ChainResources.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.commons.chain.web.javax;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
import javax.servlet.ServletContext;
import org.apache.commons.chain.Catalog;
import org.apache.commons.chain.web.CheckedConsumer;
import org.apache.commons.chain.web.CheckedFunction;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Utility methods for loading class loader and web application resources
* to configure a {@link Catalog}. These methods are shared between
* {@code ChainListener} and {@code ChainServlet}.
*
* @author Craig R. McClanahan
* @author Ted Husted
*/
final class ChainResources {
/**
* This class uses a private constructor because it is a utility class.
*/
private ChainResources() {
}
// ---------------------------------------------------------- Static Methods
/**
* Parse the specified class loader resources.
*
* @param <E> the type of the exception from parse-function
* @param resources Comma-delimited list of resources (or {@code null})
* @param parse parse-function to parse the XML document
*/
static <E extends Exception> void parseClassResources(String resources,
CheckedConsumer<URL, E> parse) {
ClassLoader loader =
Thread.currentThread().getContextClassLoader();
if (loader == null) {
loader = ChainResources.class.getClassLoader();
}
parseResources(loader::getResource, resources, parse);
}
/**
* Parse the specified web application resources.
*
* @param <E> the type of the exception from parse-function
* @param context {@code ServletContext} for this web application
* @param resources Comma-delimited list of resources (or {@code null})
* @param parse parse-function to parse the XML document
*/
static <E extends Exception> void parseWebResources(ServletContext context,
String resources,
CheckedConsumer<URL, E> parse) {
parseResources(context::getResource, resources, parse);
}
/**
* Parse the specified resources with a resource-get-function.
*
* @param <ER> the type of the exception from resource-function
* @param <EP> the type of the exception from parse-function
* @param resourceFunction function to get the {@link URL} from a path
* @param resources Comma-delimited list of resources (or {@code null})
* @param parse parse-function to parse the XML document
*/
private static <ER extends Exception, EP extends Exception> void parseResources(
CheckedFunction<String, URL, ER> resourceFunction, String resources,
CheckedConsumer<URL, EP> parse) {
if (resources == null) {
return;
}
Logger logger = LoggerFactory.getLogger(ChainResources.class);
String[] paths = getResourcePaths(resources);
String path = null;
try {
for (String path2 : paths) {
path = path2;
URL url = resourceFunction.apply(path);
if (url == null) {
throw new IllegalStateException("Missing chain config resource '" + path + "'");
}
logger.debug("Loading chain config resource '{}'", path);
parse.accept(url);
}
} catch (Exception e) {
throw new RuntimeException("Exception parsing chain config resource '" + path + "': "
+ e.getMessage());
}
}
/**
* Parse the resource string into an array of paths. Empty entries will
* be skipped. (That is, all entries in the array are non-empty paths.)
*
* @param resources A comma-delimited list of resource paths (or
* {@code null}).
*
* @return An array of non-empty paths. The array itself may be empty.
*
* @since Chain 1.1
*/
static String[] getResourcePaths(String resources) {
final List<String> paths = new ArrayList<>();
if (resources != null) {
String path;
int comma;
int lastComma = 0;
while ((comma = resources.indexOf(',', lastComma)) >= 0) {
path = resources.substring(lastComma, comma).trim();
if (path.length() > 0) {
paths.add(path);
}
lastComma = comma + 1;
}
path = resources.substring(lastComma).trim();
if (path.length() > 0) {
paths.add(path);
}
}
return paths.toArray(new String[0]);
}
}