Base64Utils

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/*
     * Copyright 2002-2017 the original author or authors.
     *
     * Licensed under the Apache License, Version 2.0 (the "License");
     * you may not use this file except in compliance with the License.
     * You may obtain a copy of the License at
     *
     *      http://www.apache.org/licenses/LICENSE-2.0
     *
     * Unless required by applicable law or agreed to in writing, software
     * distributed under the License is distributed on an "AS IS" BASIS,
     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     * See the License for the specific language governing permissions and
     * limitations under the License.
     */
    
    package org.springframework.util;
    
    import java.nio.charset.Charset;
    import java.nio.charset.StandardCharsets;
    import java.util.Base64;
    
    /**
     * A simple utility class for Base64 encoding and decoding.
     *
     * <p>Adapts to Java 8's {@link java.util.Base64} in a convenience fashion.
     *
     * @author Juergen Hoeller
     * @author Gary Russell
     * @since 4.1
     * @see java.util.Base64
     */
    public abstract class Base64Utils {
    
    	private static final Charset DEFAULT_CHARSET = StandardCharsets.UTF_8;
    
    
    	/**
    	 * Base64-encode the given byte array.
    	 * @param src the original byte array
    	 * @return the encoded byte array
    	 * @throws IllegalStateException if Base64 encoding between byte arrays is not
    	 * supported, i.e. neither Java 8 nor Apache Commons Codec is present at runtime
    	 */
    	public static byte[] encode(byte[] src) {
    		if (src.length == 0) {
    			return src;
    		}
    		return Base64.getEncoder().encode(src);
    	}
    
    	/**
    	 * Base64-decode the given byte array.
    	 * @param src the encoded byte array
    	 * @return the original byte array
    	 * @throws IllegalStateException if Base64 encoding between byte arrays is not
    	 * supported, i.e. neither Java 8 nor Apache Commons Codec is present at runtime
    	 */
    	public static byte[] decode(byte[] src) {
    		if (src.length == 0) {
    			return src;
    		}
    		return Base64.getDecoder().decode(src);
    	}
    
    	/**
    	 * Base64-encode the given byte array using the RFC 4648
    	 * "URL and Filename Safe Alphabet".
    	 * @param src the original byte array
    	 * @return the encoded byte array
    	 * @throws IllegalStateException if Base64 encoding between byte arrays is not
    	 * supported, i.e. neither Java 8 nor Apache Commons Codec is present at runtime
    	 * @since 4.2.4
    	 */
    	public static byte[] encodeUrlSafe(byte[] src) {
    		if (src.length == 0) {
    			return src;
    		}
    		return Base64.getUrlEncoder().encode(src);
    	}
    
    	/**
    	 * Base64-decode the given byte array using the RFC 4648
    	 * "URL and Filename Safe Alphabet".
    	 * @param src the encoded byte array
    	 * @return the original byte array
    	 * @throws IllegalStateException if Base64 encoding between byte arrays is not
    	 * supported, i.e. neither Java 8 nor Apache Commons Codec is present at runtime
    	 * @since 4.2.4
    	 */
    	public static byte[] decodeUrlSafe(byte[] src) {
    		if (src.length == 0) {
    			return src;
    		}
    		return Base64.getUrlDecoder().decode(src);
    	}
    
    	/**
    	 * Base64-encode the given byte array to a String.
    	 * @param src the original byte array (may be {@code null})
    	 * @return the encoded byte array as a UTF-8 String
    	 */
    	public static String encodeToString(byte[] src) {
    		if (src.length == 0) {
    			return "";
    		}
    		return new String(encode(src), DEFAULT_CHARSET);
    	}
    
    	/**
    	 * Base64-decode the given byte array from an UTF-8 String.
    	 * @param src the encoded UTF-8 String
    	 * @return the original byte array
    	 */
    	public static byte[] decodeFromString(String src) {
    		if (src.isEmpty()) {
    			return new byte[0];
    		}
    		return decode(src.getBytes(DEFAULT_CHARSET));
    	}
    
    	/**
    	 * Base64-encode the given byte array to a String using the RFC 4648
    	 * "URL and Filename Safe Alphabet".
    	 * @param src the original byte array
    	 * @return the encoded byte array as a UTF-8 String
    	 * @throws IllegalStateException if Base64 encoding between byte arrays is not
    	 * supported, i.e. neither Java 8 nor Apache Commons Codec is present at runtime
    	 */
    	public static String encodeToUrlSafeString(byte[] src) {
    		return new String(encodeUrlSafe(src), DEFAULT_CHARSET);
    	}
    
    	/**
    	 * Base64-decode the given byte array from an UTF-8 String using the RFC 4648
    	 * "URL and Filename Safe Alphabet".
    	 * @param src the encoded UTF-8 String
    	 * @return the original byte array
    	 * @throws IllegalStateException if Base64 encoding between byte arrays is not
    	 * supported, i.e. neither Java 8 nor Apache Commons Codec is present at runtime
    	 */
    	public static byte[] decodeFromUrlSafeString(String src) {
    		return decodeUrlSafe(src.getBytes(DEFAULT_CHARSET));
    	}
    
    }