/*
* Copyright 2004-2005 Graeme Rocher
*
* Licensed 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.grails.web.pages.ext.jsp;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.util.ClassUtils;
import javax.el.*;
import javax.servlet.jsp.JspApplicationContext;
import javax.servlet.jsp.el.ImplicitObjectELResolver;
import javax.servlet.jsp.el.ScopedAttributeELResolver;
import java.util.Iterator;
import java.util.LinkedList;
/**
* @author Graeme Rocher
* @since 1.0
*/
public class GroovyPagesJspApplicationContext implements JspApplicationContext {
private static final Log LOG = LogFactory.getLog(GroovyPagesJspApplicationContext.class);
private static final ExpressionFactory expressionFactoryImpl = findExpressionFactoryImplementation();
private final LinkedList<ELContextListener> listeners = new LinkedList<ELContextListener>();
private final CompositeELResolver elResolver = new CompositeELResolver();
private final CompositeELResolver additionalResolvers = new CompositeELResolver();
public GroovyPagesJspApplicationContext() {
elResolver.add(new ImplicitObjectELResolver());
elResolver.add(additionalResolvers);
elResolver.add(new MapELResolver());
elResolver.add(new ResourceBundleELResolver());
elResolver.add(new ListELResolver());
elResolver.add(new ArrayELResolver());
elResolver.add(new BeanELResolver());
elResolver.add(new ScopedAttributeELResolver());
}
private static ExpressionFactory findExpressionFactoryImplementation() {
ExpressionFactory ef = tryExpressionFactoryImplementation("com.sun");
if (ef == null) {
ef = tryExpressionFactoryImplementation("org.apache");
if (ef == null) {
LOG.warn("Could not find any implementation for " +
ExpressionFactory.class.getName());
}
}
return ef;
}
private static ExpressionFactory tryExpressionFactoryImplementation(String packagePrefix) {
String className = packagePrefix + ".el.ExpressionFactoryImpl";
try {
Class<?> cl = ClassUtils.forName(className, null);
if (ExpressionFactory.class.isAssignableFrom(cl)) {
LOG.info("Using " + className + " as implementation of " +
ExpressionFactory.class.getName());
return (ExpressionFactory)cl.newInstance();
}
LOG.warn("Class " + className + " does not implement " +
ExpressionFactory.class.getName());
}
catch(ClassNotFoundException e) {
// ignored
}
catch(Exception e) {
LOG.error("Failed to instantiate " + className, e);
}
return null;
}
public void addELResolver(ELResolver resolver) {
additionalResolvers.add(resolver);
}
public ExpressionFactory getExpressionFactory() {
return expressionFactoryImpl;
}
public void addELContextListener(ELContextListener elContextListener) {
synchronized(listeners) {
listeners.addLast(elContextListener);
}
}
ELContext createELContext(GroovyPagesPageContext pageCtx) {
ELContext ctx = new GroovyPagesELContext(pageCtx);
ELContextEvent event = new ELContextEvent(ctx);
synchronized(listeners) {
for (Iterator<ELContextListener> iter = listeners.iterator(); iter.hasNext();) {
iter.next().contextCreated(event);
}
}
return ctx;
}
private class GroovyPagesELContext extends ELContext {
private GroovyPagesPageContext pageCtx;
public GroovyPagesELContext(GroovyPagesPageContext pageCtx) {
this.pageCtx = pageCtx;
}
@Override
public ELResolver getELResolver() {
return elResolver;
}
@Override
public FunctionMapper getFunctionMapper() {
return null;
}
@Override
public VariableMapper getVariableMapper() {
return new VariableMapper() {
@Override
public ValueExpression resolveVariable(String name) {
Object o = pageCtx.findAttribute(name);
if (o == null) return null;
return expressionFactoryImpl.createValueExpression(o, o.getClass());
}
@Override
public ValueExpression setVariable(String name, ValueExpression valueExpression) {
ValueExpression previous = resolveVariable(name);
pageCtx.setAttribute(name, valueExpression.getValue(GroovyPagesELContext.this));
return previous;
}
};
}
}
}