Merge pull request #11498 from ioanngolovko

* pr/11498:
  Polish GSON customization support
  Allow GSON customization via properties or beans

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/gson/GsonAutoConfiguration.java

 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 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.
@@ -16,28 +16,88 @@
 
 package org.springframework.boot.autoconfigure.gson;
 
+import java.util.List;
+
 import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
 
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
+import org.springframework.boot.context.properties.EnableConfigurationProperties;
+import org.springframework.boot.context.properties.PropertyMapper;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.core.Ordered;
 
 /**
  * {@link EnableAutoConfiguration Auto-configuration} for Gson.
  *
  * @author David Liu
+ * @author Ivan Golovko
  * @since 1.2.0
  */
 @Configuration
 @ConditionalOnClass(Gson.class)
+@EnableConfigurationProperties(GsonProperties.class)
 public class GsonAutoConfiguration {
 
 	@Bean
-	@ConditionalOnMissingBean
-	public Gson gson() {
-		return new Gson();
+	public GsonBuilder gsonBuilder(List<GsonBuilderCustomizer> customizers) {
+		GsonBuilder builder = new GsonBuilder();
+		customizers.forEach(c -> c.customize(builder));
+		return builder;
+	}
+
+	@Bean
+	@ConditionalOnMissingBean(Gson.class)
+	public Gson gson(GsonBuilder gsonBuilder) {
+		return gsonBuilder.create();
+	}
+
+	@Bean
+	public StandardGsonBuilderCustomizer standardGsonBuilderCustomizer(
+			GsonProperties gsonProperties) {
+		return new StandardGsonBuilderCustomizer(gsonProperties);
+	}
+
+	private static final class StandardGsonBuilderCustomizer
+			implements GsonBuilderCustomizer, Ordered {
+
+		private final GsonProperties properties;
+
+		StandardGsonBuilderCustomizer(GsonProperties properties) {
+			this.properties = properties;
+		}
+
+		@Override
+		public int getOrder() {
+			return 0;
+		}
+
+		@Override
+		public void customize(GsonBuilder builder) {
+			GsonProperties properties = this.properties;
+			PropertyMapper map = PropertyMapper.get().alwaysApplyingWhenNonNull();
+			map.from(properties::getGenerateNonExecutableJson)
+					.toCall(builder::generateNonExecutableJson);
+			map.from(properties::getExcludeFieldsWithoutExposeAnnotation)
+					.toCall(builder::excludeFieldsWithoutExposeAnnotation);
+			map.from(properties::getSerializeNulls).toCall(builder::serializeNulls);
+			map.from(properties::getEnableComplexMapKeySerialization)
+					.toCall(builder::enableComplexMapKeySerialization);
+			map.from(properties::getDisableInnerClassSerialization)
+					.toCall(builder::disableInnerClassSerialization);
+			map.from(properties::getLongSerializationPolicy)
+					.to(builder::setLongSerializationPolicy);
+			map.from(properties::getFieldNamingPolicy).to(builder::setFieldNamingPolicy);
+			map.from(properties::getPrettyPrinting).toCall(builder::setPrettyPrinting);
+			map.from(properties::getLenient).toCall(builder::setLenient);
+			map.from(properties::getDisableHtmlEscaping)
+					.toCall(builder::disableHtmlEscaping);
+			map.from(properties::getDateFormat).to(builder::setDateFormat);
+		}
+
 	}
 
 }

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/gson/GsonBuilderCustomizer.java

+/*
+ * Copyright 2012-2018 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
+ *
+ *      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 org.springframework.boot.autoconfigure.gson;
+
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+
+/**
+ * Callback interface that can be implemented by beans wishing to further customize the
+ * {@link Gson} via {@link GsonBuilder} retaining its default auto-configuration.
+ *
+ * @author Ivan Golovko
+ * @since 2.0.0
+ */
+@FunctionalInterface
+public interface GsonBuilderCustomizer {
+
+	/**
+	 * Customize the GsonBuilder.
+	 * @param gsonBuilder the GsonBuilder to customize
+	 */
+	void customize(GsonBuilder gsonBuilder);
+}

