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Tools to assist in the reading of configuration/preferences files in
various formats
/*
* 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 org.apache.commons.configuration.beanutils;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.List;
import java.util.ArrayList;
import org.apache.commons.configuration.HierarchicalConfiguration;
import org.apache.commons.configuration.PropertyConverter;
import org.apache.commons.configuration.SubnodeConfiguration;
import org.apache.commons.configuration.ConfigurationRuntimeException;
import org.apache.commons.configuration.tree.ConfigurationNode;
import org.apache.commons.configuration.tree.DefaultConfigurationNode;
/**
*
* An implementation of the BeanDeclaration interface that is
* suitable for XML configuration files.
*
*
* This class defines the standard layout of a bean declaration in an XML
* configuration file. Such a declaration must look like the following example
* fragement:
*
*
*
*
* ...
* <personBean config-class="my.model.PersonBean"
* lastName="Doe" firstName="John">
* <address config-class="my.model.AddressBean"
* street="21st street 11" zip="1234"
* city="TestCity"/>
* </personBean>
*
*
*
*
* The bean declaration can be contained in an arbitrary element. Here it is the
* <personBean> element. In the attributes of this element
* there can occur some reserved attributes, which have the following meaning:
*
* config-class- Here the full qualified name of the bean's class can be specified. An
* instance of this class will be created. If this attribute is not specified,
* the bean class must be provided in another way, e.g. as the
*
defaultClass passed to the BeanHelper class.
* config-factory- This attribute can contain the name of the
*
{@link BeanFactory} that should be used for creating the bean.
* If it is defined, a factory with this name must have been registered at the
* BeanHelper class. If this attribute is missing, the default
* bean factory will be used.
* config-factoryParam- With this attribute a parameter can be specified that will be passed to
* the bean factory. This may be useful for custom bean factories.
*
*
*
* All further attributes starting with the config- prefix are
* considered as meta data and will be ignored. All other attributes are treated
* as properties of the bean to be created, i.e. corresponding setter methods of
* the bean will be invoked with the values specified here.
*
*
* If the bean to be created has also some complex properties (which are itself
* beans), their values cannot be initialized from attributes. For this purpose
* nested elements can be used. The example listing shows how an address bean
* can be initialized. This is done in a nested element whose name must match
* the name of a property of the enclosing bean declaration. The format of this
* nested element is exactly the same as for the bean declaration itself, i.e.
* it can have attributes defining meta data or bean properties and even further
* nested elements for complex bean properties.
*
*
* A XMLBeanDeclaration object is usually created from a
* HierarchicalConfiguration. From this it will derive a
* SubnodeConfiguration, which is used to access the needed
* properties. This subnode configuration can be obtained using the
* {@link #getConfiguration()} method. All of its properties can
* be accessed in the usual way. To ensure that the property keys used by this
* class are understood by the configuration, the default expression engine will
* be set.
*
*
* @since 1.3
* @author Oliver Heger
* @version $Id: XMLBeanDeclaration.java 766914 2009-04-20 23:38:49Z rgoers $
*/
public class XMLBeanDeclaration implements BeanDeclaration
{
/** Constant for the prefix of reserved attributes. */
public static final String RESERVED_PREFIX = "config-";
/** Constant for the prefix for reserved attributes.*/
public static final String ATTR_PREFIX = "[@" + RESERVED_PREFIX;
/** Constant for the bean class attribute. */
public static final String ATTR_BEAN_CLASS = ATTR_PREFIX + "class]";
/** Constant for the bean factory attribute. */
public static final String ATTR_BEAN_FACTORY = ATTR_PREFIX + "factory]";
/** Constant for the bean factory parameter attribute. */
public static final String ATTR_FACTORY_PARAM = ATTR_PREFIX
+ "factoryParam]";
/** Stores the associated configuration. */
private SubnodeConfiguration configuration;
/** Stores the configuration node that contains the bean declaration. */
private ConfigurationNode node;
/**
* Creates a new instance of XMLBeanDeclaration and
* initializes it from the given configuration. The passed in key points to
* the bean declaration.
*
* @param config the configuration
* @param key the key to the bean declaration (this key must point to
* exactly one bean declaration or a IllegalArgumentException
* exception will be thrown)
*/
public XMLBeanDeclaration(HierarchicalConfiguration config, String key)
{
this(config, key, false);
}
/**
* Creates a new instance of XMLBeanDeclaration and
* initializes it from the given configuration. The passed in key points to
* the bean declaration. If the key does not exist and the boolean argument
* is true, the declaration is initialized with an empty
* configuration. It is possible to create objects from such an empty
* declaration if a default class is provided. If the key on the other hand
* has multiple values or is undefined and the boolean argument is false,
* a IllegalArgumentException exception will be thrown.
*
* @param config the configuration
* @param key the key to the bean declaration
* @param optional a flag whether this declaration is optional; if set to
* true, no exception will be thrown if the passed in key is
* undefined
*/
public XMLBeanDeclaration(HierarchicalConfiguration config, String key,
boolean optional)
{
if (config == null)
{
throw new IllegalArgumentException(
"Configuration must not be null!");
}
try
{
configuration = config.configurationAt(key);
node = configuration.getRootNode();
}
catch (IllegalArgumentException iex)
{
// If we reach this block, the key does not have exactly one value
if (!optional || config.getMaxIndex(key) > 0)
{
throw iex;
}
configuration = config.configurationAt(null);
node = new DefaultConfigurationNode();
}
initSubnodeConfiguration(getConfiguration());
}
/**
* Creates a new instance of XMLBeanDeclaration and
* initializes it from the given configuration. The configuration's root
* node must contain the bean declaration.
