第一个confluence servlet插件，ClassCastException问题

2023-12-25

我正在尝试为 Confluence 制作一个“hello world”servlet 插件。在 atlassian-plugin.xml 中，我有

<servlet name="testservlet" key="testservlet" class="com.test.confluence.plugins.testservlet.TestServlet">
    <description>A test servlet.</description>
    <url-pattern>/testservlet</url-pattern>
</servlet>

在 pom.xml 中，我有

<dependency>
    <groupId>javax.servlet</groupId>
    <artifactId>servlet-api</artifactId>
    <version>2.5</version>
</dependency>

这是servlet

package com.test.confluence.plugins.testservlet;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;

public class TestServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        out.println("Hello World");
        out.close();
    }
}

它构建并安装，但是当我点击 /confluence/plugins/servlet/testservlet 处的 servlet 时，我得到一个未找到的页面，并且出现以下 ClassCastException：

[INFO] [talledLocalContainer]  -- url: /confluence/plugins/servlet/testservlet | userName: admin
[INFO] [talledLocalContainer] com.atlassian.util.concurrent.LazyReference$InitializationException: java.lang.ClassCastException: com.test.confluence.plugins.testservlet.TestServlet cannot be cast to javax.servlet.http.HttpServlet

编辑：这是完整的堆栈跟踪：

[INFO] [talledLocalContainer] 2011-08-12 09:56:57,910 ERROR [http-1990-5] [atlassian.plugin.servlet.DefaultServletModuleManager] getServlet Unable to
create servlet
[INFO] [talledLocalContainer]  -- url: /confluence/plugins/servlet/testservlet | userName: admin
[INFO] [talledLocalContainer] com.atlassian.util.concurrent.LazyReference$InitializationException: java.lang.ClassCastException: com.test.confluence.p
lugins.testservlet.TestServlet cannot be cast to javax.servlet.http.HttpServlet
[INFO] [talledLocalContainer]   at com.atlassian.util.concurrent.LazyReference.getInterruptibly(LazyReference.java:148)
[INFO] [talledLocalContainer]   at com.atlassian.util.concurrent.LazyReference.get(LazyReference.java:111)
[INFO] [talledLocalContainer]   at com.atlassian.plugin.servlet.DefaultServletModuleManager.getServlet(DefaultServletModuleManager.java:313)
[INFO] [talledLocalContainer]   at com.atlassian.plugin.servlet.DefaultServletModuleManager.getServlet(DefaultServletModuleManager.java:146)
[INFO] [talledLocalContainer]   at com.atlassian.plugin.servlet.ServletModuleContainerServlet.service(ServletModuleContainerServlet.java:41)
[INFO] [talledLocalContainer]   at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
[INFO] [talledLocalContainer]   at com.atlassian.plugin.servlet.filter.IteratingFilterChain.doFilter(IteratingFilterChain.java:46)
[INFO] [talledLocalContainer]   at com.atlassian.plugin.servlet.filter.DelegatingPluginFilter$1.doFilter(DelegatingPluginFilter.java:66)
[INFO] [talledLocalContainer]   at com.atlassian.applinks.core.rest.context.ContextFilter.doFilter(ContextFilter.java:25)
[INFO] [talledLocalContainer]   at com.atlassian.plugin.servlet.filter.DelegatingPluginFilter.doFilter(DelegatingPluginFilter.java:74)
[INFO] [talledLocalContainer]   at com.atlassian.plugin.servlet.filter.IteratingFilterChain.doFilter(IteratingFilterChain.java:42)
[INFO] [talledLocalContainer]   at com.atlassian.plugin.servlet.filter.DelegatingPluginFilter$1.doFilter(DelegatingPluginFilter.java:66)
[INFO] [talledLocalContainer]   at com.atlassian.labs.httpservice.resource.ResourceFilter.doFilter(ResourceFilter.java:59)
[INFO] [talledLocalContainer]   at com.atlassian.plugin.servlet.filter.DelegatingPluginFilter.doFilter(DelegatingPluginFilter.java:74)
[INFO] [talledLocalContainer]   at com.atlassian.plugin.servlet.filter.IteratingFilterChain.doFilter(IteratingFilterChain.java:42)
[INFO] [talledLocalContainer]   at com.atlassian.plugin.servlet.filter.ServletFilterModuleContainerFilter.doFilter(ServletFilterModuleContainerFilter.
java:77)
[INFO] [talledLocalContainer]   at com.atlassian.plugin.servlet.filter.ServletFilterModuleContainerFilter.doFilter(ServletFilterModuleContainerFilter.
java:63)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
[INFO] [talledLocalContainer]   at com.atlassian.confluence.security.websudo.MessagesDecoratorFilter.doFilter(MessagesDecoratorFilter.java:49)
[INFO] [talledLocalContainer]   at com.atlassian.core.filters.AbstractHttpFilter.doFilter(AbstractHttpFilter.java:31)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
[INFO] [talledLocalContainer]   at com.opensymphony.module.sitemesh.filter.PageFilter.parsePage(PageFilter.java:118)
[INFO] [talledLocalContainer]   at com.atlassian.confluence.util.profiling.ProfilingPageFilter.parsePage(ProfilingPageFilter.java:84)
[INFO] [talledLocalContainer]   at com.opensymphony.module.sitemesh.filter.PageFilter.doFilter(PageFilter.java:54)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
