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CSC3530 Software Technology
Tutorial 10
Assignment Two (III) Demo
Update to Assignment One
java.net package
nanoxml
XSLT,XPath
Assignment Two Part III
• Demo link
– http://sparc68.cse.cuhk.edu.hk:8080/examples/servlet/CompareXML
– http://sparc68.cse.cuhk.edu.hk:8080/examples/servlet/CompareXML1
• Flow of part III
– 1.Post a query to servlet – CompareXML (with check flag on)
– 2.For each product found in product table, find those
corresponding supplier in supplying table
– 3.Check if the price quote from supplier exceeds a certain value
• 3.1 If yes, post a query to that supplier
• 3.2 The URL is obtain in a field URL of supplier table (URL of
CompareXML1)
• 3.3 Parse the XML return from query
– 4.Update the price quote
– 5.Presents the user with details of products
• Price lower than the current site should not be display
Flow diagram of Part III
1
User post a query
DB1
5 XML data
internet
CompareXML
3.1
3.3
2,3 check if need to
CompareXML1
XML data
XML data
update
CompareXML2
4 update price quote
DB
DB2
Product - CompareXML
Product – CompareXML1
code
Category
On_hand
Price
code
Category
On_hand
Price
111
Printer
10
600
111
Printer
20
800
abc
Scanner
20
200
abc
Scanner
20
150
def
printer
10
800
defg
Scanner
50
600
supplying
Product
code
Supplier
code
price
On_han
d
Quote
111
t1
500
30
12/11
def
t2
300
50
12/10
1
2
5
supplier
code
name
URL
t1
company1
http://sparc68.cse.cuhk.edu.hk8080
/example/servlet/CompareXML1
t2
company2
http://sparc68.cse.cuhk.edu.hk8080
/example/servlet/CompareXML2
4
Get the URL and when
the quote is updated
3
Update to assignment one
database schema
• Reuse of table
– Originally, you have
• Supplying(supplier_code,product_code,price)
• Supplier(code,name,address,e-mail,tel)
• Product(code,name,category,on_hand,low_limit)
• Update
– alter table supplying add (quote date,on_hand int)
• Indicate when the price quote is updated
• How many product the supplier has
– alter table supplier add url varchar2(100)
• Store the price quote servlet URL of supplier
– alter table product add price number(10,2)
• Store the price quote of current company
Suggested SQL
• select SU.url, S.code from supplying SU, supplier S
where SU.supplier_code=S.code and SU.product_code=‘xxx’
and (SYSDATE-SU.quote)*24*60 > 30;
– Find those supplier’s price quote URL which supply product xxx
to us and the price quote is not update for 30 minutes
• update supplying set price=100, quote=SYSDATE where
supplier_code=‘xxx’ and product_code=‘yyy’;
– Update the price quote of product yyy supplied by supplier xxx
and set the time to current time
• You should not show supplier whose price quote is lower
that your company
• SYSDATE is the current date/time
• Date arithmetic is in number of days
java.net package
• How to post query to a CGI in java program?
– Use java.net.URL, java.net.URLConnection
• Java will open an http connection for your program
– No need to do socket programming
• To use
– import java.net.*;
– Import java.io.*; (for reader and writer)
• Key objects
– URL – an object to model the url (http://……)
– URLConnection – an object to model connection between server
and client
– PrintWriter – an object for you to post request to a CGI URL
– BufferedReader – and object for you to read the CGI output
(html page)
Code fragment
• Example
– http://www.cse.cuhk.edu.hk/~kcsia/csc3530/Query.java
– Please run in unix machine, and make sure sparc68 is up
URL url=new URL(“http://sparc68.cse.cuhk.edu.hk:8080/examples/servlet/CompareXML”);
URLConnection urlconnection=url.openConnection();
urlconnection.setDoOutput(true);
PrintWriter out=new PrintWriter(urlconnection.getOutputStream());
out.print(“field=id&query=111”);
out.close();
BufferedReader in=new BufferedReader(new
InputStreamReader(urlconnection.getInputStream());
String temp;
do {
temp=in.readLine();
if (temp!=null)
System.out.println(temp);
else
break;
}
in.close();
Explanation
• Construct an URL object, using the URL of price quote
CGI
• openConnection() - to obtain an URLConnection object
• setDoOutput(true) - to enable sending data to CGI
• new PrintWriter – obtain an writer object for sending
request to CGI
• out.println() - send query data to CGI
• out.close() – close the writer
• … getInputStream() - get the stream for reading CGI
output (xml data)
• in.close() – close the reader
• Parse the XML … (use nanoXML)
XML for exchanging data
Tag
<products>
<product>
<id>ABCD</id>
<description>rogue spear</description>
<category>computer games</category>
<company>
<name>Amazon</name>
<price>200.2</price>
<onhand>50</onhand>
</company>
</product>
<product>
<id>EFGH</id>
<description>black thorn</description>
