Allow GSON customization via properties or beans

Update GSON support to allow customization with either properties or
customize beans.

See gh-11498

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 2012-2014 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 +16,145 @@
 
 package org.springframework.boot.autoconfigure.gson;
 
+import java.util.List;
+
+import com.google.gson.FieldNamingPolicy;
 import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+import com.google.gson.LongSerializationPolicy;
 
 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.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Primary;
+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)
 public class GsonAutoConfiguration {
 
-	@Bean
-	@ConditionalOnMissingBean
-	public Gson gson() {
-		return new Gson();
+	@Configuration
+	static class GsonConfiguration {
+
+		@Bean
+		@Primary
+		@ConditionalOnMissingBean(Gson.class)
+		public Gson gson(GsonBuilder gsonBuilder) {
+			return gsonBuilder.create();
+		}
+	}
+
+	@Configuration
+	static class GsonBuilderConfiguration {
+
+		@Bean
+		public GsonBuilder gsonBuilder(List<GsonBuilderCustomizer> customizers) {
+			final GsonBuilder gsonBuilder = new GsonBuilder();
+			customizers.forEach(c -> c.customize(gsonBuilder));
+			return gsonBuilder;
+		}
+
+	}
+
+	@Configuration
+	@EnableConfigurationProperties(GsonProperties.class)
+	static class GsonBuilderCustomizerConfiguration {
+
+		@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 gsonBuilder) {
+
+				boolean generateNonExecutableJson = this.properties
+						.isGenerateNonExecutableJson();
+				if (generateNonExecutableJson) {
+					gsonBuilder.generateNonExecutableJson();
+				}
+
+				boolean excludeFieldsWithoutExposeAnnotation = this.properties
+						.isExcludeFieldsWithoutExposeAnnotation();
+				if (excludeFieldsWithoutExposeAnnotation) {
+					gsonBuilder.excludeFieldsWithoutExposeAnnotation();
+				}
+
+				boolean serializeNulls = this.properties.isSerializeNulls();
+				if (serializeNulls) {
+					gsonBuilder.serializeNulls();
+				}
+
+				boolean enableComplexMapKeySerialization = this.properties
+						.isEnableComplexMapKeySerialization();
+				if (enableComplexMapKeySerialization) {
+					gsonBuilder.enableComplexMapKeySerialization();
+				}
+
+				boolean disableInnerClassSerialization = this.properties
+						.isDisableInnerClassSerialization();
+				if (disableInnerClassSerialization) {
+					gsonBuilder.disableInnerClassSerialization();
+				}
+
+				LongSerializationPolicy longSerializationPolicy = this.properties
+						.getLongSerializationPolicy();
+				if (longSerializationPolicy != null) {
+					gsonBuilder.setLongSerializationPolicy(longSerializationPolicy);
+				}
+
+				FieldNamingPolicy fieldNamingPolicy = this.properties
+						.getFieldNamingPolicy();
+				if (fieldNamingPolicy != null) {
+					gsonBuilder.setFieldNamingPolicy(fieldNamingPolicy);
+				}
+
+				boolean prettyPrinting = this.properties.isPrettyPrinting();
+				if (prettyPrinting) {
+					gsonBuilder.setPrettyPrinting();
+				}
+
+				boolean isLenient = this.properties.isLenient();
+				if (isLenient) {
+					gsonBuilder.setLenient();
+				}
+
+				boolean disableHtmlEscaping = this.properties.isDisableHtmlEscaping();
+				if (disableHtmlEscaping) {
+					gsonBuilder.disableHtmlEscaping();
+				}
+
+				String dateFormat = this.properties.getDateFormat();
+				if (dateFormat != null) {
+					gsonBuilder.setDateFormat(dateFormat);
+				}
+			}
+		}
 	}
 
