uk.org.lidalia.slf4jtest.OverridableProperties Maven / Gradle / Ivy

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package uk.org.lidalia.slf4jtest;

import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;

import com.google.common.base.Function;
import com.google.common.base.Optional;
import uk.org.lidalia.lang.Exceptions;

import static com.google.common.base.Optional.fromNullable;
import static uk.org.lidalia.lang.Exceptions.throwUnchecked;

class OverridableProperties {
    private static final Properties EMPTY_PROPERTIES = new Properties();
    private final String propertySourceName;
    private final Properties properties;

    OverridableProperties(final String propertySourceName) throws IOException {
        this.propertySourceName = propertySourceName;
        this.properties = getProperties();
    }

    private Properties getProperties() throws IOException {
        final Optional resourceAsStream = fromNullable(Thread.currentThread().getContextClassLoader()
                .getResourceAsStream(propertySourceName + ".properties"));
        return resourceAsStream.transform(loadProperties).or(EMPTY_PROPERTIES);
    }

    private static final Function loadProperties = new Function() {
        @Override
        public Properties apply(final InputStream propertyResource) {
            boolean throwing = false;
            try {
                final Properties loadedProperties = new Properties();
                loadedProperties.load(propertyResource);
                return loadedProperties;
            } catch (IOException ioException) {
                throwing = true;
                return throwUnchecked(ioException, null);
            } finally {
                try {
                    propertyResource.close();
                } catch (IOException e) {
                    if (!throwing) {
                        Exceptions.throwUnchecked(e);
                    }
                }
            }
        }
    };

    String getProperty(final String propertyKey, final String defaultValue) {
        final String propertyFileProperty = properties.getProperty(propertyKey, defaultValue);
        return System.getProperty(propertySourceName + "." + propertyKey, propertyFileProperty);
    }
}