package com.commafeed.backend.service;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import org.apache.commons.jexl2.JexlContext;
import org.apache.commons.jexl2.JexlEngine;
import org.apache.commons.jexl2.JexlException;
import org.apache.commons.jexl2.JexlInfo;
import org.apache.commons.jexl2.MapContext;
import org.apache.commons.jexl2.Script;
import org.apache.commons.jexl2.introspection.JexlMethod;
import org.apache.commons.jexl2.introspection.JexlPropertyGet;
import org.apache.commons.jexl2.introspection.Uberspect;
import org.apache.commons.jexl2.introspection.UberspectImpl;
import org.apache.commons.lang3.StringUtils;
import org.apache.commons.logging.LogFactory;
import org.jsoup.Jsoup;
import com.commafeed.backend.model.FeedEntry;
public class FeedEntryFilteringService {
private static final JexlEngine ENGINE = initEngine();
private static JexlEngine initEngine() {
// classloader that prevents object creation
ClassLoader cl = new ClassLoader() {
@Override
public Class<?> loadClass(String name) throws ClassNotFoundException {
return null;
}
@Override
protected Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundException {
return null;
}
};
// uberspect that prevents access to .class and .getClass()
Uberspect uberspect = new UberspectImpl(LogFactory.getLog(JexlEngine.class)) {
@Override
public JexlPropertyGet getPropertyGet(Object obj, Object identifier, JexlInfo info) {
if ("class".equals(identifier)) {
return null;
}
return super.getPropertyGet(obj, identifier, info);
}
@Override
public JexlMethod getMethod(Object obj, String method, Object[] args, JexlInfo info) {
if ("getClass".equals(method)) {
return null;
}
return super.getMethod(obj, method, args, info);
}
};
JexlEngine engine = new JexlEngine(uberspect, null, null, null);
engine.setStrict(true);
engine.setClassLoader(cl);
return engine;
}
private ExecutorService executor = Executors.newCachedThreadPool();
public boolean filterMatchesEntry(String filter, FeedEntry entry) throws FeedEntryFilterException {
if (StringUtils.isBlank(filter)) {
return true;
}
Script script = null;
try {
script = ENGINE.createScript(filter);
} catch (JexlException e) {
throw new FeedEntryFilterException("Exception while parsing expression " + filter, e);
}
JexlContext context = new MapContext();
context.set("title", Jsoup.parse(entry.getContent().getTitle()).text().toLowerCase());
context.set("author", entry.getContent().getAuthor().toLowerCase());
context.set("content", Jsoup.parse(entry.getContent().getContent()).text().toLowerCase());
context.set("url", entry.getUrl().toLowerCase());
Callable<Object> callable = script.callable(context);
Future<Object> future = executor.submit(callable);
Object result = null;
try {
result = future.get(500, TimeUnit.MILLISECONDS);
} catch (InterruptedException e) {
throw new FeedEntryFilterException("interrupted while evaluating expression " + filter, e);
} catch (ExecutionException e) {
throw new FeedEntryFilterException("Exception while evaluating expression " + filter, e);
} catch (TimeoutException e) {
throw new FeedEntryFilterException("Took too long evaluating expression " + filter, e);
}
try {
return (boolean) result;
} catch (ClassCastException e) {
throw new FeedEntryFilterException(e.getMessage(), e);
}
}
@SuppressWarnings("serial")
public static class FeedEntryFilterException extends Exception {
public FeedEntryFilterException(String message, Throwable t) {
super(message, t);
}
}
}