无法将Maven强制转换为javax.servlet.Filter [英] Maven cannot be cast to javax.servlet.Filter
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问题描述
我开始使用Maven开发项目，但是当我启动它时，它说我的过滤器无法转换为javax.servle.Filter.
I'm beginning to develope a project using maven but when I launch it it say that my Filter cannot be cast to javax.servle.Filter.
这是一个例外:
GRAVE: Exception starting filter FilterLogin
java.lang.ClassCastException: it.tgi.cd.servlet.FilterLogin cannot be cast to javax.servlet.Filter
at org.apache.catalina.core.ApplicationFilterConfig.getFilter(ApplicationFilterConfig.java:260)
at org.apache.catalina.core.ApplicationFilterConfig.<init>(ApplicationFilterConfig.java:107)
at org.apache.catalina.core.StandardContext.filterStart(StandardContext.java:4775)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5452)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1559)
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1549)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
这是我的 pom.xml
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>it.project</groupId>
<artifactId>Projet</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>war</packaging>
<dependencies>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-core</artifactId>
<version>5.2.2.Final</version>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>4.0.0-b01</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.7.21</version>
</dependency>
<dependency>
<groupId>org.apache.tomcat</groupId>
<artifactId>tomcat-catalina</artifactId>
<version>8.0.32</version>
</dependency>
</dependencies>
<build>
<finalName>SimpleProject</finalName>
<plugins>
<!-- Config: Maven Tomcat Plugin -->
<!-- http://mvnrepository.com/artifact/org.apache.tomcat.maven/tomcat7-maven-plugin -->
<plugin>
<groupId>org.apache.tomcat.maven</groupId>
<artifactId>tomcat7-maven-plugin</artifactId>
<version>2.2</version>
<!-- Config: contextPath and Port (Default - /SimpleProject : 8080) -->
<!--
<configuration>
<path>/</path>
<port>8899</port>
</configuration>
-->
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>1.7</source>
<target>1.7</target>
</configuration>
</plugin>
</plugins>
</build>
</project>
为什么我会收到此错误?
Why I'm getting this error?
FilteLogin
package it.tgi.cd.servlet;
import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebFilter(urlPatterns = {"/index.jsp", "/insert.jsp", "/search.jsp", "/addSongs.jsp", "/delete.jsp"}, filterName = "FilterLogin")
public class FilterLogin implements javax.servlet.Filter {
public void destroy() {
}
public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException {
HttpServletRequest request = (HttpServletRequest) req;
HttpServletResponse response = (HttpServletResponse) resp;
if(request.getSession().getAttribute("user") != null) {
chain.doFilter(req, resp);
} else {
response.sendRedirect("/login.jsp");
}
}
public void init(FilterConfig config) throws ServletException {
}
}
我按照建议使用了"provide"，但该异常消失了，但是现在当我尝试转到"localhost ecc .."时，出现了一个异常
I used "provide" as suggested and the exception disappear but now when I try to go to "localhost ecc.." there is an exception
INFORMAZIONI: Starting ProtocolHandler ["http-bio-8080"]
ott 04, 2016 3:06:42 PM org.apache.catalina.core.StandardWrapperValve invoke
GRAVE: Servlet.service() for servlet [jsp] in context with path [/CDStore] threw exception [java.lang.NullPointerException] with root cause
java.lang.NullPointerException
at org.apache.jsp.login_jsp._jspInit(login_jsp.java:31)
at org.apache.jasper.runtime.HttpJspBase.init(HttpJspBase.java:49)
at org.apache.jasper.servlet.JspServletWrapper.getServlet(JspServletWrapper.java:180)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:369)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:953)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1041)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:603)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
我不知道这是否正常，但仍然停留在"INFORMAZIONI:正在启动ProtocolHandler ["http-bio-8080"]"
I don't know if it is normal but it remainsstuck on "INFORMAZIONI: Starting ProtocolHandler ["http-bio-8080"]"
然后我进入本地主机，该异常消失.
Then I go to the localhost and the exception disappears.
在WEB-INF/lib下，我没有任何jar文件. 这是我的构建路径
Under WEB-INF/lib I didn't have any jar file. This is my build path
推荐答案
1)，如下所示在pom.xml中添加servlet依赖项:
1) Add the servlet dependency in pom.xml as below:
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>3.0.1</version>
<scope>provided</scope>
</dependency>
2)确保没有用多个不同版本的javax.servlet.Filter类填充您的类路径.
检查servlet-api.jar文件夹中是否存在servlet-api.jar.您必须在pom.xml或build-path中添加依赖项.
2) Make sure that your classpath is not populated with multiple different versions of javax.servlet.Filter classes.
Check for servlet-api.jar does exists in /WEB-INF/libfolder. you must add the dependency either in pom.xml or in your build-path.
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