Advanced Topics

1. Advanced Topics BCIS 3680 Enterprise Programming

2. Overview • Cookies • Mobile Apps • Android • SQLite

3. Cookie • A cookie is piece of textual data (name-value pair) that is stored on the client hard drive. • The server saves a cookie to the client. In the future, when revisiting the same server, the client includes the cookie in its request for pages from the server. • Cookies can be set to persist for up to 3 years. • Browsers generally accept only 20 cookies from each site and 300 cookies in total. They can also limit each cookie to 4 KB. • A cookie is usually associated with the domain of the server that sets the cookie. But it can be set to associate to other domains.

4. Pattern in Making a Cookie • Gather the info to store in the cookie (values of various properties of the cookie) • Create a Cookie object (needs cookie name and its value) • Set additional cookie attributes if necessary • Write cookie to the client

5. Creating Cookies • With the exception of the session cookie, the programmer must create cookies manually. • Cookie is not an implicit object. To create a cookie, call the constructor of the Cookie class. Its signature is: Cookie(String cookieName, String cookieValue); • For example, Cookie c = new Cookie("Type", "Chocolate Chips"); • Neither the cookie name nor the cookie value should contain white space or any of the following characters: [ ] ( ) = , “ / ? @ : ;

6. Setting Cookie Attributes • Before adding the cookie, you can set additional attributes of the cookie. • Typically attributes are maximum age, path, domain, etc. • To set an attribute, use its corresponding setter method: • setMaxAge(intmaxAgeInSeconds), e.g., c.setMaxAge(60*60*24*365); sets the age at 1 year. • setPath(String path), e.g., c.setPath("/") makes the cookie accessible anywhere in the entire application. • When you’re ready to write the cookie to the client, call the addCookie() method of the response object, for example: response.addCookie(c);

7. Pattern in Reading a Cookie • Declare an array of Cookie objects • Retrieve all cookies from the client • Loop through array and compare the name of each cookie to that of the cookie you are looking for • Read attributes from the matching cookie

8. Reading Cookies • All cookies are returned from the client as fields added to the HTTP request headers. • Before reading the cookies, first collect them all through the request object: request.getCookies(); • This method returns an array of Cookie objects that have been sent to client previously. • If there is no cookie in request, it returns null. • Before everything else, use an if statement to check whether cookies exist. • Proceed to steps in the next slide if array is not null.

9. Reading Cookie Value and Attributes • Loop through the cookie array. • During each iteration, use the getName() method to retrieve the name of the cookie. • Compare the name of that cookie to the name of the cookie you’re looking for. • If found, use the getValue() method to retrieve the value stored in the cookie. • Use the proper get<Attribute>() method(s) to retrieve the value of additional cookie attribute(s) that is (are) of interest to you.

10. Updating & Removing a Cookie • To update a cookie, write a cookie with the same name but the new value. • To remove a cookie, find the cookie in the cookies array, set its maximum age to 0.

11. Mobile Apps • Android apps are Java applications. • An Android project includes, among other things: • An /src subfolder that contains source code files for the app. • The naming convention is the same for regular Java packages. So if an app is named edu.unt.Droid. The .java files for the app are then stored in /src/edu/unt/Droid. • A manifest file called AndroidManifest.xml, which contains configuration info for the app. Its function is similar to the manifest file in a JAR file.

12. Developing Android Apps • Java SE JDK • Make sure it’s installed. • Android SDK • Makes use of the Java SE JDK. • Provides the API libraries and developer tools necessary to build, test, and debug apps for Android. • Download it from http://developer.android.com/sdk/index.html. • The ADT bundle contains a version of the Eclipse IDE pre-configured for Android development. • Eclipse IDE • If you already have the Eclipse IDE installed, you add a plug-in for the Android Developer Tools (ADT).

13. SQLite • SQLite is an embedded DBMS. • Does not use the client-server architecture. • No independent service or process that manages the DBMS. • The DBMS engine is integrated in the application itself. • No network or server configuration is needed – less complex. • Uses one single file for a database. • Moving or backing up is as easy as copying the file. • Suited for embedded systems running limited OS. • Using the default configuration, the compiled SQLite library is less than 700 KB in size and requires less than 4 MB of memory to operate. Without advanced features, the size can decrease to 300 KB or less and the required memory to 256 KB.

14. Traditional DBMS Architecture Source: Kreibich, J.A. Using SQLite, O’Reilly, 2010.

15. SQLite Architecture Source: Kreibich, J.A. Using SQLite, O’Reilly, 2010.

16. Programming SQLite • Although SQLite comes with a command line tool for running queries and performing administrative tasks, the native SQLite API is in C. • When building applications, use SQLite API and link to the SQLite DLLs. • When the apps runs and needs access to data, load the SQLite DLLs to interact with the database engine. • Extensions are available for scripting languages (e.g., JSP) to access the functionalities of the APIs. • A JDBC driver for SQLite can be obtained from https://bitbucket.org/xerial/sqlite-jdbc.