SOA: Refactoring Mainframe Applications into Dynamic Web Applications, Part 2 : Page 4

XMLHttpRequest Object Methods and Properties
The XMLHttpRequest has a set of methods and properties common to all supported environments (browsers). Table 1 shows the most frequently used XMLHttpRequest object methods. Table 1. The table lists frequently used XMLHttpRequest object methods.

Method	Description
abort()	Stops the current request
getAllResponseHeaders()	Returns complete set of headers (labels and values) as a string
getResponseHeader("headerLabel")	Returns the string value of a single header label
open("method", "URL"[, asyncFlag[, "userName"[, "password"]]])	Assigns destination URL, method, and other optional attributes of a pending request
send(content)	Transmits the request, optionally with a POST string or DOM object data
setRequestHeader("label", "value")	Assigns a label/value pair to the header to be sent with a request

The XMLHttpRequest object also shares a common set of properties across all supported environments. Table 2 shows the XMLHttpRequest object properties.

Table 2. The table shows a list of frequently used XMLHttpRequest object properties.

Property	Description
onreadystatechange	Event handler for an event that fires at every state change
readyState	Status: 0 = uninitialized 1 = loading 2 = loaded 3 = interactive 4 = complete
responseText	String version of data returned from server process
responseXML	DOM-compatible document object of data returned from server process
status	Numeric code returned by server, such as 404 for "Not Found" or 200 for "OK"
statusText	String message accompanying the status code

At this point, you've seen how to refactor a mainframe application into deployable Web services using service-oriented techniques and a standard Java servlet framework. This article discussed how to access that framework using queries from a the now-ubiquitous browser-based XMLHttpRequest object to invoke the Web services and provide data from the mainframe directly to the client application rather than screen-scraping and reformatting to provide data to a desktop application.

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