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An XML-Based JDBC Connector Servlet Framework
Geng Tang
03/05/2001
What is JCS ?
JDBC Connector Servlet
Com.jresources.servlets PackageClass JDBCConnectorServlet package com.jresources.servlets;
import javax.servlet.*; import javax.servlet.http.*; import java.io.*; import com.jresources.jcs.*; import java.util.Enumeration; import java.util.Properties; public class JDBCConnectorServlet extends HttpServlet { private java.util.Properties initProps = new Properties(); public void init(ServletConfig config) throws ServletException { super.init(config); Enumeration e = config.getInitParameterNames(); while(e.hasMoreElements()) { String currParam = (String)e.nextElement(); initProps.put(currParam, config.getInitParameter(currParam)); } }
public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {
jcsEngine mainMod = new jcsEngine(); try { String qryDoc; if(request.getPathInfo()==null) { qryDoc =
getServletConfig().getServletContext().getRealPath(request.getServletPath()); }else { qryDoc = request.getPathTranslated(); } mainMod.processRequest(request, this.initProps ,qryDoc); if(mainMod.getResponseType()==jcsEngine.RESPONSE_REDIRECT) { response.sendRedirect(mainMod.getResponse()); } else { PrintWriter out = response.getWriter(); response.setContentType(mainMod.getMIMEType()); out.println(mainMod.getResponse()); }
}catch(Exception e) { String errorMsg = "An error occurred while executing the query " +
– request.getServletPath() + " with the JCS servlet: " + e.toString(); this.getServletContext().log(errorMsg, e); if(mainMod.getErrorPage()=="") { throw new ServletException(errorMsg, e); }else { response.sendRedirect(mainMod.getErrorPage()); } } } public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException,
ServletException { doGet(request, response); } }
Method in jcsEngine public void processRequest(HttpServletRequest request, String qryDoc) throws Exception { this.processRequest(request, null, qryDoc); } /** * Executes the request with custom properties */ public void processRequest(HttpServletRequest request, Properties customProps, String qryDoc) throws Exception { //our results StringBuffer strResults = new StringBuffer(""); //open the script String qryContent = FunctionLib.OpenFile(qryDoc); qryContent = this.insertFormVariables(qryContent, request); //check for custom properties...if exist, then apply if(customProps!=null) { qryContent = this.insertJCSVariables(qryContent, customProps); } //process SQLEncode function calls String[] workingQuery = new String[1]; workingQuery[0] = qryContent; this.processSQLEncode(workingQuery, new StringBuffer()); qryContent = workingQuery[0]; //parse the query script jcsQuery objQuery = new jcsQuery(qryContent); //TODO: reimplement this code as a finite state machine to make it cleaner and more extensible //set the errorpage for error handling errorPage = objQuery.getErrorPage(); //create a string array to hold the template text String[] workingTemplate = new String[1];
//open the template file if(objQuery.getTemplateDoc()!="") { workingTemplate[0] = objQuery.getTemplateDoc(); //process any server-side includes it might have this.processSSI(workingTemplate, new StringBuffer(), qryDoc, 0); } //instantiate and register the JDBC driver Class.forName(objQuery.getJDBCDriver()); //connect to the database and create a statement Connection conn = DriverManager.getConnection(objQuery.getJDBCURL(),
objQuery.getUID(), objQuery.getPWD()); Statement s = conn.createStatement(); //if it's a "write" query, execute it and redirect to the redirectURL //if there is no redirect url, add the template to the results stringbuffer if(objQuery.IsTransaction()) { s.executeUpdate(objQuery.getSQL()); //System.out.println(objQuery.getRedirectURL()); if(objQuery.getRedirectURL()!="") { conn.close(); //clean up the db connection this.response = objQuery.getRedirectURL(); this.responseType = jcsEngine.RESPONSE_REDIRECT; return; }else { strResults.append(workingTemplate[0]); } }
//otherwise, further parse the template for the jcs:resultset tag... //execute the query, loop thru the rs, apply the template's
display else{ if(objQuery.getMaxRows() > -1){ s.setMaxRows(objQuery.getMaxRows()); } ResultSet rs =
s.executeQuery(objQuery.getSQL()); //if there is no template, then send the default //XML document if(objQuery.getTemplateDoc().equals("")) { XMLSerializableResultset xrs = new
XMLSerializableResultset(rs); this.response = xrs.getXML(); this.MIMEType = "text/xml"; this.responseType =
jcsEngine.RESPONSE_WRITE; rs.close(); conn.close(); return;
}else { jcsTemplateParser template = new jcsTemplateParser(); template.setTemplate(workingTemplate[0]); strResults.append(template.getHeader()); ResultSetMetaData rsMetadata = rs.getMetaData(); int intFields = rsMetadata.getColumnCount(); String recordOutput; String currFieldValue; String AdjFieldValue; int recordCount = 0; while(rs.next()) { recordOutput = template.getBody(); for(int i =1; i <= intFields; i++) { currFieldValue = FunctionLib.EncodeSpecialCharacters(rs.getString(i)); AdjFieldValue = objQuery.UseHTMLLineBreak()?
