ChangeExecListenerUtils.java

package liquibase.integration.commandline;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.lang.reflect.Constructor;
import java.util.Properties;

import liquibase.changelog.visitor.ChangeExecListener;
import liquibase.database.Database;
import liquibase.logging.LogFactory;
import liquibase.logging.Logger;
import liquibase.resource.ResourceAccessor;

public final class ChangeExecListenerUtils {
	private ChangeExecListenerUtils() {
	}
	
	public static ChangeExecListener getChangeExecListener(
			Database database, ResourceAccessor resourceAccessor, 
			String changeExecListenerClass, String changeExecListenerPropertiesFile) throws Exception {
		
		ChangeExecListener changeExecListener = null;
		
		if (changeExecListenerClass != null) {
			Logger logger = LogFactory.getInstance().getLog();
			
			logger.debug("Setting ChangeExecListener: " + changeExecListenerClass);
			
			ClassLoader classLoader = resourceAccessor.toClassLoader();
			Class<?> clazz = Class.forName(changeExecListenerClass, true, classLoader);
			
			Properties properties = loadProperties(changeExecListenerPropertiesFile);
			Constructor<?> cons = getConstructor(clazz, Database.class, Properties.class);
			if (cons != null) {
				logger.debug("Create " + clazz.getSimpleName() + "(Database, Properties)");
				changeExecListener = (ChangeExecListener) cons.newInstance(database, properties);
			} else {
				cons = getConstructor(clazz, Properties.class, Database.class);
				if (cons != null) {
					logger.debug("Create " + clazz.getSimpleName() + "(Properties, Database)");
					changeExecListener = (ChangeExecListener) cons.newInstance(properties, database);
				} else {
					cons = getConstructor(clazz, Database.class);
					if (cons != null) {
						logger.debug("Create " + clazz.getSimpleName() + "(Database)");
						changeExecListener = (ChangeExecListener) cons.newInstance(database);
					} else {
						cons = getConstructor(clazz, Properties.class);
						if (cons != null) {
							logger.debug("Create " + clazz.getSimpleName() + "(Properties)");
							changeExecListener = (ChangeExecListener) cons.newInstance(properties);
						} else {
							logger.debug("Create " + clazz.getSimpleName() + "()");
							changeExecListener = (ChangeExecListener) clazz.newInstance();
						}
					}
				}
			}
		}
		return changeExecListener;
	}

	private static Constructor<?> getConstructor(Class<?> clazz, Class<?> ... params) {
		try {
			return clazz.getConstructor(params);
		} catch (Exception e) {
			return null;
		}
	}
	
    private static Properties loadProperties(String propertiesFile) throws IOException {
    	if (propertiesFile != null) {
	    	File file = new File(propertiesFile);
	        if (file.exists()) {
	        	Properties properties = new Properties();
	            FileInputStream inputStream = new FileInputStream(propertiesFile);
	            try {
	            	properties.load(inputStream);
	            } finally {
	                inputStream.close();
	            }
	            return properties;
	        } else {
	            throw new FileNotFoundException(propertiesFile);
	        }
    	} else {
    		return null;
    	}
    }
}