org.apache.jasper.compiler.ELInterpreterFactory Maven / Gradle / Ivy
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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.jasper.compiler;
import javax.servlet.ServletContext;
import org.apache.jasper.JspCompilationContext;
/**
* Provides {@link ELInterpreter} instances for JSP compilation.
*
* The search order is as follows:
*
* - ELInterpreter instance or implementation class name provided as a
* ServletContext attribute
* - Implementation class named in a ServletContext initialisation parameter
*
* - Default implementation
*
*/
public class ELInterpreterFactory {
public static final String EL_INTERPRETER_CLASS_NAME =
ELInterpreter.class.getName();
private static final ELInterpreter DEFAULT_INSTANCE =
new DefaultELInterpreter();
/**
* Obtain the correct EL Interpreter for the given web application.
* @param context The Servlet context
* @return the EL interpreter
* @throws Exception If an error occurs creating the interpreter
*/
public static ELInterpreter getELInterpreter(ServletContext context)
throws Exception {
ELInterpreter result = null;
// Search for an implementation
// 1. ServletContext attribute (set by application or cached by a
// previous call to this method).
Object attribute = context.getAttribute(EL_INTERPRETER_CLASS_NAME);
if (attribute instanceof ELInterpreter) {
return (ELInterpreter) attribute;
} else if (attribute instanceof String) {
result = createInstance(context, (String) attribute);
}
// 2. ServletContext init parameter
if (result == null) {
String className =
context.getInitParameter(EL_INTERPRETER_CLASS_NAME);
if (className != null) {
result = createInstance(context, className);
}
}
// 3. Default
if (result == null) {
result = DEFAULT_INSTANCE;
}
// Cache the result for next time
context.setAttribute(EL_INTERPRETER_CLASS_NAME, result);
return result;
}
private static ELInterpreter createInstance(ServletContext context,
String className) throws Exception {
return (ELInterpreter) context.getClassLoader().loadClass(
className).getConstructor().newInstance();
}
private ELInterpreterFactory() {
// Utility class. Hide default constructor.
}
public static class DefaultELInterpreter implements ELInterpreter {
@Override
public String interpreterCall(JspCompilationContext context,
boolean isTagFile, String expression,
Class expectedType, String fnmapvar) {
return JspUtil.interpreterCall(isTagFile, expression, expectedType,
fnmapvar);
}
}
}