Return Response from Server

I'm working on a program to allow several Minecraft servers to communicate, but I need to have a way to return a string from a method that essentially 'waits' for a response. When a plugin attempts to retrieve what I'm calling Server Properties, a request is sent to the target server for that property. Since this uses a sort of event system, where another method, defined by the plugin, is run when information is received. I'll explain more in the code below.

public final ServerResponse retrieveProperty(String property) {
    if (!PropertyHandler.isValidProperty()) {
        return null;
    }
    try {
        return Handler.retrieveProperty(property,
                CONNECTIONS.get(entryPoint).getKey().getName());
    } catch (Exception e) {
        return null;
    }
}

When a String is received from the target server, CSC (my plugin), handles the information based on the syntax and contents, and deals with it accordingly. How would a plugin the access this information? The ServerResponse class is below.

public final class ServerResponse {

    private String plugin;
    private String identifier;

    private boolean hasResponse = false;
    private String response = null;

    protected ServerResponse(String plugin) {
        this.plugin = plugin;
        this.identifier = UUID.randomUUID().toString().replaceAll("-", "")
            .substring(0, 7);
    }

    public String getPlugin() {
        return new String(this.plugin);
    }

    public String getIdentifier() {
        return this.identifier;
    }

    public boolean hasResponse() {
        return this.hasResponse;
    }

    protected void respond(String response) {
        this.hasResponse = true;
        this.response = response;
    }

    public String getResponse() {
        return this.response;
    }

}  

The example I have created is shown below, but I highly doubt it is the most efficient method. Basically, how can I tell the program to wait until it has a response to return a string?

public String property(String property) {
    ServerResponse response = super.retrieveProperty(property);
    String aResponse = response.getResponse();
    if (!response.hasResponse()) {
        while (true) {
            if (!response.hasResponse())
                continue;
            else {
                aResponse = response.getResponse();
                break;
            }
        }
    }
    return aResponse;
}