Provide auto-configuration for Gson

Closes #1339

spring-boot-autoconfigure/pom.xml

@@ -50,6 +50,11 @@
 			<artifactId>jackson-datatype-jsr310</artifactId>
 			<optional>true</optional>
 		</dependency>
+		<dependency>
+			<groupId>com.google.code.gson</groupId>
+			<artifactId>gson</artifactId>
+			<optional>true</optional>
+		</dependency>
 		<dependency>
 			<groupId>org.flywaydb</groupId>
 			<artifactId>flyway-core</artifactId>

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

@@ -0,0 +1,43 @@
+/*
+ * 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.
+ * 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 org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+import com.google.gson.Gson;
+
+/**
+ * {@link EnableAutoConfiguration Auto-configuration} for Gson.
+ *
+ * @author David Liu
+ * @since 1.2.0
+ */
+@Configuration
+@ConditionalOnClass(Gson.class)
+public class GsonAutoConfiguration {
+
+	@Bean
+	@ConditionalOnMissingBean
+	public Gson gson() {
+		return new Gson();
+	}
+
+}

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/HttpMessageConvertersAutoConfiguration.java

@@ -23,15 +23,18 @@ import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
+import org.springframework.boot.autoconfigure.gson.GsonAutoConfiguration;
 import org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Import;
 import org.springframework.http.converter.HttpMessageConverter;
+import org.springframework.http.converter.json.GsonHttpMessageConverter;
 import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;
 
 import com.fasterxml.jackson.databind.ObjectMapper;
+import com.google.gson.Gson;
 
 /**
  * {@link EnableAutoConfiguration Auto-configuration} for {@link HttpMessageConverter}s.
@@ -40,10 +43,11 @@ import com.fasterxml.jackson.databind.ObjectMapper;
  * @author Christian Dupuis
  * @author Piotr Maj
  * @author Oliver Gierke
+ * @author David Liu
  */
 @Configuration
 @ConditionalOnClass(HttpMessageConverter.class)
-@Import(JacksonAutoConfiguration.class)
+@Import({ JacksonAutoConfiguration.class, GsonAutoConfiguration.class })
 public class HttpMessageConvertersAutoConfiguration {
 
 	@Autowired(required = false)
@@ -75,4 +79,18 @@ public class HttpMessageConvertersAutoConfiguration {
 
 	}
 
+	@Configuration
+	@ConditionalOnClass(Gson.class)
+	protected static class GsonConfiguration {
+
+		@Bean
+		@ConditionalOnMissingBean
+		public GsonHttpMessageConverter gsonHttpMessageConverter(Gson gson) {
+			GsonHttpMessageConverter converter = new GsonHttpMessageConverter();
+			converter.setGson(gson);
+			return converter;
+		}
+
+	}
+
 }

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

@@ -0,0 +1,64 @@
+/*
+ * 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.
+ * 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 org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+
+import com.google.gson.Gson;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * Tests for {@link GsonAutoConfiguration}.
+ *
+ * @author David Liu
+ */
+public class GsonAutoConfigurationTests {
+
+	AnnotationConfigApplicationContext context;
+
+	@Before
+	public void setUp() {
+		this.context = new AnnotationConfigApplicationContext();
+	}
+
+	@After
+	public void tearDown() {
+		if (this.context != null) {
+			this.context.close();
+		}
+	}
+
+	@Test
+	public void gsonRegistration() {
+		this.context.register(GsonAutoConfiguration.class);
+		this.context.refresh();
+		Gson gson = this.context.getBean(Gson.class);
+		assertEquals("{\"data\":\"hello\"}", gson.toJson(new DataObject()));
+	}
+
+	public class DataObject {
+
+		@SuppressWarnings("unused")
+		private String data = "hello";
+
+	}
+
+}

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/HttpMessageConvertersAutoConfigurationTests.java

@@ -21,9 +21,11 @@ import org.junit.Test;
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.http.converter.json.GsonHttpMessageConverter;
 import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;
 
 import com.fasterxml.jackson.databind.ObjectMapper;
+import com.google.gson.Gson;
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
@@ -33,6 +35,7 @@ import static org.junit.Assert.assertTrue;
  *
  * @author Dave Syer
  * @author Oliver Gierke
+ * @author David Liu
  */
 public class HttpMessageConvertersAutoConfigurationTests {
 
@@ -76,4 +79,32 @@ public class HttpMessageConvertersAutoConfigurationTests {
 
 	}
 
+	@Test
+	public void customGsonConverter() throws Exception {
+		this.context.register(GsonConfig.class,
+				HttpMessageConvertersAutoConfiguration.class);
+		this.context.refresh();
+		GsonHttpMessageConverter converter = this.context
+				.getBean(GsonHttpMessageConverter.class);
+		assertEquals(this.context.getBean(Gson.class), converter.getGson());
+		HttpMessageConverters converters = this.context
+				.getBean(HttpMessageConverters.class);
+		assertTrue(converters.getConverters().contains(converter));
+	}
+
+	@Configuration
+	protected static class GsonConfig {
+
+		@Bean
+		public GsonHttpMessageConverter gsonMessageConverter() {
+			GsonHttpMessageConverter converter = new GsonHttpMessageConverter();
+			converter.setGson(gson());
+			return converter;
+		}
+
+		@Bean
+		public Gson gson() {
+			return new Gson();
+		}
+	}
 }

spring-boot-dependencies/pom.xml

@@ -75,6 +75,7 @@
 		<hornetq.version>2.4.3.Final</hornetq.version>
 		<hsqldb.version>2.3.2</hsqldb.version>
 		<jackson.version>2.4.2</jackson.version>
+		<gson.version>2.3</gson.version>
 		<janino.version>2.6.1</janino.version>
 		<javassist.version>3.18.1-GA</javassist.version> <!-- Same as Hibernate -->
 		<javax-cache.version>1.0.0</javax-cache.version>
@@ -398,6 +399,11 @@
 				<artifactId>metrics-servlets</artifactId>
 				<version>${codahale-metrics.version}</version>
 			</dependency>
+			<dependency>
+				<groupId>com.google.code.gson</groupId>
+				<artifactId>gson</artifactId>
+				<version>${gson.version}</version>
+			</dependency>
 			<dependency>
 				<groupId>org.codehaus.btm</groupId>
 				<artifactId>btm</artifactId>