apache.wicket.WicketRuntimeException;
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import org.apache.wicket.markup.ComponentTag;
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import org.apache.wicket.markup.IMarkupCacheKeyProvider;
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import org.apache.wicket.markup.IMarkupResourceStreamProvider;
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import org.apache.wicket.markup.MarkupStream;
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import org.apache.wicket.markup.html.panel.Panel;
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import org.apache.wicket.model.IModel;
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import org.apache.wicket.model.Model;
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import org.apache.wicket.util.resource.IResourceStream;
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import org.apache.wicket.util.resource.StringResourceStream;
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import org.apache.wicket.util.string.Strings;
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import com.gitblit.utils.StringUtils;
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import freemarker.template.Template;
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import freemarker.template.TemplateException;
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/**
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* This class allows FreeMarker to be used as a Wicket preprocessor or as a
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* snippet injector for something like a CMS. There are some cases where Wicket
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* is not flexible enough to generate content, especially when you need to generate
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* hybrid HTML/JS content outside the scope of Wicket.
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*
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* @author James Moger
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*
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*/
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@SuppressWarnings("unchecked")
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public class FreemarkerPanel extends Panel
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implements
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IMarkupResourceStreamProvider,
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IMarkupCacheKeyProvider
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{
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private static final long serialVersionUID = 1L;
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private final String template;
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private boolean parseGeneratedMarkup;
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private boolean escapeHtml;
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private boolean throwFreemarkerExceptions;
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private transient String stackTraceAsString;
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private transient String evaluatedTemplate;
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/**
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* Construct.
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*
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* @param id
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* Component id
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* @param template
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* The Freemarker template
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* @param values
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* values map that can be substituted by Freemarker.
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*/
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public FreemarkerPanel(final String id, String template, final Map<String, Object> values)
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{
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this(id, template, Model.ofMap(values));
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}
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/**
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* Construct.
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*
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* @param id
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* Component id
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* @param templateResource
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* The Freemarker template as a string resource
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* @param model
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* Model with variables that can be substituted by Freemarker.
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*/
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public FreemarkerPanel(final String id, final String template, final IModel< ? extends Map<String, Object>> model)
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{
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super(id, model);
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this.template = template;
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}
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/**
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* Gets the Freemarker template.
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*
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* @return the Freemarker template
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*/
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private Template getTemplate()
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{
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if (StringUtils.isEmpty(template))
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{
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throw new IllegalArgumentException("Template not specified!");
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}
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try {
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return Freemarker.getTemplate(template);
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} catch (IOException e) {
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onException(e);
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}
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return null;
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}
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/**
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* @see org.apache.wicket.markup.html.panel.Panel#onComponentTagBody(org.apache.wicket.markup.
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* MarkupStream, org.apache.wicket.markup.ComponentTag)
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*/
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@Override
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protected void onComponentTagBody(MarkupStream markupStream, ComponentTag openTag)
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{
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if (!Strings.isEmpty(stackTraceAsString))
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{
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// TODO: only display the Freemarker error/stacktrace in development
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// mode?
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replaceComponentTagBody(markupStream, openTag, Strings
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.toMultilineMarkup(stackTraceAsString));
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}
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else if (!parseGeneratedMarkup)
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{
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// check that no components have been added in case the generated
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// markup should not be
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// parsed
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if (size() > 0)
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{
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throw new WicketRuntimeException(
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"Components cannot be added if the generated markup should not be parsed.");
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}
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if (evaluatedTemplate == null)
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{
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// initialize evaluatedTemplate
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getMarkupResourceStream(null, null);
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}
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replaceComponentTagBody(markupStream, openTag, evaluatedTemplate);
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}
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else
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{
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super.onComponentTagBody(markupStream, openTag);
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}
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}
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/**
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* Either print or rethrow the throwable.
