libjava/classpath/gnu/java/beans/decoder/Context.java

/* gnu.java.beans.decoder.Context
   Copyright (C) 2004 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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02110-1301 USA.

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making a combined work based on this library.  Thus, the terms and
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permission to link this library with independent modules to produce an
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package gnu.java.beans.decoder;

/** A Context is the environment for an object which is being assembler. If there
 * are no errors each handler creates one Context.
 * <p>Depending on the result of isStatement() a Context can be statement or an
 * expression. An expression returns a value to the Context of its parent handler,
 * a statement does not. Whenever a Context is a statement the parent handler's
 * Context is informed about that through the {@link notifyStatement}-method.</p>
 *
 * @author Robert Schuster
 */
interface Context
{
  /** Adds a parameter object to the context. This method is used when
   * sub-Contexts return their result.
   *
   * Some Contexts do not accept more than a certain amount of objects
   * and throw an AssemblerException if the amount is exceeded.
   *
   * @param o The object added to this context.
   */
  void addParameterObject(Object o) throws AssemblyException;

  /** Notifies that the next element is a statement. This can mean
   * that an argument list is complete to be called.
   *
   */
  void notifyStatement(Context outerContext) throws AssemblyException;

  /** Notifies that the context ends and the returns the appropriate result
   * object.
   *
   * @param outerContext
   * @return
   */
  Object endContext(Context outerContext) throws AssemblyException;

  /** Notifies that the assembly of a subcontext failed and returns
   * whether this Context is affected in a way that it fails too.
   *
   * @return Whether the failure of a subcontext lets this context fail, too.
   */
  boolean subContextFailed();

  /** Calls an appropriate indexed set method if it is available or
   * throws an AssemblerException if that is not allowed on this Context.
   *
   * The behaviour of this method is equal to List.set(int, Object).
   *
   * @param index Index position to be set.
   * @param o Object to be set at the given index position.
   * @throws AssemblerException Indexed set is not allowed or otherwise failed.
   */
  void set(int index, Object o) throws AssemblyException;

  /** Calls an appropriate indexed get method if it is available or
   * throws an AssemblerException if that is not allowed on this Context.
   *
   * The behaviour of this method is equal to List.get(int).
   *
   * @param index Index position of the object return.
   * @throws AssemblerException Indexed get is not allowed or otherwise failed.
   */
  Object get(int index) throws AssemblyException;

  /** Returns the result which was calculated by calling endContext() or reportStatement().
   * Its the handler's responsibility to care that any of these two methods was called.
   *
   * This is used by sub-Contexts to access this Context's result.
   *
   * @return
   */
  Object getResult();

  /** Gives this Context a unique id. For convenience the id may be null which means
   * that no id exists at all.
   *
   * @param id
   */
  void setId(String id);

  /** Returns this Context's unique id or null if does not have such an id.
   *
   * @return This Context's id or null.
   */
  String getId();

  /** Returns whether this Context is a statement (not returning result back
   * to parent handler's Context) or not (= expression).
   *
   * @return
   */
  boolean isStatement();

  /** Sets whether this Context is a statement or not.
   *
   * @param b
   */
  void setStatement(boolean b);
}