Create StringToUuidConverter.java (#11387)

* Create StringToUuidConverter.java

Implements the `Converter` interface, to support converting back-and-forth between `String` and `UUID` (a type built into Java 5 and later).

See Issue # 11,051.
https://github.com/vaadin/framework/issues/11051

* Formatting cleanup, remove sinces

1 files changed, 99 insertions, 0 deletions

diff --git a/server/src/main/java/com/vaadin/data/converter/StringToUuidConverter.java b/server/src/main/java/com/vaadin/data/converter/StringToUuidConverter.java
new file mode 100644
index 0000000000..be4a5fce19
--- /dev/null
+++ b/server/src/main/java/com/vaadin/data/converter/StringToUuidConverter.java
@@ -0,0 +1,99 @@
+/*
+ * 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.data.converter;
+
+import java.util.UUID;
+
+import com.vaadin.data.Converter;
+import com.vaadin.data.ErrorMessageProvider;
+import com.vaadin.data.Result;
+import com.vaadin.data.ValueContext;
+
+/**
+ * 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
+ * @since
+ */
+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) {
+            // Faulty input. Let `uuid` default to null. Report error below.
+        }
+
+        if (null != uuid) {
+            return Result.ok(uuid);  // Return the UUID object, converted from String.
+        } else {
+            return Result.error( this.errorMessageProvider.apply(context) );
+        }
+    }
+
+    @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 a lowercase hexadecimal `String` in canonical
+        // 32-character format with four hyphens separating groups of digits.
+        // https://docs.oracle.com/javase/10/docs/api/java/util/UUID.html#toString()
+       return value.toString();
+    }
+}