Create config file at runtime in Java exported WAR

Question

I've made a web project with eclipse to run my webservice on Tomcat v7. I have a config file that have to define some variables that should be changed while webserver is up without need of restart it. The problem is: where I can put this file? At the moment I've put it into the "./" dir, but seems that when I export the WAR file and install it on the webserver it doesn't works. Is there a way to create this file and modify it runtime inside the WAR?

Here is part of the code of the .class file that accesses the config file

public class ToolConfigurations {
    private static final Logger log = LogManager.getLogger(ToolConfigurations.class);   //Oggetto logging

    private static ToolConfigurations instance = null;  //verificarne la necessità

    private static String defaultServerName = null;
    private static String defaultDbName = "postgres";
    private static String defaultDbUser = "postgres";
    private static String defaultDbPass = "password";
    private static int defaultDbMaxConnNum = 10;

    private static String configFilePath = ".\\";
    private static String configFileName = "tool.properties";
    private String serverName = null;
    private String dbName = null;
    private String dbUser = null;
    private String d`enter code here`bPass = null;
    private int dbMaxConnNum = -1;

    private ToolConfigurations() throws Exception {
        File file = new File(configFilePath + configFileName);
        if(file.exists()) {
            //file configurazione esiste
            FileReader in = new FileReader(file);
            BufferedReader br = new BufferedReader(in);
            String line = null;

            while((line = br.readLine()) != null) { //Leggo riga per riga il file 
                String[] values = line.split(" ");
                switch (values[0]) {
                    case "serverName":
                        serverName = values[1];
                        break;
                    case "dbName":
                        dbName = values[1];
                        break;
                    case "dbUser":
                        dbUser = values[1];
                        break;
                    case "dbPass":
                        dbPass = values[1];
                        break;
                    case "dbMaxConnNum":
                        dbMaxConnNum = Integer.parseInt(values[1]);
                        break;
                    default:
                        log.warn("Elemento inaspettato nel file di configurazione: " + values[0]);
                        break;
                }
            }

            br.close();
            in.close();
        }else {
            if(file.createNewFile() == false) {
                //Errore creazione file
                log.error("Errore creazione file di configurazione");
                throw new Exception("Errore creazione file configurazione");
            }
            //CREO FILE CONFIGURAZIONE CON IMPOSTAZIONI DI DEFAULT
            FileWriter fw = new FileWriter(file);
            fw.write("dbName " + defaultDbName + "\r\n");
            fw.write("dbUser " + defaultDbUser + "\r\n");
            fw.write("dbPass " + defaultDbPass + "\r\n");
            fw.write("dbMaxConnNum " + defaultDbMaxConnNum + "\r\n");
            fw.flush();
            fw.close();
            log.warn("File di configurazione non trovato. Path: " + file.getAbsolutePath() + ". Creato nuovo file con configurazioni di default.");
            //CARICO IMPOSTAZIONI DI DEFAULT
            dbName = defaultDbName;
            dbUser = defaultDbUser;
            dbPass = defaultDbPass;
            dbMaxConnNum = defaultDbMaxConnNum;
        }
    }

    public static synchronized ToolConfigurations getInstance() throws Exception {
        if(instance == null) {
            instance = new ToolConfigurations();
        }
        return instance;
    }
    ...

Answer 1

In web server, files other than .class are directly taken in charge by the server. You don't need to reload the server.

But try using .properties files and check the structure of the WAR when deployed on the server.

Answer 2

The best solution I found was to a ClassLoader to search for the config file that I have previously created into the main directory. The example of use is:

 ClassLoader classLoader = Thread.currentThread().getContextClassLoader(); InputStream fileInput = classLoader.getResourceAsStream(configFileName); if(fileInput == null){ //File not found }else{ //File found InputStreamReader sr = new InputStreamReader(fileInput); BufferedReader br = new BufferedReader(sr); try { while((line = br.readLine()) != null) { //Read file line by line } }catch (IOException e) { throw new IOException("Error parsing file: " + e.getMessage()); } }