EncodedResource.java

package com.firefly.utils.io;

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.nio.charset.Charset;

import com.firefly.utils.Assert;
import com.firefly.utils.ObjectUtils;

/**
 * Holder that combines a {@link Resource} descriptor with a specific encoding
 * or {@code Charset} to be used for reading from the resource.
 *
 * <p>
 * Used as an argument for operations that support reading content with a
 * specific encoding, typically via a {@code java.io.Reader}.
 *
 * @see java.io.Reader
 * @see java.nio.charset.Charset
 */
public class EncodedResource implements InputStreamSource {

	private final Resource resource;

	private final String encoding;

	private final Charset charset;

	/**
	 * Create a new {@code EncodedResource} for the given {@code Resource}, not
	 * specifying an explicit encoding or {@code Charset}.
	 * 
	 * @param resource
	 *            the {@code Resource} to hold (never {@code null})
	 */
	public EncodedResource(Resource resource) {
		this(resource, null, null);
	}

	/**
	 * Create a new {@code EncodedResource} for the given {@code Resource},
	 * using the specified {@code encoding}.
	 * 
	 * @param resource
	 *            the {@code Resource} to hold (never {@code null})
	 * @param encoding
	 *            the encoding to use for reading from the resource
	 */
	public EncodedResource(Resource resource, String encoding) {
		this(resource, encoding, null);
	}

	/**
	 * Create a new {@code EncodedResource} for the given {@code Resource},
	 * using the specified {@code Charset}.
	 * 
	 * @param resource
	 *            the {@code Resource} to hold (never {@code null})
	 * @param charset
	 *            the {@code Charset} to use for reading from the resource
	 */
	public EncodedResource(Resource resource, Charset charset) {
		this(resource, null, charset);
	}

	private EncodedResource(Resource resource, String encoding, Charset charset) {
		super();
		Assert.notNull(resource, "Resource must not be null");
		this.resource = resource;
		this.encoding = encoding;
		this.charset = charset;
	}

	/**
	 * Return the {@code Resource} held by this {@code EncodedResource}.
	 */
	public final Resource getResource() {
		return this.resource;
	}

	/**
	 * Return the encoding to use for reading from the
	 * {@linkplain #getResource() resource}, or {@code null} if none specified.
	 */
	public final String getEncoding() {
		return this.encoding;
	}

	/**
	 * Return the {@code Charset} to use for reading from the
	 * {@linkplain #getResource() resource}, or {@code null} if none specified.
	 */
	public final Charset getCharset() {
		return this.charset;
	}

	/**
	 * Determine whether a {@link Reader} is required as opposed to an
	 * {@link InputStream}, i.e. whether an {@linkplain #getEncoding() encoding}
	 * or a {@link #getCharset() Charset} has been specified.
	 * 
	 * @see #getReader()
	 * @see #getInputStream()
	 */
	public boolean requiresReader() {
		return (this.encoding != null || this.charset != null);
	}

	/**
	 * Open a {@code java.io.Reader} for the specified resource, using the
	 * specified {@link #getCharset() Charset} or {@linkplain #getEncoding()
	 * encoding} (if any).
	 * 
	 * @throws IOException
	 *             if opening the Reader failed
	 * @see #requiresReader()
	 * @see #getInputStream()
	 */
	public Reader getReader() throws IOException {
		if (this.charset != null) {
			return new InputStreamReader(this.resource.getInputStream(), this.charset);
		} else if (this.encoding != null) {
			return new InputStreamReader(this.resource.getInputStream(), this.encoding);
		} else {
			return new InputStreamReader(this.resource.getInputStream());
		}
	}

	/**
	 * Open a {@code java.io.InputStream} for the specified resource, ignoring
	 * any specified {@link #getCharset() Charset} or {@linkplain #getEncoding()
	 * encoding}.
	 * 
	 * @throws IOException
	 *             if opening the InputStream failed
	 * @see #requiresReader()
	 * @see #getReader()
	 */
	@Override
	public InputStream getInputStream() throws IOException {
		return this.resource.getInputStream();
	}

	@Override
	public boolean equals(Object other) {
		if (this == other) {
			return true;
		}
		if (!(other instanceof EncodedResource)) {
			return false;
		}
		EncodedResource otherResource = (EncodedResource) other;
		return (this.resource.equals(otherResource.resource)
				&& ObjectUtils.nullSafeEquals(this.charset, otherResource.charset)
				&& ObjectUtils.nullSafeEquals(this.encoding, otherResource.encoding));
	}

	@Override
	public int hashCode() {
		return this.resource.hashCode();
	}

	@Override
	public String toString() {
		return this.resource.toString();
	}

}