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package io;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.HashSet;
import java.util.Scanner;
import java.util.Set;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.apache.commons.io.Charsets;
import org.apache.commons.io.IOUtils;
import org.json.JSONException;
import org.json.JSONObject;
import provider.ResultListener;
/**
* This class writes the JSON objects for tweets and users to (separate) files.
*
* @author Maurice Laveaux
*/
public class DataWriter implements ResultListener {
/**
* The writer for the tweet stream.
*/
private final Store m_tweet;
/**
* the writer for the profile stream.
*/
private final Store m_profile;
/**
* the buffer of tweet ids that already exist.
*/
private final Set<Long> m_tweetIdSet;
/**
* the buffer of profile ids that already exist.
*/
private final Set<Long> m_profileIdSet;
public final static String CFG_PROFILE_FILENAME = "profiles-filename";
public final static String CFG_TWEETS_FILENAME = "tweets-filename";
/**
* Opens a stream to every single file that data will be streamed to.
*
* @param profilesName The file to write the profiles to.
* @param tweetsName The file to write the tweets to.
* @throws java.io.IOException if the files cannot be read or written.
*/
public DataWriter(final String profilesName, final String tweetsName)
throws IOException {
m_profile = getStore(profilesName);
try {
m_profileIdSet = readIds(m_profile);
} catch (IOException ex) {
m_profile.close();
throw ex;
}
m_tweet = getStore(tweetsName);
try {
m_tweetIdSet = readIds(m_tweet);
} catch (IOException ex) {
m_profile.close();
m_tweet.close();
throw ex;
}
}
/**
* For a given filename, get an instance that provides I/O.
*
* @param filename File to read/write.
* @return A Store instance providing read and write access.
* @throws IOException if the target file cannot be read or written.
*/
protected Store getStore(String filename) throws IOException {
return new SimpleFileStore(filename);
}
public void close() {
m_tweet.close();
m_profile.close();
}
@Override
public void profileGenerated(JSONObject obj) {
writeObject(obj, m_profile.getOutputStream(), m_profileIdSet);
}
@Override
public void tweetGenerated(JSONObject obj) {
writeObject(obj, m_tweet.getOutputStream(), m_tweetIdSet);
}
/**
* Read the current existing tweetName and profileName filenames and fill
* the existing id set.
*
* @param is An input stream that provides JSON objects.
* @return The set of ids, may be empty if the fill does not exist.
*/
private Set<Long> readIds(Store store) throws IOException {
Set<Long> idSet = new HashSet<>();
InputStream is = null;
try {
is = store.getInputStream();
Scanner reader = new Scanner(is);
// parse each line into a JSONObject, read the id and add it to
// the set of ids.
while (reader.hasNext()) {
JSONObject obj = new JSONObject(reader.nextLine());
long id = obj.getLong("id");
idSet.add(id);
}
} catch (FileNotFoundException ex) {
// ignore, file will be created if necessary.
} catch (JSONException ex) {
getLogger().log(Level.WARNING, store.getFileName()
+ ": Corrupt file?", ex);
throw new IOException(ex);
} finally {
IOUtils.closeQuietly(is);
}
return idSet;
}
/**
* Writes the JSONObject to a writer and update the idSet.
*
* @param obj The object to write.
* @param output The stream to write objects to.
* @param idSet The id set to add the obj id to.
*/
private void writeObject(JSONObject obj, OutputStream output,
Set<Long> idSet) {
try {
long id = obj.getLong("id");
if (!idSet.contains(id)) {
// Write a single profile into the profile file.
try {
output.write((obj.toString() + "\n").getBytes(Charsets.UTF_8));
idSet.add(id);
} catch (IOException ex) {
getLogger().log(Level.WARNING, "Cannot write to file", ex);
}
}
} catch (JSONException ex) {
getLogger().log(Level.WARNING, "ID not found?!", ex);
}
}
private Logger getLogger() {
return Logger.getLogger(getClass().getName());
}
abstract class Store {
private final String filename;
protected OutputStream os;
Store(String filename) {
this.filename = filename;
}
/**
* @return The file name associated with this store.
*/
public String getFileName() {
return filename;
}
/**
* Properly closes a file, flushing any buffers.
*/
public void close() {
try {
os.close();
} catch (IOException ex) {
Logger.getLogger(getClass().getName()).log(Level.WARNING,
"Could not close " + getFileName(), ex);
}
}
/**
* Returns a previously opened writable file stream.
*
* @return A stream to which JSON objects can be written (one per line).
*/
public OutputStream getOutputStream() {
return os;
}
/**
* Opens a new input stream for the file.
*
* @return A stream from which JSON objects can be read (one per line).
* @throws IOException if no input file can be retrieved.
*/
abstract public InputStream getInputStream() throws IOException;
}
class SimpleFileStore extends Store {
SimpleFileStore(String filename) throws FileNotFoundException {
super(filename);
os = new FileOutputStream(getFileName(), true);
}
@Override
public InputStream getInputStream() throws FileNotFoundException {
return new FileInputStream(getFileName());
}
}
}
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