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/gson/GsonProperties.java

+/*
+ * Copyright 2012-2018 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
+ *
+ *      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 org.springframework.boot.autoconfigure.gson;
+
+import com.google.gson.FieldNamingPolicy;
+import com.google.gson.Gson;
+import com.google.gson.LongSerializationPolicy;
+
+import org.springframework.boot.context.properties.ConfigurationProperties;
+
+/**
+ * Configuration properties to configure {@link Gson}.
+ *
+ * @author Ivan Golovko
+ * @since 2.0.0
+ */
+@ConfigurationProperties(prefix = "spring.gson")
+public class GsonProperties {
+
+	/**
+	 * Whether to generate non executable JSON by prefixing the output with some special
+	 * text.
+	 */
+	private Boolean generateNonExecutableJson;
+
+	/**
+	 * Whether to exclude all fields from consideration for serialization or
+	 * deserialization that do not have the "Expose" annotation.
+	 */
+	private Boolean excludeFieldsWithoutExposeAnnotation;
+
+	/**
+	 * Whether to to serialize null fields.
+	 */
+	private Boolean serializeNulls;
+
+	/**
+	 * Whether to enabled serialization of complex map keys (i.e. non-primitives).
+	 */
+	private Boolean enableComplexMapKeySerialization;
+
+	/**
+	 * Whether to exclude inner classes during serialization.
+	 */
+	private Boolean disableInnerClassSerialization;
+
+	/**
+	 * Serialization policy for Long and long types.
+	 */
+	private LongSerializationPolicy longSerializationPolicy;
+
+	/**
+	 * The naming policy that should be applied to an object's field during serialization
+	 * and deserialization.
+	 */
+	private FieldNamingPolicy fieldNamingPolicy;
+
+	/**
+	 * Whether to output serialized JSON that fits in a page for pretty printing.
+	 */
+	private Boolean prettyPrinting;
+
+	/**
+	 * Whether to be lenient about parsing JSON that doesn't conform to RFC 4627.
+	 */
+	private Boolean lenient;
+
+	/**
+	 * Whether to disable the escaping of HTML characters such as '<' '>' etc.
+	 */
+	private Boolean disableHtmlEscaping;
+
+	/**
+	 * The format to use when serializing Date objects.
+	 */
+	private String dateFormat;
+
+	public Boolean getGenerateNonExecutableJson() {
+		return this.generateNonExecutableJson;
+	}
+
+	public void setGenerateNonExecutableJson(Boolean generateNonExecutableJson) {
+		this.generateNonExecutableJson = generateNonExecutableJson;
+	}
+
+	public Boolean getExcludeFieldsWithoutExposeAnnotation() {
+		return this.excludeFieldsWithoutExposeAnnotation;
+	}
+
+	public void setExcludeFieldsWithoutExposeAnnotation(
+			Boolean excludeFieldsWithoutExposeAnnotation) {
+		this.excludeFieldsWithoutExposeAnnotation = excludeFieldsWithoutExposeAnnotation;
+	}
+
+	public Boolean getSerializeNulls() {
+		return this.serializeNulls;
+	}
+
+	public void setSerializeNulls(Boolean serializeNulls) {
+		this.serializeNulls = serializeNulls;
+	}
+
+	public Boolean getEnableComplexMapKeySerialization() {
+		return this.enableComplexMapKeySerialization;
+	}
+
+	public void setEnableComplexMapKeySerialization(
+			Boolean enableComplexMapKeySerialization) {
+		this.enableComplexMapKeySerialization = enableComplexMapKeySerialization;
+	}
+
+	public Boolean getDisableInnerClassSerialization() {
+		return this.disableInnerClassSerialization;
+	}
+
+	public void setDisableInnerClassSerialization(
+			Boolean disableInnerClassSerialization) {
+		this.disableInnerClassSerialization = disableInnerClassSerialization;
+	}
+
+	public LongSerializationPolicy getLongSerializationPolicy() {
+		return this.longSerializationPolicy;
+	}
+
+	public void setLongSerializationPolicy(
+			LongSerializationPolicy longSerializationPolicy) {
+		this.longSerializationPolicy = longSerializationPolicy;
+	}
+
+	public FieldNamingPolicy getFieldNamingPolicy() {
+		return this.fieldNamingPolicy;
+	}
+
+	public void setFieldNamingPolicy(FieldNamingPolicy fieldNamingPolicy) {
+		this.fieldNamingPolicy = fieldNamingPolicy;
+	}
+
+	public Boolean getPrettyPrinting() {
+		return this.prettyPrinting;
+	}
+
+	public void setPrettyPrinting(Boolean prettyPrinting) {
+		this.prettyPrinting = prettyPrinting;
+	}
+
+	public Boolean getLenient() {
+		return this.lenient;
+	}
+
+	public void setLenient(Boolean lenient) {
+		this.lenient = lenient;
+	}
+
+	public Boolean getDisableHtmlEscaping() {
+		return this.disableHtmlEscaping;
+	}
+
+	public void setDisableHtmlEscaping(Boolean disableHtmlEscaping) {
+		this.disableHtmlEscaping = disableHtmlEscaping;
+	}
+
+	public String getDateFormat() {
+		return this.dateFormat;
+	}
+
+	public void setDateFormat(String dateFormat) {
+		this.dateFormat = dateFormat;
+	}
+
+}