*
* @param config the configuration with the bean declaration
*/
public XMLBeanDeclaration(HierarchicalConfiguration config)
{
this(config, (String) null);
}
/**
* Creates a new instance of XMLBeanDeclaration and
* initializes it with the configuration node that contains the bean
* declaration.
*
* @param config the configuration
* @param node the node with the bean declaration.
*/
public XMLBeanDeclaration(SubnodeConfiguration config,
ConfigurationNode node)
{
if (config == null)
{
throw new IllegalArgumentException(
"Configuration must not be null!");
}
if (node == null)
{
throw new IllegalArgumentException("Node must not be null!");
}
this.node = node;
configuration = config;
initSubnodeConfiguration(config);
}
/**
* Returns the configuration object this bean declaration is based on.
*
* @return the associated configuration
*/
public SubnodeConfiguration getConfiguration()
{
return configuration;
}
/**
* Returns the node that contains the bean declaration.
*
* @return the configuration node this bean declaration is based on
*/
public ConfigurationNode getNode()
{
return node;
}
/**
* Returns the name of the bean factory. This information is fetched from
* the config-factory attribute.
*
* @return the name of the bean factory
*/
public String getBeanFactoryName()
{
return getConfiguration().getString(ATTR_BEAN_FACTORY);
}
/**
* Returns a parameter for the bean factory. This information is fetched
* from the config-factoryParam attribute.
*
* @return the parameter for the bean factory
*/
public Object getBeanFactoryParameter()
{
return getConfiguration().getProperty(ATTR_FACTORY_PARAM);
}
/**
* Returns the name of the class of the bean to be created. This information
* is obtained from the config-class attribute.
*
* @return the name of the bean's class
*/
public String getBeanClassName()
{
return getConfiguration().getString(ATTR_BEAN_CLASS);
}
/**
* Returns a map with the bean's (simple) properties. The properties are
* collected from all attribute nodes, which are not reserved.
*
* @return a map with the bean's properties
*/
public Map getBeanProperties()
{
Map props = new HashMap();
for (Iterator it = getNode().getAttributes().iterator(); it.hasNext();)
{
ConfigurationNode attr = (ConfigurationNode) it.next();
if (!isReservedNode(attr))
{
props.put(attr.getName(), interpolate(attr .getValue()));
}
}
return props;
}
/**
* Returns a map with bean declarations for the complex properties of the
* bean to be created. These declarations are obtained from the child nodes
* of this declaration's root node.
*
* @return a map with bean declarations for complex properties
*/
public Map getNestedBeanDeclarations()
{
Map nested = new HashMap();
for (Iterator it = getNode().getChildren().iterator(); it.hasNext();)
{
ConfigurationNode child = (ConfigurationNode) it.next();
if (!isReservedNode(child))
{
if (nested.containsKey(child.getName()))
{
Object obj = nested.get(child.getName());
List list;
if (obj instanceof List)
{
list = (List) obj;
}
else
{
list = new ArrayList();
list.add(obj);
nested.put(child.getName(), list);
}
list.add(createBeanDeclaration(child));
}
else
{
nested.put(child.getName(), createBeanDeclaration(child));
}
}
}
return nested;
}
/**
* Performs interpolation for the specified value. This implementation will
* interpolate against the current subnode configuration's parent. If sub
* classes need a different interpolation mechanism, they should override
* this method.
*
* @param value the value that is to be interpolated
* @return the interpolated value
*/
protected Object interpolate(Object value)
{
return PropertyConverter.interpolate(value, getConfiguration()
.getParent());
}
/**
* Checks if the specified node is reserved and thus should be ignored. This
* method is called when the maps for the bean's properties and complex
* properties are collected. It checks whether the given node is an
* attribute node and if its name starts with the reserved prefix.
*
* @param nd the node to be checked
* @return a flag whether this node is reserved (and does not point to a
* property)
*/
protected boolean isReservedNode(ConfigurationNode nd)
{
return nd.isAttribute()
&& (nd.getName() == null || nd.getName().startsWith(
RESERVED_PREFIX));
}
/**
* Creates a new BeanDeclaration for a child node of the
* current configuration node. This method is called by
* getNestedBeanDeclarations() for all complex sub properties
* detected by this method. Derived classes can hook in if they need a
* specific initialization. This base implementation creates a
* XMLBeanDeclaration that is properly initialized from the
* passed in node.
*
* @param node the child node, for which a BeanDeclaration is
* to be created
* @return the BeanDeclaration for this child node
* @since 1.6
*/
protected BeanDeclaration createBeanDeclaration(ConfigurationNode node)
{
List list = getConfiguration().configurationsAt(node.getName());
if (list.size() == 1)
{
return new XMLBeanDeclaration((SubnodeConfiguration) list.get(0), node);
}
else
{
Iterator iter = list.iterator();
while (iter.hasNext())
{
SubnodeConfiguration config = (SubnodeConfiguration) iter.next();
if (config.getRootNode().equals(node))
{
return new XMLBeanDeclaration(config, node);
}
}
throw new ConfigurationRuntimeException("Unable to match node for " + node.getName());
}
}
/**
* Initializes the internally managed subnode configuration. This method
* will set some default values for some properties.
*
* @param conf the configuration to initialize
*/
private void initSubnodeConfiguration(SubnodeConfiguration conf)
{
conf.setThrowExceptionOnMissing(false);
conf.setExpressionEngine(null);
}
}