Summer A-2000, Project Course-- Carnegie Mellon University 1 Financial Engineering Project Course

Summer A-2000, Project Course--Carnegie Mellon University

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Financial Engineering Project Course


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Lecture 5

• Validation against a DTD

• More Java Details

• Validating the swap agreement using Sun’s JAXP API


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Checking the Structure of an XML documentwith an XML parser

Document

Structure Rules(DTD)

ValidXML

InvalidXML

XML Rules Checker(Parser)


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Operation of a Tree-based Parser

Tree-BasedParser

ApplicationLogic

Document Tree

Valid

XML DTD

XML Document


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The Agreement.xml file<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE FixedFloatSwap SYSTEM "FixedFloatSwap.dtd"><FixedFloatSwap> <Notional>100</Notional> <Fixed_Rate>5</Fixed_Rate> <NumYears>3</NumYears> <NumPayments>6</NumPayments></FixedFloatSwap>

This document declares itselfas conforming to this dtd.


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The FixedFloatSwap.dtd

<?xml version="1.0" encoding="utf-8"?><!ELEMENT FixedFloatSwap (Notional, Fixed_Rate, NumYears, NumPayments) ><!ELEMENT Notional (#PCDATA) ><!ELEMENT Fixed_Rate (#PCDATA) ><!ELEMENT NumYears (#PCDATA) ><!ELEMENT NumPayments (#PCDATA) >


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<?xml version="1.0" encoding="utf-8"?><!ELEMENT FixedFloatSwap (Notional, Fixed_Rate, NumYears, NumPayments) >

A document that conforms to this dtd musthave these elements in this order.


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<!ELEMENT Notional (#PCDATA) ><!ELEMENT Fixed_Rate (#PCDATA) ><!ELEMENT NumYears (#PCDATA) ><!ELEMENT NumPayments (#PCDATA) >

The tag names in the xml document.

The content of each element


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Before we validate we have to cover some more Java

• Inner classes

• Exception Handling


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Inner Classes

• Nested Top Level Classes (not inner)

• Member Classes

• Local Classes

• Anonymous Classes


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Nested Top Level Class

• Nested top-level classes are not inner classes.• Use as a convenient way to group related classes• Since the class must be static and has no 'this' pointer, it has no access to the instance data of objects for its enclosing class.• It behaves just like a 'normal' class or interface.


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//NestedTopLevelExample.java

class Top { int i,j; static class SomeClass { // static makes it top-level nested int k; SomeClass() { System.out.println("Constructing SomeClass"); } void foo() { System.out.println("Hello"); } } Top() { System.out.println("Constructing a Top object"); }

}


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public class NestedTopLevelExample {

public static void main(String args[]) {

Top myTop = new Top();

Top.SomeClass myObject = new Top.SomeClass(); myObject.foo(); }}

Output

Constructing a Top objectConstructing SomeClassHello


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Member Classes

• Member classes (there is no such thing as a 'member‘ interface)• This inner class (it's not a top-level class) has no static keyword and can access the members of each object of its outer class.• The class 'appears in every instance'.•


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•The parent class must declare an instance of an inner class, before it can invoke the inner class methods, assign to data fields (including private ones), and so on.•Unlike nested top-level classes, inner classes are not directly part of a package and are not visible outside the class in which they are nested.• Inner classes are often used for GUI event handlers.


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// MemberClassExample.javaclass Top { int i = 33; public class SomeClass { // access the outer object's state. private int k = i; SomeClass() { System.out.println("Constructing SomeClass"); } void foo() { System.out.println("Hello"); } } Top() { System.out.println("Constructing a Top object"); SomeClass sc = new SomeClass(); System.out.println(sc.k); }}


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public class MemberClassExample {


Top myObject = new Top(); }}

// OUTPUTConstructing a Top objectConstructing SomeClass33


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Local Classes

•A Local class is an inner class. Typically, a local class is declared within a method. It is not a member of an enclosing class. It is visible only within the block.

•These classes are used primarily as "adapter classes".