FunctionLib.HTMLLineBreak(currFieldValue):currFieldValue; recordOutput = FunctionLib.Replace(recordOutput, "#" + rsMetadata.getColumnName(i) + "#",
AdjFieldValue); } strResults.append(recordOutput); recordCount++; } if(recordCount == 0) { strResults.append(objQuery.getEmptyResultsetOutput()); } strResults.append(template.getFooter()); } rs.close();
} //end sql check conn.close(); this.MIMEType = objQuery.getMIMEType(); this.responseType = jcsEngine.RESPONSE_WRITE; //make sure we fill out any form or cgi variables in the
template... String tmpResponse =
insertFormVariables(strResults.toString(),request); //check for custom properties...if exist, then apply if(customProps!=null) { tmpResponse = this.insertJCSVariables(tmpResponse,
customProps); } this.response=tmpResponse; return; }
Some important files
jcs_taglib.tldweb.xml
jcs_taglib.tld <?xml version="1.0" encoding="ISO-8859-1" ?> <!DOCTYPE taglib PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.1//EN" "http://java.sun.com/j2ee/dtds/web-jsptaglibrary_1_1.dtd">
<!-- a tab library descriptor -->
<taglib> <tlibversion>1.0</tlibversion> <jspversion>1.1</jspversion> <shortname>jcs</shortname> <uri></uri> <info> A custom JSP tag implementation of the JResources.com DB Connector servlet </info>
<tag> <name>query_object</name> <tagclass>com.jresources.jcs.jcsCustomTag</tagclass> <teiclass>com.jresources.jcs.jcsCustomTagOutput</teiclass> <info>A custom JSP tag implementation of the JResources.com DB Connector servlet</info> <attribute> <name>url</name> <required>true</required> </attribute> <attribute> <name>outputvariable</name> <required>true</required> </attribute> </tag> </taglib>
Web.xml
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.2//EN" "http://java.sun.com/j2ee/dtds/web-app_2.2.dtd">
<web-app> <display-name>JResources.com Database Connector Servlet</display-name> <description> The JResources.com Database Connector Servlet is a Java servlet that provides an XML-based interface to JDBC data sources. With the JResources.com DB connector servlet, web developers now have an easy way to query and modify JDBC databases without writing a line of Java code. </description> <context-param> <param-name>jdbc_url</param-name> <param-value>jdbc:odbc:guestbook</param-value> <description> The default URL for the guestbook app's database </description> </context-param>
(continued)
<context-param> <param-name>output</param-name> <param-value> This is an example of using JCS from a JSP with custom properties read from the web application's context parameters. In Tomcat, these are set up in the WEB-INF/web.xml file </param-value> <description> Sample output for the guestbook app </description> </context-param> <servlet> <servlet-name> JCS </servlet-name> <servlet-class> com.jresources.servlets.JDBCConnectorServlet </servlet-class> <init-param> <param-name> defaultDriver </param-name> <param-value> sun.jdbc.odbc.JdbcOdbcDriver </param-value> </init-param>
</servlet>
(continued)
<servlet-mapping> <servlet-name> JCS </servlet-name> <url-pattern> *.jcs </url-pattern> </servlet-mapping> <taglib> <taglib-uri> http://www.jresources.com/jcs/jcs_taglib.tld </taglib-uri> <taglib-location> /WEB-INF/jcs_taglib.tld </taglib-location> </taglib> </web-app>
Guestbook application
Create a SELECT queryAdding and modifying dataGenerating XML output from queryUsing JCS from within a JSPUsing XSLT with JCS
