javax.servlet.ServletException：过滤器执行引发异常 - java.lang.ExceptionInInitializerError

Question

我正在为学校做一个用户管理 Web 应用程序项目，当我部署到 Tomcat 时，出现此错误。

其他：在web.xml上，当我尝试添加时，Intellij无法识别UserFilter类。我有一个名为 UserFilter 的类，具有正确的路径。

HTTP Status 500 - Filter execution threw an exception
type Exception report

message Filter execution threw an exception

description The server encountered an internal error that prevented it from fulfilling this request.

exception

javax.servlet.ServletException: Filter execution threw an exception
root cause

java.lang.ExceptionInInitializerError
    teste.web.SecurityFilter.openSession(SecurityFilter.java:26)
    teste.web.SecurityFilter.doFilter(SecurityFilter.java:19)
root cause

java.lang.NullPointerException
    java.util.Properties$LineReader.readLine(Properties.java:434)
    java.util.Properties.load0(Properties.java:353)
    java.util.Properties.load(Properties.java:341)
    teste.pluginSession.PluginFactory.<clinit>(PluginFactory.java:12)
    teste.web.SecurityFilter.openSession(SecurityFilter.java:26)
    teste.web.SecurityFilter.doFilter(SecurityFilter.java:19)
note The full stack trace of the root cause is available in the Apache Tomcat/9.0.0.M6 logs.

Apache Tomcat/9.0.0.M6

SecurityFilter.java

package teste.web;

import javax.servlet.*;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

import teste.pluginSession.*;

public class  SecurityFilter implements Filter {

    @Override
    public void init (FilterConfig filterConfig) throws ServletException{

    }

    @Override
    public void doFilter (ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException{
        HttpServletResponse response = (HttpServletResponse) servletResponse;
        openSession (servletRequest,filterChain, response);
    }

    private void openSession(ServletRequest servletRequest, FilterChain filterChain, HttpServletResponse response) throws IOException, ServletException{
        RegisterSession plugin = null;

        try {
            plugin = (RegisterSession) PluginFactory.getPlugin(RegisterSession.class);
            plugin.openSession(servletRequest,filterChain,response);
        } catch (ClassNotFoundException e){
            e.printStackTrace();
        }catch (IllegalAccessException e){
            e.printStackTrace();
        }catch (InstantiationException e){
            e.printStackTrace();
        }

    }


    @Override
    public void destroy() {

    }
}

PluginFactory

package teste.pluginSession;

import java.io.IOException;
import java.util.Properties;

public class PluginFactory
{
    static Properties properties = new Properties();
    static
    {
        try {
            properties.load(PluginFactory.class.getResourceAsStream("/plugins.properties"));
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static Object getPlugin(Class iface) throws ClassNotFoundException, IllegalAccessException, InstantiationException
    {
        String classNameVerdadeiro = properties.getProperty(iface.getName());
        return Class.forName(classNameVerdadeiro).newInstance();
    }
}

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4"
         xmlns="http://java.sun.com/xml/ns/j2ee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"  >


    <filter>
        <filter-name>UserFilter</filter-name>
        <filter-class>teste.web.UserFilter</filter-class>
    </filter>

    <filter-mapping>
        <filter-name>UserFilter</filter-name>
        <url-pattern>/user/*</url-pattern>
    </filter-mapping>


    <filter>
        <filter-name>SecurityFilter</filter-name>
        <filter-class>teste.web.SecurityFilter</filter-class>
    </filter>

    <filter-mapping>
        <filter-name>SecurityFilter</filter-name>
        <url-pattern>*</url-pattern>
    </filter-mapping>

    <servlet>
        <servlet-name>LoginServlet</servlet-name>
        <servlet-class>teste.web.LoginServlet</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>LoginServlet</servlet-name>
        <url-pattern>/login</url-pattern>
    </servlet-mapping>


    <servlet>
        <servlet-name>LogoutServlet</servlet-name>
        <servlet-class>teste.web.LogoutServlet</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>LogoutServlet</servlet-name>
        <url-pattern>/logout</url-pattern>
    </servlet-mapping>

    <servlet>
        <servlet-name>Rest</servlet-name>
        <servlet-class>teste.web.RestServlet</servlet-class>
    </servlet>


    <servlet-mapping>
        <servlet-name>Rest</servlet-name>
        <url-pattern>/soa</url-pattern>
    </servlet-mapping>



    <error-page>
        <error-code>404</error-code>
        <location>/errors/erro404.jsp</location>
    </error-page>

    <!--START FILES-->
    <welcome-file-list>
        <welcome-file>login.jsp</welcome-file>
    </welcome-file-list>


</web-app>

login.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ page import="teste.web.LoginServlet" %>
<html>
<head>
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.4.1/css/bootstrap.min.css">

    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>

    <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.4.1/js/bootstrap.min.js"></script>
    <title>Login</title>
    <style>
        .login-form {
        border: hidden;
            padding: 20px;
            position: fixed;
            left: 50%;
            top: 50%;
            transform: translate(-50%, -50%);
        }
        .form-group{
            padding-left:40px;
            padding-right:40px;
        }
        h3{
            text-align: center;
        }

        body{
            background-color: darkslateblue;
        }
    </style>
</head>
<body>
<div class="container" style="text-align:center;color:white;transform: translate(0%, 400%);">
    <h2><strong>Soft</strong>Ware</h2>
</div>

<div class="container login-form">
    <div class="panel panel-default">
        <div class="panel-body">
            <form class="form-horizontal" action="<%=request.getContextPath()%>/login" method="POST">
                <div class="input-group" style="padding-bottom: 10px;">
                    <span class="input-group-addon"><i class="glyphicon glyphicon-user"></i></span>
                    <input id="username" class="form-control" placeholder="Username" type="text" name="username">
                </div>

                <div class="input-group">
                    <span class="input-group-addon"><i class="glyphicon glyphicon-lock"></i></span>
                    <input id="password" class="form-control" placeholder="Password" type="password" name="password">
                </div>
                <div class="form-group" style="text-align: center;padding-top: 10px;">
                    <button type="submit" class="btn btn-success" onclick=""><span class="glyphicon glyphicon-ok"></span>  Submeter</button>
                </div>
            </form>
        </div>
    </div>
</div>

</body>
</html>

非常感谢！