Luckily, we will never have to write code for it, because there are plenty of free, fully-functional parsers on the Web. This process is very complicated and prone to errors of all kinds. The parser will read the file using one of the various techniques presented later in this chapter. Atlanta USA Sydney Australia Athens Greece īased on the information stored in this XML document, we can easily check who is on vacation and where. It also keeps track of who is on vacation and demonstrates the parsing process with the currently most common parsing methods.Įxample: cities.xml To illustrate more clearly what parsing an XML file really means, the following example was created which contains information about some cities.
EXCHANGE PUBLIC FOLDER XML EXTRACT SOFTWARE
Then, any client software can use methods of the interface provided by the parser API to access the information the parser retrieved from the XML file.Īll in all, the parser shields the user from dealing with the complex details of XML like assembling information distributed over several XML files, checking for well-formedness constraints, and so on. a set of Java class files) that reads a given document and checks if it is well-formed according to the W3C specification. The parser usually is a class library (e.g. What a parser does Īlmost all programs that need to process XML documents use an XML parser to extract the information stored in the XML document in order to avoid any of the difficulties that occur when reading and interpreting raw XML data. Moreover, it has to provide the content of the document through an interface, so that other applications can access it without difficulty. From a more general point of view, the structure and semantics of an XML file is determined by the makeup of the document, its tags and attributes – hence, we need a device that is able to recognize and understand this structure and can point out any errors in it. Obviously, this approach is not suitable for extracting information from large and complex XML documents, since we would have to know exactly what the file looks like and where the information needed is located. Finally, we declare the text string in between these two patterns to be the value of the surrounding. Then, we would further scan the document for the end pattern (i.e. Using straight text parsing, we would scan the file for the character sequence and call it the start pattern. Let’s say we are interested in the value of the house. One way to extract data from an XML document is simple text parsing – browsing all characters in the document and check for a desired pattern: In other words, a client application accesses the content of the XML document through an interface, instead of having to interpret the XML code on its own! Now, in order to be able to read XML files, we use a parser which basically exposes the document’s content through a so-called API (application programming interface). One goal of the XML format was to enhance raw data formats like plain text by including detailed descriptions of the meaning of the content. 3 Parser APIs (Application Programming Interface).
0 kommentar(er)
