java-springboot下使用websocket运行单侧时报异常：javax.websocket.server.ServerContainer not available

一：原因：spring boot内带tomcat，tomcat中的websocket会有冲突出现问题

二：解决方法：

1. 为SpringbootTest注解指定参数classes和webEnvironment：@SpringBootTest(classes = WebsocketServerTestApplication.class, webEnvironment = SpringBootTest.WebEnvironment.DEFINED_PORT)

或者

2. 指定webEnvironment也可以：@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.DEFINED_PORT)

三：解析

因为WebSocket是servlet容器所支持的，所以需要加载servlet容器：
webEnvironment参数为springboot指定ApplicationContext类型。
webEnvironment = SpringBootTest.WebEnvironment.DEFINED_PORT表示内嵌的服务器将会在一个随机的端口启动。
webEnvironment 主要的值可以参考SpringbootTest源码：

/**
	 * An enumeration web environment modes.
	 */
	enum WebEnvironment {
 
		/**
		 * Creates a {@link WebApplicationContext} with a mock servlet environment if
		 * servlet APIs are on the classpath, a {@link ReactiveWebApplicationContext} if
		 * Spring WebFlux is on the classpath or a regular {@link ApplicationContext}
		 * otherwise.
		 */
		MOCK(false),
 
		/**
		 * Creates a web application context (reactive or servlet based) and sets a
		 * {@code server.port=0} {@link Environment} property (which usually triggers
		 * listening on a random port). Often used in conjunction with a
		 * {@link LocalServerPort} injected field on the test.
		 */
		RANDOM_PORT(true),
 
		/**
		 * Creates a (reactive) web application context without defining any
		 * {@code server.port=0} {@link Environment} property.
		 */
		DEFINED_PORT(true),
 
		/**
		 * Creates an {@link ApplicationContext} and sets
		 * {@link SpringApplication#setWebApplicationType(WebApplicationType)} to
		 * {@link WebApplicationType#NONE}.
		 */
		NONE(false);
 
		private final boolean embedded;
 
		WebEnvironment(boolean embedded) {
			this.embedded = embedded;
		}
 
		/**
		 * Return if the environment uses an {@link ServletWebServerApplicationContext}.
		 * @return if an {@link ServletWebServerApplicationContext} is used.
		 */
		public boolean isEmbedded() {
			return this.embedded;
		}
 
	}