初学者学servlet遇到有关问题，思考了2天还没解决
日期：2014-05-20 浏览次数：20869 次
菜鸟学servlet遇到问题，思考了2天还没解决
编译通过，运行错误
description The server encountered an internal error () that prevented it from fulfilling this request.
exception
javax.servlet.ServletException: Error allocating a servlet instance
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286)
org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
java.lang.Thread.run(Thread.java:619)
root cause
java.lang.NoClassDefFoundError: coreservlets9/ShowItems (wrong name: coreservlets/ShowItems)
java.lang.ClassLoader.defineClass1(Native Method)
java.lang.ClassLoader.defineClass(ClassLoader.java:620)
…………………………
源代码（书上的代码无错、路径也没问题，其他测试servlet文件都能通过 唯独这个）：
package coreservlets;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.util.*;
public class ShowItems extends HttpServlet {
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
HttpSession session = request.getSession();
ArrayList previousItems =
(ArrayList)session.getAttribute("previousItems");
if (previousItems == null) {
previousItems = new ArrayList();
session.setAttribute("previousItems", previousItems);
}
String newItem = request.getParameter("newItem");
response.setContentType("text/html");
PrintWriter out = response.getWriter();
String title = "Items Purchased";
String docType =
"<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.0 " +
"Transitional//EN\">\n";
out.println(docType +
"<HTML>\n" +
"<HEAD><TITLE>" + title + "</TITLE></HEAD>\n" +
"<BODY BGCOLOR=\"#FDF5E6\">\n" +
"<H1>" + title + "</H1>");
synchronized(previousItems) {
if ((newItem != null) &&
(!newItem.trim().equals(""))) {
previousItems.add(newItem);
}
if (previousItems.size() == 0) {
out.println("<I>No items</I>");
} else {
out.println("<UL>");
for(int i=0; i<previousItems.size(); i++) {
out.println("<LI>" + (String)previousItems.get(i));
}
out.println("</UL>");
}
}
out.println("</BODY></HTML>");
}
}
--------------------------------
以下内容为自动编辑的内容，并非楼主的发贴内容,此仅用于显示而已，并无任何其他特殊作用
楼主【hppby】截止到2008-08-04 20:46:28的历史汇总数据(不包括此帖)：
发帖的总数量:0 发帖的总分数:0 每贴平均分数:0
回帖的总数量:0 得分贴总数量:0 回帖的得分率:0%
编译通过，运行错误
description The server encountered an internal error () that prevented it from fulfilling this request.
exception
javax.servlet.ServletException: Error allocating a servlet instance
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286)
org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
java.lang.Thread.run(Thread.java:619)
root cause
java.lang.NoClassDefFoundError: coreservlets9/ShowItems (wrong name: coreservlets/ShowItems)
java.lang.ClassLoader.defineClass1(Native Method)
java.lang.ClassLoader.defineClass(ClassLoader.java:620)
…………………………
源代码（书上的代码无错、路径也没问题，其他测试servlet文件都能通过 唯独这个）：
package coreservlets;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.util.*;
public class ShowItems extends HttpServlet {
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
HttpSession session = request.getSession();
ArrayList previousItems =
(ArrayList)session.getAttribute("previousItems");
if (previousItems == null) {
previousItems = new ArrayList();
session.setAttribute("previousItems", previousItems);
}
String newItem = request.getParameter("newItem");
response.setContentType("text/html");
PrintWriter out = response.getWriter();
String title = "Items Purchased";
String docType =
"<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.0 " +
"Transitional//EN\">\n";
out.println(docType +
"<HTML>\n" +
"<HEAD><TITLE>" + title + "</TITLE></HEAD>\n" +
"<BODY BGCOLOR=\"#FDF5E6\">\n" +
"<H1>" + title + "</H1>");
synchronized(previousItems) {
if ((newItem != null) &&
(!newItem.trim().equals(""))) {
previousItems.add(newItem);
}
if (previousItems.size() == 0) {
out.println("<I>No items</I>");
} else {
out.println("<UL>");
for(int i=0; i<previousItems.size(); i++) {
out.println("<LI>" + (String)previousItems.get(i));
}
out.println("</UL>");
}
}
out.println("</BODY></HTML>");
}
}
--------------------------------
以下内容为自动编辑的内容，并非楼主的发贴内容,此仅用于显示而已，并无任何其他特殊作用
楼主【hppby】截止到2008-08-04 20:46:28的历史汇总数据(不包括此帖)：
发帖的总数量:0 发帖的总分数:0 每贴平均分数:0
回帖的总数量:0 得分贴总数量:0 回帖的得分率:0%
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