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/*
* Copyright (C) 2009 Google Inc. All rights reserved.
*
* 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 com.google.polo.wire.json;
import com.google.polo.exception.PoloException;
import com.google.polo.json.JSONException;
import com.google.polo.json.JSONObject;
import com.google.polo.pairing.PairingContext;
import com.google.polo.pairing.PoloUtil;
import com.google.polo.pairing.message.PoloMessage;
import com.google.polo.pairing.message.PoloMessage.PoloMessageType;
import com.google.polo.wire.PoloWireInterface;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
/**
* A {@link PoloWireInterface} which uses JavaScript Object Notation (JSON) for
* the message representation.
* <p>
* Messages are streamed over the wire prepended with an integer which indicates
* the total length, in bytes, of the message which follows. The format of the
* message is JSON.
* <p>
* See {@link JsonMessageBuilder} for the underlying message translation
* implementation.
*/
public class JsonWireAdapter implements PoloWireInterface {
/**
* The output coming from the peer.
*/
private final DataInputStream mInputStream;
/**
* The input going to the peer.
*/
private final DataOutputStream mOutputStream;
/**
* Constructor.
*
* @param input the {@link InputStream} from the peer
* @param output the {@link OutputStream} to the peer
*/
public JsonWireAdapter(InputStream input, OutputStream output) {
mInputStream = new DataInputStream(input);
mOutputStream = new DataOutputStream(output);
}
/**
* Generates a new instance from a {@link PairingContext}.
*
* @param context the {@link PairingContext}
* @return the new instance
*/
public static JsonWireAdapter fromContext(PairingContext context) {
return new JsonWireAdapter(context.getPeerInputStream(), context
.getPeerOutputStream());
}
public PoloMessage getNextMessage() throws IOException, PoloException {
byte[] payloadLenBytes = new byte[4];
mInputStream.readFully(payloadLenBytes);
long payloadLen = PoloUtil.intBigEndianBytesToLong(payloadLenBytes);
byte[] outerJsonBytes = new byte[(int) payloadLen];
mInputStream.readFully(outerJsonBytes);
return parseOuterMessageString(new String(outerJsonBytes));
}
public PoloMessage parseOuterMessageString(String outerString)
throws PoloException {
JSONObject outerMessage;
try {
outerMessage = new JSONObject(outerString);
} catch (JSONException e) {
throw new PoloException("Error parsing incoming message", e);
}
return JsonMessageBuilder.outerJsonToPoloMessage(outerMessage);
}
public PoloMessage getNextMessage(PoloMessageType type) throws IOException,
PoloException {
PoloMessage message = getNextMessage();
if (message.getType() != type) {
throw new PoloException("Wrong message type (wanted " + type + ", got "
+ message.getType() + ")");
}
return message;
}
public void sendErrorMessage(Exception exception) throws IOException {
try {
writeJson(JsonMessageBuilder.getErrorJson(exception));
} catch (PoloException e) {
throw new IOException("Error sending error message");
}
}
public void sendMessage(PoloMessage message) throws IOException {
String outString;
JSONObject outerJson;
try {
outerJson = JsonMessageBuilder.getOuterJson(message);
} catch (PoloException e) {
throw new IOException("Error generating message");
}
System.out.println("Sending JSON: " + outerJson.toString());
writeJson(outerJson);
}
/**
* Writes a {@link JSONObject} to the output stream as a {@link String}.
*
* @param message the message to write
* @throws IOException on error generating the serialized message
*/
private void writeJson(JSONObject message) throws IOException {
byte[] outBytes = message.toString().getBytes();
mOutputStream.write(PoloUtil.intToBigEndianIntBytes(outBytes.length));
mOutputStream.write(outBytes);
}
}
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