访问 Cookie

You can set and retrieve cookies in your rich Internet application (RIA). Cookies can enhance the capabilities of your RIA. For example, consider the scenario where you have applets on various web pages. An applet on a web page cannot directly access or share information with an applet on another web page. In this scenario, cookies provide an important connection between applets and help one applet pass information to another applet on a different web page. Java Web Start applications can also use cookies to store information on the client.

The Cookie Applet example has a CookieAccessor class that retrieves and sets cookies.

Retrieving Cookies

The following code snippet shows the getCookieUsingCookieHandler method of the CookieAccessor class:

public void getCookieUsingCookieHandler() { 
    try {       
        // Instantiate CookieManager;
        // make sure to set CookiePolicy
        CookieManager manager = new CookieManager();
        manager.setCookiePolicy(CookiePolicy.ACCEPT_ALL);
        CookieHandler.setDefault(manager);

        // get content from URLConnection;
        // cookies are set by web site
        URL url = new URL("http://host.example.com");
        URLConnection connection = url.openConnection();
        connection.getContent();

        // get cookies from underlying
        // CookieStore
        CookieStore cookieJar =  manager.getCookieStore();
        List <HttpCookie> cookies =
            cookieJar.getCookies();
        for (HttpCookie cookie: cookies) {
          System.out.println("CookieHandler retrieved cookie: " + cookie);
        }
    } catch(Exception e) {
        System.out.println("Unable to get cookie using CookieHandler");
        e.printStackTrace();
    }
}  

The CookieManager class is the main entry point for cookie management. Create an instance of the CookieManager class and set its CookiePolicy. Set this instance of the CookieManager as the default CookieHandler.

Open a URLConnection to the website of your choice.

Next, retrieve cookies from the underlying CookieStore by using the getCookies method.

Setting Cookies

The following code snippet shows the setCookieUsingCookieHandler method of the CookieAccessor class:

public void setCookieUsingCookieHandler() {
    try {
        // instantiate CookieManager
        CookieManager manager = new CookieManager();
        CookieHandler.setDefault(manager);
        CookieStore cookieJar =  manager.getCookieStore();

        // create cookie
        HttpCookie cookie = new HttpCookie("UserName", "John Doe");

        // add cookie to CookieStore for a
        // particular URL
        URL url = new URL("http://host.example.com");
        cookieJar.add(url.toURI(), cookie);
        System.out.println("Added cookie using cookie handler");
    } catch(Exception e) {
        System.out.println("Unable to set cookie using CookieHandler");
        e.printStackTrace();
    }
}

As shown in Retrieving Cookies, the CookieManager class is the main entry point for cookie management. Create an instance of the CookieManager class and set the instance as the default CookieHandler.

Create the desired HttpCookie with the necessary information. In our example, we have created a new HttpCookie that sets the UserName as John Doe.

Next, add the cookie to the underlying cookie store.

Running the Cookie Applet Example

To access cookies, you must sign your RIA JAR file and request permission to run outside of the security sandbox. See the documentation for the jarsigner tool to learn how to sign JAR files. See Security in Rich Internet Applications for information on requesting permissions.

Download source codefor the Cookie Applet example to experiment further.