src/main/java/freemarker/core/CustomAttribute.java - freemarker - Git at Google

 /*
  * 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 freemarker.core;

 import freemarker.template.Configuration;
 import freemarker.template.Template;

 /**
  * A class that allows one to associate custom data with a {@link Configuration}, a {@link Template}, or
  * {@link Environment}.
  *
  * <p>This API has similar approach to that of {@link ThreadLocal} (which allows one to associate
  * custom data with a thread). With an example:</p>
  *
  * <pre>
  * // The object identity itself will serve as the attribute identifier; there's no attribute name String:
  * public static final CustomAttribute MY_ATTR = new CustomAttribute(CustomAttribute.SCOPE_CONFIGURATION);
  * ...
  *     // Set the attribute in this particular Configuration object:
  *     MY_ATTR.set(myAttrValue, cfg);
  *     ...
  *     // Read the attribute from this particular Configuration object:
  *     myAttrValue = MY_ATTR.get(cfg);
  * </pre>
  */
 public class CustomAttribute {

     /**
      * Constant used in the constructor specifying that this attribute is {@link Environment}-scoped.
      */
     public static final int SCOPE_ENVIRONMENT = 0;

     /**
      * Constant used in the constructor specifying that this attribute is {@link Template}-scoped.
      */
     public static final int SCOPE_TEMPLATE = 1;

     /**
      * Constant used in the constructor specifying that this attribute is {@link Configuration}-scoped.
      */
     public static final int SCOPE_CONFIGURATION = 2;

     // We use an internal key instead of 'this' so that malicious subclasses
     // overriding equals() and hashCode() can't gain access to other attribute
     // values. That's also the reason why get() and set() are marked final.
     private final Object key = new Object();
     private final int scope;

     /**
      * Creates a new custom attribute with the specified scope
      * @param scope one of <tt>SCOPE_</tt> constants.
      */
     public CustomAttribute(int scope) {
         if (scope != SCOPE_ENVIRONMENT &&
            scope != SCOPE_TEMPLATE &&
            scope != SCOPE_CONFIGURATION) {
                 throw new IllegalArgumentException();
             }
         this.scope = scope;
     }

     /**
      * This method is invoked when {@link #get()} is invoked without
      * {@link #set(Object)} being invoked before it to define the value in the
      * current scope. Override it to create the attribute value on-demand.
      * @return the initial value for the custom attribute. By default returns null.
      */
     protected Object create() {
         return null;
     }

     /**
      * Gets the attribute from the appropriate scope that's accessible through the specified {@link Environment}. If
      * the attribute has {@link #SCOPE_ENVIRONMENT} scope, it will be get from the given {@link Environment} directly.
      * If the attribute has {@link #SCOPE_TEMPLATE} scope, it will be get from the parent of the given
      * {@link Environment} (that is, in {@link Environment#getParent()}) directly). If the attribute has
      * {@link #SCOPE_CONFIGURATION} scope, it will be get from {@link Environment#getConfiguration()}.
      *
      * @throws NullPointerException
      *             If {@code env} is null
      *
      * @return The new value of the attribute (possibly {@code null}), or {@code null} if the attribute doesn't exist.
      *
      * @since 2.3.22
      */
     public final Object get(Environment env) {
         return getScopeConfigurable(env).getCustomAttribute(key, this);
     }

     /**
      * Same as {@link #get(Environment)}, but uses {@link Environment#getCurrentEnvironment()} to fill the 2nd argument.
      *
      * @throws IllegalStateException
      *             If there is no current {@link Environment}, which is usually the case when the current thread isn't
      *             processing a template.
      */
     public final Object get() {
         return getScopeConfigurable(getRequiredCurrentEnvironment()).getCustomAttribute(key, this);
     }

     /**
      * Gets the value of a {@link Template}-scope attribute from the given {@link Template}.
      *
      * @throws UnsupportedOperationException
      *             If this custom attribute has different scope than {@link #SCOPE_TEMPLATE}.
      * @throws NullPointerException
      *             If {@code template} is null
      */
     public final Object get(Template template) {
         if (scope != SCOPE_TEMPLATE) {
             throw new UnsupportedOperationException("This is not a template-scope attribute");
         }
         return ((Configurable) template).getCustomAttribute(key, this);
     }

