JacksonInternationalizationUnitTests.java

/*
 * Copyright 2020 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.hateoas.support;

import static org.assertj.core.api.Assertions.*;

import lombok.RequiredArgsConstructor;

import java.io.IOException;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.util.List;
import java.util.Locale;

import org.junit.jupiter.api.BeforeAll;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.TestInstance;
import org.junit.jupiter.api.TestInstance.Lifecycle;
import org.springframework.context.MessageSource;
import org.springframework.context.i18n.LocaleContextHolder;
import org.springframework.context.support.MessageSourceAccessor;
import org.springframework.context.support.StaticMessageSource;

import com.fasterxml.jackson.annotation.JsonAutoDetect;
import com.fasterxml.jackson.annotation.JsonAutoDetect.Visibility;
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.BeanDescription;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationConfig;
import com.fasterxml.jackson.databind.SerializerProvider;
import com.fasterxml.jackson.databind.module.SimpleModule;
import com.fasterxml.jackson.databind.ser.BeanPropertyWriter;
import com.fasterxml.jackson.databind.ser.BeanSerializerModifier;
import com.fasterxml.jackson.databind.ser.std.ToStringSerializer;
import com.jayway.jsonpath.DocumentContext;
import com.jayway.jsonpath.JsonPath;

/**
 * @author Oliver Drotbohm
 */
@TestInstance(Lifecycle.PER_CLASS)
class JacksonInternationalizationUnitTests {

	ObjectMapper mapper = new ObjectMapper();

	@BeforeAll
	void setUp() {

		StaticMessageSource messageSource = new StaticMessageSource();
		messageSource.addMessage("message", Locale.US, "message");
		messageSource.addMessage("message", Locale.GERMAN, "Botschaft");

		mapper.registerModule(new I18nModule(messageSource));
		mapper.setDefaultVisibility(JsonAutoDetect.Value //
				.defaultVisibility() //
				.withFieldVisibility(Visibility.ANY));

	}

	@Test
	void rendersAnnotatedPropertyUsingMessageSource() throws Exception {

		Sample sample = new Sample();
		sample.message = "message";
		sample.plainValue = "plainValue";

		LocaleContextHolder.setLocale(Locale.GERMAN);

		DocumentContext parse = JsonPath.parse(mapper.writeValueAsString(sample));

		assertThat(parse.read("$.message", String.class)).isEqualTo("Botschaft");
		assertThat(parse.read("$.plainValue", String.class)).isEqualTo("plainValue");
	}

	@Test
	void rejectsAnnotationOnNonStringProperty() {

		assertThatExceptionOfType(IllegalStateException.class)
				.isThrownBy(() -> mapper.writeValueAsString(new InvalidExample()));
	}

	static class Sample {

		@JsonInternationalized String message;
		String plainValue;
	}

	static class InvalidExample {
		@JsonInternationalized Integer invalid;
	}

	@Retention(RetentionPolicy.RUNTIME)
	@interface JsonInternationalized {}

	@RequiredArgsConstructor
	static class I18nModule extends SimpleModule {

		private static final long serialVersionUID = -6745718985183239662L;

		private final MessageSource messageSource;

		@Override
		public void setupModule(SetupContext context) {

			MessageSourceAccessor accessor = new MessageSourceAccessor(messageSource);
			InternationalizedSerializer serializer = new InternationalizedSerializer(accessor);
			context.addBeanSerializerModifier(new InternationalizingBeanSerializerModifier(serializer));
		}

		@RequiredArgsConstructor
		static class InternationalizingBeanSerializerModifier extends BeanSerializerModifier {

			private static final String PROPERTY_MUST_BE_STRING = "Invalid use of @"
					+ JsonInternationalized.class.getSimpleName() + " on %s! Can only be used on properties of type String!";

			private final InternationalizedSerializer serializer;

			/*
			 * (non-Javadoc)
			 * @see com.fasterxml.jackson.databind.ser.BeanSerializerModifier#changeProperties(com.fasterxml.jackson.databind.SerializationConfig, com.fasterxml.jackson.databind.BeanDescription, java.util.List)
			 */
			@Override
			public List<BeanPropertyWriter> changeProperties(SerializationConfig config, BeanDescription beanDesc,
					List<BeanPropertyWriter> beanProperties) {

				for (BeanPropertyWriter writer : beanProperties) {

					if (writer.getAnnotation(JsonInternationalized.class) != null) {

						if (!writer.getType().isTypeOrSubTypeOf(String.class)) {
							throw new IllegalStateException(String.format(PROPERTY_MUST_BE_STRING, writer));
						}

						writer.assignSerializer(serializer);
					}
				}

				return beanProperties;
			}
		}

		/**
		 * Serializer that resolves an object's to String
		 *
		 * @author Oliver Drotbohm
		 */
		@RequiredArgsConstructor
		static class InternationalizedSerializer extends ToStringSerializer {

			private static final long serialVersionUID = -2391442803792997283L;

			private final MessageSourceAccessor accessor;

			/*
			 * (non-Javadoc)
			 * @see com.fasterxml.jackson.databind.ser.std.ToStringSerializerBase#serialize(java.lang.Object, com.fasterxml.jackson.core.JsonGenerator, com.fasterxml.jackson.databind.SerializerProvider)
			 */
			@Override
			public void serialize(Object value, JsonGenerator gen, SerializerProvider provider) throws IOException {
				gen.writeString(accessor.getMessage(value.toString()));
			}
		}
	}
}