src/java/org/apache/commons/jelly/tags/core/UseBeanTag.java - commons-jelly - Git at Google

 /*
  * Copyright 2002,2004 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.commons.jelly.tags.core;

 import java.lang.reflect.InvocationTargetException;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Iterator;
 import java.util.Map;
 import java.util.Set;

 import org.apache.commons.beanutils.BeanUtils;
 import org.apache.commons.beanutils.PropertyUtils;
 import org.apache.commons.jelly.JellyTagException;
 import org.apache.commons.jelly.MapTagSupport;
 import org.apache.commons.jelly.MissingAttributeException;
 import org.apache.commons.jelly.XMLOutput;
 import org.apache.commons.jelly.impl.BeanSource;
 import org.apache.commons.jelly.util.ClassLoaderUtils;

 /**
  * A tag which instantiates an instance of the given class
  * and then sets the properties on the bean.
  * The class can be specified via a {@link java.lang.Class} instance or
  * a String which will be used to load the class using either the current
  * thread's context class loader or the class loader used to load this
  * Jelly library.
  *
  * This tag can be used it as follows,
  * <pre>
  * &lt;j:useBean var="person" class="com.acme.Person" name="James" location="${loc}"/&gt;
  * &lt;j:useBean var="order" class="${orderClass}" amount="12" price="123.456"/&gt;
  * </pre>
  *
  * @author <a href="mailto:jstrachan@apache.org">James Strachan</a>
  * @version $Revision: 1.3 $
  */
 public class UseBeanTag extends MapTagSupport implements BeanSource {

     /** the current bean instance */
     private Object bean;

     /** the default class to use if no Class is specified */
     private Class defaultClass;

     /**
      * a Set of Strings of property names to ignore (remove from the
      * Map of attributes before passing to ConvertUtils)
      */
     private Set ignoreProperties;

     /**
      * If this tag finds an attribute in the XML that's not
      * ignored by {@link #ignoreProperties} and isn't a
      * bean property, should it throw an exception?
      * @see #setIgnoreUnknownProperties(boolean)
      */
     private boolean ignoreUnknownProperties = false;


     public UseBeanTag() {
     }

     public UseBeanTag(Class defaultClass) {
         this.defaultClass = defaultClass;
     }

     // BeanSource interface
     //-------------------------------------------------------------------------

     /**
      * @return the bean that has just been created
      */
     public Object getBean() {
         return bean;
     }


     // Tag interface
     //-------------------------------------------------------------------------
     public void doTag(XMLOutput output) throws JellyTagException {
         Map attributes = getAttributes();
         String var = (String) attributes.get( "var" );
         Object classObject = attributes.get( "class" );
         addIgnoreProperty("class");
         addIgnoreProperty("var");

         try {
             // this method could return null in derived classes
             Class theClass = convertToClass(classObject);

             bean = newInstance(theClass, attributes, output);
             setBeanProperties(bean, attributes);

             // invoke body which could result in other properties being set
             invokeBody(output);

             processBean(var, bean);
         }
         catch (ClassNotFoundException e) {
             throw new JellyTagException(e);
         }
     }

     // Implementation methods
     //-------------------------------------------------------------------------

     /**
      * Allow derived classes to programatically set the bean
      */
     protected void setBean(Object bean) {
         this.bean = bean;
     }

     /**
      * Attempts to convert the given object to a Class instance.
      * If the classObject is already a Class it will be returned
      * otherwise it will be converted to a String and loaded
      * using the default class loading mechanism.
      */
     protected Class convertToClass(Object classObject)
     throws MissingAttributeException, ClassNotFoundException {
         if (classObject instanceof Class) {
             return (Class) classObject;
         }
         else if ( classObject == null ) {
             Class theClass = getDefaultClass();
             if (theClass == null) {
                 throw new MissingAttributeException("class");
             }
             return theClass;
         }
         else {
             String className = classObject.toString();
             return loadClass(className);
         }
     }

