This page will describe how to create an extractor using java. A lot of this code can be copied and pasted. The only major part is the processFile function. You can find this example also in our code repository at: https://opensource.ncsa.illinois.edu/stash/projects/MMDB/repos/extractors-examples/browse/java
The first step in the example is to setup some global variables that will be used in the rest of the code.
configuration
// name where rabbitmq is running
private static String rabbitmqhost = "localhost";
// name to show in rabbitmq queue list
private static String exchange = "medici";
// name to show in rabbitmq queue list
private static String extractorName = "wordCount";
// username and password to connect to rabbitmq
private static String username = null;
private static String password = null;
// accept any type of file that is text
private static String messageType = "*.file.text.#";
// secret key used to connect to medici, this will eventually be
// part of the message received.
private static String secretKey = "r1ek3rs";
A convenience function to return status messages to Medici
statusUpdate
private void statusUpdate(Channel channel, AMQP.BasicProperties header, String fileid, String status) throws IOException {
logger.debug("[" + fileid + "] : " + status);
Map<String, Object> statusreport = new HashMap<String, Object>();
statusreport.put("file_id", fileid);
statusreport.put("extractor_id", extractorName);
statusreport.put("status", status);
statusreport.put("start", dateformat.format(new Date()));
AMQP.BasicProperties props = new AMQP.BasicProperties.Builder().correlationId(header.getCorrelationId()).build();
channel.basicPublish(exchange, header.getReplyTo(), props, mapper.writeValueAsBytes(statusreport));
}
The main method will listen for messages on the message bus.
statusUpdate