LookupCustomClasses.java

package org.needle4j.configuration;

import static org.needle4j.common.Preconditions.checkArgument;

import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import java.util.StringTokenizer;

import org.needle4j.reflection.ReflectionUtil;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Function to lookup classes. Expects FQN classnames separated by colon.
 */
class LookupCustomClasses {

    private final Logger logger = LoggerFactory.getLogger(LookupCustomClasses.class);
    private final Map<String, String> configurationProperties;

    public LookupCustomClasses(final Map<String, String> configurationProperties) {
        checkArgument(configurationProperties != null, "configurationProperties must not be null!");
        this.configurationProperties = configurationProperties;
    }

    public <T> Set<Class<T>> lookup(final String key) {
        final String classesList = configurationProperties.containsKey(key) ? configurationProperties.get(key) : "";

        final Set<Class<T>> result = new HashSet<Class<T>>();
        final StringTokenizer tokenizer = new StringTokenizer(classesList, ",");

        String token = null;
        while (tokenizer.hasMoreElements()) {
            try {
                token = tokenizer.nextToken().trim();
                if (token == null || "".equals(token)) {
                    continue;
                }

                @SuppressWarnings("unchecked")
                final Class<T> clazz = (Class<T>) ReflectionUtil.forName(token);

                if (clazz != null) {
                    result.add(clazz);
                } else {
                    logger.warn("could not load class '{}'", token);
                }
            } catch (final Exception e) {
                logger.warn("could not load class '" + token + "'", e);
            }
        }

        return result;
    }
}