[INFO] [talledLocalContainer]   at com.atlassian.plugin.servlet.filter.IteratingFilterChain.doFilter(IteratingFilterChain.java:46)
[INFO] [talledLocalContainer]   at com.atlassian.plugin.servlet.filter.ServletFilterModuleContainerFilter.doFilter(ServletFilterModuleContainerFilter.
java:77)
[INFO] [talledLocalContainer]   at com.atlassian.plugin.servlet.filter.ServletFilterModuleContainerFilter.doFilter(ServletFilterModuleContainerFilter.
java:63)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
[INFO] [talledLocalContainer]   at com.atlassian.confluence.util.LoggingContextFilter.doFilter(LoggingContextFilter.java:40)
[INFO] [talledLocalContainer]   at com.atlassian.core.filters.AbstractHttpFilter.doFilter(AbstractHttpFilter.java:31)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
[INFO] [talledLocalContainer]   at com.atlassian.seraph.filter.SecurityFilter.doFilter(SecurityFilter.java:213)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
[INFO] [talledLocalContainer]   at com.atlassian.security.auth.trustedapps.filter.TrustedApplicationsFilter.doFilter(TrustedApplicationsFilter.java:98
)
[INFO] [talledLocalContainer]   at com.atlassian.confluence.util.AbstractBootstrapHotSwappingFilter.doFilter(AbstractBootstrapHotSwappingFilter.java:3
0)
[INFO] [talledLocalContainer]   at com.atlassian.core.filters.AbstractHttpFilter.doFilter(AbstractHttpFilter.java:31)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
[INFO] [talledLocalContainer]   at com.atlassian.seraph.filter.BaseLoginFilter.doFilter(BaseLoginFilter.java:144)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
[INFO] [talledLocalContainer]   at com.atlassian.plugin.servlet.filter.IteratingFilterChain.doFilter(IteratingFilterChain.java:46)
[INFO] [talledLocalContainer]   at com.atlassian.plugin.servlet.filter.DelegatingPluginFilter$1.doFilter(DelegatingPluginFilter.java:66)
[INFO] [talledLocalContainer]   at com.atlassian.oauth.serviceprovider.internal.servlet.OAuthFilter.doFilter(OAuthFilter.java:71)
[INFO] [talledLocalContainer]   at com.atlassian.plugin.servlet.filter.DelegatingPluginFilter.doFilter(DelegatingPluginFilter.java:74)
[INFO] [talledLocalContainer]   at com.atlassian.plugin.servlet.filter.IteratingFilterChain.doFilter(IteratingFilterChain.java:42)
[INFO] [talledLocalContainer]   at com.atlassian.plugin.servlet.filter.ServletFilterModuleContainerFilter.doFilter(ServletFilterModuleContainerFilter.
java:77)
[INFO] [talledLocalContainer]   at com.atlassian.plugin.servlet.filter.ServletFilterModuleContainerFilter.doFilter(ServletFilterModuleContainerFilter.
java:63)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
[INFO] [talledLocalContainer]   at com.atlassian.confluence.util.ClusterHeaderFilter.doFilter(ClusterHeaderFilter.java:34)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
[INFO] [talledLocalContainer]   at com.atlassian.johnson.filters.AbstractJohnsonFilter.doFilter(AbstractJohnsonFilter.java:72)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
[INFO] [talledLocalContainer]   at org.springframework.orm.hibernate.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:170
)
[INFO] [talledLocalContainer]   at com.atlassian.spring.filter.FlushingSpringSessionInViewFilter.doFilterInternal(FlushingSpringSessionInViewFilter.ja
va:29)
[INFO] [talledLocalContainer]   at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:75)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
[INFO] [talledLocalContainer]   at com.atlassian.confluence.util.ConfluenceErrorFilter.doFilter(ConfluenceErrorFilter.java:22)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
[INFO] [talledLocalContainer]   at com.atlassian.util.profiling.filters.ProfilingFilter.doFilter(ProfilingFilter.java:99)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
[INFO] [talledLocalContainer]   at com.atlassian.confluence.core.datetime.RequestTimeThreadLocalFilter.doFilter(RequestTimeThreadLocalFilter.java:35)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
[INFO] [talledLocalContainer]   at com.atlassian.gzipfilter.GzipFilter.doFilterInternal(GzipFilter.java:81)
[INFO] [talledLocalContainer]   at com.atlassian.gzipfilter.GzipFilter.doFilter(GzipFilter.java:51)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
[INFO] [talledLocalContainer]   at com.atlassian.core.filters.cache.AbstractCachingFilter.doFilter(AbstractCachingFilter.java:33)
[INFO] [talledLocalContainer]   at com.atlassian.core.filters.AbstractHttpFilter.doFilter(AbstractHttpFilter.java:31)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
[INFO] [talledLocalContainer]   at com.atlassian.plugin.servlet.filter.IteratingFilterChain.doFilter(IteratingFilterChain.java:46)
