Register Printer<T> and Parser<T> beans as converters

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/reactive/WebFluxAutoConfiguration.java

@@ -38,6 +38,8 @@
 import org.springframework.boot.autoconfigure.web.ResourceProperties;
 import org.springframework.boot.autoconfigure.web.format.WebConversionService;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
+import org.springframework.boot.convert.ParserConverter;
+import org.springframework.boot.convert.PrinterConverter;
 import org.springframework.boot.web.codec.CodecCustomizer;
 import org.springframework.boot.web.reactive.filter.OrderedHiddenHttpMethodFilter;
 import org.springframework.context.annotation.Bean;
@@ -48,6 +50,8 @@
 import org.springframework.core.convert.converter.GenericConverter;
 import org.springframework.format.Formatter;
 import org.springframework.format.FormatterRegistry;
+import org.springframework.format.Parser;
+import org.springframework.format.Printer;
 import org.springframework.format.support.FormattingConversionService;
 import org.springframework.http.codec.ServerCodecConfigurer;
 import org.springframework.util.ClassUtils;
@@ -185,6 +189,17 @@ public void addFormatters(FormatterRegistry registry) {
 			for (Formatter<?> formatter : getBeansOfType(Formatter.class)) {
 				registry.addFormatter(formatter);
 			}
+			for (Printer<?> printer : getBeansOfType(Printer.class)) {
+				if (!(printer instanceof Formatter<?>)) {
+					registry.addConverter(new PrinterConverter(printer));
+
+				}
+			}
+			for (Parser<?> parser : getBeansOfType(Parser.class)) {
+				if (!(parser instanceof Formatter<?>)) {
+					registry.addConverter(new ParserConverter(parser));
+				}
+			}
 		}
 
 		private <T> Collection<T> getBeansOfType(Class<T> type) {

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/servlet/WebMvcAutoConfiguration.java

@@ -55,6 +55,8 @@
 import org.springframework.boot.autoconfigure.web.ResourceProperties.Strategy;
 import org.springframework.boot.autoconfigure.web.format.WebConversionService;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
+import org.springframework.boot.convert.ParserConverter;
+import org.springframework.boot.convert.PrinterConverter;
 import org.springframework.boot.web.servlet.filter.OrderedFormContentFilter;
 import org.springframework.boot.web.servlet.filter.OrderedHiddenHttpMethodFilter;
 import org.springframework.boot.web.servlet.filter.OrderedRequestContextFilter;
@@ -74,6 +76,8 @@
 import org.springframework.core.task.AsyncTaskExecutor;
 import org.springframework.format.Formatter;
 import org.springframework.format.FormatterRegistry;
+import org.springframework.format.Parser;
+import org.springframework.format.Printer;
 import org.springframework.format.support.FormattingConversionService;
 import org.springframework.http.CacheControl;
 import org.springframework.http.MediaType;
@@ -307,6 +311,16 @@ public void addFormatters(FormatterRegistry registry) {
 			for (Formatter<?> formatter : getBeansOfType(Formatter.class)) {
 				registry.addFormatter(formatter);
 			}
+			for (Printer<?> printer : getBeansOfType(Printer.class)) {
+				if (!(printer instanceof Formatter<?>)) {
+					registry.addConverter(new PrinterConverter(printer));
+				}
+			}
+			for (Parser<?> parser : getBeansOfType(Parser.class)) {
+				if (!(parser instanceof Formatter<?>)) {
+					registry.addConverter(new ParserConverter(parser));
+				}
+			}
 		}
 
 		private <T> Collection<T> getBeansOfType(Class<T> type) {

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/reactive/WebFluxAutoConfigurationTests.java

@@ -19,6 +19,7 @@
 import java.util.Collections;
 import java.util.Date;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.concurrent.TimeUnit;
 
