Storing a Map between Runtimes

Question

I have been reading some posts on how to store data between runtimes, between HBase, Serialization, and other stuff, but is there a way to store a Map(Object, Set of difObject) easily? I have been watching videos and reading posts and I just havent been able to wrap my brain around it, also wherever I store the data cannot be human readable as it has personal information on it.

Answer 1

Use java.io.ObjectOutputStream and java.io.ObjectInputStream to persist Java objects (in your case: write/read the Map). Make sure that all objects you're persisting implement Serializable.

Example: writing data(marshalling)

Map<String, Set<Integer>> map = new HashMap<String, Set<Integer>>();
map.put("Foo", new HashSet<Integer>(Arrays.asList(1, 2, 3)));
map.put("Bla", new HashSet<Integer>(Arrays.asList(4, 5, 6)));

File file = new File("data.bin");
ObjectOutputStream out = new ObjectOutputStream(new BufferedOutputStream(new FileOutputStream(file)));
try {
    out.writeObject(map);
    out.flush();
} finally {
    out.close();
}

Reading the stored data (unmarshalling)

File file = new File("data.bin");
if (file.exists()) {
    ObjectInputStream in = new ObjectInputStream(new BufferedInputStream(new FileInputStream(file)));
    try {
        Map<String, Set<Integer>> read = (Map<String, Set<Integer>>) in.readObject();
        for (String key : read.keySet()) {
            System.out.print(key + ": ");
            Set<Integer> values = read.get(key);
            for (Integer value : values) {
                System.out.print(value + " ");
            }
            System.out.println();
        }
    } finally {
        in.close();
    }
}