[INFO] [talledLocalContainer]   at com.atlassian.plugin.servlet.filter.DelegatingPluginFilter$1.doFilter(DelegatingPluginFilter.java:66)
[INFO] [talledLocalContainer]   at com.atlassian.confluence.extra.webdav.servlet.filter.AbstractHttpFilter.doFilter(AbstractHttpFilter.java:43)
[INFO] [talledLocalContainer]   at com.atlassian.plugin.servlet.filter.DelegatingPluginFilter.doFilter(DelegatingPluginFilter.java:74)
[INFO] [talledLocalContainer]   at com.atlassian.plugin.servlet.filter.IteratingFilterChain.doFilter(IteratingFilterChain.java:42)
[INFO] [talledLocalContainer]   at com.atlassian.plugin.servlet.filter.ServletFilterModuleContainerFilter.doFilter(ServletFilterModuleContainerFilter.
java:77)
[INFO] [talledLocalContainer]   at com.atlassian.plugin.servlet.filter.ServletFilterModuleContainerFilter.doFilter(ServletFilterModuleContainerFilter.
java:63)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
[INFO] [talledLocalContainer]   at com.atlassian.confluence.web.filter.validateparam.RequestParamValidationFilter.doFilter(RequestParamValidationFilte
r.java:58)
[INFO] [talledLocalContainer]   at com.atlassian.core.filters.AbstractHttpFilter.doFilter(AbstractHttpFilter.java:31)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
[INFO] [talledLocalContainer]   at com.atlassian.confluence.plugin.servlet.filter.ActionContextCleanUp.doFilter(ActionContextCleanUp.java:71)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
[INFO] [talledLocalContainer]   at com.atlassian.confluence.web.filter.LanguageExtractionFilter.doFilter(LanguageExtractionFilter.java:52)
[INFO] [talledLocalContainer]   at com.atlassian.core.filters.AbstractHttpFilter.doFilter(AbstractHttpFilter.java:31)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
[INFO] [talledLocalContainer]   at com.atlassian.confluence.util.RequestCacheThreadLocalFilter.doFilter(RequestCacheThreadLocalFilter.java:25)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
[INFO] [talledLocalContainer]   at com.atlassian.core.filters.encoding.AbstractEncodingFilter.doFilter(AbstractEncodingFilter.java:41)
[INFO] [talledLocalContainer]   at com.atlassian.core.filters.AbstractHttpFilter.doFilter(AbstractHttpFilter.java:31)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
[INFO] [talledLocalContainer]   at com.atlassian.core.filters.HeaderSanitisingFilter.doFilter(HeaderSanitisingFilter.java:44)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
[INFO] [talledLocalContainer]   at com.atlassian.confluence.servlet.FourOhFourErrorLoggingFilter.doFilter(FourOhFourErrorLoggingFilter.java:65)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
[INFO] [talledLocalContainer]   at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
[INFO] [talledLocalContainer]   at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:567)
[INFO] [talledLocalContainer]   at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
[INFO] [talledLocalContainer]   at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
[INFO] [talledLocalContainer]   at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:849)
[INFO] [talledLocalContainer]   at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
[INFO] [talledLocalContainer]   at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:454)
[INFO] [talledLocalContainer]   at java.lang.Thread.run(Thread.java:662)
[INFO] [talledLocalContainer] Caused by: java.lang.ClassCastException: com.test.confluence.plugins.testservlet.TestServlet cannot be cast to javax.ser
vlet.http.HttpServlet
[INFO] [talledLocalContainer]   at com.atlassian.plugin.servlet.descriptors.ServletModuleDescriptor.getModule(ServletModuleDescriptor.java:50)
[INFO] [talledLocalContainer]   at com.atlassian.plugin.servlet.DelegatingPluginServlet.<init>(DelegatingPluginServlet.java:33)
[INFO] [talledLocalContainer]   at com.atlassian.plugin.servlet.DefaultServletModuleManager$LazyLoadedServletReference.create(DefaultServletModuleMana
ger.java:430)
[INFO] [talledLocalContainer]   at com.atlassian.plugin.servlet.DefaultServletModuleManager$LazyLoadedServletReference.create(DefaultServletModuleMana
ger.java:416)
[INFO] [talledLocalContainer]   at com.atlassian.util.concurrent.LazyReference$Sync.run(LazyReference.java:316)
[INFO] [talledLocalContainer]   at com.atlassian.util.concurrent.LazyReference.getInterruptibly(LazyReference.java:142)
[INFO] [talledLocalContainer]   ... 130 more

依赖于servlet-api应始终声明为provided，因为在运行时它已经由 servlet 容器提供了：

<dependency>
    <groupId>javax.servlet</groupId>
    <artifactId>servlet-api</artifactId>
    <version>2.5</version>
    <scope>provided</scope>
</dependency>

否则，您将获得由不同类加载器加载的两组 servlet API 类，从而不可避免地出现类转换问题。

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