Add support for converting String to Pattern

See gh-24311

Author: valfirst

spring-core/src/main/java/org/springframework/core/convert/support/DefaultConversionService.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2022 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.
@@ -20,6 +20,7 @@
 import java.util.Currency;
 import java.util.Locale;
 import java.util.UUID;
+import java.util.regex.Pattern;
 
 import org.springframework.core.convert.ConversionService;
 import org.springframework.core.convert.converter.ConverterRegistry;
@@ -166,6 +167,9 @@ private static void addScalarConverters(ConverterRegistry converterRegistry) {
 
 		converterRegistry.addConverter(new StringToUUIDConverter());
 		converterRegistry.addConverter(UUID.class, String.class, new ObjectToStringConverter());
+
+		converterRegistry.addConverter(new StringToPatternConverter());
+		converterRegistry.addConverter(Pattern.class, String.class, new ObjectToStringConverter());
 	}
 
 }

spring-core/src/main/java/org/springframework/core/convert/support/StringToPatternConverter.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright 2002-2022 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.
+ */
+
+package org.springframework.core.convert.support;
+
+import java.util.regex.Pattern;
+
+import org.springframework.core.convert.converter.Converter;
+
+/**
+ * Convert a String to a {@link Pattern}.
+ *
+ * @author Valery Yatsynovich
+ * @since 5.2
+ */
+class StringToPatternConverter implements Converter<String, Pattern> {
+
+	@Override
+	public Pattern convert(String source) {
+		return Pattern.compile(source);
+	}
+
+}

spring-core/src/test/java/org/springframework/core/convert/converter/DefaultConversionServiceTests.java

@@ -40,6 +40,7 @@
 import java.util.Set;
 import java.util.TimeZone;
 import java.util.UUID;
+import java.util.regex.Pattern;
 import java.util.stream.Stream;
 
 import org.junit.jupiter.api.Test;
@@ -318,6 +319,18 @@ void uuidToStringAndStringToUuid() {
 		assertThat(convertToUUID).isEqualTo(uuid);
 	}
 
+	@Test
+	void stringToPattern() {
+		String regex = "\\s";
+		assertThat(conversionService.convert(regex, Pattern.class)).extracting(Pattern::pattern).isEqualTo(regex);
+	}
+
+	@Test
+	void patternToString() {
+		String regex = "\\d";
+		assertThat(conversionService.convert(Pattern.compile(regex), String.class)).isEqualTo(regex);
+	}
+
 	@Test
 	void numberToNumber() {
 		assertThat(conversionService.convert(1, Long.class)).isEqualTo(Long.valueOf(1));