Java: encode URL query parameters

SpringUtil.java

/*
 * Copyright 2002-2019 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
 *
 *      https://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.
 */
//From https://github.com/spring-projects/spring-framework HierarchicalUriComponents

package uriencoder;

import java.io.ByteArrayOutputStream;
import java.nio.charset.Charset;

public class SpringUtil {
    
    
	public static String encodeUriComponent(String source, Charset charset, Type type) {
		if (!hasLength(source)) {
			return source;
		}
		//Assert.notNull(charset, "Charset must not be null");
		//Assert.notNull(type, "Type must not be null");

		byte[] bytes = source.getBytes(charset);
		ByteArrayOutputStream bos = new ByteArrayOutputStream(bytes.length);
		boolean changed = false;
		for (byte b : bytes) {
			if (b < 0) {
				b += 256;
			}
			if (type.isAllowed(b)) {
				bos.write(b);
			}
			else {
				bos.write('%');
				char hex1 = Character.toUpperCase(Character.forDigit((b >> 4) & 0xF, 16));
				char hex2 = Character.toUpperCase(Character.forDigit(b & 0xF, 16));
				bos.write(hex1);
				bos.write(hex2);
				changed = true;
			}
		}
		return (changed ? new String(bos.toByteArray(), charset) : source);
	}

	/**
	 * Enumeration used to identify the allowed characters per URI component.
	 * <p>Contains methods to indicate whether a given character is valid in a specific URI component.
	 * @see <a href="https://www.ietf.org/rfc/rfc3986.txt">RFC 3986</a>
	 */
	public enum Type {

		SCHEME {
			@Override
			public boolean isAllowed(int c) {
				return isAlpha(c) || isDigit(c) || '+' == c || '-' == c || '.' == c;
			}
		},
		AUTHORITY {
			@Override
			public boolean isAllowed(int c) {
				return isUnreserved(c) || isSubDelimiter(c) || ':' == c || '@' == c;
			}
		},
		USER_INFO {
			@Override
			public boolean isAllowed(int c) {
				return isUnreserved(c) || isSubDelimiter(c) || ':' == c;
			}
		},
		HOST_IPV4 {
			@Override
			public boolean isAllowed(int c) {
				return isUnreserved(c) || isSubDelimiter(c);
			}
		},
		HOST_IPV6 {
			@Override
			public boolean isAllowed(int c) {
				return isUnreserved(c) || isSubDelimiter(c) || '[' == c || ']' == c || ':' == c;
			}
		},
		PORT {
			@Override
			public boolean isAllowed(int c) {
				return isDigit(c);
			}
		},
		PATH {
			@Override
			public boolean isAllowed(int c) {
				return isPchar(c) || '/' == c;
			}
		},
		PATH_SEGMENT {
			@Override
			public boolean isAllowed(int c) {
				return isPchar(c);
			}
		},
		QUERY {
			@Override
			public boolean isAllowed(int c) {
				return isPchar(c) || '/' == c || '?' == c;
			}
		},
		QUERY_PARAM {
			@Override
			public boolean isAllowed(int c) {
				if ('=' == c || '&' == c) {
					return false;
				}
				else {
					return isPchar(c) || '/' == c || '?' == c;
				}
			}
		},
		FRAGMENT {
			@Override
			public boolean isAllowed(int c) {
				return isPchar(c) || '/' == c || '?' == c;
			}
		},
		URI {
			@Override
			public boolean isAllowed(int c) {
				return isUnreserved(c);
			}
		};

		/**
		 * Indicates whether the given character is allowed in this URI component.
		 * @return {@code true} if the character is allowed; {@code false} otherwise
		 */
		public abstract boolean isAllowed(int c);

		/**
		 * Indicates whether the given character is in the {@code ALPHA} set.
		 * @see <a href="https://www.ietf.org/rfc/rfc3986.txt">RFC 3986, appendix A</a>
		 */
		protected boolean isAlpha(int c) {
			return (c >= 'a' && c <= 'z' || c >= 'A' && c <= 'Z');
		}

		/**
		 * Indicates whether the given character is in the {@code DIGIT} set.
		 * @see <a href="https://www.ietf.org/rfc/rfc3986.txt">RFC 3986, appendix A</a>
		 */
		protected boolean isDigit(int c) {
			return (c >= '0' && c <= '9');
		}

		/**
		 * Indicates whether the given character is in the {@code gen-delims} set.
		 * @see <a href="https://www.ietf.org/rfc/rfc3986.txt">RFC 3986, appendix A</a>
		 */
		protected boolean isGenericDelimiter(int c) {
			return (':' == c || '/' == c || '?' == c || '#' == c || '[' == c || ']' == c || '@' == c);
		}

		/**
		 * Indicates whether the given character is in the {@code sub-delims} set.
		 * @see <a href="https://www.ietf.org/rfc/rfc3986.txt">RFC 3986, appendix A</a>
		 */
		protected boolean isSubDelimiter(int c) {
			return ('!' == c || '$' == c || '&' == c || '\'' == c || '(' == c || ')' == c || '*' == c || '+' == c ||
					',' == c || ';' == c || '=' == c);
		}

		/**
		 * Indicates whether the given character is in the {@code reserved} set.
		 * @see <a href="https://www.ietf.org/rfc/rfc3986.txt">RFC 3986, appendix A</a>
		 */
		protected boolean isReserved(int c) {
			return (isGenericDelimiter(c) || isSubDelimiter(c));
		}

		/**
		 * Indicates whether the given character is in the {@code unreserved} set.
		 * @see <a href="https://www.ietf.org/rfc/rfc3986.txt">RFC 3986, appendix A</a>
		 */
		protected boolean isUnreserved(int c) {
			return (isAlpha(c) || isDigit(c) || '-' == c || '.' == c || '_' == c || '~' == c);
		}

		/**
		 * Indicates whether the given character is in the {@code pchar} set.
		 * @see <a href="https://www.ietf.org/rfc/rfc3986.txt">RFC 3986, appendix A</a>
		 */
		protected boolean isPchar(int c) {
			return (isUnreserved(c) || isSubDelimiter(c) || ':' == c || '@' == c);
		}
	}

        //from SpringFramework's StringUtil:
	public static boolean hasLength(CharSequence str) {
		return (str != null && str.length() > 0);
	}

}