FilterUtil.java

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package com.buglabs.util.osgi;

import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.SortedMap;
import java.util.TreeMap;

import org.osgi.framework.BundleContext;
import org.osgi.framework.Constants;
import org.osgi.framework.Filter;
import org.osgi.framework.InvalidSyntaxException;

/**
 * A helper class for constructing OSGi filters.
 * 
 */
public final class FilterUtil {

	/**
	 * Non-constructible utility class.
	 */
	private FilterUtil() {
		
	}
	/**
	 * Generate a service filter string for a single service.
	 * @param clazz Service name
	 * @return Filter as a String
	 */
	public static String generateServiceFilter(String clazz) {
		return "(" + Constants.OBJECTCLASS + "=" + clazz + ")";
	}
	
	/**
	 * @param services A variable number of services.
	 * @return A LDAP filter string that can be used to construct a Filter.  If null passed in, null is returned to caller.
	 */
	public static String generateServiceFilter(String ... services) {
		return generateServiceFilter(Arrays.asList(services));
	}
	
	/**
	 * Generate a Filter as a String for a List of services.
	 * 
	 * @param services A String List of class names.
	 * @return A LDAP filter string that can be used to construct a Filter.  If null passed in, null is returned to caller.
	 */
	public static String generateServiceFilter(List<String> services) {
		if (services == null) {
			return null;
		} 
		
		if (services.size() == 1) {
			return "(" + Constants.OBJECTCLASS + "=" + services.get(0) + ")";
		} else if (services.size() > 1) {
			return "(|" + generateServiceFilter(services.subList(0, 1)) 
				+ generateServiceFilter(services.subList(1, services.size())) + ")";
		}

		return "";
	}

	/**
	 * Generate a Filter object from an array of Service names and a bundle
	 * context.
	 * 
	 * @param context BundleContext used to create the Filter instance
	 * @param services String List of services
	 * @return Filter representing services
	 * @throws InvalidSyntaxException thrown if a syntax error is found in the generated Filter.
	 */
	public static Filter generateServiceFilter(BundleContext context, String[] services) throws InvalidSyntaxException {
		 String filterString = generateServiceFilter(Arrays.asList(services));
		 
		 return context.createFilter(filterString);
	}

	/**
	 * servicesMap is SortedMap<String, Map<String, String>> where the key is
	 * the service name and the map is a map of service properties.
	 * 
	 * (| (& (objectClass=com.buglabs.bug.module.bugbee.pub.IBUGBeeControl) (&
	 * (Provider=com.buglabs.bug.module.bugbee.BUGBeeModlet)(Slot=2))) (| (&
	 * (objectClass=com.buglabs.module.IModuleControl)) (&
	 * (objectClass=org.osgi.service.http.HttpService)(port=8082))))
	 * 
	 * @param servicesMap Map of services to generate filter with.
	 * @return Filter as a string.
	 * 
	 */
	public static String generateServiceFilter(SortedMap<String, Map<String, String>> servicesMap) {
		if (servicesMap.size() == 1) {
			return "(&(" + Constants.OBJECTCLASS + "=" + servicesMap.firstKey() + ")"
					+ generatePropertiesFilter(new TreeMap(servicesMap.get(servicesMap.firstKey()))) + ")";
		} else if (servicesMap.size() > 1) {
			return "(|" + generateServiceFilter(servicesMap.subMap(servicesMap.firstKey(), servicesMap.firstKey() + "\0"))
					+ generateServiceFilter(servicesMap.tailMap(servicesMap.firstKey() + "\0")) + ")";
		}
		return "";
	}

	/**
	 * Generate a Filter as a String given a Map of property/value pairs.
	 * (& (prop1=value1) (& (prop2=value1)))
	 * 
	 * @param propertiesMap Map of properties
	 * @return Filter as a String
	 */
	public static String generatePropertiesFilter(SortedMap<String, String> propertiesMap) {
		if (propertiesMap.size() == 1) {
			return "(" + propertiesMap.firstKey() + "=" + propertiesMap.get(propertiesMap.firstKey()) + ")";
		} else if (propertiesMap.size() > 1) {
			return "(&" + generatePropertiesFilter(propertiesMap.subMap(propertiesMap.firstKey(), 
					propertiesMap.firstKey() + "\0")) + generatePropertiesFilter(
							propertiesMap.tailMap(propertiesMap.firstKey() + "\0")) + ")";
		}
		return "";
	}
}