使用JBang运行Camel应用时无法暴露Jetty组件路由的问题

用jbang RestCamelJbang.java执行代码时，能正常暴露8080端口的REST端点；但用camel run FirstCamel.java运行含Jetty组件的路由时，控制台无报错却显示0路由启动，http://localhost:8081/hello端点无响应。而采用REST DSL的代码通过camel run WelcomeRoute.java可正常运行，请问是否遗漏配置或需要额外服务器？

成功运行的代码（jbang执行） #

///usr/bin/env jbang "$0" "$0" : exit $?
// camel-k: language=java

//DEPS org.apache.camel:camel-bom:3.20.1@pom
//DEPS org.apache.camel:camel-core
//DEPS org.apache.camel:camel-main
//DEPS org.apache.camel:camel-jetty
//DEPS org.slf4j:slf4j-nop:2.0.6
//DEPS org.slf4j:slf4j-api:2.0.6

import org.apache.camel.*;
import org.apache.camel.builder.*;
import org.apache.camel.main.*;
import org.apache.camel.spi.*;

import static java.lang.System.*;

public class RestCamelJbang{

 public static void main(String ... args) throws Exception{
        out.println("Starting camel route...");
        setProperty("org.slf4j.simpleLogger.logFile", "System.out");
        Main main = new Main();

        main.configure().addRoutesBuilder(new RouteBuilder(){
            public void configure() throws Exception{
   out.println("Camel configuration started...");
     from("jetty:http://localhost:8080/hello")
       .transform().simple("First Message of Camel"); 
           }
         });
        main.run();
    }
}

无法正常运行的代码（camel run执行） #

///usr/bin/env jbang "$0" "$0" : exit $?
// camel-k: language=java

import org.apache.camel.*;
import org.apache.camel.builder.*;
import org.apache.camel.main.*;
import org.apache.camel.spi.*;

public class FirstCamel extends RouteBuilder{

   @Override
   public void configure() throws Exception{
      from("jetty:http://localhost:8081/hello")
       .transform().simple("First Message of Camel")
       .log("${body}");
   } 
}

控制台输出 #

2023-02-13 21:10:22.056  INFO 6884 --- [           main] org.apache.camel.main.MainSupport        : Apache Camel (JBang) 3.20.1 is starting
2023-02-13 21:10:22.511  INFO 6884 --- [           main] org.apache.camel.main.MainSupport        : Using Java 17.0.1 with PID 6884. Started by thirumurthi in C:\thiru\learn\camel\camel_lessons\lesson
2023-02-13 21:10:22.543  INFO 6884 --- [           main] he.camel.cli.connector.LocalCliConnector : Camel CLI enabled (local)
2023-02-13 21:10:24.180  INFO 6884 --- [           main] .main.download.MavenDependencyDownloader : Downloaded: org.apache.camel:camel-rest:3.20.1 (took: 1s55ms)
2023-02-13 21:10:24.471  INFO 6884 --- [           main] e.camel.impl.engine.AbstractCamelContext : Apache Camel 3.20.1 (CamelJBang) is starting
2023-02-13 21:10:24.893  INFO 6884 --- [           main] e.camel.impl.engine.AbstractCamelContext : Routes startup (started:0)
2023-02-13 21:10:24.893  INFO 6884 --- [           main] e.camel.impl.engine.AbstractCamelContext : Apache Camel 3.20.1 (CamelJBang) started in 950ms (build:289ms init:241ms start:420ms JVM-uptime:5s)

正常运行的REST DSL代码（camel run执行） #

import org.apache.camel.*;
import org.apache.camel.builder.RouteBuilder;

public class WelcomeRoute extends RouteBuilder {

   @Override
   public void configure() throws Exception {

          restConfiguration().bindingMode("auto");

                rest("/api")
                        .get("/demo/{info}")
                        .to("log:info")
                        .to("direct:msg");
                from("direct:msg")
                                .transform().simple("msg received - ${header.info}");
   }
}

问题原因与解决方案 #

核心原因 #

无法运行的代码缺少Jetty组件依赖声明。Camel CLI的camel run命令默认不会自动下载所有组件依赖，REST DSL代码能运行是因为Camel自动引入了camel-rest相关依赖（控制台日志也显示下载了camel-rest），但Jetty作为独立组件需要显式声明。

解决方案 #

修改FirstCamel.java，添加Jetty及必要依赖的声明：

///usr/bin/env jbang "$0" "$0" : exit $?
// camel-k: language=java

//DEPS org.apache.camel:camel-bom:3.20.1@pom
//DEPS org.apache.camel:camel-core
//DEPS org.apache.camel:camel-main
//DEPS org.apache.camel:camel-jetty
//DEPS org.slf4j:slf4j-nop:2.0.6
//DEPS org.slf4j:slf4j-api:2.0.6

import org.apache.camel.*;
import org.apache.camel.builder.*;
import org.apache.camel.main.*;
import org.apache.camel.spi.*;

public class FirstCamel extends RouteBuilder{

   @Override
   public void configure() throws Exception{
      from("jetty:http://localhost:8081/hello")
       .transform().simple("First Message of Camel")
       .log("${body}");
   } 
}

重新执行camel run FirstCamel.java，此时Camel会自动下载Jetty组件依赖，路由即可正常启动，http://localhost:8081/hello端点也能正常响应。

补充说明 #

• 成功运行的jbang代码中已经显式声明了所有依赖，所以能正常加载Jetty组件；
• 也可以通过命令行参数指定依赖，无需修改代码：camel run FirstCamel.java --dependency org.apache.camel:camel-jetty:3.20.1

内容的提问来源于stack exchange，提问作者Tim