调用处理程序之前使用Tomcat 8和Spring 4 ClassCastException的websockets

问题描述

我正在尝试使用一个简单的websocket来集成到我的应用程序中。但是我无法使用Spring API，在调用我的处理程序尝试将Tomcat类型转换为javax对象之前的某个地方使用ClassCastException。如果我只是在没有Spring的情况下直接使用Tomcat（那么javax.websocket对象和注释）它可以很好地工作，所以我真的不确定为什么Spring存在问题。

I am trying to get a simple websocket to work to integrate into my application. However I have not been able to get it to work with the Spring API's, with a ClassCastException somewhere before my handler is invoked trying to convert a Tomcat type to a javax object. If I just use Tomcat directly without Spring (so the javax.websocket objects and annotations) it works perfectly, so I am really not sure why there is an issue with Spring.

08-May-2014 01:10:12.048 SEVERE [http-nio-8084-exec-88] org.apache.catalina.core.StandardWrapperValve.invoke Servlet.service() for servlet [dispatcher] in context with path [/WebsocketSpringTest] threw exception [Request processing failed; nested exception is org.springframework.web.socket.server.HandshakeFailureException: Uncaught failure for request http://localhost:8084/WebsocketSpringTest/socket; nested exception is java.lang.ClassCastException: org.apache.tomcat.websocket.server.WsServerContainer cannot be cast to javax.websocket.server.ServerContainer] with root cause
java.lang.ClassCastException: org.apache.tomcat.websocket.server.WsServerContainer cannot be cast to javax.websocket.server.ServerContainer
at org.springframework.web.socket.server.standard.AbstractStandardUpgradeStrategy.getContainer(AbstractStandardUpgradeStrategy.java:67)

TestSocket.java

TestSocket.java

import org.springframework.web.socket.WebSocketHandler;
public class TestSocket implements WebSocketHandler {
    ...

web.xml

<servlet>
    <servlet-name>dispatcher</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
    <servlet-name>dispatcher</servlet-name>
    <url-pattern>/</url-pattern>
</servlet-mapping>

dispatcher-servlet.xml

dispatcher-servlet.xml

<context:component-scan base-package="com.willnewbery.websocketspringtest" />
<context:annotation-config />
<mvc:annotation-driven />
<mvc:resources mapping="/resources/**" location="/resources/" />
<bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver"
        p:prefix="/WEB-INF/views/" p:suffix=".jsp" />
<websocket:handlers>
    <websocket:mapping path="/socket" handler="socket"/>
</websocket:handlers>
<bean id="socket" class="com.willnewbery.websocketspringtest.TestSocket"/>

pom.xml

<properties>
    <endorsed.dir>${project.build.directory}/endorsed</endorsed.dir>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <spring.version>4.0.4.RELEASE</spring.version>
    <tomcat.version>8.0.3</tomcat.version>
</properties>

<dependencies>
    <!--javax-->
    <dependency>
        <groupId>javax</groupId>
        <artifactId>javaee-web-api</artifactId>
        <version>7.0</version>
        <scope>provided</scope>
    </dependency>
    <dependency>
        <groupId>javax.websocket</groupId>
        <artifactId>javax.websocket-api</artifactId>
        <version>1.0</version>
    </dependency>
    <!--spring-->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-core</artifactId>
        <version>${spring.version}</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-web</artifactId>
        <version>${spring.version}</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-webmvc</artifactId>
        <version>${spring.version}</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-websocket</artifactId>
        <version>${spring.version}</version>
    </dependency>
    <!--tomcat-->
</dependencies>

推荐答案

javax.websocket-api依赖关系可能是问题。它已经包含在服务器库中，因此您至少将其范围提供或尝试删除它，您很可能在应用程序pom中不需要它。

The "javax.websocket-api" dependency may be the issue. It is already included in the server lib so you at least make it scope "provided" or try removing it, there is a good chance you don't need it in the application pom.

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