@@ -40,7 +41,10 @@
 import org.springframework.context.annotation.Import;
 import org.springframework.core.Ordered;
 import org.springframework.core.annotation.Order;
+import org.springframework.core.convert.ConversionService;
 import org.springframework.core.io.ClassPathResource;
+import org.springframework.format.Parser;
+import org.springframework.format.Printer;
 import org.springframework.format.support.FormattingConversionService;
 import org.springframework.http.CacheControl;
 import org.springframework.http.codec.ServerCodecConfigurer;
@@ -373,6 +377,17 @@ void cacheControl() {
 		Assertions.setExtractBareNamePropertyMethods(true);
 	}
 
+	@Test
+	void customPrinterAndParserShouldBeRegisteredAsConverters() {
+		this.contextRunner.withUserConfiguration(ParserConfiguration.class, PrinterConfiguration.class)
+				.run((context) -> {
+					Foo foo = new Foo("bar");
+					ConversionService conversionService = context.getBean(ConversionService.class);
+					assertThat(conversionService.convert(foo, String.class)).isEqualTo("bar");
+					assertThat(conversionService.convert("bar", Foo.class)).extracting(Foo::toString).isEqualTo("bar");
+				});
+	}
+
 	private Map<PathPattern, Object> getHandlerMap(ApplicationContext context) {
 		HandlerMapping mapping = context.getBean("resourceHandlerMapping", HandlerMapping.class);
 		if (mapping instanceof SimpleUrlHandlerMapping) {
@@ -545,4 +560,57 @@ private static class MyRequestMappingHandlerMapping extends RequestMappingHandle
 
 	}
 
+	@Configuration(proxyBeanMethods = false)
+	static class PrinterConfiguration {
+
+		@Bean
+		public Printer<Foo> fooPrinter() {
+			return new FooPrinter();
+		}
+
+		private static class FooPrinter implements Printer<Foo> {
+
+			@Override
+			public String print(Foo foo, Locale locale) {
+				return foo.toString();
+			}
+
+		}
+
+	}
+
+	@Configuration(proxyBeanMethods = false)
+	static class ParserConfiguration {
+
+		@Bean
+		public Parser<Foo> fooParser() {
+			return new FooParser();
+		}
+
+		private static class FooParser implements Parser<Foo> {
+
+			@Override
+			public Foo parse(String source, Locale locale) {
+				return new Foo(source);
+			}
+
+		}
+
+	}
+
+	static class Foo {
+
+		private final String name;
+
+		Foo(String name) {
+			this.name = name;
+		}
+
+		@Override
+		public String toString() {
+			return this.name;
+		}
+
+	}
+
 }

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/servlet/WebMvcAutoConfigurationTests.java

@@ -56,6 +56,8 @@
 import org.springframework.core.io.ClassPathResource;
 import org.springframework.core.io.Resource;
 import org.springframework.core.task.AsyncTaskExecutor;
+import org.springframework.format.Parser;
+import org.springframework.format.Printer;
 import org.springframework.format.support.FormattingConversionService;
 import org.springframework.http.CacheControl;
 import org.springframework.http.HttpHeaders;
@@ -773,6 +775,17 @@ void whenUserDefinesARequestContextFilterRegistrationTheAutoConfiguredFilterBack
 		});
 	}
 
+	@Test
+	void customPrinterAndParserShouldBeRegisteredAsConverters() {
+		this.contextRunner.withUserConfiguration(ParserConfiguration.class, PrinterConfiguration.class)
+				.run((context) -> {
+					Foo foo = new Foo("bar");
+					ConversionService conversionService = context.getBean(ConversionService.class);
+					assertThat(conversionService.convert(foo, String.class)).isEqualTo("bar");
+					assertThat(conversionService.convert("bar", Foo.class)).extracting(Foo::toString).isEqualTo("bar");
+				});
+	}
+
 	private void assertCacheControl(AssertableWebApplicationContext context) {
 		Map<String, Object> handlerMap = getHandlerMap(context.getBean("resourceHandlerMapping", HandlerMapping.class));
 		assertThat(handlerMap).hasSize(2);
@@ -1093,4 +1106,57 @@ public FilterRegistrationBean<RequestContextFilter> customRequestContextFilterRe
 
