ConditionalModule

ConditionalModule.java

import com.google.common.base.Optional;
import com.google.inject.Binder;
import com.google.inject.Module;
import io.airlift.configuration.ConfigurationAwareModule;
import io.airlift.configuration.ConfigurationFactory;

import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkState;

public class ConditionalModule
        implements ConfigurationAwareModule
{
    public static ConfigurationAwareModule installIfPropertyDefined(Module module, String property)
    {
        return new ConditionalModule(module, property, Optional.<String>absent());
    }

    public static ConfigurationAwareModule installIfPropertyEquals(Module module, String property, String expectedValue)
    {
        checkNotNull(expectedValue, "expectedValue is null");
        return new ConditionalModule(module, property, Optional.of(expectedValue));
    }

    private final Module module;
    private final String property;
    private final Optional<String> expectedValue;
    private ConfigurationFactory configurationFactory;

    private ConditionalModule(Module module, String property, Optional<String> expectedValue)
    {
        this.module = checkNotNull(module, "module is null");
        this.property = checkNotNull(property, "property is null");
        this.expectedValue = checkNotNull(expectedValue, "expectedValue is null");
    }

    @Override
    public void setConfigurationFactory(ConfigurationFactory configurationFactory)
    {
        this.configurationFactory = checkNotNull(configurationFactory, "configurationFactory is null");
        configurationFactory.consumeProperty(property);

        // consume properties if we are not going to install the module
        if (!shouldInstall()) {
            configurationFactory.registerConfigurationClasses(module);
        }
    }

    @Override
    public void configure(Binder binder)
    {
        checkState(configurationFactory != null, "configurationFactory was not set");
        if (shouldInstall()) {
            binder.install(module);
        }
    }

    private boolean shouldInstall()
    {
        if (expectedValue.isPresent()) {
            return expectedValue.get().equals(configurationFactory.getProperties().get(property));
        }
        return configurationFactory.getProperties().containsKey(property);
    }
}