     /**
      * Loads the given class using the default class loading mechanism
      * which is to try use the current Thread's context class loader first
      * otherise use the class loader which loaded this class.
      */
     protected Class loadClass(String className) throws ClassNotFoundException {
         return ClassLoaderUtils.loadClass(className, getClass());
     }

     /**
      * Creates a new instance of the given class, which by default will invoke the
      * default constructor.
      * Derived tags could do something different here.
      */
     protected Object newInstance(Class theClass, Map attributes, XMLOutput output)
     throws JellyTagException {
         try {
             return theClass.newInstance();
         } catch (IllegalAccessException e) {
             throw new JellyTagException(e.toString());
         } catch (InstantiationException e) {
             throw new JellyTagException(e.toString());
         }
     }

     /**
      * Sets the properties on the bean. Derived tags could implement some custom
      * type conversion etc.
      * <p/>
      * This method ignores all property names in the Set returned by {@link #getIgnorePropertySet()}.
      */
     protected void setBeanProperties(Object bean, Map attributes) throws JellyTagException {
         Map attrsToUse = new HashMap(attributes);
         attrsToUse.keySet().removeAll(getIgnorePropertySet());

         validateBeanProperties(bean, attrsToUse);

         try {
             BeanUtils.populate(bean, attrsToUse);
         } catch (IllegalAccessException e) {
             throw new JellyTagException("could not set the properties of the bean",e);
         } catch (InvocationTargetException e) {
             throw new JellyTagException("could not set the properties of the bean",e);
         }
     }

     /**
      * If {@link #isIgnoreUnknownProperties()} returns true, make sure that
      * every non-ignored ({@see #addIgnoreProperty(String)}) property
      * matches a writable property on the target bean.
      * @param bean the bean to validate
      * @param attributes the list of properties to validate
      * @throws JellyTagException when a property is not writeable
      */
     protected void validateBeanProperties(Object bean, Map attributes) throws JellyTagException {
         if (!isIgnoreUnknownProperties()) {
             for (Iterator i=attributes.keySet().iterator();i.hasNext();) {
                 String attrName = (String)i.next();
                 if (! PropertyUtils.isWriteable(bean, attrName)) {
                     throw new JellyTagException("No bean property found: " + attrName);
                 }
             }
         }
     }

     /**
      * By default this will export the bean using the given variable if it is defined.
      * This Strategy method allows derived tags to process the beans in different ways
      * such as to register this bean with its parent tag etc.
      */
     protected void processBean(String var, Object bean) throws JellyTagException {
         if (var != null) {
             context.setVariable(var, bean);
         }
         else {
             ArgTag parentArg = (ArgTag)(findAncestorWithClass(ArgTag.class));
             if(null != parentArg) {
                 parentArg.setValue(bean);
             }
         }
     }

     /**
      * Allows derived classes to provide a default bean implementation class
      */
     protected Class getDefaultClass() {
         return defaultClass;
     }

     /**
      * Adds a name to the Set of property names that will be skipped when setting
      * bean properties. In other words, names added here won't be set into the bean
      * if they're present in the attribute Map.
      * @param name
      */
     protected void addIgnoreProperty(String name) {
         getIgnorePropertySet().add(name);
     }

     /**
      * @return the Set of property names that should be ignored when setting the
      * properties of the bean.
      */
     protected Set getIgnorePropertySet() {
         if (ignoreProperties == null) {
             ignoreProperties = new HashSet();
         }

         return ignoreProperties;
     }

     /**
      * @see {@link #setIgnoreUnknownProperties(boolean)}
      * @return
      */
     public boolean isIgnoreUnknownProperties() {
         return ignoreUnknownProperties;
     }