guestbook.jcs <?xml version="1.0"?> <jcs:query xmlns:jcs="http://www.jresources.com/xml/jcs/1.0"> <jcs:jdbc_url>jdbc:odbc:guestbook</jcs:jdbc_url> <jcs:sql>select * from guestbook order by date</jcs:sql> <jcs:template> <
(Continued)
<jcs:include> templates\footer.inc </jcs:include> ]]> </jcs:template>
<jcs:empty_resultset_output> <![CDATA[ <tr> <td colspan="2"> <font color="red">There are no entries in the guestbook.</font> </td> </tr> ]]> </jcs:empty_resultset_output>
<jcs:line_break_character>HTML</jcs:line_break_character> </jcs:query>
guestbook_xml_default.jcs
<?xml version="1.0"?> <jcs:query xmlns:jcs="http://www.jresources.com/xml/jcs/1.0"> <jcs:jdbc_url>jdbc:odbc:guestbook</jcs:jdbc_url> <jcs:sql>select * from guestbook order by date</jcs:sql> </jcs:query>
guestbook_xml.jcs
<?xml version="1.0"?> <jcs:query xmlns:jcs="http://www.jresources.com/xml/jcs/1.0"> <jcs:mime_type>text/xml</jcs:mime_type> <jcs:jdbc_url>jdbc:odbc:guestbook</jcs:jdbc_url> <jcs:sql>select * from guestbook order by date</jcs:sql> <jcs:template> <![CDATA[ <?xml version="1.0"?> <guestbook date="#system.date#"> <jcs:resultset> <entry id="#ID#"> <visitor fname="#fname#" lname="#lname#"/> <comments> #comments# </comments> <date>#date#</date> <host>#host#</host> </entry> </jcs:resultset> </guestbook> ]]> </jcs:template> </jcs:query>
guestbook.jsp
<jsp:useBean id="jcs" scope="request" class="com.jresources.jcs.jcsEngine" />
<% try{ jcs.processRequest(request, getServletConfig().getServletContext().getRealPath("/samples/guestbook/guestbook.jcs")); } catch(Exception e){} if(jcs.getResponseType()==com.jresources.jcs.jcsEngine.RESPONSE_REDIRECT) { response.sendRedirect(jcs.getResponse()); }else { %> <%=jcs.getResponse()%> <% } %>
guestbook_tag.jsp
<%@ taglib uri="http://www.jresources.com/jcs/jcs_taglib.tld" prefix="jcs" %>
<jcs:query_object url="/samples/guestbook/guestbook.jcs" outputvariable="guestbook" />
<%=guestbook%>
guestbook_custom.jsp
<jsp:useBean id="jcs" scope="request" class="com.jresources.jcs.jcsEngine" />
<% java.util.Properties prop = new java.util.Properties(); prop.put("jdbc_url", "jdbc:odbc:guestbook"); prop.put("output", "This is an example of using JCS from a JSP with custom properties passed from the JSP
script to the JCS engine"); try{ jcs.processRequest(request, prop, getServletConfig().getServletContext().getRealPath("/samples/guestbook/
jsp.guestbook.jcs")); }catch(Exception e){} if(jcs.getResponseType()==com.jresources.jcs.jcsEngine.RESPONSE_REDIRECT) { response.sendRedirect(jcs.getResponse()); }else { %> <%=jcs.getResponse()%> <% } %>
Jsp.guestbook.jcs
<?xml version="1.0"?> <jcs:query xmlns:jcs="http://www.jresources.com/xml/jcs/1.0"> <jcs:jdbc_url>#jcs.jdbc_url#</jcs:jdbc_url> <jcs:sql>select * from guestbook order by date</jcs:sql> <jcs:template> <
<jcs:resultset> <tr> <td> <a href="guestbook_view_entry.jcs?ID=#ID#">#fname# #lname#</a> </td> <td> <i>#date#</i> </td> </tr> </jcs:resultset> </table> <p><b>#jcs.output#</b></p> <jcs:include> templates/footer.inc </jcs:include> ]]> </jcs:template> <jcs:line_break_character>HTML</jcs:line_break_character> </jcs:query>
guestbook_xsl.jsp
<%@ page import="org.xml.sax.SAXException,org.apache.xalan.xslt.XSLTProcessorFactory,org.apache.xalan.xslt.XSLTInputSource,org.apache.xalan.xslt.XSLTResultTarget,org.apache.xalan.xslt.XSLTProcessor" %>
