package liquibase.precondition;
import liquibase.exception.UnexpectedLiquibaseException;
import liquibase.servicelocator.ServiceLocator;
import java.util.HashMap;
import java.util.Map;
public class PreconditionFactory {
@SuppressWarnings("unchecked")
private final Map<String, Class<? extends Precondition>> preconditions;
private static PreconditionFactory instance;
@SuppressWarnings("unchecked")
private PreconditionFactory() {
preconditions = new HashMap<String, Class<? extends Precondition>>();
Class[] classes;
try {
classes = ServiceLocator.getInstance().findClasses(Precondition.class);
for (Class<? extends Precondition> clazz : classes) {
register(clazz);
}
} catch (Exception e) {
throw new UnexpectedLiquibaseException(e);
}
}
public static PreconditionFactory getInstance() {
if (instance == null) {
instance = new PreconditionFactory();
}
return instance;
}
public static void reset() {
instance = new PreconditionFactory();
}
public Map<String, Class<? extends Precondition>> getPreconditions() {
return preconditions;
}
public void register(Class<? extends Precondition> clazz) {
try {
preconditions.put(clazz.newInstance().getName(), clazz);
} catch (Exception e) {
throw new UnexpectedLiquibaseException(e);
}
}
public void unregister(String name) {
preconditions.remove(name);
}
/**
* Create a new Precondition subclass based on the given tag name.
*/
public Precondition create(String tagName) {
Class<?> aClass = preconditions.get(tagName);
if (aClass == null) {
return null;
}
try {
return (Precondition) aClass.newInstance();
} catch (Exception e) {
throw new RuntimeException(e);
}
}
}