How to implement a reloadable MessageResources for Struts
Commons Configuration support for reloadable files can be leveraged to implement a dynamic resource bundle for Struts. This is done easily by extending the MessageResourcesFactory and MessageResources classes provided by Struts.
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/*
* Copyright 2004 Emmanuel Bourg
*
* 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.
*/
import java.net.URL;
import java.util.Locale;
import java.util.Map;
import org.apache.commons.configuration.Configuration;
import org.apache.commons.configuration.ConfigurationException;
import org.apache.commons.configuration.PropertiesConfiguration;
import org.apache.commons.configuration.reloading.FileChangedReloadingStrategy;
import org.apache.struts.util.MessageResources;
import org.apache.struts.util.MessageResourcesFactory;
/**
* MessageResources based on reloadble configurations.
*
* @author Emmanuel Bourg
*/
public class ConfigurationMessageResources extends MessageResources {
/** Configurations associées à leur Locale respective. */
protected Map configurations;
public ConfigurationMessageResources(MessageResourcesFactory factory, String config, boolean returnNull) {
super(factory, config, returnNull);
}
public String getMessage(Locale locale, String key) {
// get the configuration for the specified locale
Configuration resource = getConfiguration(this.config + "_" + locale.getLanguage() + ".properties");
if (resource == null || !resource.containsKey(key)) {
// look for the key in the root configuration
resource = getConfiguration(this.config + ".properties");
}
return resource != null ? resource.getString(key, null) : null;
}
/**
* Load the specified configuration from the classpath and initialize it.
*/
private Configuration getConfiguration(String name) {
Configuration configuration = null;
URL url = Thread.currentThread().getContextClassLoader().getResource(name);
if (url != null) {
PropertiesConfiguration pc = new PropertiesConfiguration();
PropertiesConfiguration.setDelimiter('\uffff'); // disable string splitting
pc.setURL(url);
pc.setReloadingStrategy(new FileChangedReloadingStrategy());
try {
pc.load();
configuration = pc;
} catch (ConfigurationException e) {
e.printStackTrace();
}
}
return configuration;
}
}
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/*
* Copyright 2004 Emmanuel Bourg
*
* 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.
*/
import org.apache.struts.util.MessageResourcesFactory;
import org.apache.struts.util.MessageResources;
/**
* Factory for ConfigurationMessageResources.
*
* @author Emmanuel Bourg
*/
public class ConfigurationMessageResourceFactory extends MessageResourcesFactory {
public MessageResources createResources(String config) {
return new ConfigurationMessageResources(this, config, this.returnNull);
}
}
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struts-config.xml
The last step is to declare the factory in the struts-config.xml file:
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<?xml version="1.0"?>
<struts-config>
...
<message-resources factory="ConfigurationMessageResourceFactory" parameter="yourResourceBundle"/>
</struts-config>
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