PropertiesPropertySource.java

package com.netflix.governator;

import java.util.Properties;

import com.google.inject.Binder;
import com.google.inject.Module;
import com.netflix.governator.spi.PropertySource;

/**
 * Implementation of a PropertySource using a standard {@link Properties} object.
 * 
 * PropertiesPropertySource is also a Guice module and can be installed to provide a
 * self binding to PropertySource.class.  
 */
public final class PropertiesPropertySource extends AbstractPropertySource implements Module {
    private Properties props;

    public PropertiesPropertySource(Properties props) {
        this.props = new Properties(props);
    }

    public PropertiesPropertySource() {
        this(new Properties());
    }

    public static PropertiesPropertySource from(Properties props) {
        return new PropertiesPropertySource(props);
    }
    
    public PropertiesPropertySource setProperty(String key, String value) {
        props.setProperty(key, value);
        return this;
    }
    
    @Override
    public boolean hasProperty(String key) {
        return props.containsKey(key);
    }
    
    @Override
    public String get(String key) {
        return props.getProperty(key);
    }

    @Override
    public String get(String key, String defaultValue) {
        return props.getProperty(key, defaultValue);
    }

    @Override
    public void configure(Binder binder) {
        binder.bind(PropertySource.class).toInstance(this);
    }
    
    @Override
    public int hashCode() {
        return getClass().hashCode();
    }

    @Override
    public boolean equals(Object obj) {
        // equals() is used by Guice to dedup multiple installs.  This is module has state so we only
        // allow one instance of it to ever be installed.  This equals() implementation
        // forces guice to dedup as long as it is the same exact object.  Installing multiple 
        // PropertiesPropertySource instances will result in duplicate binding errors for PropertySource
        // where the errors will provide details about where the multiple installs came from.
        return this == obj;
    }

    @Override
    public String toString() {
        return "PropertiesPropertySource[count=" + props.size() + "]";
    }
}