| 1 | package org.amicofragile.webclient; |
| 2 | |
| 3 | import java.io.UnsupportedEncodingException; |
| 4 | import java.net.URLEncoder; |
| 5 | import java.util.Collection; |
| 6 | import java.util.Collections; |
| 7 | import java.util.LinkedList; |
| 8 | import java.util.List; |
| 9 | |
| 10 | /** |
| 11 | * Utility class who provides URL creation. |
| 12 | * @author Pietro Martinelli |
| 13 | */ |
| 14 | public class URLBuilder { |
| 15 | private static final String SLASH = "/"; |
| 16 | private static final char PARAMETER_DEFINITION_CHAR = '='; |
| 17 | private static final String PARAMETERS_SEPARATOR = "&"; |
| 18 | private static final char QUERY_STRING_SEPARATOR = '?'; |
| 19 | /** |
| 20 | * Default character set for parameters encoding. |
| 21 | */ |
| 22 | public static final String DEFAULT_ENCODING = "UTF-8"; |
| 23 | /** |
| 24 | * Base URL (without parameters). |
| 25 | */ |
| 26 | private final String baseURL; |
| 27 | /** |
| 28 | * URL's parameters. |
| 29 | */ |
| 30 | private final List<Parameter> parameters; |
| 31 | /** |
| 32 | * Charset for URL parameters encoding. |
| 33 | */ |
| 34 | private final String encoding; |
| 35 | /** |
| 36 | * Initializes new instance. |
| 37 | * @param url An URL, eventually including parameters. |
| 38 | * @param encoding Charset to be used for parameters URL-encoding. |
| 39 | */ |
| 40 | public URLBuilder(final String url, final String encoding) { |
| 41 | this.baseURL = parseBaseUrl(url); |
| 42 | this.parameters = new LinkedList<Parameter>(); |
| 43 | this.parameters.addAll(parseBaseUrlParameters(url)); |
| 44 | this.encoding = parseBaseUrl(encoding); |
| 45 | } |
| 46 | |
| 47 | /** |
| 48 | * Extracts parameters from base URL. |
| 49 | * @param baseURL A base URL, eventually including parameters. |
| 50 | * @return Given URL's parameters, if any. |
| 51 | */ |
| 52 | private List<? extends Parameter> parseBaseUrlParameters(final String baseURL) { |
| 53 | final List<Parameter> baseParameters = new LinkedList<Parameter>(); |
| 54 | if (baseURL.indexOf(QUERY_STRING_SEPARATOR) >= 0) { |
| 55 | final String queryString = baseURL.substring(baseURL.indexOf(QUERY_STRING_SEPARATOR) + 1); |
| 56 | final String[] stringParameters = queryString.split(PARAMETERS_SEPARATOR); |
| 57 | for (String stringParam : stringParameters) { |
| 58 | final int separator = stringParam.indexOf(PARAMETER_DEFINITION_CHAR); |
| 59 | baseParameters.add(new Parameter(stringParam.substring(0, separator), stringParam.substring(separator + 1))); |
| 60 | } |
| 61 | } |
| 62 | return baseParameters; |
| 63 | } |
| 64 | |
| 65 | /** |
| 66 | * Extracts base URL (without parameters) from given URL. |
| 67 | * @param url An URL-representing {@link java.lang.String} |
| 68 | * @return Base URL (without parameters) |
| 69 | */ |
| 70 | private String parseBaseUrl(final String url) { |
| 71 | if (url.indexOf(QUERY_STRING_SEPARATOR) < 0) { |
| 72 | return url; |
| 73 | } |
| 74 | return url.substring(0, url.indexOf(QUERY_STRING_SEPARATOR)); |
| 75 | } |
| 76 | /** |
| 77 | * Initializes an instance with default charset for parameters encoding. |
| 78 | * @param url An URL, eventually including parameters. |
| 79 | */ |
| 80 | public URLBuilder(final String url) { |
| 81 | this(url, DEFAULT_ENCODING); |
| 82 | } |
| 83 | |
| 84 | /** |
| 85 | * Registers new parameter, as name/value couple. |
| 86 | * @param name URL parameter's name |
| 87 | * @param value URL parameter's value |
| 88 | */ |
| 89 | public final void addParam(final String name, final String value) { |
| 90 | this.parameters.add(new Parameter(parseBaseUrl(name), parseBaseUrl(value))); |
| 91 | } |
| 92 | |
| 93 | /** |
| 94 | * Renders URL as {@link java.lang.String}, using a |
| 95 | * {@link java.lang.StringBuilder}. |
| 96 | * @return URL as {@link java.lang.String} |
| 97 | */ |
| 98 | public final String renderURL() { |
| 99 | final StringBuilder builder = new StringBuilder(this.baseURL); |
| 100 | if (this.baseURL.endsWith(SLASH)) { |
| 101 | deleteLastChar(builder); |
| 102 | } |
| 103 | |
| 104 | builder.append(QUERY_STRING_SEPARATOR); |
| 105 | |
| 106 | for (Parameter param : this.parameters) { |
| 107 | builder.append(param.render()).append(PARAMETERS_SEPARATOR); |
| 108 | } |
| 109 | deleteLastChar(builder); |
| 110 | return builder.toString(); |
| 111 | } |
| 112 | |
| 113 | /** |
| 114 | * URL-encodes input {@link java.lang.String}, using encoding specified at |
| 115 | * construction time. |
| 116 | * @param in {@link java.lang.String} to encode |
| 117 | * @return <tt>in</tt>'s URL-encoding |
| 118 | */ |
| 119 | private final String encode(final String in) { |
| 120 | try { |
| 121 | return URLEncoder.encode(parseBaseUrl(in), this.encoding); |
| 122 | } catch (UnsupportedEncodingException e) { |
| 123 | throw new RuntimeException(e); |
| 124 | } |
| 125 | } |
| 126 | |
| 127 | /** |
| 128 | * Deletes last char from <tt>builder</tt>. |
| 129 | * @param builder {@link java.lang.StringBuilder} from which delete last |
| 130 | * char |
| 131 | */ |
| 132 | private void deleteLastChar(final StringBuilder builder) { |
| 133 | builder.deleteCharAt(builder.length() - 1); |
| 134 | } |
| 135 | |
| 136 | /** |
| 137 | * URL parameter's abstraction. This class represents single URL parameter, |
| 138 | * encapsulating its URL generation logic. |
| 139 | * @author Pietro Martinelli |
| 140 | */ |
| 141 | private final class Parameter { |
| 142 | /** |
| 143 | * URL parameter's name. |
| 144 | */ |
| 145 | private final String name; |
| 146 | /** |
| 147 | * URL parameter's value. |
| 148 | */ |
| 149 | private final String value; |
| 150 | |
| 151 | /** |
| 152 | * Initializes an instance by specifying parameter's name and value. |
| 153 | * @param name URL parameter's name. |
| 154 | * @param value URL parameter's value. |
| 155 | */ |
| 156 | public Parameter(final String name, final String value) { |
| 157 | super(); |
| 158 | this.name = name; |
| 159 | this.value = value; |
| 160 | } |
| 161 | |
| 162 | /** |
| 163 | * Renders {@link Parameter} as {@link java.lang.String}, taking care of |
| 164 | * name/value's encoding, if necessary. |
| 165 | * @return {@link Parameter} as {@link java.lang.String} |
| 166 | */ |
| 167 | public final String render() { |
| 168 | return encode(this.name) + PARAMETER_DEFINITION_CHAR + encode(this.value); |
| 169 | } |
| 170 | } |
| 171 | } |