org.hawkular.cmdgw.api.ApiDeserializer Maven / Gradle / Ivy
/*
* Copyright 2014-2016 Red Hat, Inc. and/or its affiliates
* and other contributors as indicated by the @author tags.
*
* 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.hawkular.cmdgw.api;
import java.io.IOException;
import java.io.InputStream;
import org.hawkular.bus.common.AbstractMessage;
import org.hawkular.bus.common.BasicMessage;
import org.hawkular.bus.common.BasicMessageWithExtraData;
import org.hawkular.bus.common.BinaryData;
/**
* Given the special syntax of "apiName=JSON" this will deserialize the JSON into the appropriate API POJO.
*/
public class ApiDeserializer {
// note that this assumes this class is in the same package as all the API POJOs
private static final String API_PKG = ApiDeserializer.class.getPackage().getName();
/**
* Returns a string that encodes the given object as a JSON message but then
* prefixes that JSON with additional information that a Hawkular client will
* need to be able to deserialize the JSON.
*
* This string can be used to deserialize the object via {@link #deserialize(String)}.
*
* @param msg the message object that will be serialized into JSON
* @return a string that includes the JSON that can be used by other Hawkular endpoints to deserialize the message.
*/
public static String toHawkularFormat(BasicMessage msg) {
return String.format("%s=%s", msg.getClass().getSimpleName(), msg.toJSON());
}
/**
* Returns a BinaryData object (which is a stream) that encodes the given message
* just like {@link #toHawkularFormat(BasicMessage)} does but also packages the given
* input stream as extra data with the JSON message.
*
* The returned object can be used to deserialize the msg and extra data via {@link #deserialize(InputStream)}.
*
* @param msg the message object that will be serialized into JSON
* @param extraData the extra data to be packages with the given message
* @return an object that can be used by other Hawkular endpoints to deserialize the message.
*/
public static BinaryData toHawkularFormat(BasicMessage msg, InputStream extraData) {
String msgJson = toHawkularFormat(msg);
return new BinaryData(msgJson.getBytes(), extraData);
}
private static String[] fromHawkularFormat(String msg) {
String[] nameAndJsonArray = msg.split("=", 2);
if (nameAndJsonArray.length != 2) {
throw new IllegalArgumentException("Cannot deserialize: [" + msg + "]");
}
return nameAndJsonArray;
}
public ApiDeserializer() {
}
/**
* Deserializes a JSON string in {@link #toHawkularFormat(BasicMessage) Hawkular format}.
* The JSON object is returned.
*
* @param nameAndJson the string to be deserialized
* @return the object represented by the JSON
*/
public BasicMessageWithExtraData deserialize(String nameAndJson) {
String[] nameAndJsonArray = fromHawkularFormat(nameAndJson);
String name = nameAndJsonArray[0];
String json = nameAndJsonArray[1];
// The name is the actual name of the POJO that is used to deserialize the JSON.
// If not fully qualified with a package then assume it is in our package.
if (name.indexOf(".") == -1) {
name = String.format("%s.%s", API_PKG, name);
}
try {
Class pojo = (Class) Class.forName(name);
return new BasicMessageWithExtraData(AbstractMessage.fromJSON(json, pojo), null);
} catch (Exception e) {
throw new RuntimeException("Cannot deserialize: [" + nameAndJson + "]", e);
}
}
/**
* Reads a JSON string in {@link #toHawkularFormat(BasicMessage) Hawkular format} that
* is found in the given input stream and converts the JSON string to a particular message object.
* The input stream will remain open so the caller can stream any extra data that might appear after it.
*
* Because of the way the JSON parser works, some extra data might have been read from the stream
* that wasn't part of the JSON message but was part of the extra data that came with it. Because of this,
* the caller should no longer use the given stream but instead read the extra data via the returned
* object (see {@link BasicMessageWithExtraData#getBinaryData()}) since it will handle this condition
* properly.
*
* @param in input stream that has the Hawkular formatted JSON string at the head.
*
* @return a POJO that contains a message object that was represented by the JSON string found
* in the stream. This returned POJO will also contain a {@link BinaryData} object that you
* can use to stream any additional data that came in the given input stream.
*/
public BasicMessageWithExtraData deserialize(InputStream input) {
// We know the format is "name=json" with possible extra data after it.
// So first find the "name"
StringBuilder nameBuilder = new StringBuilder();
boolean foundSeparator = false;
while (!foundSeparator) {
int currentChar;
try {
currentChar = input.read();
} catch (IOException ioe) {
throw new RuntimeException("Cannot deserialize stream due to read error", ioe);
}
if (currentChar == -1) {
throw new RuntimeException("Cannot deserialize stream - doesn't look valid");
} else if (currentChar == '=') {
foundSeparator = true;
} else {
nameBuilder.append((char) currentChar);
}
}
// The name is the actual name of the POJO that is used to deserialize the JSON.
// If not fully qualified with a package then assume it is in our package.
String name = nameBuilder.toString();
if (name.indexOf(".") == -1) {
name = String.format("%s.%s", API_PKG, name);
}
// We now have the name and the input stream is pointing at the JSON
try {
Class pojo = (Class) Class.forName(name);
BasicMessageWithExtraData results = AbstractMessage.fromJSON(input, pojo);
return results;
} catch (Exception e) {
throw new RuntimeException("Cannot deserialize stream with object [" + name + "]", e);
}
}
}
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