     /**
      * If this tag finds an attribute in the XML that's not
      * ignored by {@link #ignoreProperties} and isn't a
      * bean property, should it throw an exception?
      * @param ignoreUnknownProperties Sets {@link #ignoreUnknownProperties}.
      */
     public void setIgnoreUnknownProperties(boolean ignoreUnknownProps) {
         this.ignoreUnknownProperties = ignoreUnknownProps;
     }
 }
	/*
	* Copyright 2002,2004 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.commons.jelly.tags.core;

	import java.lang.reflect.InvocationTargetException;
	import java.util.HashMap;
	import java.util.HashSet;
	import java.util.Iterator;
	import java.util.Map;
	import java.util.Set;

	import org.apache.commons.beanutils.BeanUtils;
	import org.apache.commons.beanutils.PropertyUtils;
	import org.apache.commons.jelly.JellyTagException;
	import org.apache.commons.jelly.MapTagSupport;
	import org.apache.commons.jelly.MissingAttributeException;
	import org.apache.commons.jelly.XMLOutput;
	import org.apache.commons.jelly.impl.BeanSource;
	import org.apache.commons.jelly.util.ClassLoaderUtils;

	/**
	* A tag which instantiates an instance of the given class
	* and then sets the properties on the bean.
	* The class can be specified via a {@link java.lang.Class} instance or
	* a String which will be used to load the class using either the current
	* thread's context class loader or the class loader used to load this
	* Jelly library.
	*
	* This tag can be used it as follows,
	* <pre>
	* <j:useBean var="person" class="com.acme.Person" name="James" location="${loc}"/>
	* <j:useBean var="order" class="${orderClass}" amount="12" price="123.456"/>
	* </pre>
	*
	* @author <a href="mailto:jstrachan@apache.org">James Strachan</a>
	* @version $Revision: 1.3 $
	*/
	public class UseBeanTag extends MapTagSupport implements BeanSource {

	/** the current bean instance */
	private Object bean;

	/** the default class to use if no Class is specified */
	private Class defaultClass;

	/**
	* a Set of Strings of property names to ignore (remove from the
	* Map of attributes before passing to ConvertUtils)
	*/
	private Set ignoreProperties;

	/**
	* If this tag finds an attribute in the XML that's not
	* ignored by {@link #ignoreProperties} and isn't a
	* bean property, should it throw an exception?
	* @see #setIgnoreUnknownProperties(boolean)
	*/
	private boolean ignoreUnknownProperties = false;


	public UseBeanTag() {
	}

	public UseBeanTag(Class defaultClass) {
	this.defaultClass = defaultClass;
	}

	// BeanSource interface
	//-------------------------------------------------------------------------

	/**
	* @return the bean that has just been created
	*/
	public Object getBean() {
	return bean;
	}


	// Tag interface
	//-------------------------------------------------------------------------
	public void doTag(XMLOutput output) throws JellyTagException {
	Map attributes = getAttributes();
	String var = (String) attributes.get( "var" );
	Object classObject = attributes.get( "class" );
	addIgnoreProperty("class");
	addIgnoreProperty("var");

	try {
	// this method could return null in derived classes
	Class theClass = convertToClass(classObject);

	bean = newInstance(theClass, attributes, output);
	setBeanProperties(bean, attributes);

	// invoke body which could result in other properties being set
	invokeBody(output);

	processBean(var, bean);
	}
	catch (ClassNotFoundException e) {
	throw new JellyTagException(e);
	}
	}

	// Implementation methods
	//-------------------------------------------------------------------------

	/**
	* Allow derived classes to programatically set the bean
	*/
	protected void setBean(Object bean) {
	this.bean = bean;
	}

	/**
	* Attempts to convert the given object to a Class instance.
	* If the classObject is already a Class it will be returned
	* otherwise it will be converted to a String and loaded
	* using the default class loading mechanism.
	*/
	protected Class convertToClass(Object classObject)
	throws MissingAttributeException, ClassNotFoundException {
	if (classObject instanceof Class) {
	return (Class) classObject;
	}
	else if ( classObject == null ) {
	Class theClass = getDefaultClass();
	if (theClass == null) {
	throw new MissingAttributeException("class");
	}
	return theClass;
	}
	else {
	String className = classObject.toString();
	return loadClass(className);
	}
	}