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/gson/GsonAutoConfigurationTests.java

 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 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.
@@ -16,12 +16,22 @@
 
 package org.springframework.boot.autoconfigure.gson;
 
+import java.lang.reflect.Field;
+import java.util.Date;
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+import com.google.gson.ExclusionStrategy;
+import com.google.gson.FieldAttributes;
+import com.google.gson.FieldNamingPolicy;
 import com.google.gson.Gson;
-import org.junit.After;
-import org.junit.Before;
+import com.google.gson.LongSerializationPolicy;
+import org.joda.time.DateTime;
 import org.junit.Test;
 
-import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.boot.autoconfigure.AutoConfigurations;
+import org.springframework.boot.test.context.runner.ApplicationContextRunner;
+import org.springframework.context.annotation.Bean;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
@@ -29,36 +39,233 @@ import static org.assertj.core.api.Assertions.assertThat;
  * Tests for {@link GsonAutoConfiguration}.
  *
  * @author David Liu
+ * @author Ivan Golovko
  */
 public class GsonAutoConfigurationTests {
 
-	AnnotationConfigApplicationContext context;
+	private final ApplicationContextRunner contextRunner = new ApplicationContextRunner()
+			.withConfiguration(AutoConfigurations.of(GsonAutoConfiguration.class));
 
-	@Before
-	public void setUp() {
-		this.context = new AnnotationConfigApplicationContext();
+	@Test
+	public void gsonRegistration() {
+		this.contextRunner.run(context -> {
+			Gson gson = context.getBean(Gson.class);
+			assertThat(gson.toJson(new DataObject())).isEqualTo("{\"data\":1}");
+		});
 	}
 
-	@After
-	public void tearDown() {
-		if (this.context != null) {
-			this.context.close();
+	@Test
+	public void generateNonExecutableJson() {
+		this.contextRunner
+				.withPropertyValues("spring.gson.generate-non-executable-json:true")
+				.run(context -> {
+					Gson gson = context.getBean(Gson.class);
+					assertThat(gson.toJson(new DataObject()))
+							.isNotEqualTo("{\"data\":1}");
+					assertThat(gson.toJson(new DataObject())).endsWith("{\"data\":1}");
+				});
 	}
+
+	@Test
+	public void excludeFieldsWithoutExposeAnnotation() {
+		this.contextRunner
+				.withPropertyValues(
+						"spring.gson.exclude-fields-without-expose-annotation:true")
+				.run(context -> {
+					Gson gson = context.getBean(Gson.class);
+					assertThat(gson.toJson(new DataObject())).isEqualTo("{}");
+				});
 	}
 
