WebSocket 端点未得到解决：错误代码：404答案

【问题标题】：WebSocket EndPoint not getting resolved: Error Code: 404WebSocket 端点未得到解决：错误代码：404
【发布时间】：2021-01-16 14:16:05
【问题描述】：

我正在尝试创建一个非常基本的网络套接字应用程序。后续步骤：

创建 EchoServer java 类

    import javax.websocket.OnMessage;
    import javax.websocket.server.ServerEndpoint;
    
    @ServerEndpoint("/echo")
    public class EchoServer {
    
        @OnMessage
        public String echo(String incomingMessage) {
            return "I got this (" + incomingMessage + ") so I am sending it back";
        }
    }

使用调用上述端点的 javascript 创建 html

 <html>
 <head>
     <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
     <title>Web Socket JavaScript Echo Client</title>
     <script language="javascript" type="text/javascript">
         var echo_websocket;
         function init() {
             output = document.getElementById("output");
         }
         function send_echo() {
             var wsUri = "ws://localhost:7003/wspractice/echo";
             writeToScreen("Connecting to " + wsUri);
             echo_websocket = new WebSocket(wsUri);
             echo_websocket.onopen = function (evt) {
                 writeToScreen("Connected !");
                 doSend(textID.value);
             };
             echo_websocket.onmessage = function (evt) {
                 writeToScreen("Received message: " + evt.data);
                 echo_websocket.close();
             };
             echo_websocket.onerror = function (evt) {
                 writeToScreen('<span style="color: red;">ERROR:</span> '
                     + evt.data);
                 echo_websocket.close();
             };
         }
         function doSend(message) {
             echo_websocket.send(message);
             writeToScreen("Sent message: " + message);
         }
         function writeToScreen(message) {
             var pre = document.createElement("p");
             pre.style.wordWrap = "break-word";
             pre.innerHTML = message;
             output.appendChild(pre);
         }
         window.addEventListener("load", init, false);
     </script>
 </head>
 <body>
 <h1>Echo Server</h1>
 <div style="text-align: left;">
     <form action="">
         <input onclick="send_echo()" value="Press to send"
                type="button">
         <input id="textID" name="message" value="Hello Web Sockets"
                type="text">
         <br>
     </form>
 </div>
 <div id="output"></div>
 </body>
 </html>

在 WebLogic Server 版本：14.1.1.0.0 服务器中将上述项目部署为 war 文件（上下文路径：wspractice）。
named server configuration on weblogic(listening on port 7003)
application deployed on named server

在尝试上述 html 时，出现“WebSocket connection to 'ws://localhost:7003/wspractice/echo' failed: Error during WebSocket handshake: Unexpected response code: 404”错误。

当我尝试在 WEB-INF 中访问另一个正常的 jsp 时，它得到了正确的解析，但只有 web-socket 没有得到解析。结果如下图所示。

我知道当服务器无法找到服务时会发生 404（在这种情况下为回显），但即使“回显”端点可用，我也不明白为什么会在这种情况下发生。

Result in browser.
在 chrome、firefox 中尝试过，但结果相同。请帮助我了解为什么会这样。

【问题讨论】：

标签： javascript java websocket weblogic web-deployment

【解决方案1】：

我尝试对您的代码进行尽可能少的更改。将其作为参考。

EchoServer.java 方法 onMessage 应该有不同的签名。

import java.io.IOException;
import javax.websocket.*;
import javax.websocket.server.ServerEndpoint;

@ServerEndpoint(value = "/echo")
public class EchoServer {
    @OnMessage
    public void onMessage(final Session session, String msg) {
        System.out.println("Msg: " + msg);
        try {
            session.getBasicRemote().sendText(msg);
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }
}

html中有错别字

<html>
    <head>
        <meta charset="UTF-8">
        <title>Web Socket JavaScript Echo Client</title>
        <script language="javascript" type="text/javascript">
            var echo_websocket;
            function init() {
                output = document.getElementById("output");
            }
            function send_echo() {
                var wsUri = "ws://localhost:8080/test1/echo";
                writeToScreen("Connecting to " + wsUri);
                echo_websocket = new WebSocket(wsUri);
                echo_websocket.onopen = function (evt) {
                    writeToScreen("Connected !");
                    doSend(document.getElementById("textID").value);
                };
                echo_websocket.onmessage = function (evt) {
                    writeToScreen("Received message: " + evt.data);
                    echo_websocket.close();
                };
                echo_websocket.onerror = function (evt) {
                    writeToScreen('<span style="color: red;">ERROR:</span> ' + evt);
                    console.log(evt)
                    echo_websocket.close();
                };
            }
            function doSend(message) {
                echo_websocket.send(message);
                writeToScreen("Sent message: " + message);
            }
            function writeToScreen(message) {
                var pre = document.createElement("p");
                pre.style.wordWrap = "break-word";
                pre.innerHTML = message;
                output.appendChild(pre);
            }
            window.addEventListener("load", init, false);
        </script>
    </head>
    <body>
        <div style="text-align: left;">
            <form action="">
                <input onclick="send_echo()" value="Press to send" type="button">
                <input id="textID" name="message" value="Hello Web Sockets" type="text">
                <br>
            </form>
        </div>
        <div id="output"></div>
    </body>
</html>

以下 pom 引用 glassfish 嵌入式服务器，因此您可以通过运行以下命令测试 sn-ps

mvn package embedded-glassfish:run

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>com.smirnov</groupId>
    <artifactId>test1</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>war</packaging>

    <name>test1</name>

    <properties>
        <endorsed.dir>${project.build.directory}/endorsed</endorsed.dir>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>
    
    <dependencies>
        <dependency>
            <groupId>javax</groupId>
            <artifactId>javaee-web-api</artifactId>
            <version>7.0</version>
            <scope>provided</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.1</version>
                <configuration>
                    <source>1.7</source>
                    <target>1.7</target>
                    <compilerArguments>
                        <endorseddirs>${endorsed.dir}</endorseddirs>
                    </compilerArguments>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-war-plugin</artifactId>
                <version>2.3</version>
                <configuration>
                    <failOnMissingWebXml>false</failOnMissingWebXml>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-dependency-plugin</artifactId>
                <version>2.6</version>
                <executions>
                    <execution>
                        <phase>validate</phase>
                        <goals>
                            <goal>copy</goal>
                        </goals>
                        <configuration>
                            <outputDirectory>${endorsed.dir}</outputDirectory>
                            <silent>true</silent>
                            <artifactItems>
                                <artifactItem>
                                    <groupId>javax</groupId>
                                    <artifactId>javaee-endorsed-api</artifactId>
                                    <version>7.0</version>
                                    <type>jar</type>
                                </artifactItem>
                            </artifactItems>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>org.glassfish.embedded</groupId>
                <artifactId>maven-embedded-glassfish-plugin</artifactId>
                <version>4.0</version>
                <configuration>
                    <goalPrefix>embedded-glassfish</goalPrefix>
                    <app>${basedir}/target/${project.artifactId}-${project.version}.war</app>
                    <autoDelete>true</autoDelete>
                    <port>8080</port>
                    <name>test1</name>
                    <contextRoot>test1</contextRoot>
                </configuration>
                <executions>
                    <execution>
                        <goals>
                            <goal>deploy</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>

你可以看到这个小项目here。

【讨论】：