Websockets with Tomcat 8 and Spring 4 ClassCastException before calling the handler

Question

I am trying to get a simple websocket to work for integration into my application. However, I was not able to get it to work with the Spring API with a ClassCastException exception somewhere before a handler was called trying to convert the Tomcat type to a javax object. If I just use Tomcat directly without Spring (so javax.websocket objects and annotations) it works fine, so I'm really not sure why there is a problem 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

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

<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>

Answer 1

"javax.websocket-api" . , "" , , pom.

Answer 2

tomcat-embed-websocket spring -boot-starter-web;

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
            <exclusions>
                <exclusion>
                    <artifactId>tomcat-embed-logging-juli</artifactId>
                    <groupId>org.apache.tomcat.embed</groupId>
                </exclusion>
                <exclusion>
                    <artifactId>tomcat-embed-websocket</artifactId>
                    <groupId>org.apache.tomcat.embed</groupId>
                </exclusion>
                <exclusion>
                    <artifactId>tomcat-embed-el</artifactId>
                    <groupId>org.apache.tomcat.embed</groupId>
                </exclusion>
            </exclusions>
        </dependency>

Answer 3

tomcat-embed-websocket - *. jar .

build.gradle

providedCompile("org.apache.tomcat.embed:tomcat-embed-websocket")

Maven:

 <dependency>
        <groupId>org.apache.tomcat.embed</groupId>
        <artifactId>tomcat-embed-websocket</artifactId>
        <version>${tomcat.version}</version>
 </dependency>

Answer 4

When it comes to creating a WAR file using Spring Boot, the referenced documents indicate that you need to turn Tomcat into a provided dependency. Recommended practices for Maven and Gradle can be seen in the help docs here => http://docs.spring.io/spring-boot/docs/current/reference/htmlsingle/#howto-create-a-deployable-war-file