为什么我们使用 <cxf:rsServer>与普通的 <jaxrs:server> 不同.使用 CXF-RS 组件时?

问题描述

作为this question的后续，我仍然对如何正确使用CXF-RS有点困惑组件.

As a follow-up to this question, I'm still a bit confused about how to properly use the CXF-RS component.

当我可以使用 <jaxrs:server> 标签非常好.

I'm confused why we need the <cxf:rsServer> tag for specifying CXF-RS endpoints (or is there even such a concept?), when I can use the <jaxrs:server> tag perfectly fine.

这是我对 Camel 和 CXF 的配置 XML:

Here's my configuration XML for both Camel and CXF:

<beans xmlns="http://www.51sjk.com/Upload/Articles/1/0/336/336738_20221115094851810.jpg"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xmlns:context="http://www.51sjk.com/Upload/Articles/1/0/336/336738_20221115094852574.jpg"
    xmlns:jaxrs="http://www.51sjk.com/Upload/Articles/1/0/336/336738_20221115094904653.jpg"
    xmlns:camel="http://www.51sjk.com/Upload/Articles/1/0/336/336738_20221115094905340.jpg"
    xsi:schemaLocation="http://www.51sjk.com/Upload/Articles/1/0/336/336738_20221115094851810.jpg http://www.51sjk.com/Upload/Articles/1/0/336/336738_20221115094851810.jpg/spring-beans.xsd
        http://www.51sjk.com/Upload/Articles/1/0/336/336738_20221115094852574.jpg http://www.51sjk.com/Upload/Articles/1/0/336/336738_20221115094852574.jpg/spring-context.xsd      
        http://www.51sjk.com/Upload/Articles/1/0/336/336738_20221115094853247.jpg http://www.51sjk.com/Upload/Articles/1/0/336/336738_20221115094903309.xsd
        http://www.51sjk.com/Upload/Articles/1/0/336/336738_20221115094903561.jpg http://www.51sjk.com/Upload/Articles/1/0/336/336738_20221115094904496.xsd
        http://www.51sjk.com/Upload/Articles/1/0/336/336738_20221115094904653.jpg http://www.51sjk.com/Upload/Articles/1/0/336/336738_20221115094905169.xsd
        http://www.51sjk.com/Upload/Articles/1/0/336/336738_20221115094905340.jpg http://www.51sjk.com/Upload/Articles/1/0/336/336738_20221115094905340.jpg/camel-spring.xsd">

    <jaxrs:server id="userService" address="/users">
        <jaxrs:serviceBeans>
            <bean class="com.example.UserServiceNoop" />
        </jaxrs:serviceBeans>
        <jaxrs:providers>
            <bean class="org.codehaus.jackson.jaxrs.JacksonJaxbJsonProvider" />
        </jaxrs:providers>
    </jaxrs:server>
    
    <bean id="user" class="org.apache.camel.component.direct.DirectComponent" />
    
    <camel:camelContext id="someCamelContext">
        <camel:route id="userServiceRoute">
            <camel:from uri="cxfrs:bean:userService" />
            <camel:routingSlip>
                <camel:simple>user:${header.operationName}</camel:simple>
            </camel:routingSlip>
        </camel:route>

        <camel:route id="userServiceRetrieveUser">
            <from uri="user:retrieveUser" />
            <!-- Assume this is going to a useful Processor -->
        
        </camel:route>  
    </camel:camelContext>
</beans>

UserService.java:

package com.example;

/* a bunch of imports... */

public interface UserService {
    @GET
    @Path(value="/{user.id}")
    @Produces({MediaType.APPLICATION_JSON})
    public User retrieveUser(
        @PathParam("user.id") Integer id
    );
}

UserServiceNoop.java

package com.example;

/* a bunch of imports ... */

public class UserServiceNoop implements UserService 
{
    @Override
    public User retrieveUser(Integer id) {
        throw new RuntimeException();
    }
}

在这个例子中，我没有使用任何 <cxf:rsServer> 标签，但它工作正常.我知道它通过 CXF-RS 组件，因为当我运行应用程序时，它不会抛出任何 RuntimeExceptions，这是使用 CXF-RS 时的预期行为(服务中的方法实现类不会被调用).

In this example, I'm not using any <cxf:rsServer> tag, yet it works fine. I know it goes through the CXF-RS component, because when I run the application, it doesn't throw any RuntimeExceptions, which is the expected behavior when using CXF-RS (the method implementation in the service class will not be called).