 	@Test
-	public void gsonRegistration() {
-		this.context.register(GsonAutoConfiguration.class);
-		this.context.refresh();
-		Gson gson = this.context.getBean(Gson.class);
-		assertThat(gson.toJson(new DataObject())).isEqualTo("{\"data\":\"hello\"}");
+	public void serializeNulls() {
+		this.contextRunner.withPropertyValues("spring.gson.serialize-nulls:true")
+				.run(context -> {
+					Gson gson = context.getBean(Gson.class);
+					assertThat(gson.serializeNulls()).isTrue();
+				});
+	}
+
+	@Test
+	public void enableComplexMapKeySerialization() {
+		this.contextRunner
+				.withPropertyValues(
+						"spring.gson.enable-complex-map-key-serialization:true")
+				.run(context -> {
+					Gson gson = context.getBean(Gson.class);
+					Map<DataObject, String> original = new LinkedHashMap<>();
+					original.put(new DataObject(), "a");
+					assertThat(gson.toJson(original)).isEqualTo("[[{\"data\":1},\"a\"]]");
+				});
+	}
+
+	@Test
+	public void notDisableInnerClassSerialization() {
+		this.contextRunner.run(context -> {
+			Gson gson = context.getBean(Gson.class);
+			WrapperObject wrapperObject = new WrapperObject();
+			assertThat(gson.toJson(wrapperObject.new NestedObject()))
+					.isEqualTo("{\"data\":\"nested\"}");
+		});
+	}
+
+	@Test
+	public void disableInnerClassSerialization() {
+		this.contextRunner
+				.withPropertyValues("spring.gson.disable-inner-class-serialization:true")
+				.run(context -> {
+					Gson gson = context.getBean(Gson.class);
+					WrapperObject wrapperObject = new WrapperObject();
+					assertThat(gson.toJson(wrapperObject.new NestedObject()))
+							.isEqualTo("null");
+				});
+	}
+
+	@Test
+	public void withLongSerializationPolicy() {
+		this.contextRunner.withPropertyValues(
+				"spring.gson.long-serialization-policy:" + LongSerializationPolicy.STRING)
+				.run(context -> {
+					Gson gson = context.getBean(Gson.class);
+					assertThat(gson.toJson(new DataObject()))
+							.isEqualTo("{\"data\":\"1\"}");
+				});
+	}
+
+	@Test
+	public void withFieldNamingPolicy() {
+		FieldNamingPolicy fieldNamingPolicy = FieldNamingPolicy.UPPER_CAMEL_CASE;
+		this.contextRunner
+				.withPropertyValues(
+						"spring.gson.field-naming-policy:" + fieldNamingPolicy)
+				.run(context -> {
+					Gson gson = context.getBean(Gson.class);
+					assertThat(gson.fieldNamingStrategy()).isEqualTo(fieldNamingPolicy);
+				});
+	}
+
+	@Test
+	public void additionalGsonBuilderCustomization() {
+		this.contextRunner.withUserConfiguration(GsonBuilderCustomConfig.class)
+				.run(context -> {
+					Gson gson = context.getBean(Gson.class);
+					assertThat(gson.toJson(new DataObject())).isEqualTo("{}");
+				});
+	}
+
+	@Test
+	public void withPrettyPrinting() {
+		this.contextRunner.withPropertyValues("spring.gson.pretty-printing:true")
+				.run(context -> {
+					Gson gson = context.getBean(Gson.class);
+					assertThat(gson.toJson(new DataObject()))
+							.isEqualTo("{\n  \"data\": 1\n}");
+				});
+	}
+
+	@Test
+	public void withoutLenient() throws Exception {
+		this.contextRunner.run(context -> {
+			Gson gson = context.getBean(Gson.class);
+			/*
+			 * It seems, that lenient setting not work in version 2.8.2 We get access to
+			 * it via reflection
+			 */
+			Field lenientField = gson.getClass().getDeclaredField("lenient");
+			lenientField.setAccessible(true);
+			boolean lenient = lenientField.getBoolean(gson);
+
+			assertThat(lenient).isFalse();
+		});
+	}
+
+	@Test
+	public void withLenient() throws Exception {
+		this.contextRunner.withPropertyValues("spring.gson.lenient:true").run(context -> {
+			Gson gson = context.getBean(Gson.class);
+
+			/*
+			 * It seems, that lenient setting not work in version 2.8.0 of gson We get
+			 * access to it via reflection
+			 */
+			Field lenientField = gson.getClass().getDeclaredField("lenient");
+			lenientField.setAccessible(true);
+			boolean lenient = lenientField.getBoolean(gson);
+
+			assertThat(lenient).isTrue();
+		});
+	}
+
+	@Test
+	public void withHtmlEscaping() {
+		this.contextRunner.run(context -> {
+			Gson gson = context.getBean(Gson.class);
+			assertThat(gson.htmlSafe()).isTrue();
+		});
+	}
+
+	@Test
+	public void withoutHtmlEscaping() {
+		this.contextRunner.withPropertyValues("spring.gson.disable-html-escaping:true")
+				.run(context -> {
+					Gson gson = context.getBean(Gson.class);
+					assertThat(gson.htmlSafe()).isFalse();
+				});
+
+	}
+
+	@Test
+	public void customDateFormat() {
+		this.contextRunner.withPropertyValues("spring.gson.date-format:H")
+				.run(context -> {
+					Gson gson = context.getBean(Gson.class);
+					DateTime dateTime = new DateTime(1988, 6, 25, 20, 30);
+					Date date = dateTime.toDate();
+					assertThat(gson.toJson(date)).isEqualTo("\"20\"");
+				});
+	}
+
+	protected static class GsonBuilderCustomConfig {
+
+		@Bean
+		public GsonBuilderCustomizer customSerializationExclusionStrategy() {
+			return (gsonBuilder) -> gsonBuilder
+					.addSerializationExclusionStrategy(new ExclusionStrategy() {
+						@Override
+						public boolean shouldSkipField(FieldAttributes fieldAttributes) {
+							return "data".equals(fieldAttributes.getName());
+						}
+
+						@Override
+						public boolean shouldSkipClass(Class<?> aClass) {
+							return false;
+						}
+					});
+		}
+
 	}
 
