Merge pull request spring-projects#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

@@ -1,5 +1,5 @@
 /*
- * 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

@@ -0,0 +1,37 @@
+/*
+ * 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

@@ -0,0 +1,184 @@
+/*
+ * 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;
+	}
+
+}