1. Ch.16 JDBC (Java DataBase Connectivity) PIKE Lab. 석사 2 학기 이 은 정

2. CONTENTS IntroductionIntroduction Needed SoftwareNeeded Software Generating XML from JDBCGenerating XML from JDBC Using XML for distributed JDBC App.Using XML for distributed JDBC App. SummarySummary

3. INTRODUCTION(1/2) Challenge –To create JDBC Applications that allow platform_neutral, device_independent access to data  By XML-enabling the JDBC application XML with J2EE + Standard Internet Protocol(HTTP)  Enterprise applications that provide universal data access to JDBC data sources

4. INTRODUCTION(2/2) In this chapter … how to integrate XML with JDBC in J2EE applications –Some examples of how to integrate XML with JDBC in J2EE applications that are device-and – platform independent universal data access There ’ re 2 scenarios … –Generating XML from a JDBC data source A XML gateway architecture for JDBC –Using XML to update a JDBC data source How to use WebRowSets to distributed JDBC applications

5. Needed Software JDK1.3 - http://java.sun.com http://java.sun.com Xalan XSLT Processor for Java - http://xml.apache.org http://xml.apache.org Java packages to implement the WebRowSet framework –sun.jdbc.rowset Package –javax.sql Package : JDBC 2.0 standard extension API Tomcat 3.1 : java servlet API - http://jakarta.apache.org http://jakarta.apache.org A JDBC data source & Driver(Oracle, SQL Server … )

6. Generating XML from JDBC Create an architecture that allows you to extract data from a JDBC data source Serialize the JDBC result set to XML Send it to the requesting client, using XSLT as appropriate to create output that targets a particular device

7. Generating XML from JDBC A simple XML Gateway Architecture for JDBC –JDBC2XML class –JDBC2XML class : control access to the JDBC data source Execute a SQL statement against the specified JDBC data source Serialize the returned JDBC result set as XML Return the XML document to the calling client Reused by two java servlets –XMLDataGateway : a generic XML-over-HTTP interface to JDBC data sources for XML – enabled applications –JDBC2HTML : return JDBC result sets as a HTML to web browsers using the specified XSL stylesheet like a filter

8. JDBC Data Source JDBC2XML class XMLDataGateway Servleet XSL Stylesheet JDBC2HTML Servlet XML-enabled Application Web browser JDBC HTTP GET or POST XML over HTTP In-process call XML serialized resultset HTTP GET or POST HTML over HTTP XML serialized resultset In-process call XSL T Delegated to

9. Creating & Using the Architecture Develop the JDBC2XML class Develop the XMLDataGateway servlet Query a JDBC data source using the XMLDataGateway servlet Develop the JDBC2HTML servlet Write an XSL stylesheet that defines HTML presentation logic for our XML schema Query a JDBC data source using the JDBC2HTML servlet

10. The JDBC2XML Class package com.jresources.jdbc; import java.sql.*; import java.util.*; JDBC2XML public class JDBC2XML { public JDBC2XML() { super(); } Include the functionality to query a JDBC Data source to return the Results of that query as a well-formed XML document

11. public String SQLEncode(String content) { return Replace(content, "\'", "\'\'"); } /** * Applies XML encoding rules to special characters */ String encodeXML(String sData) { String[] before = {"&"," ","\"", "\'"}; String[] after = {"&","<",">",""", "&apos;"}; if(sData!=null) { for(int i=0;i<before.length;i++) { sData = Replace(sData, before[i], after[i]); } }else {sData="";} return sData; } String Replace(String content, String oldWord, String newWord) { int position = content.indexOf(oldWord); while (position > -1) { content = content.substring(0,position) + newWord + content.substring(position+oldWord.length()); position = content.indexOf(oldWord,position+newWord.length()); } return content; } <field name="field name goes here" datatype="field's datatype goes here"/> field's value goes here String writeXML(ResultSet rs) { StringBuffer strResults = new StringBuffer("<?xml version=\"1.0\" encoding=\"ISO-8859-1\"?>\r\n \r\n"); try { ResultSetMetaData rsMetadata = rs.getMetaData(); int intFields = rsMetadata.getColumnCount(); strResults.append(" \r\n"); for(int h =1; h <= intFields; h++) { strResults.append("<field name=\"" + rsMetadata.getColumnName(h) + "\" datatype=\"" + rsMetadata.getColumnTypeName(h) + "\"/>\r\n"); } strResults.append(" \r\n \r\n"); while(rs.next()) { strResults.append(" \r\n"); for(int i =1; i <= intFields; i++) { strResults.append("<field name=\"" + rsMetadata.getColumnName(i) + "\">" + encodeXML(rs.getString(i)) + " \r\n"); } strResults.append(" \r\n"); } }catch(Exception e) {} strResults.append(" \r\n "); return strResults.toString(); } public String execute(String driver, String url, String uid, String pwd, String sql) { String output = new String(); try { //instantiate and register the JDBC driver Class.forName(driver); //connect to the database and create a statement Connection conn = DriverManager.getConnection(url, uid, pwd); Statement s = conn.createStatement(); ResultSet rs = s.executeQuery(sql); writeXML(rs); output = writeXML(rs); rs.close(); conn.close(); }catch(Exception e) { output = " " + encodeXML(e.toString()) + " "; } return output; }

