SPR-9488 Add GsonHttpMessageConverter

build.gradle

@@ -22,6 +22,7 @@ configure(allprojects) { project ->
 	ext.hibVal5Version       = "5.1.1.Final"
 	ext.hsqldbVersion        = "2.3.2"
 	ext.jackson2Version      = "2.3.3"
+	ext.gsonVersion          = "2.2.4"
 	ext.jasperReportsVersion = "5.5.2"
 	ext.jettyVersion         = "9.1.5.v20140505"
 	ext.jodaVersion          = "2.3"
@@ -621,6 +622,8 @@ project("spring-web") {
 		optional("org.apache.httpcomponents:httpclient:4.3.3")
 		optional("org.apache.httpcomponents:httpasyncclient:4.0.1")
 		optional("com.fasterxml.jackson.core:jackson-databind:${jackson2Version}")
+		optional("com.google.code.gson:gson:${gsonVersion}")
+		optional("commons-codec:commons-codec:1.9")
 		optional("rome:rome:1.0")
 		optional("org.eclipse.jetty:jetty-servlet:${jettyVersion}") {
 			exclude group: "javax.servlet", module: "javax.servlet-api"

spring-web/src/main/java/org/springframework/http/converter/json/GsonBase64ByteArrayJsonTypeAdapter.java

@@ -0,0 +1,64 @@
+/*
+ * Copyright 2002-2014 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.http.converter.json;
+
+import java.lang.reflect.Type;
+import java.nio.charset.Charset;
+
+import org.apache.commons.codec.binary.Base64;
+
+import com.google.gson.GsonBuilder;
+import com.google.gson.JsonDeserializationContext;
+import com.google.gson.JsonDeserializer;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonParseException;
+import com.google.gson.JsonPrimitive;
+import com.google.gson.JsonSerializationContext;
+import com.google.gson.JsonSerializer;
+import com.google.gson.TypeAdapter;
+
+/**
+ * Custom Gson {@link TypeAdapter} for serialization or deserialization of
+ * {@code byte[]}. By default Gson converts byte arrays to JSON arrays instead
+ * of a Base64 encoded string. Use this type adapter with
+ * {@link org.springframework.http.converter.json.GsonHttpMessageConverter
+ * GsonHttpMessageConverter} to read and write Base64 encoded byte arrays.
+ *
+ * @author Roy Clarkson
+ * @since 4.1
+ * @see GsonBuilder#registerTypeHierarchyAdapter(Class, Object)
+ */
+final class GsonBase64ByteArrayJsonTypeAdapter implements JsonSerializer<byte[]>, JsonDeserializer<byte[]> {
+
+	public static final Charset DEFAULT_CHARSET = Charset.forName("UTF-8");
+
+	private final Base64 base64 = new Base64();
+
+
+	@Override
+	public JsonElement serialize(byte[] src, Type typeOfSrc, JsonSerializationContext context) {
+		return new JsonPrimitive(new String(this.base64.encode(src), DEFAULT_CHARSET));
+	}
+
+	@Override
+	public byte[] deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
+			throws JsonParseException {
+
+		return this.base64.decode(json.getAsString().getBytes(DEFAULT_CHARSET));
+	}
+
+}

spring-web/src/main/java/org/springframework/http/converter/json/GsonFactoryBean.java

