Quelle JspContext.java Sprache: JAVA

/*
* 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 jakarta.servlet.jsp;

import java.util.Enumeration;

import jakarta.el.ELContext;

/**
* 
* <code>JspContext</code> serves as the base class for the PageContext class and abstracts all information that is not
* specific to servlets. This allows for Simple Tag Extensions to be used outside of the context of a request/response
* Servlet.
* 
* The JspContext provides a number of facilities to the page/component author and page implementor, including:
* <ul>
* <li>a single API to manage the various scoped namespaces
* <li>a mechanism to obtain the JspWriter for output
* <li>a mechanism to expose page directive attributes to the scripting environment
* </ul>
* 
* Methods Intended for Container Generated Code
* 
* The following methods enable the management of nested JspWriter streams to implement Tag Extensions:
* <code>pushBody()</code> and <code>popBody()</code>
* 
* Methods Intended for JSP authors
* 
* Some methods provide uniform access to the diverse objects representing scopes. The implementation must use
* the underlying machinery corresponding to that scope, so information can be passed back and forth between the
* underlying environment (e.g. Servlets) and JSP pages. The methods are: <code>setAttribute()</code>,
* <code>getAttribute()</code>, <code>findAttribute()</code>, <code>removeAttribute()</code>,
* <code>getAttributesScope()</code> and <code>getAttributeNamesInScope()</code>.
* 
* The following methods provide convenient access to implicit objects: <code>getOut()</code>
* 
* The following methods provide programmatic access to the Expression Language evaluator:
* <code>getExpressionEvaluator()</code>, <code>getVariableResolver()</code>
*
* @since JSP 2.0
*/

public abstract class JspContext {

 /**
 * Sole constructor. (For invocation by subclass constructors, typically implicit.)
 */
 public JspContext() {
 // NOOP by default
 }

 /**
 * Register the name and value specified with page scope semantics. If the value passed in is <code>null</code>,
 * this has the same effect as calling <code>removeAttribute( name, PageContext.PAGE_SCOPE )</code>.
 *
 * @param name the name of the attribute to set
 * @param value the value to associate with the name, or null if the attribute is to be removed from the page scope.
 *
 * @throws NullPointerException if the name is null
 */

 public abstract void setAttribute(String name, Object value);

 /**
 * Register the name and value specified with appropriate scope semantics. If the value passed in is
 * <code>null</code>, this has the same effect as calling <code>removeAttribute( name, scope )</code>.
 *
 * @param name the name of the attribute to set
 * @param value the object to associate with the name, or null if the attribute is to be removed from the specified
 * scope.
 * @param scope the scope with which to associate the name/object
 *
 * @throws NullPointerException if the name is null
 * @throws IllegalArgumentException if the scope is invalid
 * @throws IllegalStateException if the scope is PageContext.SESSION_SCOPE but the page that was requested does
 * not participate in a session or the session has been invalidated.
 */

 public abstract void setAttribute(String name, Object value, int scope);

 /**
 * Returns the object associated with the name in the page scope or null if not found.
 *
 * @param name the name of the attribute to get
 *
 * @return the object associated with the name in the page scope or null if not found.
 *
 * @throws NullPointerException if the name is null
 */

 public abstract Object getAttribute(String name);

 /**
 * Return the object associated with the name in the specified scope or null if not found.
 *
 * @param name the name of the attribute to set
 * @param scope the scope with which to associate the name/object
 *
 * @return the object associated with the name in the specified scope or null if not found.
 *
 * @throws NullPointerException if the name is null
 * @throws IllegalArgumentException if the scope is invalid
 * @throws IllegalStateException if the scope is PageContext.SESSION_SCOPE but the page that was requested does
 * not participate in a session or the session has been invalidated.
 */

 public abstract Object getAttribute(String name, int scope);

 /**
 * Searches for the named attribute in page, request, session (if valid), and application scope(s) in order and
 * returns the value associated or null.
 *
 * @param name the name of the attribute to search for
 *
 * @return the value associated or null
 *
 * @throws NullPointerException if the name is null
 */

 public abstract Object findAttribute(String name);