     /**
      * Same as {@link #get(Template)}, but applies to a {@link TemplateConfiguration}.
      *
      * @since 2.3.24
      */
     public Object get(TemplateConfiguration templateConfiguration) {
         if (scope != SCOPE_TEMPLATE) {
             throw new UnsupportedOperationException("This is not a template-scope attribute");
         }
         return templateConfiguration.getCustomAttribute(key, this);
     }

     /**
      * Gets the value of a {@link Configuration}-scope attribute from the given {@link Configuration}.
      *
      * @throws UnsupportedOperationException
      *             If this custom attribute has different scope than {@link #SCOPE_CONFIGURATION}.
      * @throws NullPointerException
      *             If {@code cfg} is null
      *
      * @since 2.3.22
      */
     public final Object get(Configuration cfg) {
         if (scope != SCOPE_CONFIGURATION) {
             throw new UnsupportedOperationException("This is not a template-scope attribute");
         }
         return ((Configurable) cfg).getCustomAttribute(key, this);
     }

     /**
      * Sets the attribute inside the appropriate scope that's accessible through the specified {@link Environment}. If
      * the attribute has {@link #SCOPE_ENVIRONMENT} scope, it will be set in the given {@link Environment} directly. If
      * the attribute has {@link #SCOPE_TEMPLATE} scope, it will be set in the parent of the given {@link Environment}
      * (that is, in {@link Environment#getParent()}) directly). If the attribute has {@link #SCOPE_CONFIGURATION} scope,
      * it will be set in {@link Environment#getConfiguration()}.
      *
      * @param value
      *            The new value of the attribute. Can be {@code null}.
      *
      * @throws NullPointerException
      *             If {@code env} is null
      *
      * @since 2.3.22
      */
     public final void set(Object value, Environment env) {
         getScopeConfigurable(env).setCustomAttribute(key, value);
     }

     /**
      * Same as {@link #set(Object, Environment)}, but uses {@link Environment#getCurrentEnvironment()} to fill the 2nd
      * argument.
      *
      * @throws IllegalStateException
      *             If there is no current {@link Environment}, which is usually the case when the current thread isn't
      *             processing a template.
      */
     public final void set(Object value) {
         getScopeConfigurable(getRequiredCurrentEnvironment()).setCustomAttribute(key, value);
     }

     /**
      * Sets the value of a {@link Template}-scope attribute in the given {@link Template}.
      *
      * @param value
      *            The new value of the attribute. Can be {@code null}.
      *
      * @throws UnsupportedOperationException
      *             If this custom attribute has different scope than {@link #SCOPE_TEMPLATE}.
      * @throws NullPointerException
      *             If {@code template} is null
      */
     public final void set(Object value, Template template) {
         if (scope != SCOPE_TEMPLATE) {
             throw new UnsupportedOperationException("This is not a template-scope attribute");
         }
         ((Configurable) template).setCustomAttribute(key, value);
     }

     /**
      * Same as {@link #set(Object, Template)}, but applicable to a {@link TemplateConfiguration}.
      *
      * @since 2.3.24
      */
     public final void set(Object value, TemplateConfiguration templateConfiguration) {
         if (scope != SCOPE_TEMPLATE) {
             throw new UnsupportedOperationException("This is not a template-scope attribute");
         }
         templateConfiguration.setCustomAttribute(key, value);
     }

     /**
      * Sets the value of a {@link Configuration}-scope attribute in the given {@link Configuration}.
      *
      * @param value
      *            The new value of the attribute. Can be {@code null}.
      *
      * @throws UnsupportedOperationException
      *             If this custom attribute has different scope than {@link #SCOPE_CONFIGURATION}.
      * @throws NullPointerException
      *             If {@code cfg} is null
      *
      * @since 2.3.22
      */
     public final void set(Object value, Configuration cfg) {
         if (scope != SCOPE_CONFIGURATION) {
             throw new UnsupportedOperationException("This is not a configuration-scope attribute");
         }
         ((Configurable) cfg).setCustomAttribute(key, value);
     }

     private Environment getRequiredCurrentEnvironment() {
         Environment c = Environment.getCurrentEnvironment();
         if (c == null) {
             throw new IllegalStateException("No current environment");
         }
         return c;
     }

     private Configurable getScopeConfigurable(Environment env) throws Error {
         switch (scope) {
         case SCOPE_ENVIRONMENT:
             return env;
         case SCOPE_TEMPLATE:
             return env.getParent();
         case SCOPE_CONFIGURATION:
             return env.getParent().getParent();
         default:
             throw new BugException();
         }
     }