• For example, a block of code that creates a Button object could use a local class to define a simple implementation of the ActionListener Interface. Then it could instantiate this simple implementation and pass the resulting object to the button's ActionListener method, thereby connecting the button to the "callback" code that is executed when the button is pressed.


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// Local Class exampleclass Top { int i = 33; Top() { System.out.println("Constructing a Top object"); // define a class within a method class Wow { int t; Wow() { System.out.println("Building a Wow"); i = 8; t = 9; } } Wow h = new Wow(); System.out.println(" h.t == " + h.t); System.out.println(" i == " + i); }}


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public class LocalExample {


Top myObject = new Top(); }}

// OUTPUT

Constructing a Top objectBuilding a Wow h.t == 9 i == 8


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• An anonymous class is refinement of inner classes.• It allows you to combine the definition of the class with the instance allocation.• Since it is instantiated in the same expression that defines it, it can only be instantiated once. This is very similar to local classes. • When writing a simple adapter class, the choice between a named local class and an unnamed anonymous class typically comes down to a matter of style and code clarity, rather than any difference in functionality.•The new class can't have a constructor.

Anonymous Classes


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// Anonymous.java

interface SmallClass { public void foo();}

class Top { int i = 33; void someMethod(SmallClass s) { s.foo(); } void anotherMethod() { someMethod(new SmallClass() { public void foo() { System.out.println("Really fun"); } }); }


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Top() { System.out.println("Constructing a Top object"); someMethod(new SmallClass() { public void foo() { System.out.println("Strange but fun"); } }); }}


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public class Anonymous {


// We can't create interface objects // error: SmallClass s = new SmallClass();

Top myObject = new Top(); myObject.anotherMethod(); }}// OUTPUTConstructing a Top objectStrange but funReally fun


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Validating two Agreement.xml files

import java.io.File;import org.w3c.dom.*;import javax.xml.parsers.DocumentBuilderFactory;import javax.xml.parsers.DocumentBuilder;import org.xml.sax.SAXException;import org.xml.sax.SAXParseException;


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public class Simulator4 { public static void main(String argv[]) { if(argv.length != 2 ) {

System.err.println("usage: java Simulator4” + “document1Name document2Name");

System.exit(1); }


Are both xml files on the command line?// imports as before


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try { DocumentBuilderFactory docBuilderFactory = DocumentBuilderFactory.newInstance(); docBuilderFactory.setValidating(true); docBuilderFactory.setNamespaceAware(true);

DocumentBuilder docBuilder = docBuilderFactory.newDocumentBuilder();

This factory will produceparsers that validate!


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docBuilder.setErrorHandler(

new org.xml.sax.ErrorHandler() {

public void fatalError(SAXParseException e) throws SAXException {} public void error(SAXParseException e) throws SAXParseException { throw e; } public void warning(SAXParseException err) throws SAXParseException { System.out.println("** Warning" + ", line " + err.getLineNumber() + ", uri " + err.getSystemId()); System.out.println(" " + err.getMessage()); } } );

Document doc1 = docBuilder.parse(new File(argv[0]));Document doc2 = docBuilder.parse(new File(argv[1]));

The new object to handlevalidation errors

End of method call


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docBuilder.setErrorHandler(

new org.xml.sax.ErrorHandler() {

public void fatalError(SAXParseException e) throws SAXException {} public void error(SAXParseException e) throws SAXParseException { throw e; } public void warning(SAXParseException err) throws SAXParseException { System.out.println("** Warning" + ", line " + err.getLineNumber() + ", uri " + err.getSystemId()); System.out.println(" " + err.getMessage()); } } );

Document doc1 = docBuilder.parse(new File(argv[0]));Document doc2 = docBuilder.parse(new File(argv[1]));

Validation errors caughthere.


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Lab Exercise:

I would like everyone to be checked off for writingA short Java program that validates the agreement.xml file against the FixedFloatSwap.dtd. If, for example, the notionaltag appears twice in the xml file your program shoulddisplay “oops” before terminating.

Documents

Summer A-2000, Project Course-- Carnegie Mellon University 1 Financial Engineering Project Course