 /**
 * Remove the object reference associated with the given name from all scopes. Does nothing if there is no such
 * object.
 *
 * @param name The name of the object to remove.
 *
 * @throws NullPointerException if the name is null
 */

 public abstract void removeAttribute(String name);

 /**
 * Remove the object reference associated with the specified name in the given scope. Does nothing if there is no
 * such object.
 *
 * @param name The name of the object to remove.
 * @param scope The scope where to look.
 *
 * @throws IllegalArgumentException if the scope is invalid
 * @throws IllegalStateException if the scope is PageContext.SESSION_SCOPE but the page that was requested does
 * not participate in a session or the session has been invalidated.
 * @throws NullPointerException if the name is null
 */

 public abstract void removeAttribute(String name, int scope);

 /**
 * Get the scope where a given attribute is defined.
 *
 * @param name the name of the attribute to return the scope for
 *
 * @return the scope of the object associated with the name specified or 0
 *
 * @throws NullPointerException if the name is null
 */

 public abstract int getAttributesScope(String name);

 /**
 * Enumerate all the attributes in a given scope.
 *
 * @param scope the scope to enumerate all the attributes for
 *
 * @return an enumeration of names ({@link String}) of all the attributes the specified scope
 *
 * @throws IllegalArgumentException if the scope is invalid
 * @throws IllegalStateException if the scope is PageContext.SESSION_SCOPE but the page that was requested does
 * not participate in a session or the session has been invalidated.
 */

 public abstract Enumeration<String> getAttributeNamesInScope(int scope);

 /**
 * The current value of the out object (a JspWriter).
 *
 * @return the current JspWriter stream being used for client response
 */
 public abstract JspWriter getOut();

 /**
 * Provides programmatic access to the ExpressionEvaluator. The JSP Container must return a valid instance of an
 * ExpressionEvaluator that can parse EL expressions.
 *
 * @return A valid instance of an ExpressionEvaluator.
 *
 * @since JSP 2.0
 *
 * @deprecated As of JSP 2.1, replaced by JspApplicationContext.getExpressionFactory()
 */
 @Deprecated
 public abstract jakarta.servlet.jsp.el.ExpressionEvaluator getExpressionEvaluator();

 /**
 * Obtain the ELContext for this JSPContext. Each JSPContext has a dedicated ELContext.
 *
 * @return the ELContext for this JSPContext
 */
 public abstract ELContext getELContext();

 /**
 * Returns an instance of a VariableResolver that provides access to the implicit objects specified in the JSP
 * specification using this JspContext as the context object.
 *
 * @return A valid instance of a VariableResolver.
 *
 * @since JSP 2.0
 *
 * @deprecated As of JSP 2.1, replaced by jakarta.el.ELContext.getELResolver() which can be obtained by
 * jspContext.getELContext().getELResolver()
 */
 @Deprecated
 public abstract jakarta.servlet.jsp.el.VariableResolver getVariableResolver();

 /**
 * Return a new JspWriter object that sends output to the provided Writer. Saves the current "out" JspWriter, and
 * updates the value of the "out" attribute in the page scope attribute namespace of the JspContext.
 * 
 * The returned JspWriter must implement all methods and behave as though it were unbuffered. More specifically:
 * 
 * <ul>
 * <li>clear() must throw an IOException</li>
 * <li>clearBuffer() does nothing</li>
 * <li>getBufferSize() always returns 0</li>
 * <li>getRemaining() always returns 0</li>
 * </ul>
 *
 * @param writer The Writer for the returned JspWriter to send output to.
 *
 * @return a new JspWriter that writes to the given Writer.
 *
 * @since JSP 2.0
 */
 public JspWriter pushBody(java.io.Writer writer) {
 return null; // XXX to implement
 }

 /**
 * Return the previous JspWriter "out" saved by the matching pushBody(), and update the value of the "out" attribute
 * in the page scope attribute namespace of the JspContext.
 *
 * @return the saved JspWriter.
 */
 public JspWriter popBody() {
 return null; // XXX to implement
 }
}

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