I am practicing "An On-Line Store Using a Shopping Cart and Session Tracking" or coreservlet tutorial. I have found exception while running CatalogPage servlet. The stacktrace is given below:
SEVERE: Allocate exception for servlet CatalogPage
java.lang.InstantiationException
at sun.reflect.InstantiationExceptionConstructorAccessorImpl.newInstance(InstantiationExceptionConstructorAccessorImpl.java:30)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at java.lang.Class.newInstance0(Class.java:355)
at java.lang.Class.newInstance(Class.java:308)
at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1149)
at org.apache.catalina.core.StandardWrapper.allocate(StandardWrapper.java:827)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:129)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:861)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:606)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
at java.lang.Thread.run(Thread.java:619)
CatalogPage.java is an abstract servlet class which is extend by two class, each has init() defination separately. The codes are given bellow:
public abstract class CatalogPage extends HttpServlet {
private Item[] items;
private String[] itemIDs;
private String title;
protected void setItems(String[] itemIDs) {
this.itemIDs = itemIDs;
items = new Item[itemIDs.length];
}
protected void setTitle(String title) {
this.title = title;
}
@Override
protected void doGet(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html");
if (items == null) {
response.sendError(response.SC_NOT_FOUND, "Missing Items.");
return;
}
PrintWriter out = response.getWriter();
out.println(ServletUtilities.headWithTitle(title)
+ "<BODY BGCOLOR=\"#FDF5E6\">\n" + "<H1 ALIGN=\"CENTER\">"
+ title + "</H1>");
Item item;
for (int i = 0; i < items.length; i++) {
out.println("<HR>");
item = items[i];
// Show error message if subclass lists item ID
// that’s not in the catalog.
if (item == null) {
out.println("<FONT COLOR=\"RED\">" + "Unknown item ID "
+ itemIDs[i] + "</FONT>");
} else {
out.println();
String formURL = "OrderPage";
// Pass URLs that reference own site through encodeURL.
formURL = response.encodeURL(formURL);
out.println("<FORM ACTION=\"" + formURL + "\">\n"
+ "<INPUT TYPE=\"HIDDEN\" NAME=\"itemID\" "
+ " VALUE=\"" + item.getItemID() + "\">\n"
+ "<H2>" + item.getShortDescription() + " ($"
+ item.getCost() + ")</H2>\n"
+ item.getLongDescription() + "\n" + "<P>\n<CENTER>\n"
+ "<INPUT TYPE=\"SUBMIT\" "
+ "VALUE=\"Add to Shopping Cart\">\n"
+ "</CENTER>\n<P>\n</FORM>");
}
}
out.println("<HR>\n</BODY></HTML>");
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
public class KidsBooksPage extends CatalogPage {
public void init() {
String[] ids = { "lewis001", "alexander001", "rowling001" };
setItems(ids);
setTitle("All-Time Best Children’s Fantasy Books");
}
}
public class TechBooksPage extends CatalogPage {
public void init() {
String[] ids = { "hall001", "hall002" };
setItems(ids);
setTitle("All-Time Best Computer Books");
}
}
The sevlet mapping in web.xml is given below:
<servlet>
<servlet-name>CatalogPage</servlet-name>
<servlet-class>com.servletcontroller.CatalogPage</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>CatalogPage</servlet-name>
<url-pattern>/CatalogPage</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>KidsBooksPage</servlet-name>
<servlet-class>com.servletcontroller.KidsBooksPage</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>KidsBooksPage</servlet-name>
<url-pattern>/KidsBooksPage</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>TechBooksPage</servlet-name>
<servlet-class>com.servletcontroller.TechBooksPage</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>TechBooksPage</servlet-name>
<url-pattern>/TechBooksPage</url-pattern>
</servlet-mapping>
Please help me to find the root cause of that exception.