@@ -0,0 +1,215 @@
+/*
+ * Copyright 2002-2014 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.http.converter.json;
+
+import java.text.SimpleDateFormat;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.springframework.beans.factory.BeanClassLoaderAware;
+import org.springframework.beans.factory.FactoryBean;
+import org.springframework.beans.factory.InitializingBean;
+import org.springframework.util.ClassUtils;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+
+
+/**
+ * A {@link FactoryBean} for creating a Google Gson 2.x {@link Gson}
+ *
+ * @author Roy Clarkson
+ * @since 4.1
+ */
+public class GsonFactoryBean implements FactoryBean<Gson>, BeanClassLoaderAware, InitializingBean {
+
+	private static final boolean base64Present = ClassUtils.isPresent(
+			"org.apache.commons.codec.binary.Base64", GsonFactoryBean.class.getClassLoader());
+
+	private final Log logger = LogFactory.getLog(getClass());
+
+	private Gson gson;
+
+	private GsonBuilder gsonBuilder;
+
+	private Boolean prettyPrint;
+
+	private Boolean serializeNulls;
+
+	private Boolean disableHtmlEscaping;
+
+	private SimpleDateFormat dateFormat;
+
+	private Boolean base64EncodeByteArrays;
+
+	private ClassLoader beanClassLoader;
+
+
+	/**
+	 * Set the GsonBuilder instance to use. If not set, the GsonBuilder will be created
+	 * using its default constructor.
+	 */
+	public void setGsonBuilder(GsonBuilder gsonBuilder) {
+		this.gsonBuilder = gsonBuilder;
+	}
+
+	/**
+	 * Return the GsonBuilder instance being used.
+	 * @return the GsonBuilder instance
+	 */
+	public GsonBuilder getGsonBuilder() {
+		return this.gsonBuilder;
+	}
+
+	/**
+	 * Whether to use the {@link GsonBuilder#setPrettyPrinting()} when writing JSON. This
+	 * is a shortcut for setting up a {@code Gson} as follows:
+	 *
+	 * <pre class="code">
+	 * new GsonBuilder().setPrettyPrinting().create();
+	 * </pre>
+	 */
+	public void setPrettyPrint(boolean prettyPrint) {
+		this.prettyPrint = prettyPrint;
+	}
+
+	/**
+	 * Whether to use the {@link GsonBuilder#serializeNulls()} option when writing JSON.
+	 * This is a shortcut for setting up a {@code Gson} as follows:
+	 *
+	 * <pre class="code">
+	 * new GsonBuilder().serializeNulls().create();
+	 * </pre>
+	 */
+	public void setSerializeNulls(boolean serializeNulls) {
+		this.serializeNulls = serializeNulls;
+	}
+
+	/**
+	 * Whether to use the {@link GsonBuilder#disableHtmlEscaping()} when writing JSON. Set
+	 * to {@code true} to disable HTML escaping in JSON. This is a shortcut for setting up
+	 * a {@code Gson} as follows:
+	 *
+	 * <pre class="code">
+	 * new GsonBuilder().disableHtmlEscaping().create();
+	 * </pre>
+	 */
+	public void setDisableHtmlEscaping(boolean disableHtmlEscaping) {
+		this.disableHtmlEscaping = disableHtmlEscaping;
+	}
+
+	/**
+	 * Define the format for date/time with the given {@link SimpleDateFormat}.
+	 * This is a shortcut for setting up a {@code Gson} as follows:
+	 *
+	 * <pre class="code">
+	 * new GsonBuilder().setDateFormat(dateFormatPattern).create();
+	 * </pre>
+	 *
+	 * @see #setSimpleDateFormat(String)
+	 */
+	public void setSimpleDateFormat(SimpleDateFormat dateFormat) {
+		this.dateFormat = dateFormat;
+	}
+
+	/**
+	 * Define the date/time format with a {@link SimpleDateFormat}.
+	 * This is a shortcut for setting up a {@code Gson} as follows:
+	 *
+	 * <pre class="code">
+	 * new GsonBuilder().setDateFormat(dateFormatPattern).create();
+	 * </pre>
+	 *
+	 * @see #setSimpleDateFormat(SimpleDateFormat)
+	 */
+	public void setSimpleDateFormat(String format) {
+		this.dateFormat = new SimpleDateFormat(format);
+	}
+
+	/**
+	 * Whether to Base64 encode {@code byte[]} properties when reading and
+	 * writing JSON.
+	 *
+	 * <p>When set to {@code true} a custom {@link com.google.gson.TypeAdapter}
+	 * is registered via {@link GsonBuilder#registerTypeHierarchyAdapter(Class, Object)}
+	 * that serializes a {@code byte[]} property to and from a Base64 encoded
+	 * string instead of a JSON array.
+	 *
+	 * <p><strong>NOTE:</strong> Use of this option requires the presence of
+	 * Apache commons-codec on the classpath. Otherwise it is ignored.
+	 *
+	 * @see org.springframework.http.converter.json.GsonBase64ByteArrayJsonTypeAdapter
+	 */
+	public void setBase64EncodeByteArrays(boolean base64EncodeByteArrays) {
+		this.base64EncodeByteArrays = base64EncodeByteArrays;
+	}
+
+	@Override
+	public void setBeanClassLoader(ClassLoader beanClassLoader) {
+		this.beanClassLoader = beanClassLoader;
+	}
+
+
+	@Override
+	public void afterPropertiesSet() throws Exception {
+		if (gsonBuilder == null) {
+			this.gsonBuilder = new GsonBuilder();
+		}
+		if (this.prettyPrint != null && this.prettyPrint) {
+			this.gsonBuilder = this.gsonBuilder.setPrettyPrinting();
+		}
+		if (this.serializeNulls != null && this.serializeNulls) {
+			this.gsonBuilder = this.gsonBuilder.serializeNulls();
+		}
+		if (this.disableHtmlEscaping != null && this.disableHtmlEscaping) {
+			this.gsonBuilder = this.gsonBuilder.disableHtmlEscaping();
+		}
+		if (this.dateFormat != null) {
+			this.gsonBuilder.setDateFormat(this.dateFormat.toPattern());
+		}
+		if (base64Present) {
+			if (this.base64EncodeByteArrays != null && this.base64EncodeByteArrays) {
+				this.gsonBuilder.registerTypeHierarchyAdapter(byte[].class, new GsonBase64ByteArrayJsonTypeAdapter());
+			}
+		}
+		else if (logger.isDebugEnabled()) {
+			logger.debug("org.apache.commons.codec.binary.Base64 is not available on the class path. Gson Base64 encoding is disabled.");
+		}
+		this.gson = this.gsonBuilder.create();
+	}
+
+
+	/**
+	 * Return the singleton Gson.
+	 */
+	@Override
+	public Gson getObject() throws Exception {
+		return this.gson;
+	}
+
+	@Override
+	public Class<?> getObjectType() {
+		return Gson.class;
+	}
+
+	@Override
+	public boolean isSingleton() {
+		return true;
+	}
+
+}