    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017
    018package org.apache.commons.jexl3;
    019
    020import java.util.concurrent.Callable;
    021import java.util.concurrent.atomic.AtomicBoolean;
    022
    023/**
    024 * Manages variables which can be referenced in a JEXL expression.
    025 *
    026 * <p>JEXL variable names in their simplest form are 'java-like' identifiers.
    027 * JEXL also considers 'ant' inspired variables expressions as valid.
    028 * For instance, the expression 'x.y.z' is an 'antish' variable and will be resolved as a whole by the context,
    029 * i.e. using the key "x.y.z". This proves to be useful to solve "fully qualified class names".</p>
    030 *
    031 * <p>The interpreter variable resolution algorithm will try the different sequences of identifiers till it finds
    032 * one that exists in the context; if "x" is an object known in the context (JexlContext.has("x") returns true),
    033 * "x.y" will <em>not</em> be looked up in the context but will most likely refer to "x.getY()".</p>
    034 *
    035 * <p>Note that JEXL may use '$jexl' and '$ujexl' variables for internal purpose; setting or getting those
    036 * variables may lead to unexpected results unless specified otherwise.</p>
    037 *
    038 * @since 1.0
    039 */
    040public interface JexlContext {
    041
    042    /**
    043     * Gets the value of a variable.
    044     *
    045     * @param name the variable's name
    046     * @return the value
    047     */
    048    Object get(String name);
    049
    050    /**
    051     * Sets the value of a variable.
    052     *
    053     * @param name the variable's name
    054     * @param value the variable's value
    055     */
    056    void set(String name, Object value);
    057
    058    /**
    059     * Checks whether a variable is defined in this context.
    060     *
    061     * <p>A variable may be defined with a null value; this method checks whether the
    062     * value is null or if the variable is undefined.</p>
    063     *
    064     * @param name the variable's name
    065     * @return true if it exists, false otherwise
    066     */
    067    boolean has(String name);
    068
    069    /**
    070     * A marker interface of the JexlContext that declares how to resolve a namespace from its name;
    071     * it is used by the interpreter during evaluation.
    072     *
    073     * <p>In JEXL, a namespace is an object that serves the purpose of encapsulating functions; for instance,
    074     * the "math" namespace would be the proper object to expose functions like "log(...)", "sinus(...)", etc.</p>
    075     *
    076     * In expressions like "ns:function(...)", the resolver is called with resolveNamespace("ns").
    077     *
    078     * <p>JEXL itself reserves 'jexl' and 'ujexl' as namespaces for internal purpose; resolving those may lead to
    079     * unexpected results.</p>
    080     *
    081     * @since 3.0
    082     */
    083    interface NamespaceResolver {
    084
    085        /**
    086         * Resolves a namespace by its name.
    087         * @param name the name
    088         * @return the namespace object
    089         */
    090        Object resolveNamespace(String name);
    091    }
    092
    093    /**
    094     * A marker interface that solves a simple class name into a fully-qualified one.
    095     * @since 3.3
    096     */
    097    interface ClassNameResolver {
    098        /**
    099         * Resolves a class name.
    100         * @param name the simple class name
    101         * @return the fully qualified class name
    102         */
    103        String resolveClassName(String name);
    104    }
    105
    106    /**
    107     * A marker interface of the JexlContext, NamespaceFunctor allows creating an instance
    108     * to delegate namespace methods calls to.
    109     *
    110     * <p>The functor is created once during the lifetime of a script evaluation.</p>
    111     */
    112    interface NamespaceFunctor {
    113        /**
    114         * Creates the functor object that will be used instead of the namespace.
    115         * @param context the context
    116         * @return the namespace functor instance
    117         */
    118        Object createFunctor(JexlContext context);
    119    }
    120
    121    /**
    122     * A marker interface  of the JexlContext that indicates the interpreter to put this context
    123     * in the JexlEngine thread local context instance during evaluation.
    124     * This allows user functions or methods to access the context during a call.
    125     * Note that the usual caveats wrt using thread local apply (caching/leaking references, etc.); in particular,
    126     * keeping a reference to such a context is to be considered with great care and caution.
    127     * It should also be noted that sharing such a context between threads should implicate synchronizing variable
    128     * accessing the implementation class.