	/**
	* Loads the given class using the default class loading mechanism
	* which is to try use the current Thread's context class loader first
	* otherise use the class loader which loaded this class.
	*/
	protected Class loadClass(String className) throws ClassNotFoundException {
	return ClassLoaderUtils.loadClass(className, getClass());
	}

	/**
	* Creates a new instance of the given class, which by default will invoke the
	* default constructor.
	* Derived tags could do something different here.
	*/
	protected Object newInstance(Class theClass, Map attributes, XMLOutput output)
	throws JellyTagException {
	try {
	return theClass.newInstance();
	} catch (IllegalAccessException e) {
	throw new JellyTagException(e.toString());
	} catch (InstantiationException e) {
	throw new JellyTagException(e.toString());
	}
	}

	/**
	* Sets the properties on the bean. Derived tags could implement some custom
	* type conversion etc.
	* <p/>
	* This method ignores all property names in the Set returned by {@link #getIgnorePropertySet()}.
	*/
	protected void setBeanProperties(Object bean, Map attributes) throws JellyTagException {
	Map attrsToUse = new HashMap(attributes);
	attrsToUse.keySet().removeAll(getIgnorePropertySet());

	validateBeanProperties(bean, attrsToUse);

	try {
	BeanUtils.populate(bean, attrsToUse);
	} catch (IllegalAccessException e) {
	throw new JellyTagException("could not set the properties of the bean",e);
	} catch (InvocationTargetException e) {
	throw new JellyTagException("could not set the properties of the bean",e);
	}
	}

	/**
	* If {@link #isIgnoreUnknownProperties()} returns true, make sure that
	* every non-ignored ({@see #addIgnoreProperty(String)}) property
	* matches a writable property on the target bean.
	* @param bean the bean to validate
	* @param attributes the list of properties to validate
	* @throws JellyTagException when a property is not writeable
	*/
	protected void validateBeanProperties(Object bean, Map attributes) throws JellyTagException {
	if (!isIgnoreUnknownProperties()) {
	for (Iterator i=attributes.keySet().iterator();i.hasNext();) {
	String attrName = (String)i.next();
	if (! PropertyUtils.isWriteable(bean, attrName)) {
	throw new JellyTagException("No bean property found: " + attrName);
	}
	}
	}
	}

	/**
	* By default this will export the bean using the given variable if it is defined.
	* This Strategy method allows derived tags to process the beans in different ways
	* such as to register this bean with its parent tag etc.
	*/
	protected void processBean(String var, Object bean) throws JellyTagException {
	if (var != null) {
	context.setVariable(var, bean);
	}
	else {
	ArgTag parentArg = (ArgTag)(findAncestorWithClass(ArgTag.class));
	if(null != parentArg) {
	parentArg.setValue(bean);
	}
	}
	}

	/**
	* Allows derived classes to provide a default bean implementation class
	*/
	protected Class getDefaultClass() {
	return defaultClass;
	}

	/**
	* Adds a name to the Set of property names that will be skipped when setting
	* bean properties. In other words, names added here won't be set into the bean
	* if they're present in the attribute Map.
	* @param name
	*/
	protected void addIgnoreProperty(String name) {
	getIgnorePropertySet().add(name);
	}

	/**
	* @return the Set of property names that should be ignored when setting the
	* properties of the bean.
	*/
	protected Set getIgnorePropertySet() {
	if (ignoreProperties == null) {
	ignoreProperties = new HashSet();
	}

	return ignoreProperties;
	}

	/**
	* @see {@link #setIgnoreUnknownProperties(boolean)}
	* @return
	*/
	public boolean isIgnoreUnknownProperties() {
	return ignoreUnknownProperties;
	}

	/**
	* If this tag finds an attribute in the XML that's not
	* ignored by {@link #ignoreProperties} and isn't a
	* bean property, should it throw an exception?
	* @param ignoreUnknownProperties Sets {@link #ignoreUnknownProperties}.
	*/
	public void setIgnoreUnknownProperties(boolean ignoreUnknownProps) {
	this.ignoreUnknownProperties = ignoreUnknownProps;
	}
	}