Question

我在一个项目中工作，我需要创建一个实时的Web应用程序。我已经开发了一个用Apache Tomcat测试WebSockets的小程序，但是它不起作用而是抛出AbstractMethodError异常。 servlet编译并且Web应用程序部署得很好。

这是servlet的代码。

public class TestWebSocket extends WebSocketServlet {

    private static final long serialVersionUID = 1L;

    @Override
    protected boolean verifyOrigin(String origin) {
        System.out.println("Origin: {}" + origin);
        return true;
    }

    @Override
    protected StreamInbound createWebSocketInbound(String subProtocol, HttpServletRequest request) {
        return new WebSocketConnection();
    }

    private static class WebSocketConnection extends MessageInbound {

        @Override
        protected void onOpen(WsOutbound outbound) {
            System.out.println("Conexión abierta");
        }

        @Override
        protected void onClose(int status) {
            System.out.println("Conexión cerrada");
        }

        @Override
        protected void onBinaryMessage(ByteBuffer byteBuffer) throws IOException {
            System.out.println("No se soportan mensajes binarios");
            throw new UnsupportedOperationException("No se soportan mensajes binarios");
        }

        @Override
        protected void onTextMessage(CharBuffer charBuffer) throws IOException {
            final String user = charBuffer.toString();
            System.out.println("Mensaje recibido: {}" + user);
            getWsOutbound().writeTextMessage(CharBuffer.wrap("Hola " + user + " desde WebSocket"));
        }
    }
}

这是部署描述符 - web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
  <display-name>TestWebSocket</display-name>
  <servlet>
    <servlet-name>TestWebSocket</servlet-name>
    <servlet-class>com.test.TestWebSocket</servlet-class>
  </servlet> 
  <servlet-mapping>
    <servlet-name>TestWebSocket</servlet-name>
    <url-pattern>/testWebSocket</url-pattern>
  </servlet-mapping>
</web-app>

客户端代码 - testSocket.js：

/*
 * For Testing websockets
 */
$(function(){

    console.log("URL :" + 'ws://' + location.host  + '/TestTomcatWebSocket/testWebSocket');
    var ws = new WebSocket('ws://' + location.host  + '/TestTomcatWebSocket/testWebSocket');

    ws.onopen = function() {
        console.log("Websocket Ready!!");
        sendMessage();
    };

    ws.onmessage= function(data) {
        console.log("message received : " + data);
    };

    function sendMessage() { ws.send("Test"); };
});

执行后，应用程序完成以下java.lang.AbstractMethodError异常：

INFO: Server startup in 495 ms
Origin: {}http://localhost:8080
Dec 17, 2012 1:58:51 AM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet [TestWebSocket] in context with path [/TestTomcatWebSocket] threw exception [Servlet execution threw an exception] with root cause
java.lang.AbstractMethodError: org.apache.catalina.websocket.WebSocketServlet.createWebSocketInbound(Ljava/lang/String;)Lorg/apache/catalina/websocket/StreamInbound;
    at org.apache.catalina.websocket.WebSocketServlet.doGet(WebSocketServlet.java:125)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:225)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:927)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:999)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:565)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:307)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)

我使用的是Apache Tomcat 7.0.33。

Answer 1

问题解决了。基本上我使用的是旧版本的eclipse，它根据tomcat的早期配置在其中运行tomcat来配置tomcat。因此，当我使用eclipse的最新版本JUNO时，它使用tomcats最新配置配置它，其中包括catilina.policy文件中的websocket配置。

//使用WebSocket的应用程序需要能够访问此程序包权限java.lang.RuntimePermission "accessClassInPackage.org.apache.catalina.websocket";

当自定义servlet运行时，Tomcat会为WebSocketServlet.createWebSocketInbound（）抛出AbstractMethodError

1 个答案: