com.peterphi.std.guice.common.serviceprops.composite.GuiceConfigVariableResolver Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of stdlib-guice-common Show documentation

stdlib guice common

There is a newer version: 9.2.0

package com.peterphi.std.guice.common.serviceprops.composite;

import com.google.common.cache.Cache;
import com.google.common.cache.CacheBuilder;
import ognl.Node;
import ognl.Ognl;
import ognl.OgnlContext;
import org.apache.commons.io.IOUtils;
import org.apache.commons.lang.StringUtils;
import org.apache.commons.lang.text.StrLookup;

import java.io.FileReader;
import java.io.IOException;
import java.io.InputStream;
import java.util.concurrent.ExecutionException;

class GuiceConfigVariableResolver extends StrLookup
{
	/**
	 * OGNL cache
	 */
	private final Cache ognlCache = CacheBuilder.newBuilder().maximumSize(1024).softValues().build();

	private final GuiceConfig properties;


	GuiceConfigVariableResolver(final GuiceConfig properties)
	{
		this.properties = properties;
	}


	@Override
	public String lookup(final String key)
	{
		if (StringUtils.contains(key, ':'))
		{
			if (StringUtils.startsWith(key, "env:"))
			{
				final String[] parts = key.split(":", 2);

				final String name = parts[1];

				final String resolution = System.getenv(name);
				if (resolution == null)
					return "";
				else
					return resolution;
			}
			else if (StringUtils.startsWith(key, "resource:"))
			{
				final String[] parts = key.split(":", 2);
				final String resource = parts[1];

				try (final InputStream is = getClass().getResourceAsStream(resource))
				{
					return IOUtils.toString(is);
				}
				catch (IOException e)
				{
					throw new RuntimeException("Error reading classpath resource " + resource, e);
				}
			}
			else if (StringUtils.startsWithIgnoreCase(key, "file:"))
			{
				final String[] parts = key.split(":", 2);
				final String file = parts[1];

				try (final FileReader fr = new FileReader(file))
				{
					return IOUtils.toString(fr);
				}
				catch (IOException e)
				{
					throw new RuntimeException("Error reading File " + file, e);
				}
			}
			else if (StringUtils.startsWith(key, "ognl:"))
			{
				final String[] parts = key.split(":", 2);

				return lookupOGNL(parts[1]);
			}
		}

		// Fall back to resolving the property
		return properties.get(key, "");
	}


	private String lookupOGNL(final String part)
	{
		final String expression = part;

		// Compile the OGNL expression (or read it from cache)
		final Node node;
		try
		{
			node = ognlCache.get(expression, () -> Ognl.compileExpression(new OgnlContext(), properties, expression));
		}
		catch (ExecutionException e)
		{
			throw new RuntimeException("Error compiling OGNL string '" + expression + "'", e);
		}

		try
		{
			final Object obj = node.getValue(new OgnlContext(), properties);

			if (obj == null)
				return "";
			else
				return obj.toString();
		}
		catch (Throwable t)
		{
			throw new RuntimeException("Error evaluating OGNL expression '" + expression + "'", t);
		}
	}
}