    129     *
    130     * @see JexlEngine#setThreadContext(JexlContext.ThreadLocal)
    131     * @see JexlEngine#getThreadContext()
    132     */
    133    interface ThreadLocal extends JexlContext {
    134        // no specific method
    135    }
    136
    137    /**
    138     * A marker interface of the JexlContext that processes annotations.
    139     * It is used by the interpreter during evaluation to execute annotation evaluations.
    140     * <p>If the JexlContext is not an instance of an AnnotationProcessor, encountering an annotation will generate
    141     * an error or a warning depending on the engine strictness.
    142     * @since 3.1
    143     */
    144    interface AnnotationProcessor {
    145        /**
    146         * Processes an annotation.
    147         * <p>All annotations are processed through this method; the statement 'call' is to be performed within
    148         * the processAnnotation method. The implementation <em>must</em> perform the call explicitly.
    149         * <p>The arguments and the statement <em>must not</em> be referenced or cached for longer than the duration
    150         * of the processAnnotation call.
    151         *
    152         * @param name the annotation name
    153         * @param args the arguments of the annotation, evaluated as arguments of this call
    154         * @param statement the statement that was annotated; the processor should invoke this statement 'call' method
    155         * @return the result of statement.call()
    156         * @throws Exception if annotation processing fails
    157         */
    158        Object processAnnotation(String name, Object[] args, Callable<Object> statement) throws Exception;
    159    }
    160
    161    /**
    162     * A marker interface of the JexlContext that processes module definitions.
    163     * It is used by the interpreter during evaluation of the pragma module definitions.
    164     * @since 3.3
    165     */
    166    interface ModuleProcessor {
    167        /**
    168         * Defines a module.
    169         * The module name will be the namespace mapped to the object returned by the evaluation
    170         * of its body.
    171         * @param engine the engine evaluating this module pragma
    172         * @param info the info at the pragma location
    173         * @param name the module name
    174         * @param body the module definition which can be its location or source
    175         * @return the module object
    176         */
    177        Object processModule(JexlEngine engine, JexlInfo info, String name, String body);
    178    }
    179
    180    /**
    181     * A marker interface of the JexlContext that exposes runtime evaluation options.
    182     * @since 3.2
    183     */
    184    interface OptionsHandle {
    185        /**
    186         * Retrieves the current set of options though the context.
    187         * <p>
    188         * This method will be called once at beginning of evaluation and an interpreter private copy
    189         * of the context handled JexlOptions instance used for the duration of the execution;
    190         * the context handled JexlOptions instance being only used as the source of that copy,
    191         * it can safely alter its boolean flags during execution with no effect, avoiding any behavior ambiguity.
    192         * @return the engine options
    193         */
    194        JexlOptions getEngineOptions();
    195    }
    196
    197    /**
    198     * A marker interface of the JexlContext that processes pragmas.
    199     * It is called by the engine before interpreter creation; as a marker of
    200     * JexlContext, it is expected to have access and interact with the context
    201     * instance.
    202     * @since 3.2
    203     */
    204    interface PragmaProcessor {
    205        /**
    206         * Process one pragma.
    207         * <p>Never called in 3.3, must be implemented for 3.2 binary compatibility reasons.</p>
    208         * <p>Typical implementation in 3.3:</p>
    209         * <code>
    210         *         &#64;Override
    211         *         public void processPragma(String key, Object value) {
    212         *             processPragma(null, key, value);
    213         *         }
    214         * </code>
    215         * @param key the key
    216         * @param value the value
    217         * @deprecated 3.3
    218         */
    219        @Deprecated
    220        void processPragma(String key, Object value);
    221
    222        /**
    223         * Process one pragma.
    224         * @param opts the current evaluator options
    225         * @param key the key
    226         * @param value the value
    227         * @since 3.3
    228         */
    229        default void processPragma(final JexlOptions opts, final String key, final Object value) {
    230            processPragma(key, value);
    231        }
    232    }
    233
    234    /**
    235     * A marker interface of the JexlContext sharing a cancelling flag.
    236     * <p>A script running in a thread can thus be notified through this reference
    237     * of its cancellation through the context. It uses the same interpreter logic
    238     * that reacts to cancellation and is an alternative to using callable() and/or
    239     * interrupting script interpreter threads.
    240     * @since 3.2
    241     */
    242    interface CancellationHandle {
    243        /**
    244         * @return a cancelable boolean used by the interpreter
    245         */
    246        AtomicBoolean getCancellation();
    247    }
    248}