 	public class DataObject {
 
+		public static final String STATIC_DATA = "bye";
+
+		@SuppressWarnings("unused")
+		private Long data = 1L;
+
+		public void setData(Long data) {
+			this.data = data;
+		}
+
+	}
+
+	public class WrapperObject {
+
 		@SuppressWarnings("unused")
-		private String data = "hello";
+		class NestedObject {
 
+			private String data = "nested";
+
+		}
 	}
 
 }

spring-boot-project/spring-boot-docs/src/main/asciidoc/appendix-application-properties.adoc

@@ -340,6 +340,19 @@ content into your application. Rather, pick only the properties that you need.
 	spring.jackson.serialization.*= # Jackson on/off features that affect the way Java objects are serialized.
 	spring.jackson.time-zone= #  Time zone used when formatting dates. For instance, "America/Los_Angeles" or "GMT+10".
 
+	# GSON ({sc-spring-boot-autoconfigure}/gson/GsonProperties.{sc-ext}[GsonProperties])
+	spring.gson.date-format= # The format to use when serializing Date objects.
+	spring.gson.disable-html-escaping= # Whether to disable the escaping of HTML characters such as '<' '>' etc.
+	spring.gson.disable-inner-class-serialization= # Whether to exclude inner classes during serialization.
+	spring.gson.enable-complex-map-key-serialization= # Whether to enabled serialization of complex map keys (i.e. non-primitives).
+	spring.gson.exclude-fields-without-expose-annotation= # Whether to exclude all fields from consideration for serialization or deserialization that do not have the "Expose" annotation.
+	spring.gson.field-naming-policy= # The naming policy that should be applied to an object's field during serialization and deserialization.
+	spring.gson.generate-non-executable-json= # Whether to generate non executable JSON by prefixing the output with some special text.
+	spring.gson.lenient= # Whether to be lenient about parsing JSON that doesn't conform to RFC 4627.
+	spring.gson.long-serialization-policy= # Serialization policy for Long and long types.
+	spring.gson.pretty-printing= # Whether to output serialized JSON that fits in a page for pretty printing.
+	spring.gson.serialize-nulls= # Whether to to serialize null fields.
+
 	# JERSEY ({sc-spring-boot-autoconfigure}/jersey/JerseyProperties.{sc-ext}[JerseyProperties])
 	spring.jersey.application-path= # Path that serves as the base URI for the application. If specified, overrides the value of "@ApplicationPath".
 	spring.jersey.filter.order=0 # Jersey filter chain order.