 }
	/*
	* 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 freemarker.core;

	import freemarker.template.Configuration;
	import freemarker.template.Template;

	/**
	* A class that allows one to associate custom data with a {@link Configuration}, a {@link Template}, or
	* {@link Environment}.
	*
	* <p>This API has similar approach to that of {@link ThreadLocal} (which allows one to associate
	* custom data with a thread). With an example:</p>
	*
	* <pre>
	* // The object identity itself will serve as the attribute identifier; there's no attribute name String:
	* public static final CustomAttribute MY_ATTR = new CustomAttribute(CustomAttribute.SCOPE_CONFIGURATION);
	* ...
	* // Set the attribute in this particular Configuration object:
	* MY_ATTR.set(myAttrValue, cfg);
	* ...
	* // Read the attribute from this particular Configuration object:
	* myAttrValue = MY_ATTR.get(cfg);
	* </pre>
	*/
	public class CustomAttribute {

	/**
	* Constant used in the constructor specifying that this attribute is {@link Environment}-scoped.
	*/
	public static final int SCOPE_ENVIRONMENT = 0;

	/**
	* Constant used in the constructor specifying that this attribute is {@link Template}-scoped.
	*/
	public static final int SCOPE_TEMPLATE = 1;

	/**
	* Constant used in the constructor specifying that this attribute is {@link Configuration}-scoped.
	*/
	public static final int SCOPE_CONFIGURATION = 2;

	// We use an internal key instead of 'this' so that malicious subclasses
	// overriding equals() and hashCode() can't gain access to other attribute
	// values. That's also the reason why get() and set() are marked final.
	private final Object key = new Object();
	private final int scope;

	/**
	* Creates a new custom attribute with the specified scope
	* @param scope one of <tt>SCOPE_</tt> constants.
	*/
	public CustomAttribute(int scope) {
	if (scope != SCOPE_ENVIRONMENT &&
	scope != SCOPE_TEMPLATE &&
	scope != SCOPE_CONFIGURATION) {
	throw new IllegalArgumentException();
	}
	this.scope = scope;
	}

	/**
	* This method is invoked when {@link #get()} is invoked without
	* {@link #set(Object)} being invoked before it to define the value in the
	* current scope. Override it to create the attribute value on-demand.
	* @return the initial value for the custom attribute. By default returns null.
	*/
	protected Object create() {
	return null;
	}

	/**
	* Gets the attribute from the appropriate scope that's accessible through the specified {@link Environment}. If
	* the attribute has {@link #SCOPE_ENVIRONMENT} scope, it will be get from the given {@link Environment} directly.
	* If the attribute has {@link #SCOPE_TEMPLATE} scope, it will be get from the parent of the given
	* {@link Environment} (that is, in {@link Environment#getParent()}) directly). If the attribute has
	* {@link #SCOPE_CONFIGURATION} scope, it will be get from {@link Environment#getConfiguration()}.
	*
	* @throws NullPointerException
	* If {@code env} is null
	*
	* @return The new value of the attribute (possibly {@code null}), or {@code null} if the attribute doesn't exist.
	*
	* @since 2.3.22
	*/
	public final Object get(Environment env) {
	return getScopeConfigurable(env).getCustomAttribute(key, this);
	}

	/**
	* Same as {@link #get(Environment)}, but uses {@link Environment#getCurrentEnvironment()} to fill the 2nd argument.
	*
	* @throws IllegalStateException
	* If there is no current {@link Environment}, which is usually the case when the current thread isn't
	* processing a template.
	*/
	public final Object get() {
	return getScopeConfigurable(getRequiredCurrentEnvironment()).getCustomAttribute(key, this);
	}

	/**
	* Gets the value of a {@link Template}-scope attribute from the given {@link Template}.
	*
	* @throws UnsupportedOperationException
	* If this custom attribute has different scope than {@link #SCOPE_TEMPLATE}.
	* @throws NullPointerException
	* If {@code template} is null
	*/
	public final Object get(Template template) {
	if (scope != SCOPE_TEMPLATE) {
	throw new UnsupportedOperationException("This is not a template-scope attribute");
	}
	return ((Configurable) template).getCustomAttribute(key, this);
	}