不使用这个标签是不是我错过了什么?

Am I missing something by not using this tag?

推荐答案

正如另一个答案所说， cxf:rsServer 主要用于由 Camel 路由处理，如 jaxrs:server 请求的处理由经典控制器完成.

As the other answer says, the cxf:rsServer is mainly used to be processed by a Camel route as in the jaxrs:server the processing of the request is done by a classic controller.

例如:

经典 JAXRS 服务器:

您将声明一个经典的 Bean Rest(控制器)并在其中注入一个服务.

You will declare a classic Bean Rest (Controller) and inject a Service inside.

XML 配置示例(摘录):

<jaxrs:server id="deviceServiceSvcV1" address="/device/v1">
    <jaxrs:serviceBeans>
        <ref component-id="deviceServiceRest" />
    </jaxrs:serviceBeans>
    <!-- and other providers, interceptors, etc... here --> 
</jaxrs:server>

<!-- Service bean -->
<bean id="deviceServiceRest" class="org.mycomp.device.rest.v1.ws.api.DeviceServiceRest">
    <property name="deviceService" ref="deviceService" />
</bean>

Controller 类将以经典方式处理请求/响应(例如调用注入服务).

The Controller class will process the request / response in a classic way (e.g. calling an injected service).

cxf:rsServer

Camel route with cxf:rsServer

XML 配置示例(摘录):

<cxf:rsServer id="rsServer" address="/device/v1"
    serviceClass="org.mycomp.device.rest.v1.ws.api.DeviceServiceRest">
    <cxf:properties>
        <!-- whatever here -->
    </cxf:properties>
    <!-- and other interceptors, etc... here -->         
</cxf:rsServer>

在课堂上:

@Produces({ MediaType.APPLICATION_XML })
@Path("/")
public class DeviceServiceRest {

    @GET
    public Response listDevicess( 
            @QueryParam("model") String model,
            @QueryParam("sid") String sid,
    ) {
        return null; // never used
    }

    @GET
    @Path("{id}")
    public Response getDeviceById(
            @PathParam("id") String id,
            @QueryParam("model") String model,
            @QueryParam("sid") String sid
    ){               
        return null; // never used
    }
}

REST 控制器有空方法(返回 null)，但我认为最新的 camel-cxf 现在支持 Interface，它比返回的方法更优雅空.现在，请求处理可以通过 Camel Route 来实现，如下所示:

The REST Controller has empty methods (returning null) but I think the latest camel-cxf supports now an Interface which is more elegant than having methods returning null. Now, the request processing can be implemented by a Camel Route like this:

from("cxfrs:bean:rsServer?synchronous=true")
    .routeId("cxf-device-rest-v1")
    .process( new CheckAuthenticationProcessor())
    .choice()
        .when(header("operationName").isEqualTo("listDevice"))
            .setHeader("backenOperation").constant("list")
            .setHeader("backendResource").constant("device")
            
        .endChoice()
        .when(header("operationName").isEqualTo("getDeviceById"))
            .setHeader("backenOperation").constant("retrieve")
            .setHeader("backendResource").constant("device")
        .endChoice()
    .end()
    .bean("requestProcessor")
    .to(InOut, backendEndpoint)
    .process(checkResponseStatusCode())
    .bean(new HttpResponseProcessor())
;

您还可以从路由中根据需要控制请求/响应处理.

And you can also control the request / response processing as you want from the route.

这是两种不同的实现 REST API(服务器端)的方式，但在我看来这有点老派，因为像 spring-boot 这样的现代框架不需要这些.

These are two different kind of implementing a REST API (server side) but in my opinion this is a bit old school as modern framework like spring-boot does not need any of these.

我发现第二种方法有点矫枉过正，因为我喜欢 Camel 用于集成目的，但将它用于 REST API 可能需要讨论.我可以看到的一个用例是用于异步处理的 HTTP REST Web 服务，响应 202 Accepted 的服务和 Camel Route 在异步模式下集成请求，特别是当可以轻松使用特定的 Camel 组件而不是复杂的组件时类(或任何需要 EIP 模式).

I found the second way a bit too much overkill as I like Camel for integration purpose but using it for a REST API could be subject to discussion. One use-case I can see is a HTTP REST Web-Service for asynchronous processing, the service responding 202 Accepted and the Camel Route making an integration of the request in asynchronous mode especially when a specific Camel Component can be easily used instead of a complex class (or any need of the EIP patterns).