Question

我编写了以下代码来从JSP页面调用servlet

JSP代码;

   <form method="post" action="${pageContext.request.contextPath}/Survey" name="_F_Surv">


         <button type="submit" name="button" value="button3">Button 3</button>

   </form>

Servlet代码

 package survey;

 import java.io.IOException;
 import java.io.PrintWriter;

  import javax.servlet.ServletException;
 import javax.servlet.annotation.WebServlet;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;

 /**
 * Servlet implementation class Survey
  */
  @WebServlet("/Survey")
 public class Survey extends HttpServlet {
    private static final long serialVersionUID = 1L;

/**
 * @see HttpServlet#HttpServlet()
 */
public Survey() {
    super();
    // TODO Auto-generated constructor stub
}

/**
 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
 */
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    // TODO Auto-generated method stub
    response.getWriter().append("Served at: ").append(request.getContextPath());
    PrintWriter out = response.getWriter();
    out.println("Hello World");
}

/**
 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
 */
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    // TODO Auto-generated method stub
    doGet(request, response);
}

}

网页，XML

  <?xml version="1.0" encoding="UTF-8"?>
  <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"        xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
    <display-name>Struts2 Application</display-name>
   <servlet>
    <servlet-name>SimpleCaptcha</servlet-name>
   <servlet-class>nl.captcha.servlet.SimpleCaptchaServlet</servlet-class>
    </servlet>
    <servlet-mapping>
      <servlet-name>SimpleCaptcha</servlet-name>
      <url-pattern>/simpleCaptcha.jpg</url-pattern>
    </servlet-mapping>

    <servlet>
        <servlet-name>Survey</servlet-name>
        <servlet-class>survey.Survey</servlet-class>
    </servlet>

    <servlet-mapping>
       <servlet-name>Survey</servlet-name>
       <url-pattern>/Survey</url-pattern>
    </servlet-mapping>


     <filter>
        <filter-name>struts2</filter-name>
         <filter-class>
            org.apache.struts2.dispatcher.FilterDispatcher
         </filter-class>
      </filter>
      <filter-mapping>
           <filter-name>struts2</filter-name>
           <url-pattern>/*</url-pattern>
     </filter-mapping>
      <session-config>
          <session-timeout>1</session-timeout>
      </session-config>
      <welcome-file-list>
          <welcome-file>survey.jsp</welcome-file>
      </welcome-file-list>
      </web-app>

单击“提交”按钮时，不会调用Servlet。我在控制台中收到以下错误

Jan 26, 2017 10:49:55 AM org.apache.struts2.dispatcher.DefaultDispatcherErrorHandler error
SEVERE: Exception occurred during processing request: null
java.lang.NullPointerException
    at org.apache.struts2.impl.StrutsActionProxy.getErrorMessage(StrutsActionProxy.java:69)
    at com.opensymphony.xwork2.DefaultActionProxy.prepare(DefaultActionProxy.java:185)
    at org.apache.struts2.impl.StrutsActionProxy.prepare(StrutsActionProxy.java:63)
    at org.apache.struts2.impl.StrutsActionProxyFactory.createActionProxy(StrutsActionProxyFactory.java:37)
    at com.opensymphony.xwork2.DefaultActionProxyFactory.createActionProxy(DefaultActionProxyFactory.java:58)
    at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:557)
    at org.apache.struts2.dispatcher.FilterDispatcher.doFilter(FilterDispatcher.java:434)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:218)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:956)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:442)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1083)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:640)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)
    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Unknown Source)

你能告诉我在这里做的错误吗？提前致谢

Answer 1

问题是你为每个URL定义了一个过滤器，攻击Struts Dispachter。请查看struts2 ignore particular pattern和Can I exclude some concrete urls from <url-pattern> inside <filter-mapping>?，了解如何忽略过滤器中的网址。或，更改过滤器以点击/struts/*之类的网址，并将所有struts操作更改为此新模式：/struts/{yourAction}。

无法调用Servlet

1 个答案: