一、问题描述
1）项目一开始采用JAX-RS 2.1+Jersey 2.26调用REST服务能正常调用并获得正确响应；
2）当项目引入dubbo 2.6.2后也用到rest而dubbo要用到RESTEasy，项目就引入了RESTEasy；
3）项目引入RESTEasy后，JAX-RS 2.1+Jersey 2.26调用REST服务出现异常！异常信息如下：
javax.ws.rs.ProcessingException: RESTEASY004655: Unable to invoke request at org.jboss.resteasy.client.jaxrs.engines.ApacheHttpClient4Engine.invoke(ApacheHttpClient4Engine.java:321) at org.jboss.resteasy.client.jaxrs.internal.ClientInvocation.invoke(ClientInvocation.java:439) at org.jboss.resteasy.client.jaxrs.internal.ClientInvocation.invoke(ClientInvocation.java:61) at org.jboss.resteasy.client.jaxrs.internal.ClientInvocationBuilder.post(ClientInvocationBuilder.java:219) at com.lutao.pigeon.iclient.ibeplus.common.IBEPlusCaller.invoke(IBEPlusCaller.java:63) at com.lutao.pigeon.gds.ibe.service.impl.IbeGdsShoppingService.flightShopping(IbeGdsShoppingService.java:89) at com.lutao.pigeon.gds.resource.impl.GdsShoppingResource.flightShopping(GdsShoppingResource.java:37) at com.lutao.pigeon.gds.resource.impl.GdsShoppingResource$$FastClassBySpringCGLIB$$77b131d0.invoke(<generated>) at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204) at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:746) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163) at org.springframework.aop.aspectj.MethodInvocationProceedingJoinPoint.proceed(MethodInvocationProceedingJoinPoint.java:88) at com.lutao.openservice.common.aspect.BaseRestAspectProcessor.syncAroundHandle(BaseRestAspectProcessor.java:340) at com.lutao.openservice.common.aspect.BaseRestAspectProcessor.lambda$asyncAroundHandle$0(BaseRestAspectProcessor.java:267) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at java.lang.Thread.run(Thread.java:748) Caused by: javax.ws.rs.ProcessingException: RESTEASY003215: could not find writer for content-type text/html type: java.lang.String at org.jboss.resteasy.core.interception.ClientWriterInterceptorContext.throwWriterNotFoundException(ClientWriterInterceptorContext.java:40) at org.jboss.resteasy.core.interception.AbstractWriterInterceptorContext.getWriter(AbstractWriterInterceptorContext.java:146) at org.jboss.resteasy.core.interception.AbstractWriterInterceptorContext.proceed(AbstractWriterInterceptorContext.java:121) at org.jboss.resteasy.client.jaxrs.internal.ClientInvocation.writeRequestBody(ClientInvocation.java:394) at org.jboss.resteasy.client.jaxrs.engines.ApacheHttpClient4Engine.writeRequestBodyToOutputStream(ApacheHttpClient4Engine.java:666) at org.jboss.resteasy.client.jaxrs.engines.ApacheHttpClient4Engine.buildEntity(ApacheHttpClient4Engine.java:631) at org.jboss.resteasy.client.jaxrs.engines.ApacheHttpClient4Engine.loadHttpMethod(ApacheHttpClient4Engine.java:509) at org.jboss.resteasy.client.jaxrs.engines.ApacheHttpClient4Engine.invoke(ApacheHttpClient4Engine.java:310) ... 16 more
二、问题分析
1）从异常错误信息看调用REST服务端的代码变成了RESTEasy，而不是原正常的Jersey咯
2）在网上找问题看到一位同学讲把clientConfig参数去掉可解决问题，讲的应该有道这个clientConfig是Jersey包的代码而从异常错信息来看客户端用的是RESTEasy的代码；不过我的有这个clientConfig配置，所以我并没有去验证这位同学讲的解决方法；
3）创建代码，如下：
Client client = ClientBuilder.newBuilder(clientConfig)
.register(feature)
.build();
4）阅读 ClientBuilder.newBuilder() 源码发现，ClientBuilder的构建是这样子的：会加载 META-INF/services/javax.ws.rs.client.ClientBuilder 文件的的实现类并使用，如果在META-INF/services/javax.ws.rs.client.ClientBuilder 文件中未加载则默认使用 org.glassfish.jersey.client.JerseyClientBuilder 类；从这个逻辑中看出来之前rest服务正常调用是没有引入RESTEasy jar包，肯定设置使用的是Jersey，猜测RESTEasy jar包中应该有 META-INF/services/javax.ws.rs.client.ClientBuilder 文件并配置了RESTEasy的ClientBuilder的继承类才会导致JAX-RS加载到RESTEasy并使用RESTEasy作为客户端调用REST服务；
5）接着查找一下是否有RESTEasy的META-INF/services/javax.ws.rs.client.ClientBuilder，结果是有的，如下：
6）问题确认了我们就好处理咯。
三、问题解决
1）修改客户代码，指定使用Jersey，如下：
由
Client client = ClientBuilder.newBuilder(clientConfig)
.register(feature)
.build();
改为（直接指定使用JerseyClientBuilder.createClient(...)创建，这样、JAX-RX就不会根据 META-INF/services/javax.ws.rs.client.ClientBuilder 文件中去加载了）
Client client = JerseyClientBuilder.createClient(clientConfig)
.register(feature);
2）修改后，再次调用测试，能正常调用并响应正常。
end.