/*
* 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;
/**
* <p>
* <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.
* <p>
* 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>
* <p>
* <B>Methods Intended for Container Generated Code</B>
* <p>
* The following methods enable the <B>management of nested</B> JspWriter streams to implement Tag Extensions:
* <code>pushBody()</code> and <code>popBody()</code>
* <p>
* <B>Methods Intended for JSP authors</B>
* <p>
* Some methods provide <B>uniform access</B> 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>.
* <p>
* The following methods provide <B>convenient access</B> to implicit objects: <code>getOut()</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();
/**
* Obtain the ELContext for this JSPContext. Each JSPContext has a dedicated ELContext.
*
* @return the ELContext for this JSPContext
*/
public abstract ELContext getELContext();
/**
* 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.
* <p>
* The returned JspWriter must implement all methods and behave as though it were unbuffered. More specifically:
* </p>
* <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
}
}