<category>computer games</category>
<company>
<name>Amazon</name>
<price>150.3</price>
<onhand>200</onhand>
</company>
</product>
</products>
Name
Content
nanoxml
• How to interpret the XML return from other URL
– Use XML parser
– http://nanoxml.sourceforge.net/index.html
version 1.6.8
– http://www.cse.cuhk.edu.hk/~kcsia/csc3530/nanoxml.jar
• To use
– Place nanoxml.jar in the same directory with your code or
set CLASSPATH to include nanoxml.jar
– import nanoxml.*;
• XMLElement (a class in nanoxml)
– It models a node in the DOM tree
– Methods to use
•
•
•
•
parseString()
getChildren()
getTagName()
getContents()
DOM Tree and XMLElement
All nodes are XMLElement object
products
getTagName() returns the node’s
name
product
id
description
getChildren() returns the child
nodes contained in a Vector
object
category
company
price
name
getContents(), e.g. when call on price XMLElement
it will return 150.3
How to use XML
Sample: http://www.cse.cuhk.edu.hk/~kcsia/csc3530/QueryXML.java
…
String xml=“<products><product><company><price>200</price>
</company></product></products>”;
XMLElement root=new XMLElement();
root.parseString(xml);
XMLElement product=findTag(root,"product");
if (product!=null) {
XMLElement company=findTag(product,"company");
if (company!=null) {
XMLElement price=findTag(company,"price");
if (price!=null) {
System.out.println("The price is:“+
price.getContents());
}
}
}
}
// findTag is a function that you have written
How to use XML
private static XMLElement findTag(XMLElement src,String str) {
Vector v = src.getChildren();
for (int i = 0; i < v.size(); i++) {
XMLElement e = (XMLElement)(v.elementAt(i));
if (e.getTagName().compareTo(str) == 0) {
return e;
}
}
return null;
}
• To use Vector, you should import java.util.*;
• getChildren() is a method of XMLElement
– If you call product.getChildren, it will return a vector containing XMLElement:
id, description, category and company.
• getTagName() and getContents() (refer to page 9)
XSLT, XPath
• How to present the XML in a browser?
– Specify a XSL file in the XML
– <?xml:stylesheet type="text/xsl"
href="http://www.cse.cuhk.edu.hk/~kcsia/display.xsl"?>
– XSL - eXtensible Stylesheet Language
• To transform XML document to HTML (mainly)
• XSL has two standard versions
– <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
version="1.0">
• version 1.0 (supported by IE 6, need to install msxml 3.0 in replace mode)
• http://www.cse.cuhk.edu.hk/~kcsia/csc3530/XmlInst.exe
– <xsl:stylesheet xmlns:xsl="http://www.w3.org/TR/WD-xsl">
• Working draft (supported by IE 5.5)
Sample XSL file
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
<xsl:template match="/">
<HTML>
<HEAD>
<TITLE>Query Result</TITLE>
</HEAD>
<BODY>
<H1>Query Result</H1>
<xsl:for-each select="/products/product">
Product ID: <xsl:value-of select="id"/><BR/>
Product Code: <xsl:value-of select="description"/><BR/>
Product Category: <xsl:value-of select="category"/><BR/>
<TABLE BORDER="1">
<TR>
<TH>company name</TH>
<TH>price</TH>
<TH>on hand</TH>
</TR>
Sample XSL file
<xsl:for-each select="company">
<xsl:sort select="price" data-type="number" order="ascending" />
<TR>
<TD><xsl:value-of select="name"/></TD>
<TD><xsl:value-of select="price"/></TD>
<TD><xsl:value-of select="onhand"/></TD>
</TR>
</xsl:for-each>
</TABLE><BR/>
</xsl:for-each>
</BODY>
</HTML>
</xsl:template>
</xsl:stylesheet>
XPath
• XPath is to enable the addressing of, or navigation to,
chosen part of XML document
• XSL use XPath for testing whether or not an node
matches a pattern
• <xsl:template match="/">
– Xsl will process the whole xml file, / means the root
• <xsl:for-each select="/products/product">
– XPath: /products/product
– Find the nodes named product, with parent node named products
– For-each loop will take out these node and do an iteration
• <xsl:sort select="id" data-type="text" order="ascending" />
•
– Sort the selected nodes according to the content in child node id
– Sort function is supported in XSLT version 1.0
<xsl:value-of select="name"/>
– Display the value (content) in node named “name”
XPath
• Describe a path through the XML hierarchy with a
slash-separated list of child element names
• Identify all the elements that match the path
• Simple query mechanism
authors
author (period)
name
nationality
authors/*/name
authors/author/*
authors/author[nationality=‘Russian’]/name
authors/author/[@period=“classical”]
IE Setting
Prompt or Enable
Reference
• TopXML
– http://www.topxml.com/default.asp
• Servlet 2.1 Documentation
– http://java.sun.com/products/servlet/2.1/api/packages.html
• JDK1.3 Documentation
– http://java.sun.com/j2se/1.3/docs/api/index.html
• Java Tutorial
– http://java.sun.com/docs/books/tutorial/