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*
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* @param exception
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* the cause
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* @param markupStream
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* the markup stream
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* @param openTag
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* the open tag
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*/
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private void onException(final Exception exception)
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{
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if (!throwFreemarkerExceptions)
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{
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// print the exception on the panel
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stackTraceAsString = Strings.toString(exception);
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}
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else
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{
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// rethrow the exception
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throw new WicketRuntimeException(exception);
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}
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}
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/**
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* Gets whether to escape HTML characters.
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*
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* @return whether to escape HTML characters. The default value is false.
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*/
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public void setEscapeHtml(boolean value)
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{
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this.escapeHtml = value;
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}
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/**
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* Evaluates the template and returns the result.
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*
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* @param templateReader
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* used to read the template
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* @return the result of evaluating the velocity template
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*/
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private String evaluateFreemarkerTemplate(Template template)
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{
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if (evaluatedTemplate == null)
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{
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// Get model as a map
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final Map<String, Object> map = (Map<String, Object>)getDefaultModelObject();
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// create a writer for capturing the Velocity output
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StringWriter writer = new StringWriter();
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// string to be used as the template name for log messages in case
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// of error
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try
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{
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// execute the Freemarker script and capture the output in writer
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Freemarker.evaluate(template, map, writer);
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// replace the tag's body the Freemarker output
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evaluatedTemplate = writer.toString();
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if (escapeHtml)
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{
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// encode the result in order to get valid html output that
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// does not break the rest of the page
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evaluatedTemplate = Strings.escapeMarkup(evaluatedTemplate).toString();
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}
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return evaluatedTemplate;
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}
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catch (IOException e)
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{
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onException(e);
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}
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catch (TemplateException e)
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{
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onException(e);
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}
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return null;
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}
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return evaluatedTemplate;
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}
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/**
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* Gets whether to parse the resulting Wicket markup.
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*
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* @return whether to parse the resulting Wicket markup. The default is false.
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*/
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public void setParseGeneratedMarkup(boolean value)
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{
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this.parseGeneratedMarkup = value;
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}
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/**
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* Whether any Freemarker exception should be trapped and displayed on the panel (false) or thrown
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* up to be handled by the exception mechanism of Wicket (true). The default is false, which
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* traps and displays any exception without having consequences for the other components on the
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* page.
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* <p>
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* Trapping these exceptions without disturbing the other components is especially useful in CMS
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* like applications, where 'normal' users are allowed to do basic scripting. On errors, you
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* want them to be able to have them correct them while the rest of the application keeps on
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* working.
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* </p>
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*
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* @return Whether any Freemarker exceptions should be thrown or trapped. The default is false.
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*/
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public void setThrowFreemarkerExceptions(boolean value)
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{
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this.throwFreemarkerExceptions = value;
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}
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/**
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* @see org.apache.wicket.markup.IMarkupResourceStreamProvider#getMarkupResourceStream(org.apache
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* .wicket.MarkupContainer, java.lang.Class)
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*/
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@Override
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public final IResourceStream getMarkupResourceStream(MarkupContainer container,
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Class< ? > containerClass)
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{
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Template template = getTemplate();
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if (template == null)
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{
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throw new WicketRuntimeException("could not find Freemarker template for panel: " + this);
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}
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// evaluate the template and return a new StringResourceStream
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StringBuffer sb = new StringBuffer();
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sb.append("<wicket:panel>");
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sb.append(evaluateFreemarkerTemplate(template));
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sb.append("</wicket:panel>");
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return new StringResourceStream(sb.toString());
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}
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/**
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* @see org.apache.wicket.markup.IMarkupCacheKeyProvider#getCacheKey(org.apache.wicket.
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* MarkupContainer, java.lang.Class)
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*/
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@Override
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public final String getCacheKey(MarkupContainer container, Class< ? > containerClass)
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{
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// don't cache the evaluated template
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return null;
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}
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/**
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* @see org.apache.wicket.Component#onDetach()
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*/
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@Override
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protected void onDetach()
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{
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super.onDetach();
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stackTraceAsString = null;
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evaluatedTemplate = null;
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}
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}
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