	/**
	* Same as {@link #get(Template)}, but applies to a {@link TemplateConfiguration}.
	*
	* @since 2.3.24
	*/
	public Object get(TemplateConfiguration templateConfiguration) {
	if (scope != SCOPE_TEMPLATE) {
	throw new UnsupportedOperationException("This is not a template-scope attribute");
	}
	return templateConfiguration.getCustomAttribute(key, this);
	}

	/**
	* Gets the value of a {@link Configuration}-scope attribute from the given {@link Configuration}.
	*
	* @throws UnsupportedOperationException
	* If this custom attribute has different scope than {@link #SCOPE_CONFIGURATION}.
	* @throws NullPointerException
	* If {@code cfg} is null
	*
	* @since 2.3.22
	*/
	public final Object get(Configuration cfg) {
	if (scope != SCOPE_CONFIGURATION) {
	throw new UnsupportedOperationException("This is not a template-scope attribute");
	}
	return ((Configurable) cfg).getCustomAttribute(key, this);
	}

	/**
	* Sets the attribute inside the appropriate scope that's accessible through the specified {@link Environment}. If
	* the attribute has {@link #SCOPE_ENVIRONMENT} scope, it will be set in the given {@link Environment} directly. If
	* the attribute has {@link #SCOPE_TEMPLATE} scope, it will be set in the parent of the given {@link Environment}
	* (that is, in {@link Environment#getParent()}) directly). If the attribute has {@link #SCOPE_CONFIGURATION} scope,
	* it will be set in {@link Environment#getConfiguration()}.
	*
	* @param value
	* The new value of the attribute. Can be {@code null}.
	*
	* @throws NullPointerException
	* If {@code env} is null
	*
	* @since 2.3.22
	*/
	public final void set(Object value, Environment env) {
	getScopeConfigurable(env).setCustomAttribute(key, value);
	}

	/**
	* Same as {@link #set(Object, Environment)}, but uses {@link Environment#getCurrentEnvironment()} to fill the 2nd
	* argument.
	*
	* @throws IllegalStateException
	* If there is no current {@link Environment}, which is usually the case when the current thread isn't
	* processing a template.
	*/
	public final void set(Object value) {
	getScopeConfigurable(getRequiredCurrentEnvironment()).setCustomAttribute(key, value);
	}

	/**
	* Sets the value of a {@link Template}-scope attribute in the given {@link Template}.
	*
	* @param value
	* The new value of the attribute. Can be {@code null}.
	*
	* @throws UnsupportedOperationException
	* If this custom attribute has different scope than {@link #SCOPE_TEMPLATE}.
	* @throws NullPointerException
	* If {@code template} is null
	*/
	public final void set(Object value, Template template) {
	if (scope != SCOPE_TEMPLATE) {
	throw new UnsupportedOperationException("This is not a template-scope attribute");
	}
	((Configurable) template).setCustomAttribute(key, value);
	}

	/**
	* Same as {@link #set(Object, Template)}, but applicable to a {@link TemplateConfiguration}.
	*
	* @since 2.3.24
	*/
	public final void set(Object value, TemplateConfiguration templateConfiguration) {
	if (scope != SCOPE_TEMPLATE) {
	throw new UnsupportedOperationException("This is not a template-scope attribute");
	}
	templateConfiguration.setCustomAttribute(key, value);
	}

	/**
	* Sets the value of a {@link Configuration}-scope attribute in the given {@link Configuration}.
	*
	* @param value
	* The new value of the attribute. Can be {@code null}.
	*
	* @throws UnsupportedOperationException
	* If this custom attribute has different scope than {@link #SCOPE_CONFIGURATION}.
	* @throws NullPointerException
	* If {@code cfg} is null
	*
	* @since 2.3.22
	*/
	public final void set(Object value, Configuration cfg) {
	if (scope != SCOPE_CONFIGURATION) {
	throw new UnsupportedOperationException("This is not a configuration-scope attribute");
	}
	((Configurable) cfg).setCustomAttribute(key, value);
	}

	private Environment getRequiredCurrentEnvironment() {
	Environment c = Environment.getCurrentEnvironment();
	if (c == null) {
	throw new IllegalStateException("No current environment");
	}
	return c;
	}

	private Configurable getScopeConfigurable(Environment env) throws Error {
	switch (scope) {
	case SCOPE_ENVIRONMENT:
	return env;
	case SCOPE_TEMPLATE:
	return env.getParent();
	case SCOPE_CONFIGURATION:
	return env.getParent().getParent();
	default:
	throw new BugException();
	}
	}

	}