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VertxExample.java
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VertxExample.java
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// MIT License
//
// Copyright (c) 2016-2022 Michel Kraemer
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
package vertx;
import java.util.function.Supplier;
import de.undercouch.actson.JsonEvent;
import de.undercouch.actson.JsonParser;
import io.vertx.core.AsyncResult;
import io.vertx.core.Future;
import io.vertx.core.Handler;
import io.vertx.core.Vertx;
import io.vertx.core.file.AsyncFile;
import io.vertx.core.file.OpenOptions;
/**
* This example demonstrates how Actson can be used together with Vert.x. It
* does the same as {@link simple.SimpleExample} or {@link rxjava.RxJavaExample}
* but works completely asynchronously and non-blocking.
* @author Michel Kraemer
*/
public class VertxExample {
private final Vertx vertx = Vertx.vertx();
/**
* The main program. Accepts one argument: the name of the file to parse
* @param args the program arguments
*/
public static void main(String[] args) {
if (args.length != 1) {
System.err.println("Usage: VertxExample <json file>");
System.exit(1);
}
VertxExample example = new VertxExample();
example.parseFile(args[0], ar -> {
if (ar.failed()) {
System.err.println("Could not parse file");
ar.cause().printStackTrace();
System.exit(1);
} else {
System.exit(0);
}
});
}
/**
* Asynchronously parse a file and print JSON events to System.out
* @param filename the name of the JSON file to parse
* @param handler a handler that will be called when the file has been parsed
* or when an error has occurred
*/
private void parseFile(String filename, Handler<AsyncResult<Void>> handler) {
OpenOptions options = new OpenOptions()
.setRead(true)
.setWrite(false);
// asynchronously open the file
vertx.fileSystem().open(filename, options, ar -> {
if (ar.failed()) {
handler.handle(Future.failedFuture(ar.cause()));
return;
}
JsonParser parser = new JsonParser();
AsyncFile f = ar.result();
Supplier<Boolean> processEvents = () -> {
// process events from the parser until it needs more input
int event;
do {
event = parser.nextEvent();
// print all events to System.out
if (event != JsonEvent.NEED_MORE_INPUT) {
System.out.println("JSON event: " + event);
}
// handle values, errors, and end of file
if (event == JsonEvent.VALUE_STRING) {
System.out.println("VALUE: " + parser.getCurrentString());
} else if (event == JsonEvent.EOF) {
handler.handle(Future.succeededFuture());
return false;
} else if (event == JsonEvent.ERROR) {
handler.handle(Future.failedFuture("Syntax error"));
return false;
}
} while (event != JsonEvent.NEED_MORE_INPUT);
return true;
};
f.exceptionHandler(t -> handler.handle(Future.failedFuture(t)));
f.handler(buf -> {
// forward bytes read from the file to the parser
byte[] bytes = buf.getBytes();
int i = 0;
while (i < bytes.length) {
i += parser.getFeeder().feed(bytes, i, bytes.length - i);
if (!processEvents.get()) {
f.handler(null);
f.endHandler(null);
break;
}
}
});
f.endHandler(v -> {
// process events one last time
parser.getFeeder().done();
processEvents.get();
});
});
}
}