108 lines
3.6 KiB
Java
108 lines
3.6 KiB
Java
/*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The ASF licenses this file to You under the Apache License, Version 2.0
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* (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.apache.jasper.compiler;
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import javax.servlet.ServletContext;
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import org.apache.jasper.JspCompilationContext;
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/**
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* Provides {@link ELInterpreter} instances for JSP compilation.
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*
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* The search order is as follows:
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* <ol>
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* <li>ELInterpreter instance or implementation class name provided as a
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* ServletContext attribute</li>
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* <li>Implementation class named in a ServletContext initialisation parameter
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* </li>
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* <li>Default implementation</li>
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* </ol>
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*/
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public class ELInterpreterFactory {
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public static final String EL_INTERPRETER_CLASS_NAME =
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ELInterpreter.class.getName();
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private static final ELInterpreter DEFAULT_INSTANCE =
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new DefaultELInterpreter();
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/**
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* Obtain the correct EL Interpreter for the given web application.
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* @param context The Servlet context
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* @return the EL interpreter
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* @throws Exception If an error occurs creating the interpreter
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*/
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public static ELInterpreter getELInterpreter(ServletContext context)
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throws Exception {
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ELInterpreter result = null;
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// Search for an implementation
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// 1. ServletContext attribute (set by application or cached by a
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// previous call to this method).
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Object attribute = context.getAttribute(EL_INTERPRETER_CLASS_NAME);
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if (attribute instanceof ELInterpreter) {
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return (ELInterpreter) attribute;
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} else if (attribute instanceof String) {
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result = createInstance(context, (String) attribute);
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}
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// 2. ServletContext init parameter
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if (result == null) {
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String className =
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context.getInitParameter(EL_INTERPRETER_CLASS_NAME);
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if (className != null) {
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result = createInstance(context, className);
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}
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}
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// 3. Default
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if (result == null) {
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result = DEFAULT_INSTANCE;
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}
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// Cache the result for next time
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context.setAttribute(EL_INTERPRETER_CLASS_NAME, result);
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return result;
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}
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private static ELInterpreter createInstance(ServletContext context,
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String className) throws Exception {
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return (ELInterpreter) context.getClassLoader().loadClass(
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className).getConstructor().newInstance();
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}
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private ELInterpreterFactory() {
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// Utility class. Hide default constructor.
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}
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public static class DefaultELInterpreter implements ELInterpreter {
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@Override
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public String interpreterCall(JspCompilationContext context,
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boolean isTagFile, String expression,
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Class<?> expectedType, String fnmapvar) {
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return JspUtil.interpreterCall(isTagFile, expression, expectedType,
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fnmapvar);
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}
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}
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}
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