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    1   /*
    2    * Copyright 1999-2004 The Apache Software Foundation
    3    *
    4    * Licensed under the Apache License, Version 2.0 (the "License");
    5    * you may not use this file except in compliance with the License.
    6    * You may obtain a copy of the License at
    7    *
    8    *     http://www.apache.org/licenses/LICENSE-2.0
    9    *
    10   * Unless required by applicable law or agreed to in writing, software
    11   * distributed under the License is distributed on an "AS IS" BASIS,
    12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13   * See the License for the specific language governing permissions and
    14   * limitations under the License.
    15   */
    16  package org.apache.commons.jxpath;
    17
    18  import java.util.Iterator;
    19
    20  /***
    21   * Represents a compiled XPath. The interpretation of compiled XPaths
    22   * may be faster, because it bypasses the compilation step. The reference
    23   * implementation of JXPathContext also globally caches some of the
    24   * results of compilation, so the direct use of JXPathContext is not
    25   * always less efficient than the use of CompiledExpression.
    26   * <p>
    27   * Use CompiledExpression only when there is a need to evaluate the
    28   * same expression multiple times and the CompiledExpression can be
    29   * conveniently cached.
    30   * <p>
    31   * To acqure a CompiledExpression, call {@link JXPathContext#compile
    32   * JXPathContext.compile}
    33   *
    34   * @author Dmitri Plotnikov
    35   * @version $Revision: 1.6 $ $Date: 2004/02/29 14:17:42 $
    36   */
    37  public interface CompiledExpression {
    38
    39      /***
    40       * Evaluates the xpath and returns the resulting object. Primitive
    41       * types are wrapped into objects.
    42       */
    43      Object getValue(JXPathContext context);
    44
    45      /***
    46       * Evaluates the xpath, converts the result to the specified class and
    47       * returns the resulting object.
    48       */
    49      Object getValue(JXPathContext context, Class requiredType);
    50
    51      /***
    52       * Modifies the value of the property described by the supplied xpath.
    53       * Will throw an exception if one of the following conditions occurs:
    54       * <ul>
    55       * <li>The xpath does not in fact describe an existing property
    56       * <li>The property is not writable (no public, non-static set method)
    57       * </ul>
    58       */
    59      void setValue(JXPathContext context, Object value);
    60
    61      /***
    62       * Creates intermediate elements of
    63       * the path by invoking an AbstractFactory, which should first be
    64       * installed on the context by calling "setFactory".
    65       */
    66      Pointer createPath(JXPathContext context);
    67
    68      /***
    69       * The same as setValue, except it creates intermediate elements of
    70       * the path by invoking an AbstractFactory, which should first be
    71       * installed on the context by calling "setFactory".
    72       * <p>
    73       * Will throw an exception if one of the following conditions occurs:
    74       * <ul>
    75       * <li>Elements of the xpath aleady exist, by the path does not in
    76       *  fact describe an existing property
    77       * <li>The AbstractFactory fails to create an instance for an intermediate
    78       * element.
    79       * <li>The property is not writable (no public, non-static set method)
    80       * </ul>
    81       */
    82      Pointer createPathAndSetValue(JXPathContext context, Object value);
    83
    84      /***
    85       * Traverses the xpath and returns a Iterator of all results found
    86       * for the path. If the xpath matches no properties
    87       * in the graph, the Iterator will not be null.
    88       */
    89      Iterator iterate(JXPathContext context);
    90
    91      /***
    92       * Traverses the xpath and returns a Pointer.
    93       * A Pointer provides easy access to a property.
    94       * If the xpath matches no properties
    95       * in the graph, the pointer will be null.
    96       */
    97      Pointer getPointer(JXPathContext context, String xpath);
    98
    99      /***
    100      * Traverses the xpath and returns an Iterator of Pointers.
    101      * A Pointer provides easy access to a property.
    102      * If the xpath matches no properties
    103      * in the graph, the Iterator be empty, but not null.
    104      */
    105     Iterator iteratePointers(JXPathContext context);
    106
    107     /***
    108      * Remove the graph element described by this expression
    109      */
    110     void removePath(JXPathContext context);
    111
    112     /***
    113      * Remove all graph elements described by this expression
    114      */
    115     void removeAll(JXPathContext context);
    116 }