[GitHub] [commons-beanutils] SethFalco commented on a change in pull request #47: Add Converters for Additional Types

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SethFalco commented on a change in pull request #47:
URL: https://github.com/apache/commons-beanutils/pull/47#discussion_r550395208



##########
File path: src/main/java/org/apache/commons/beanutils2/converters/ColorConverter.java
##########
@@ -0,0 +1,216 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you 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.apache.commons.beanutils2.converters;
+
+import java.awt.Color;
+import java.util.Objects;
+
+/**
+ * <p>Converts a configuration property into a Java {@link Color} object.</p>
+ *
+ * <p>
+ *     This converter aims to be compatible with some some of the web color
+ *     formats supported by browsers with CSS, rather than only support
+ *     literal interpretations of numbers, such as:
+ * </p>
+ *
+ * <ul>
+ *     <li>#RGB</li>
+ *     <li>#RGBA</li>
+ *     <li>#RRGGBBAA</li>
+ * </ul>
+ *
+ * <p>
+ *     This converter will use the web based hexadecimal interpretations if
+ *     the value is prefixed with {@link #HEX_COLOR_PREFIX}.
+ *
+ *     If using a literal number, or {@link Color#decode(String)} is desired, you must
+ *     prefix your value with <code>0x</code> instead of {@link #HEX_COLOR_PREFIX}.
+ * </p>
+ *
+ * @since 2.0.0
+ */
+public class ColorConverter extends AbstractConverter {
+
+    /** To be a web based hexadecimal color, it must be prefixed with this. */
+    private static final String HEX_COLOR_PREFIX = "#";
+
+    /**
+     * Construct a <b>{@link Color}</b> <i>Converter</i> that throws
+     * a {@code ConversionException} if an error occurs.
+     */
+    public ColorConverter() {
+        super();
+    }
+
+    /**
+     * @param defaultValue The default value to be returned
+     * if the value to be converted is missing or an error
+     * occurs converting the value.
+     */
+    public ColorConverter(final Object defaultValue) {
+        super(defaultValue);
+    }
+
+    @Override
+    protected Class<?> getDefaultType() {
+        return Color.class;
+    }
+
+    /**
+     * <p>
+     *     Convert the configuration value to a Java {@link Color} object,
+     *     by reading the hexadecimal {@link String} and converting each component.
+     * </p>
+     *
+     * <p>
+     *     This can also interpret raw color names based on the standard colors
+     *     defined in Java, such as the following:
+     * </p>
+     *
+     * <ul>
+     *     <li>{@link Color#WHITE}</li>
+     *     <li>{@link Color#LIGHT_GRAY}</li>
+     *     <li>{@link Color#GRAY}</li>
+     *     <li>{@link Color#DARK_GRAY}</li>
+     *     <li>{@link Color#BLACK}</li>
+     *     <li>{@link Color#RED}</li>
+     *     <li>{@link Color#PINK}</li>
+     *     <li>{@link Color#ORANGE}</li>
+     *     <li>{@link Color#YELLOW}</li>
+     *     <li>{@link Color#GREEN}</li>
+     *     <li>{@link Color#MAGENTA}</li>
+     *     <li>{@link Color#CYAN}</li>
+     *     <li>{@link Color#BLUE}</li>
+     * </ul>
+     *
+     * <small>
+     *     Implementation Notes: We specifically avoid the use of {@link Color#decode(String)}
+     *     for hexadecimal {@link String}s starting with {@link #HEX_COLOR_PREFIX}
+     *     as it does not provide the desired result.
+     *     The {@link Color#decode(String)} method uses {@link Integer#decode(String)}
+     *     under the hood to convert the input to a number, which means input like
+     *     <code>#FFF</code> gets interpreted incorrectly as it's literally converted
+     *     to the number <code>0xFFF</code>, rather than the color, <code>#FFFFFF</code> which
+     *     it is short hand for. It also doesn't work for <code>#FFFFFFFF</code> due to it
+     *     being unable to parse as an {@link Integer}.
+     *     If this is desired, then this method falls back to using {@link Color#decode(String)},
+     *     so for literal hexadecimal values you prefix it with <code>0x</code> instead of
+     *     {@link #HEX_COLOR_PREFIX}.
+     * </small>
+     *
+     * @param value The String property value to convert.
+     * @return A {@link Color} which represents the compiled configuration property.
+     * @throws NullPointerException If the value is null.
+     * @throws NumberFormatException If an invalid number is provided.
+     */
+    @Override
+    protected <T> T convertToType(Class<T> type, Object value) throws Throwable {
+        if (Color.class.isAssignableFrom(type)) {
+            Objects.requireNonNull(value, "Value can't be null.");
+            final String stringValue = value.toString();
+
+            switch (stringValue.toLowerCase()) {

Review comment:
       Please let me know if there are any problems with the approach I'll be taking here.
   
   I agree handling `Color#toString()` would be nice. While I was at it, I opted to support some terser versions since I was using regular expression anyway, and it wasn't much additional work:
   
   Regex:
   `^(?:[A-Za-z\d._]+)??\[?(?:r=)?(\d{1,3}),(?:g=)?(\d{1,3}),(?:b=)?(\d{1,3})\]?$`
   
   `java.awt.Color[r=255,g=255,b=255]` - The normal `Color#toString()` result.  
   `org.apache.ExtendedColor[r=255,g=0,b=255]` - If the `Color` class is extended, but `#toString()` is not overridden.  
   `[r=0,g=255,b=0]` - Without the package.  
   `r=64,g=64,b=64` - Without the backets.  
   `255,175,175` - Without the color labels.  




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