ZipFileUtil.java

package com.smartandroid.sa.zip;

import java.io.BufferedOutputStream;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.nio.charset.Charset;
import java.util.zip.ZipFile;
import java.util.zip.ZipInputStream;
import java.util.zip.ZipOutputStream;

/**
 * Mainly methods to lookup Zip* class constructors. This is needed because Java
 * 6 doesn't have constructors with Charsets that were introduced in Java 7.
 */
class ZipFileUtil {
	private static final String MISSING_METHOD_PLEASE_UPGRADE = "Your JRE doesn't support the ZipFile Charset constructor. Please upgrade JRE to 1.7 use this feature. Tried constructor ZipFile(File, Charset).";
	private static final String CONSTRUCTOR_MESSAGE_FOR_ZIPFILE = "Using constructor ZipFile(File, Charset) has failed: ";
	private static final String CONSTRUCTOR_MESSAGE_FOR_OUTPUT = "Using constructor ZipOutputStream(OutputStream, Charset) has failed: ";
	private static final String CONSTRUCTOR_MESSAGE_FOR_INPUT = "Using constructor ZipInputStream(InputStream, Charset) has failed: ";

	// Private constructor for the utility class
	private ZipFileUtil() {
	}

	/**
	 * Returns a ZipInputStream opened with a given charset.
	 */
	static ZipInputStream createZipInputStream(InputStream inStream,
			Charset charset) {
		if (charset == null)
			return new ZipInputStream(inStream);

		try {
			Constructor<ZipInputStream> constructor = ZipInputStream.class
					.getConstructor(new Class[] { InputStream.class,
							Charset.class });
			return (ZipInputStream) constructor.newInstance(new Object[] {
					inStream, charset });
		} catch (NoSuchMethodException e) {
			throw new IllegalStateException(MISSING_METHOD_PLEASE_UPGRADE, e);
		} catch (InstantiationException e) {
			throw new IllegalStateException(CONSTRUCTOR_MESSAGE_FOR_INPUT
					+ e.getMessage(), e);
		} catch (IllegalAccessException e) {
			throw new IllegalStateException(CONSTRUCTOR_MESSAGE_FOR_INPUT
					+ e.getMessage(), e);
		} catch (IllegalArgumentException e) {
			throw new IllegalStateException(CONSTRUCTOR_MESSAGE_FOR_INPUT
					+ e.getMessage(), e);
		} catch (InvocationTargetException e) {
			throw new IllegalStateException(CONSTRUCTOR_MESSAGE_FOR_INPUT
					+ e.getMessage(), e);
		}
	}

	/**
	 * Returns a ZipOutputStream opened with a given charset.
	 */
	static ZipOutputStream createZipOutputStream(
			BufferedOutputStream outStream, Charset charset) {
		if (charset == null)
			return new ZipOutputStream(outStream);

		try {
			Constructor<ZipOutputStream> constructor = ZipOutputStream.class
					.getConstructor(new Class[] { OutputStream.class,
							Charset.class });
			return (ZipOutputStream) constructor.newInstance(new Object[] {
					outStream, charset });
		} catch (NoSuchMethodException e) {
			throw new IllegalStateException(MISSING_METHOD_PLEASE_UPGRADE, e);
		} catch (InstantiationException e) {
			throw new IllegalStateException(CONSTRUCTOR_MESSAGE_FOR_OUTPUT
					+ e.getMessage(), e);
		} catch (IllegalAccessException e) {
			throw new IllegalStateException(CONSTRUCTOR_MESSAGE_FOR_OUTPUT
					+ e.getMessage(), e);
		} catch (IllegalArgumentException e) {
			throw new IllegalStateException(CONSTRUCTOR_MESSAGE_FOR_OUTPUT
					+ e.getMessage(), e);
		} catch (InvocationTargetException e) {
			throw new IllegalStateException(CONSTRUCTOR_MESSAGE_FOR_OUTPUT
					+ e.getMessage(), e);
		}
	}

	/**
	 * Returns a zipFile opened with a given charset
	 */
	static ZipFile getZipFile(File src, Charset charset) throws IOException {
		if (charset == null) {
			return new ZipFile(src);
		}

		try {
			Constructor<ZipFile> constructor = ZipFile.class
					.getConstructor(new Class[] { File.class, Charset.class });
			return (ZipFile) constructor.newInstance(new Object[] { src,
					charset });
		} catch (NoSuchMethodException e) {
			throw new IllegalStateException(MISSING_METHOD_PLEASE_UPGRADE, e);
		} catch (InstantiationException e) {
			throw new IllegalStateException(CONSTRUCTOR_MESSAGE_FOR_ZIPFILE
					+ e.getMessage(), e);
		} catch (IllegalAccessException e) {
			throw new IllegalStateException(CONSTRUCTOR_MESSAGE_FOR_ZIPFILE
					+ e.getMessage(), e);
		} catch (IllegalArgumentException e) {
			throw new IllegalStateException(CONSTRUCTOR_MESSAGE_FOR_ZIPFILE
					+ e.getMessage(), e);
		} catch (InvocationTargetException e) {
			throw new IllegalStateException(CONSTRUCTOR_MESSAGE_FOR_ZIPFILE
					+ e.getMessage(), e);
		}
	}

	/**
	 * Returns <code>true</code> if charsets are supported in this JRE.
	 */
	static boolean isCharsetSupported() throws IOException {
		try {
			ZipFile.class.getConstructor(new Class[] { File.class,
					Charset.class });
			return true;
		} catch (NoSuchMethodException e) {
			return false;
		}
	}

}