2

我MyInterceptor.java在 Struts 2 中创建了一个自定义拦截器，它获取参数值username和password来自index.jsp页面并将String这些参数中的转换为大写。

下面是我的拦截器代码，我在其中第 1java.lang.NullPointerException行。14

MyInterceptor.java：

package com.interceptor;

import com.opensymphony.xwork2.interceptor.Interceptor;
import com.opensymphony.xwork2.util.ValueStack;
import com.opensymphony.xwork2.ActionInvocation;

public class MyInterceptor implements Interceptor{
    public void init(){}
    @Override
    public String intercept(ActionInvocation ai) throws Exception {
        ValueStack stack = ai.getStack();
        String s1 = stack.findString("name");
        String s2 = stack.findString("password");
    String s3 = s1.toUpperCase();
     String s4 = s2.toUpperCase();
        stack.set("name", s3);
        
        stack.set("password", s4);
        return ai.invoke();
    }
    
    @Override
    public void destroy() {
        
    }
}

这是我的index.jsp页面：

这需要username和password "ravi"：

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<%@taglib prefix="s" uri="/struts-tags" %>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Login Page</title>
</head>
<body>
<h1>Login Here</h1>
<s:form action="login">

    <s:textfield name="name" label="Name"></s:textfield>
    <s:textfield type="password" name="password" label="Password"></s:textfield>
<s:submit label="Login"></s:submit>
</s:form>
</body>
</html>

这是动作类MyAction.java：

package com.ravi.action;
import com.opensymphony.xwork2.ActionSupport;
public class MyAction extends ActionSupport{
           public String name;
           public String password;

           public void setName(String name){
                                              this.name= name;
                        }

           public void setPassword(String password){
                                                    this.password= password;
                       }

          public String getName(){
                                    return name;
                       }

         public String getPassword(){
                                    return password;
                       }

         public String execute()throws Exception{
                    if(name.equals("RAVI") && password.equals("RAVI")){
                                                       
                                                          return "success";
                                   }
                                   else {
                                                          return "error";

                                    }

                      }


}

这是我的struts.xml：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE struts PUBLIC
"-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
"http://struts.apache.org/dtds/struts-2.0.dtd">
<struts>
    <constant name="struts.devMode" value="true" />
    <package name="default" namespace="/" extends="struts-default">

        <interceptors >
            <interceptor name="uppername" class="com.interceptor.MyInterceptor"></interceptor>
        </interceptors>

        <action name="login" class="com.ravi.action.MyAction">
                <interceptor-ref name="uppername"></interceptor-ref>
                <interceptor-ref name="defaultStack"></interceptor-ref>  

                <result name="success" >welcome.jsp</result>
                <result name="error">Error.jsp</result>
        </action>

</package>
</struts>

Stacktrace如下：

java.lang.NullPointerException 
    com.interceptor.MyInterceptor.intercept(MyInterceptor.java:14)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)
    org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:54)
    org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:567)
    org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:81)
    org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:99)
    org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
    org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
    org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)
    org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
    org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
    org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:956)
    org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
    org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:423)
    org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1079)
    org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:625)
    org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2522)
    org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2511)
    java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:1)
    java.lang.Thread.run(Unknown Source)

我猜问题在于访问MyInterceptor.java. 的ValueStack方法findString()不返回参数的值name和password。

4

2 回答 2

2

如果您需要拦截器中的参数，您应该从操作上下文中获取它。

Map<String, Object> params = ActionContext.getContext().getParameters();

您在浏览时试图从值堆栈中获取属性（不是参数）index.jsp，而值堆栈没有这样的键。

String[] s1 = (String[]) params.get("name");
String[] s2 = (String[]) params.get("password");
if (s1 != null && s2 != null) { 
  s1[0] = s1[0].toUpperCase();
  s2[0] = s2[0].toUpperCase();
}
于 2016-04-09T13:12:18.640 回答
1

我认为 问题应该是因为拦截器的顺序。你的拦截器是最后一个拦截器，所以当请求一个动作时，

  1. Struts 使new instance您的行动成为可能
  2. （parameter interceptor位于 中default stack）填充操作属性。
  3. 之后，您的拦截器将更新值堆栈，当然，没有人会使用它。
于 2016-04-09T14:42:49.207 回答