add StringToUuidConverter (#4400) (#6614)

flow-data/src/main/java/com/vaadin/flow/data/converter/StringToUuidConverter.java

@@ -0,0 +1,96 @@
+/*
+ * Copyright 2000-2018 Vaadin Ltd.
+ *
+ * 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 com.vaadin.flow.data.converter;
+
+import com.vaadin.flow.data.binder.ErrorMessageProvider;
+import com.vaadin.flow.data.binder.Result;
+import com.vaadin.flow.data.binder.ValueContext;
+import org.slf4j.LoggerFactory;
+
+import java.util.UUID;
+
+/**
+ * A converter that converts from {@link String} to {@link UUID} and back.
+ * <p>
+ * Leading and trailing white spaces are ignored when converting from a String.
+ * </p>
+ * <p>
+ * The String representation uses the canonical format of 32-characters with a hyphen
+ * to separate each of five groups of hexadecimal digits as defined in:
+ * RFC 4122: A Universally Unique IDentifier (UUID) URN Namespace
+ * http://www.ietf.org/rfc/rfc4122.txt
+ * </p>
+ *
+ * @author Vaadin Ltd
+ */
+public class StringToUuidConverter implements Converter<String, UUID> {
+
+    private ErrorMessageProvider errorMessageProvider;
+
+    /**
+     * Constructs a converter for String to UUID and back.
+     *
+     * @param errorMessage the error message to use if conversion fails
+     */
+    public StringToUuidConverter(String errorMessage) {
+        this(ctx -> errorMessage);
+    }
+
+    /**
+     * Constructs a new converter instance with the given error message provider.
+     * Empty strings are converted to <code>null</code>.
+     *
+     * @param errorMessageProvider the error message provider to use if conversion fails
+     */
+    public StringToUuidConverter(ErrorMessageProvider errorMessageProvider) {
+        this.errorMessageProvider = errorMessageProvider;
+    }
+
+    @Override
+    public Result<UUID> convertToModel(String value, ValueContext context) {
+        if (value == null) {
+            return Result.ok(null);
+        }
+
+        // Remove leading and trailing white space
+        value = value.trim();
+
+        // Parse string as UUID.
+        UUID uuid = null;
+        try {
+            uuid = UUID.fromString(value);
+        } catch (java.lang.IllegalArgumentException e) {
+            LoggerFactory.getLogger(StringToUuidConverter.class.getName()).warn(
+                    "Unable to convert String to UUID: " + value, e);
+            return Result.error(this.errorMessageProvider.apply(context));
+        }
+        return Result.ok(uuid); // Return the UUID object, converted from String.
+    }
+
+    @Override
+    public String convertToPresentation(UUID value, ValueContext context) {
+        if (value == null) {
+            return null;
+        }
+        // `java.util.UUID::toString` generates a textual representation of a
+        // UUID’s 128-bits as in a  hexadecimal `String` in 32-character canonical
+        // format with four hyphens separating groups of digits.
+        // https://docs.oracle.com/javase/10/docs/api/java/util/UUID.html#toString()
+        return value.toString();
+    }
+
+}