Question

如果我将isEmpty（）调用到我的JSP和相应的Action类中引用的属性，我会得到一个NullPointerException。

JSP：

<%@ page contentType="text/html; charset=UTF-8"%>
<!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>Registrieren - WebShop 2.0</title>
<s:head />
</head>
<body>

    <b><s:text name="welcome.title" /></b>

    <s:form action="UserRegister" focusElement="firstname">
        <s:textfield name="firstname" key="prompt.firstname" size="20"


required="true" />
    <s:textfield name="lastname" key="prompt.lastname" size="20"
        required="true" />
    <s:textfield name="username" key="prompt.username" size="20"
        required="true" />
    <s:password name="password" key="prompt.password" size="20"
        required="true" />
    <br>

    <s:submit method="execute" value="Registrieren" align="right" />
</s:form>

<font color="red"> <s:actionerror label="label" />
</font>

动作类：

package vislabWebShop.controller;

import vislabWebShop.model.User;

import com.opensymphony.xwork2.ActionSupport;

public class RegisterAction extends ActionSupport
{
  private static final long serialVersionUID = -983183915002226000L;

  private String firstname;
  private String lastname;
  private String username;
  private String password;

  @Override
  public String execute() throws Exception
  {
    if(getFirstname().isEmpty() || getLastname().isEmpty() || getUsername().isEmpty() || getPassword().isEmpty())
    {
      addActionError(getText("error.register.complete"));
      return INPUT;
    }
    else
    {
      User registeredUser = new User();
      registeredUser.setFirstname(getFirstname());
      registeredUser.setLastname(getLastname());
      registeredUser.setUsername(getUsername());
      registeredUser.setPassword(getPassword());

      addActionMessage(getText("success.register.user"));
      return SUCCESS;
    }
  }

  public String getLastname()
  {
    return lastname;
  }

  private void setLastname(String lastname)
  {
    this.lastname = lastname;
  }

  public String getFirstname()
  {
    return firstname;
  }

  private void setFirstname(String firstname)
  {
    this.firstname = firstname;
  }

  public String getUsername()
  {
    return (this.username);
  }

  public void setUsername(String username)
  {
    this.username = username;
  }

  public String getPassword()
  {
    return (this.password);
  }

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

struts.xml中：

<?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.enable.DynamicMethodInvocation" value="false" />
    <constant name="struts.devMode" value="false" />
    <constant name="struts.custom.i18n.resources" value="ApplicationResources" /> 

    <!-- Add packages here -->

        <package name="vislabWebShop" extends="struts-default">

        <!-- Add your actions here  -->

        <action name="UserForward">
            <result>/pages/Login.jsp</result>
        </action>

        <action name="UserLogin" class="vislabWebShop.controller.LoginAction">
            <result name="success">/pages/Welcome.jsp</result>
            <result name="input">/pages/Login.jsp</result>
        </action>

        <action name="UserRegister" class="vislabWebShop.controller.RegisterAction">
            <result name="success">/pages/Login.jsp</result>
            <result name="input">/pages/Register.jsp</result>
        </action>

        <action name="UserRegisterNew">
            <result>/pages/Register.jsp</result>
        </action>
    </package>


</struts>

两个属性映射成功。属性是否也可以以其他形式复制？

Answer 1

以下是错误：在RegisterAction.java我将setter方法放入private，因此无法从struts调用这些方法。将它们变成public解决了这个问题。

struts属性映射中的NullPointerException

1 个答案: