From 5444deeeb52d415ca320ccfddd34dd2e9ac217de Mon Sep 17 00:00:00 2001
From: Simon Rettberg
Date: Tue, 8 Sep 2015 14:13:57 +0200
Subject: Add Json.java

---
 pom.xml                                  |   6 ++
 src/main/java/org/openslx/util/Json.java | 122 +++++++++++++++++++++++++++++++
 2 files changed, 128 insertions(+)
 create mode 100644 src/main/java/org/openslx/util/Json.java

diff --git a/pom.xml b/pom.xml
index a097104..5f10585 100644
--- a/pom.xml
+++ b/pom.xml
@@ -121,6 +121,12 @@
 			<version>0.0.3-SNAPSHOT</version>
 			<scope>compile</scope>
 		</dependency>
+		<dependency>
+			<groupId>com.google.code.gson</groupId>
+			<artifactId>gson</artifactId>
+			<version>2.2.4</version>
+			<scope>compile</scope>
+		</dependency>
 
 	</dependencies>
 </project>
diff --git a/src/main/java/org/openslx/util/Json.java b/src/main/java/org/openslx/util/Json.java
new file mode 100644
index 0000000..847514d
--- /dev/null
+++ b/src/main/java/org/openslx/util/Json.java
@@ -0,0 +1,122 @@
+package org.openslx.util;
+
+import java.lang.reflect.Field;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.lang.reflect.Modifier;
+import java.lang.reflect.Type;
+
+import org.apache.log4j.Logger;
+import org.apache.thrift.TBase;
+
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+import com.google.gson.JsonDeserializationContext;
+import com.google.gson.JsonDeserializer;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonParseException;
+import com.google.gson.JsonSyntaxException;
+
+public class Json {
+
+	private static final Logger LOGGER = Logger.getLogger(Json.class);
+
+	/**
+	 * Global static instance. The Gson object is thread-safe.
+	 */
+	private static final Gson gson = new Gson();
+
+	private static final GsonBuilder gsonThriftBuilder = new GsonBuilder();
+
+	public static <T> void registerThriftClass(Class<T> thriftClass) {
+		if (!TBase.class.isAssignableFrom(thriftClass))
+			throw new IllegalArgumentException(thriftClass.getName() + " is not a thrift struct.");
+		gsonThriftBuilder.registerTypeAdapter(thriftClass, new ThriftDeserializer<T>(thriftClass));
+	}
+
+	/**
+	 * Deserialize the given json string to an instance of T.
+	 * This will deserialize all fields, except transient ones.
+	 * 
+	 * @param data JSON formatted data
+	 * @param classOfData class to instantiate
+	 * @return instanceof T
+	 */
+	public static <T> T deserialize(String data, Class<T> classOfData) {
+		try {
+			return gson.fromJson(data, classOfData);
+		} catch (JsonSyntaxException e) {
+			LOGGER.warn("Cannot deserialize to " + classOfData.getSimpleName(), e);
+			return null;
+		}
+	}
+
+	public static <T> T deserializeThrift(String data, Class<T> thriftClass) {
+		try {
+			return gsonThriftBuilder.create().fromJson(data, thriftClass);
+		} catch (JsonSyntaxException e) {
+			LOGGER.warn("Cannot deserialize to " + thriftClass.getSimpleName(), e);
+			return null;
+		}
+	}
+
+	/**
+	 * Serialize the given POJO. All fields except transient ones will be
+	 * serialized.
+	 * 
+	 * @param object some object to serialize
+	 * @return JSON formatted represenatation of <code>object</code>
+	 */
+	public static String serialize(Object object) {
+		return gson.toJson(object);
+	}
+
+	private static class ThriftDeserializer<T> implements JsonDeserializer<T> {
+		private final Class<T> clazz;
+
+		public ThriftDeserializer(Class<T> classOfData) {
+			this.clazz = classOfData;
+		}
+
+		@Override
+		public T deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
+				throws JsonParseException {
+			if (!(json instanceof JsonObject))
+				throw new JsonParseException("Need a json object, have " + json.getClass().getSimpleName());
+			JsonObject obj = (JsonObject) json;
+			final T inst;
+			try {
+				inst = clazz.newInstance();
+			} catch (InstantiationException | IllegalAccessException e) {
+				LOGGER.warn("Could not deserialize to class " + clazz.getName(), e);
+				throw new JsonParseException("Cannot instantiate class " + clazz.getSimpleName());
+			}
+			for (Field field : clazz.getFields()) {
+				if (Modifier.isStatic(field.getModifiers()) || Modifier.isFinal(field.getModifiers()))
+					continue;
+				final String methodName = "set" + field.getName().substring(0, 1).toUpperCase()
+						+ field.getName().substring(1);
+				final Method setter;
+				try {
+					setter = clazz.getMethod(methodName, field.getType());
+				} catch (NoSuchMethodException e) {
+					LOGGER.warn(clazz.getSimpleName() + " has no method " + methodName);
+					continue;
+				}
+				JsonElement element = obj.get(field.getName());
+				if (element == null || element.isJsonNull())
+					continue;
+				try {
+					setter.invoke(inst, context.deserialize(element, field.getType()));
+					LOGGER.info("Called " + methodName + " on " + clazz.getSimpleName());
+				} catch (IllegalAccessException | IllegalArgumentException | InvocationTargetException e) {
+					LOGGER.warn("Could not call " + methodName + " on " + clazz.getSimpleName(), e);
+				}
+			}
+			return inst;
+		}
+
+	}
+
+}
-- 
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