 	}
 
+	@Configuration(proxyBeanMethods = false)
+	static class PrinterConfiguration {
+
+		@Bean
+		public Printer<Foo> fooPrinter() {
+			return new FooPrinter();
+		}
+
+		private static class FooPrinter implements Printer<Foo> {
+
+			@Override
+			public String print(Foo foo, Locale locale) {
+				return foo.toString();
+			}
+
+		}
+
+	}
+
+	@Configuration(proxyBeanMethods = false)
+	static class ParserConfiguration {
+
+		@Bean
+		public Parser<Foo> fooParser() {
+			return new FooParser();
+		}
+
+		private static class FooParser implements Parser<Foo> {
+
+			@Override
+			public Foo parse(String source, Locale locale) {
+				return new Foo(source);
+			}
+
+		}
+
+	}
+
+	static class Foo {
+
+		private final String name;
+
+		Foo(String name) {
+			this.name = name;
+		}
+
+		@Override
+		public String toString() {
+			return this.name;
+		}
+
+	}
+
 }

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/convert/ParserConverter.java

@@ -0,0 +1,93 @@
+/*
+ * Copyright 2012-2019 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.boot.convert;
+
+import java.text.ParseException;
+import java.util.Collections;
+import java.util.Set;
+
+import org.springframework.context.i18n.LocaleContextHolder;
+import org.springframework.core.DecoratingProxy;
+import org.springframework.core.GenericTypeResolver;
+import org.springframework.core.convert.TypeDescriptor;
+import org.springframework.core.convert.converter.Converter;
+import org.springframework.core.convert.converter.GenericConverter;
+import org.springframework.format.Parser;
+import org.springframework.util.Assert;
+import org.springframework.util.StringUtils;
+
+/**
+ * {@link Converter} to convert from a {@link String} to {@code <T>} using the underlying
+ * {@link Parser}{@code <T>}.
+ *
+ * @author Dmytro Nosan
+ * @since 2.2.0
+ */
+public class ParserConverter implements GenericConverter {
+
+	private final Class<?> type;
+
+	private final Parser<?> parser;
+
+	/**
+	 * Creates a {@code Converter} to convert {@code String} to a {@code T} via parser.
+	 * @param parser parses {@code String} to a {@code T}
+	 */
+	public ParserConverter(Parser<?> parser) {
+		Assert.notNull(parser, "Parser must not be null");
+		this.type = getType(parser);
+		this.parser = parser;
+	}
+
+	@Override
+	public Set<ConvertiblePair> getConvertibleTypes() {
+		return Collections.singleton(new ConvertiblePair(String.class, this.type));
+	}
+
+	@Override
+	public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
+		String value = (String) source;
+		if (!StringUtils.hasText(value)) {
+			return null;
+		}
+		try {
+			return this.parser.parse(value, LocaleContextHolder.getLocale());
+		}
+		catch (ParseException ex) {
+			throw new IllegalArgumentException("Value [" + value + "] can not be parsed", ex);
+		}
+	}
+
+	@Override
+	public String toString() {
+		return String.class.getName() + " -> " + this.type.getName() + " : " + this.parser;
+	}
+
+	private static Class<?> getType(Parser<?> parser) {
+		Class<?> type = GenericTypeResolver.resolveTypeArgument(parser.getClass(), Parser.class);
+		if (type == null && parser instanceof DecoratingProxy) {
+			type = GenericTypeResolver.resolveTypeArgument(((DecoratingProxy) parser).getDecoratedClass(),
+					Parser.class);
+		}
+		if (type == null) {
+			throw new IllegalArgumentException("Unable to extract the parameterized type from Parser: '"
+					+ parser.getClass().getName() + "'. Does the class parameterize the <T> generic type?");
+		}
+		return type;
+	}
+
+}