<%@ taglib uri="http://www.jresources.com/jcs/jcs_taglib.tld" prefix="jcs" %> <jcs:query_object url="/samples/guestbook/guestbook_xml.jcs" outputvariable="guestbook" /> <% /* This sample uses Xalan 1.1. Download it from http://xml.apache.org. Ensure that xalan.jar and xerces.jar are
in Tomcat's classpath. */ try{ XSLTProcessor processor = XSLTProcessorFactory.getProcessor(); processor.process(new XSLTInputSource(new java.io.StringReader(guestbook.toString())), new
XSLTInputSource("file:///" + getServletConfig().getServletContext().getRealPath("/samples/guestbook/guestbook.xsl")), new XSLTResultTarget(out));
}catch(Exception e) { %> An error occurred processing your operation...<%=e.toString()%> <% } %>
guestbook_tag_custom.jsp
<%@ taglib uri="http://www.jresources.com/jcs/jcs_taglib.tld" prefix="jcs" %>
<jcs:query_object url="/samples/guestbook/jsp.guestbook.jcs" outputvariable="guestbook" />
<%=guestbook%>
guestbook_submit.jcs
<?xml version="1.0"?> <jcs:query xmlns:jcs="http://www.jresources.com/xml/jcs/1.0"> <jcs:jdbc_url>jdbc:odbc:guestbook</jcs:jdbc_url> <jcs:sql>select * from guestbook order by date</jcs:sql> <jcs:template> <
(continued)
<hr size="1"> <p><b>Other Guestbook Entries</b> (as of #system.date#)</p> <table> <tr> <td> <b>Visitor</b> </td> <td> <b>Date</b> </td> </tr> <jcs:resultset> <tr> <td> <a href="guestbook_view_entry.jcs?ID=#ID#">#fname# #lname#</a> </td> <td> <i>#date#</i> </td> </tr> </jcs:resultset> </table>
<jcs:include> templates\footer.inc </jcs:include> ]]> </jcs:template> <jcs:line_break_character>HTML</jcs:line_break_character> </jcs:query>
guestbook_add.jcs
<?xml version="1.0"?> <jcs:query xmlns:jcs="http://www.jresources.com/xml/jcs/1.0"> <jcs:jdbc_url>jdbc:odbc:guestbook</jcs:jdbc_url> <jcs:sql> INSERT INTO guestbook ("ID", "fname", "lname",
"comments", "host", "date") VALUES ('#system.UID#','<jcs:encode_sql>#form.fname#</jcs:encode_sql>','<jcs:encode_sql>#form.lname#</jcs:encode_sql>', '<jcs:encode_sql>#form.comments#</jcs:encode_sql>', '#CGI.REMOTE_ADDR#', Now())
</jcs:sql> <jcs:redirect_url>guestbook.jcs</jcs:redirect_url> <jcs:error_page>error_page.htm</jcs:error_page> </jcs:query>
guestbook_delete.jcs
<?xml version="1.0"?> <jcs:query xmlns:jcs="http://www.jresources.com/xml/jcs/1.0"> <jcs:jdbc_url>jdbc:odbc:guestbook</jcs:jdbc_url> <jcs:sql> delete from guestbook where ID = '#form.ID#' </jcs:sql> <jcs:redirect_url>guestbook.jcs</jcs:redirect_url> <jcs:error_page>error_page.htm</jcs:error_page> </jcs:query>
guestbook_view_entry.jcs
<?xml version="1.0"?> <jcs:query xmlns:jcs="http://www.jresources.com/xml/jcs/1.0"> <jcs:jdbc_url>jdbc:odbc:guestbook</jcs:jdbc_url> <jcs:sql>select * from guestbook where ID = '#form.ID#'</jcs:sql> <jcs:template> <![CDATA[ <jcs:include> templates\header.inc </jcs:include> <jcs:resultset> <p><b>#fname# #lname#'s Guestbook Entry</b></p>
<p><b>Comments: </b>#comments#</p>
<p><b>Date entered: </b>#date#</p>
<p><b>Originating Host: </b>#host#</p> <p><a href="guestbook_delete.jcs?ID=#ID#">Delete this entry</a></p> </jcs:resultset>
<jcs:include> templates\footer.inc </jcs:include> ]]> </jcs:template> <jcs:line_break_character>HTML</jcs:line_break_character> </jcs:query>
Summary
Reusableaccess the record in relational
database via JDBC without Javarapid creation of XML data serverportable
Questions ?
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