Tomcat example source code file (TagPluginContext.java)

This example Tomcat source code file (TagPluginContext.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Tomcat tags/keywords

object, object, string, string, tagplugincontext, tagplugincontext

The Tomcat TagPluginContext.java source code

/*
 * 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.jasper.compiler.tagplugin;


/**
 * This interface allows the plugin author to make inqueries about the
 * properties of the current tag, and to use Jasper resources to generate
 * direct Java codes in place of tag handler invocations.
 */

public interface TagPluginContext {
    /**
     * @return true if the body of the tag is scriptless.
     */
    boolean isScriptless();

    /**
     * @param attribute Name of the attribute
     * @return true if the attribute is specified in the tag
     */
    boolean isAttributeSpecified(String attribute);

    /**
     * @return An unique temporary variable name that the plugin can use.
     */
    String getTemporaryVariableName();

    /**
     * Generate an import statement
     * @param s Name of the import class, '*' allowed.
     */
    void generateImport(String s);

    /**
     * Generate a declaration in the of the generated class.  This can be
     * used to declare an innter class, a method, or a class variable.
     * @param id An unique ID identifying the declaration.  It is not
     *           part of the declaration, and is used to ensure that the
     *           declaration will only appear once.  If this method is
     *           invoked with the same id more than once in the translation
     *           unit, only the first declaration will be taken.
     * @param text The text of the declaration.
     **/
    void generateDeclaration(String id, String text);

    /**
     * Generate Java source codes
     */
    void generateJavaSource(String s);

    /**
     * @return true if the attribute is specified and its value is a
     *         translation-time constant.
     */
    boolean isConstantAttribute(String attribute);

    /**
     * @return A string that is the value of a constant attribute.  Undefined
     *         if the attribute is not a (translation-time) constant.
     *         null if the attribute is not specified.
     */
    String getConstantAttribute(String attribute);

    /**
     * Generate codesto evaluate value of a attribute in the custom tag
     * The codes is a Java expression.
     * NOTE: Currently cannot handle attributes that are fragments.
     * @param attribute The specified attribute
     */
    void generateAttribute(String attribute);

    /**
     * Generate codes for the body of the custom tag
     */
    void generateBody();

    /**
     * Abandon optimization for this tag handler, and instruct
     * Jasper to generate the tag handler calls, as usual.
     * Should be invoked if errors are detected, or when the tag body
     * is deemed too compilicated for optimization.
     */
    void dontUseTagPlugin();

    /**
     * Get the PluginContext for the parent of this custom tag.  NOTE:
     * The operations available for PluginContext so obtained is limited
     * to getPluginAttribute and setPluginAttribute, and queries (e.g.
     * isScriptless().  There should be no calls to generate*().
     * @return The pluginContext for the parent node.
     *         null if the parent is not a custom tag, or if the pluginConxt
     *         if not available (because useTagPlugin is false, e.g).
     */
    TagPluginContext getParentContext();

    /**
     * Associate the attribute with a value in the current tagplugin context.
     * The plugin attributes can be used for communication among tags that
     * must work together as a group.  See <c:when> for an example.
     */
    void setPluginAttribute(String attr, Object value);

    /**
     * Get the value of an attribute in the current tagplugin context.
     */
    Object getPluginAttribute(String attr);
}