com.netflix.nfsidecar.configSource.CompositeConfigSource Maven / Gradle / Ivy

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package com.netflix.nfsidecar.configSource;

import java.util.Collection;

import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableCollection;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;
import com.google.inject.Inject;
import com.google.inject.Singleton;

/**
 * A {@link IConfigSource} that delegates method calls to the underline sources.  The order in which values are provided
 * depend on the {@link IConfigSource}s provided.  If user asks for key 'foo', and this composite has three sources, it
 * will first check if the key is found in the first source, if not it will check the second and if not, the third, else
 * return null or false if {@link #contains(String)} was called.
 * 
 * Implementation note: get methods with a default are implemented in {@link AbstractConfigSource}, if the underlying
 * source overrides one of these methods, then that implementation will be ignored.
 */
@Singleton
public class CompositeConfigSource extends AbstractConfigSource 
{

    private final ImmutableCollection sources;

    @Inject
    public CompositeConfigSource(final ImmutableCollection sources) 
    {
        Preconditions.checkArgument(!sources.isEmpty(), "Can not create a composite config source without config sources!");
        this.sources = sources;
    }

    public CompositeConfigSource(final Collection sources) 
    {
        this(ImmutableList.copyOf(sources));
    }

    public CompositeConfigSource(final Iterable sources) 
    {
        this(ImmutableList.copyOf(sources));
    }

    public CompositeConfigSource(final IConfigSource... sources) 
    {
        this(ImmutableList.copyOf(sources));
    }

    @Override
    public void intialize(final String asgName, final String region) 
    {
        for (final IConfigSource source : sources) 
        {
            //TODO should this catch any potential exceptions?
            source.intialize(asgName, region);
        }
    }

    @Override
    public int size() 
    {
        int size = 0;
        for (final IConfigSource c : sources) 
        {
            size += c.size();
        }
        return size;
    }

    @Override
    public boolean isEmpty() 
    {
        return size() == 0;
    }

    @Override
    public boolean contains(final String key) 
    {
        return get(key) != null;
    }

    @Override
    public String get(final String key) 
    {
        Preconditions.checkNotNull(key);
        for (final IConfigSource c : sources) 
        {
            final String value = c.get(key);
            if (value != null) 
            {
                return value;
            }
        }
        return null;
    }

    @Override
    public void set(final String key, final String value) 
    {
        Preconditions.checkNotNull(value, "Value can not be null for configurations.");
        final IConfigSource firstSource = Iterables.getFirst(sources, null);
        // firstSource shouldn't be null because the collection is immutable, and the collection is non empty.
        Preconditions.checkState(firstSource != null, "There was no IConfigSource found at the first location?");
        firstSource.set(key, value);
    }
}