我刚开始使用AJAX。我不确定很多事情,尽管我在网上找到了一些教程并开始工作。对于粘贴大量代码,我深表歉意,但是对于我哪里出错了,我并没有太多想法。谢谢您的帮助!:-)
这是我的JSP(仅javascript部分)和servlet代码:(之后是异常,后跟等效的是我将用于普通Java应用程序的Java代码):
JSP:
//--Function to get the xmlhttp object function getHttpObject(){ var xmlhttp = null; if (window.XMLHttpRequest){xmlhttp=new XMLHttpRequest();} else if (window.ActiveXObject){xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");} else {alert("Your browser does not support XMLHTTP!");} return xmlhttp; } function populateReply(str){ xmlhttp = getHttpObject(); xmlhttp.onreadystatechange=function(){ if(xmlhttp.readyState==4){ ajxfrm.chatresponse.value=xmlhttp.responseText; } } xmlhttp.open("GET","NewServlet?chatinput="+str,true); xmlhttp.send(null); }
Servlet:
public class NewServlet extends HttpServlet implements Servlet { NetworkAimlFacade aiml = null; int status = 0; String botName; String param[]; GraphBuilder builder; public NewServlet() throws Exception{ super(); aiml = new NetworkAimlFacade(param); builder = aiml.getNetworkGraphBuilder(); builder.addDirectoryUnlessAlreadyAdded ( "C:\\Program Files\\RebeccaAIML\\aiml\\annotated_alice" ); builder.createGraph(); botName = builder.getBotPredicate("name"); } private String handleRequest(String param){ return null; } public void destroy() { try{ aiml.destroy(); }catch(Exception e){ e.printStackTrace(); } } protected void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException{ res.setContentType("text/xml"); res.setHeader("Cache-Control", "no-store, no-cache"); String input = ""; if(req.getParameter("chatinput") != null) input = req.getParameter("chatinput"); try{ String response = builder.getResponse(input); if(response!=null) res.getWriter().write(response); else res.getWriter().write("No"); }catch(Exception e){ e.printStackTrace(); } } protected void doPost(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { }}
这是我得到的错误,而不是从servlet获得响应:
Apache Tomcat / 7.0.11-错误报告
类型 例外报告
信息
描述 服务器遇到内部错误(),导致服务器无法满足此请求。
例外
javax.servlet.ServletException:实例化Servlet类NewServlet时出错 org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:498) org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100) org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:562) org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:394) org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:243) org.apache.coyote.http11.Http11Protocol $ Http11ConnectionHandler.process(Http11Protocol.java:188) org.apache.tomcat.util.net.JIoEndpoint $ SocketProcessor.run(JIoEndpoint.java:302) java.util.concurrent.ThreadPoolExecutor $ Worker.runTask(ThreadPoolExecutor.java:886) java.util.concurrent.ThreadPoolExecutor $ Worker.run(ThreadPoolExecutor.java:908) java.lang.Thread.run(Thread.java:619)
根本原因
java.lang.NullPointerException Ice.PropertiesI。<init>(PropertiesI.java:250) Ice.Util.createProperties(Util.java:29) Ice.Util.initialize(Util.java:70) Ice.Util.initialize(Util.java:49) Ice.Util.initialize(Util.java:56) rebecca.NetworkGraphBuilderAIML。<init>(未知来源) rebecca.NetworkAimlFacade。<init>(未知来源) NewServlet。<init>(NewServlet.java:27) sun.reflect.NativeConstructorAccessorImpl.newInstance0(本机方法)sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39) sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27) java.lang.reflect.Constructor.newInstance(Constructor.java:513) java.lang.Class.newInstance0(Class.java:355) java.lang.Class.newInstance(Class.java:308) org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:498) org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100) org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:562) org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:394) org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:243) org.apache.coyote.http11.Http11Protocol $ Http11ConnectionHandler.process(Http11Protocol.java:188) org.apache.tomcat.util.net.JIoEndpoint $ SocketProcessor.run(JIoEndpoint.java:302) java.util.concurrent.ThreadPoolExecutor $ Worker.runTask(ThreadPoolExecutor.java:886) java.util.concurrent.ThreadPoolExecutor $ Worker.run(ThreadPoolExecutor.java:908) java.lang.Thread.run(Thread.java:619)
note注意 在Apache Tomcat / 7.0.11日志中可以找到根本原因的完整堆栈跟踪。
这是我在普通Java应用程序中使用的等效Java代码,它工作正常!
public class Console { public static void main(String args[]) { NetworkAimlFacade aiml = null; int status = 0; try { aiml = new NetworkAimlFacade(args); GraphBuilder builder = aiml.getNetworkGraphBuilder(); builder.addDirectoryUnlessAlreadyAdded ( "C:\\Program Files\\RebeccaAIML\\aiml\\annotated_alice" ); builder.createGraph(); String botName = builder.getBotPredicate("name"); String initialResponse = builder.getResponse("connect"); System.out.println(botName + " says: " + initialResponse); while(true) { System.out.print("You say> "); BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); String input = br.readLine(); if(input.equals("/exit")) { break; } else { String response = builder.getResponse(input); System.out.println("====================="); //Print out what Rebecca says. System.out.println(botName + " says: " + response); } } aiml.destroy(); } catch(NetworkException e) { e.printStackTrace(); status = 1; } catch (Exception e) { e.printStackTrace(); status = 1; } System.exit(status); } }
以下是您的例外情况的相关摘录:
javax.servlet.ServletException: Error instantiating servlet class NewServlet ... java.lang.NullPointerException Ice.PropertiesI.<init>(PropertiesI.java:250) Ice.Util.createProperties(Util.java:29) Ice.Util.initialize(Util.java:70) Ice.Util.initialize(Util.java:49) Ice.Util.initialize(Util.java:56) rebecca.NetworkGraphBuilderAIML.<init>(Unknown Source) rebecca.NetworkAimlFacade.<init>(Unknown Source) NewServlet.<init>(NewServlet.java:27) ...
换句话说,当容器试图做
Servlet serlvet = new NewServlet();
它失败了,因为PropertiesI在第250行的类的构造函数中,某些对象期望某个对象不存在,null并尝试直接访问它,而无需事先检查是否null存在。PropertiesI在第250行检查类的源代码,并进行相应的修复。
PropertiesI
null
这些都与ajax或servlet 无关 。了解如何解释异常和堆栈跟踪。