CS 496 - Assignment 2: RESTful Web Server and Mobile Client

Hints

For full credit, make sure that your web service gracefull and correctly handles incorrect input. For example, if a PUT request contains a message body that does not contain a single Item element with Name and Quantity child elements (each with appropriate data as the element text), then the HTTP response returned to the client should indicate a status code of 400, Bad Request.

For extra credit, use thread synchronization to ensure that the inventory model object will be updated correctly even if multiple clients are accessing the web service concurrently.

Hints

To access localhost through the Android emulator, you need to use the IP address 10.0.2.2.

Use separate methods for each of the REST requests that are called from the corresponding button click callbacks. In each method instantiate the appropriate HttpGet, HttpPut, HttpPost, or HttpDelete object.

Create two methods for setting the layout - one that loads the initial one from main.xml and the other which creates a dynamic LinearLayout view. Call each of these methods as needed from button click methods. Have the dynamic layout method take an Inventory parameter (allowing it to be reused for displaying either the entire inventory retrieved from the server or an inventory consisting of just a single item).

To parse XML from a Document (e.g. from a response), you can use Elements from the org.w3c.dom library.

NodeList nodeList = doc.getElementsByTagName("Foo");

will create a list of all the Foo nodes in the document. From there you can iterate through the list and select a particular node Element as

Element element = (Element) nodeList.item(i);

The children within an Element can then be extracted (as NodeList's) in a similar fashion, e.g. to get the value of the "Bar" child (assuming there is only one) as a string

NodeList barList = element.getElementsByTagName("Bar");
Element barElement = (Element) barList.item(0);
barList = barElement.getChildNodes();
barValue = ((Node) barList.item(0)).getNodeValue();

Consider adding a fromElement(Element e) method to the Item class that takes an item element obtained from the document's NodeList and constructs a new Item object by calling this method (which will parse the XML for an item). Then add the items to an Inventory object in the application which can then be subsequently displayed.

To generate XML, you can use a XMLSerializer object to create a String as follows:

XMLSerializer serializer = new XMLSerializer();
StringWriter writer = new StringWriter();
try {
        serializer.setOutput(writer);
        serializer.startDocument("UTF-8",true);
        serializer.startTag("","Outer Tag");
        serializer.startTag("","Inner Tag");
        serializer.text("Inner Tag value");
        serializer.endTag("","Inner Tag");
        serializer.endTag("","Outer Tag");
        serializer.endDocument();
        return writer.toString();
} catch (Exception e) {
        throw new RuntimeException(e);
}

which would generate the following XML:

<?xml version="1.0" encoding="utf-8"?>
<Outer Tag>
        <Inner Tag>
        Inner Tag Value
        </Inner Tag>
</Outer Tag>

Add a method in the item class, e.g. toXML() that utilizes a similar procedure to create valid XML for an item, i.e. contains an Item that has Name and Quantity children. Then call this method for those requests that require an XML payload and create a StringEntity object from the returned string that can be placed into the request using request.setEntity().