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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()));
} catch (IllegalAccessException | IllegalArgumentException | InvocationTargetException e) {
LOGGER.warn("Could not call " + methodName + " on " + clazz.getSimpleName(), e);
}
}
return inst;
}
}
}
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