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/*
* 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 org.apache.commons.jexl3;
import java.util.concurrent.Callable;
/**
* Manages variables which can be referenced in a JEXL expression.
*
* JEXL variable names in their simplest form are 'java-like' identifiers.
* JEXL also considers 'ant' inspired variables expressions as valid.
* For instance, the expression 'x.y.z' is an 'antish' variable and will be resolved as a whole by the context,
* i.e. using the key "x.y.z". This proves to be useful to solve "fully qualified class names".
*
* The interpreter variable resolution algorithm will try the different sequences of identifiers till it finds
* one that exists in the context; if "x" is an object known in the context (JexlContext.has("x") returns true),
* "x.y" will not be looked up in the context but will most likely refer to "x.getY()".
*
* Note that JEXL may use '$jexl' and '$ujexl' variables for internal purpose; setting or getting those
* variables may lead to unexpected results unless specified otherwise.
*
* @since 1.0
*/
public interface JexlContext {
/**
* Gets the value of a variable.
*
* @param name the variable's name
* @return the value
*/
Object get(String name);
/**
* Sets the value of a variable.
*
* @param name the variable's name
* @param value the variable's value
*/
void set(String name, Object value);
/**
* Checks whether a variable is defined in this context.
*
* A variable may be defined with a null value; this method checks whether the
* value is null or if the variable is undefined.
*
* @param name the variable's name
* @return true if it exists, false otherwise
*/
boolean has(String name);
/**
* A marker interface of the JexlContext that declares how to resolve a namespace from its name;
* it is used by the interpreter during evaluation.
*
* In JEXL, a namespace is an object that serves the purpose of encapsulating functions; for instance,
* the "math" namespace would be the proper object to expose functions like "log(...)", "sinus(...)", etc.
*
* In expressions like "ns:function(...)", the resolver is called with resolveNamespace("ns").
*
* JEXL itself reserves 'jexl' and 'ujexl' as namespaces for internal purpose; resolving those may lead to
* unexpected results.
*
* @since 3.0
*/
interface NamespaceResolver {
/**
* Resolves a namespace by its name.
* @param name the name
* @return the namespace object
*/
Object resolveNamespace(String name);
}
/**
* A marker interface of the JexlContext, NamespaceFunctor allows creating an instance
* to delegate namespace methods calls to.
*
* The functor is created once during the lifetime of a script evaluation.
*/
interface NamespaceFunctor {
/**
* Creates the functor object that will be used instead of the namespace.
* @param context the context
* @return the namespace functor instance
*/
Object createFunctor(JexlContext context);
}
/**
* A marker interface of the JexlContext that indicates the interpreter to put this context
* in the JexlEngine thread local context instance during evaluation.
* This allows user functions or methods to access the context during a call.
* Note that the usual caveats wrt using thread local apply (caching/leaking references, etc.); in particular,
* keeping a reference to such a context is to be considered with great care and caution.
* It should also be noted that sharing such a context between threads should implicate synchronizing variable
* accessing the implementation class.
*
* @see JexlEngine#setThreadContext(JexlContext.ThreadLocal)
* @see JexlEngine#getThreadContext()
*/
interface ThreadLocal extends JexlContext {
// no specific method
}
/**
* A marker interface of the JexlContext that allows to process annotations.
* It is used by the interpreter during evaluation to execute annotation evaluations.
* If the JexlContext is not an instance of an AnnotationProcessor, encountering an annotation will generate
* an error or a warning depending on the engine strictness.
* @since 3.1
*/
interface AnnotationProcessor {
/**
* Processes an annotation.
*
All annotations are processed through this method; the statement 'call' is to be performed within
* the processAnnotation method. The implementation must perform the call explicitly.
*
The arguments and the statement must not be referenced or cached for longer than the duration
* of the processAnnotation call.
*
* @param name the annotation name
* @param args the arguments of the annotation, evaluated as arguments of this call
* @param statement the statement that was annotated; the processor should invoke this statement 'call' method
* @return the result of statement.call()
* @throws Exception if annotation processing fails
*/
Object processAnnotation(String name, Object[] args, Callable