12. The XMLDataGateway Servlet package com.jresources.jdbc; import javax.servlet.*; import javax.servlet.http.*; import java.io.*; public class XMLDataGateway extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { response.setContentType("text/xml"); PrintWriter out = response.getWriter(); JDBC2XML searchObj = new JDBC2XML(); out.println(searchObj.execute(request.getParameter("driver"), request.getParameter("jdbcurl"), request.getParameter("uid"), request.getParameter("pwd"), request.getParameter("sql"))); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { doGet(request, response); } POST JDBC Driver: <input type="text" size="50" name="driver" value="sun.jdbc.odbc.JdbcOdbcDriver"> JDBC URL: <input type="text" size="50" name="jdbcurl" value="jdbc:odbc:northwind"> Userid: <input type="text" size="50" name="uid"> password <input type="password" size="50" name="pwd"> SQL Statement:

13. Using XMLDataGAteway from a Web Browser

15. The JDBC2HTML Servlet import javax.servlet.*; import javax.servlet.http.*; import java.io.*; import org.xml.sax.SAXException; import org.apache.xalan.xslt.*; public class JDBC2HTML extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { String qryDoc; if(request.getPathInfo()==null) { qryDoc = getServletConfig().getServletContext().getRealPath( request.getServletPath()); }else {qryDoc = request.getPathTranslated();} response.setContentType("text/html"); PrintWriter out = response.getWriter(); JDBC2XML searchObj = new JDBC2XML(); String output = searchObj.execute(request.getParameter("driver"), request.getParameter("jdbcurl"), request.getParameter("uid"), request.getParameter("pwd"), request.getParameter("sql")); try { XSLTProcessor processor = XSLTProcessorFactory.getProcessor(); processor.process(new XSLTInputSource(new java.io.StringReader(output)), new XSLTInputSource("file:///" + qryDoc), new XSLTResultTarget(out)); }catch(SAXException se) { throw new ServletException(se); //out.println(se.toString()+", " + se.getMessage() + ", " + qryDoc); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { doGet(request, response); }

16. Writing an XSL stylesheet A JDBC Resultset in HTML Table Format A JDBC Resultset in HTML Table Format A JDBC Resultset in HTML Table Format Your request caused the following error:

17. Using XML for distributed JDBC Applications Rowset Interface –Provide a framework for writing classes that encapsulate a persistent set of rows WebRowSet Classsun.jdbc.rowset.WebRowSet Class –A rowset implementation that can serialize the data, metadata, and properties of a JDBC result set to XML –Use the information in the XML document to re-establish the connection and update the original data source

18. A distributed JDBC applications using WebRowSet WebRowSetFetchServlet class –Provide an interface for fetching a WebRowSet via HTTP GET or POST WebRowSetUpdateservlet class –Used to update the underlying JDBC data source WebRowSetHTTPClient application –Used to execute a query against a JDBC data source & return the WebRowSet –Add a record to the WebRowSet

19. Fetching a Rowset via HTTP package com.jresources.jdbc; import javax.servlet.*; import javax.servlet.http.*; import java.io.*; import javax.sql.*; import sun.jdbc.rowset.*; import java.sql.*; public class WebRowSetFetchServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {.........(omit) } public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { doGet(request, response); }

20. Performing a Batch Update via HTTP package com.jresources.jdbc; import javax.servlet.*; import javax.servlet.http.*; import java.io.*; import javax.sql.*; import sun.jdbc.rowset.*; import java.sql.*; public class WebRowSetUpdateServlet extends HttpServlet { } public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { response.sendError(403); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { response.setContentType("text/plain"); PrintWriter out = response.getWriter(); try { WebRowSet wrs = new WebRowSet(); wrs.readXml(request.getReader()); wrs.acceptChanges(); out.println("The transaction succeeded"); }catch(Exception e) { out.println("The transaction failed with the following error: " + e.getMessage()); }

21. Inserting, Updating, Deleting data at the Client executeSearch() method WebRowSetFetchServlet –Encapsulate an HTTP GET request to WebRowSetFetchServlet updateDataSource() method WebRowSetUpdateServlet –Encapsulate an HTTP POST request to WebRowSetUpdateServlet main() method –The application ’ s entry point

22. Web Application Deployment Description <!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.2//EN" "http://java.sun.com/j2ee/dtds/web-app_2.2.dtd"> Professional XML Databases: Chapter 16 (JDBC) This web app contains the sample code for Professional XML Databases: Chapter 16 (JDBC) JDBC2HTML com.jresources.jdbc.JDBC2HTML XMLDataGateway com.jresources.jdbc.XMLDataGateway WebRowSetFetchServlet com.jresources.jdbc.WebRowSetFetchServlet WebRowSetUpdateServlet com.jresources.jdbc.WebRowSetUpdateServlet JDBC2HTML *.xsl

23. Building Application Compile the Java Classes –javac -d %myClasspath% - classpath %CLASSPATH% %basepath%\*.java Package the Bytecode into a JAR –jar cvf %jarpath%\jdbcxml.jar -C %myClasspath%\. Package the Application into a WAR –jar cvf %warpath%\jdbcxml.war -C %apppath%\.

24. Summary How can use JDBC and XML to create universal data access gateways for J2EE applications How to construct a simple XML gateway architecture for JDBC that allows to execute SQL statements and return the result-set as well-formed XML data structures How to build a distributed JDBC application that allows to interact with a JDBC data source over the Internet using HTTP