java/org/apache/jasper/compiler/ELInterpreter.java

/*
 * 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.jasper.compiler;

import org.apache.jasper.JspCompilationContext;

/**
 * Defines the interface for the expression language interpreter. This allows users to provide custom EL interpreter
 * implementations that can optimise EL processing for an application by , for example, performing code generation for
 * simple expressions.
 */
public interface ELInterpreter {

    /**
     * Returns the string representing the code that will be inserted into the servlet generated for JSP. The default
     * implementation creates a call to
     * {@link org.apache.jasper.runtime.PageContextImpl#proprietaryEvaluate( String, Class, javax.servlet.jsp.PageContext, org.apache.jasper.runtime.ProtectedFunctionMapper)}
     * but other implementations may produce more optimised code.
     *
     * @param context      The compilation context
     * @param isTagFile    <code>true</code> if in a tag file rather than a JSP
     * @param expression   a String containing zero or more "${}" expressions
     * @param expectedType the expected type of the interpreted result
     * @param fnmapvar     Variable pointing to a function map.
     *
     * @return a String representing a call to the EL interpreter.
     */
    String interpreterCall(JspCompilationContext context, boolean isTagFile, String expression, Class<?> expectedType,
            String fnmapvar);
}