 }

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

+/*
+ * Copyright 2012-2017 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 2012-2017 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 com.google.gson.annotations.Expose;
+
+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 {
+
+	/**
+	 * Makes the output JSON non-executable in Javascript by prefixing the generated JSON
+	 * with some special text.
+	 */
+	private boolean generateNonExecutableJson;
+
+	/**
+	 * Configures {@link Gson} to exclude all fields from consideration for serialization
+	 * or deserialization that do not have the {@link Expose} annotation.
+	 */
+	private boolean excludeFieldsWithoutExposeAnnotation;
+
+	/**
+	 * Configure {@link Gson} to serialize null fields.
+	 */
+	private boolean serializeNulls;
+
+	/**
+	 * Enabling this feature will only change the serialized form if the map key is a
+	 * complex type (i.e. non-primitive) in its serialized JSON form
+	 */
+	private boolean enableComplexMapKeySerialization;
+
+	/**
+	 * Configures {@link Gson} to exclude inner classes during serialization.
+	 */
+	private boolean disableInnerClassSerialization;
+
+	/**
+	 * Configures {@link Gson} to apply a specific serialization policy for Long and long
+	 * objects.
+	 */
+	private LongSerializationPolicy longSerializationPolicy;
+
+	/**
+	 * Configures {@link Gson} to apply a specific naming policy to an object's field
+	 * during serialization and deserialization.
+	 */
+	private FieldNamingPolicy fieldNamingPolicy;
+
+	/**
+	 * Configures {@link Gson} to output Json that fits in a page for pretty printing.
+	 * This option only affects Json serialization.
+	 */
+	private boolean prettyPrinting;
+
+	/**
+	 * By default, {@link Gson} is strict and only accepts JSON as specified by RFC 4627.
+	 * This option makes the parser liberal in what it accepts.
+	 */
+	private boolean lenient;
+
+	/**
+	 * By default, {@link Gson} escapes HTML characters such as < > etc. Use this option
+	 * to configure Gson to pass-through HTML characters as is.
+	 */
+	private boolean disableHtmlEscaping;
+
+	/**
+	 * Configures {@link Gson} to serialize Date objects according to the pattern
+	 * provided.
+	 */
+	private String dateFormat;
+
+	public boolean isGenerateNonExecutableJson() {
+		return this.generateNonExecutableJson;
+	}
+
+	public void setGenerateNonExecutableJson(boolean generateNonExecutableJson) {
+		this.generateNonExecutableJson = generateNonExecutableJson;
+	}
+
+	public boolean isExcludeFieldsWithoutExposeAnnotation() {
+		return this.excludeFieldsWithoutExposeAnnotation;
+	}
+
+	public void setExcludeFieldsWithoutExposeAnnotation(
+			boolean excludeFieldsWithoutExposeAnnotation) {
+		this.excludeFieldsWithoutExposeAnnotation = excludeFieldsWithoutExposeAnnotation;
+	}
+
+	public boolean isSerializeNulls() {
+		return this.serializeNulls;
+	}
+
+	public void setSerializeNulls(boolean serializeNulls) {
+		this.serializeNulls = serializeNulls;
+	}
+
+	public boolean isEnableComplexMapKeySerialization() {
+		return this.enableComplexMapKeySerialization;
+	}
+
+	public void setEnableComplexMapKeySerialization(
+			boolean enableComplexMapKeySerialization) {
+		this.enableComplexMapKeySerialization = enableComplexMapKeySerialization;
+	}
+
+	public boolean isDisableInnerClassSerialization() {
+		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 isPrettyPrinting() {
+		return this.prettyPrinting;
+	}
+
+	public void setPrettyPrinting(boolean prettyPrinting) {
+		this.prettyPrinting = prettyPrinting;
+	}
+
+	public boolean isLenient() {
+		return this.lenient;
+	}
+
+	public void setLenient(boolean lenient) {
+		this.lenient = lenient;
+	}
+
+	public boolean isDisableHtmlEscaping() {
+		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 2012-2016 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.
@@ -16,49 +16,254 @@
 
 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;
-
 /**
  * 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 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 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 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 {
 
 		@SuppressWarnings("unused")
-		private String data = "hello";
+		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")
+		class NestedObject {
+			@SuppressWarnings("unused")
+			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= # Configures Gson to serialize Date objects according to the pattern provided.
+    spring.gson.disable-html-escaping=false # By default, Gson escapes HTML characters such as < > etc. Use this option to configure Gson to pass-through HTML characters as is.
+    spring.gson.disable-inner-class-serialization=false # Configures Gson to exclude inner classes during serialization.
+    spring.gson.enable-complex-map-key-serialization=false # Enabling this feature will only change the serialized form if the map key is a complex type (i.e. non-primitive) in its serialized JSON form
+    spring.gson.exclude-fields-without-expose-annotation=false # Configures Gson to exclude all fields from consideration for serialization or deserialization that do not have the Expose  annotation.
+    spring.gson.field-naming-policy= # Configures Gson to apply a specific naming policy to an object's field during serialization and deserialization.
+    spring.gson.generate-non-executable-json=false # Makes the output JSON non-executable in Javascript by prefixing the generated JSON with some special text.
+    spring.gson.lenient=false # By default, Gson is strict and only accepts JSON as specified by RFC 4627. This option makes the parser liberal in what it accepts.
+    spring.gson.long-serialization-policy= # Configures Gson to apply a specific serialization policy for Long and long objects.
+    spring.gson.pretty-printing=false # Configures Gson to output Json that fits in a page for pretty printing. This option only affects Json serialization.
+    spring.gson.serialize-nulls=false # Configure Gson 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.