CODEWITHSUNDEEP
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thangdc94
thangdc94

Reputation: 1632

Is it possible to store object to property file in Java?

Today I try to store an Object using java.util.properties. I see many example just use String or Integer. Here is an example:

public static void main(String[] args) {
    Properties prop = new Properties();

    // add some properties
    prop.setProperty("Height", "200");
    prop.put("Width", "1500");

    // print the list 
    System.out.println("" + prop);
    try {
        // store the properties list in an output stream
        prop.store(System.out, "config.properties");
    } catch (IOException ex) {
        ex.printStackTrace();
    }
}

So is it possible to store an Object in properties file or xml file?

Upvotes: 4

Views: 10426

Answers (2)

Nicolas Filotto
Nicolas Filotto

Reputation: 44965

No as it is stated into the Javadoc:

If the store or save method is called on a "compromised" Properties object that contains a non-String key or value, the call will fail.

If you really need to store your object into a Properties you could convert it into JSON as it is a well known format that is readable by a human being such that if someone adds wrong characters in the middle you can still fix it.

Here is how you could do it using ObjectMapper:

Properties prop = new Properties();

ObjectMapper mapper = new ObjectMapper();
// Convert my object foo into JSON format and put it into my Properties object
prop.put("myObj",  mapper.writeValueAsString(foo));

StringWriter output = new StringWriter();
// Store my properties
prop.store(output, null);

prop = new Properties();
// Load my properties
prop.load(new StringReader(output.toString()));

// Parse my object foo from the value of my new Properties object
Foo foo2 = mapper.readValue(prop.getProperty("myObj"), Foo.class);

Here is a good tutorial that explains how you can use ObjectMapper in more details.

Upvotes: 2

JHead
JHead

Reputation: 426

To store an object at first you should serialize it to a byte array then encode it with a Base64 encoder:

public static String toString(Object o) throws IOException {
    try (ByteArrayOutputStream baos = new ByteArrayOutputStream();
            ObjectOutputStream oos = new ObjectOutputStream(baos);) {
        oos.writeObject(o);
        return new String(Base64Coder.encode(baos.toByteArray()));
    }
}

Then you can store it safely to the property file: 

prop.put("object.instance", toString(o));

To read the object from the properties, use this function:

public static Object fromString(String s) throws IOException, ClassNotFoundException {
    byte[] data = Base64Coder.decode(s);
    Object o;
    try (ObjectInputStream ois = new ObjectInputStream(
            new ByteArrayInputStream(data))) {
        o = ois.readObject();
    }
    return o;
}

You can deserialize the object from the string:

Object o = fromString(prop.get("object.instance"));

Upvotes: 4

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