Java Spring启动连接异常未被捕获

我正在使用RestTemplate连接到另一个服务，我正在捕获一个ConnectException，但是catch块从未捕获它。异常在result=restemplate.getForEntity（uri，String.class）行中抛出，在控制台中我确实得到了以下结果：

java.net.ConnectException: Connection refused: connect
    at java.net.DualStackPlainSocketImpl.connect0(Native Method) ~[na:1.8.0_201]
    at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:79) ~[na:1.8.0_201]
    at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350) ~[na:1.8.0_201]
    at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206) ~[na:1.8.0_201]
    at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188) ~[na:1.8.0_201]
    at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172) ~[na:1.8.0_201]
    at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) ~[na:1.8.0_201]
    at java.net.Socket.connect(Socket.java:589) ~[na:1.8.0_201]
    at java.net.Socket.connect(Socket.java:538) ~[na:1.8.0_201]
    at sun.net.NetworkClient.doConnect(NetworkClient.java:180) ~[na:1.8.0_201]
    at sun.net.www.http.HttpClient.openServer(HttpClient.java:463) ~[na:1.8.0_201]
    at sun.net.www.http.HttpClient.openServer(HttpClient.java:558) ~[na:1.8.0_201]
    at sun.net.www.http.HttpClient.<init>(HttpClient.java:242) ~[na:1.8.0_201]
    at sun.net.www.http.HttpClient.New(HttpClient.java:339) ~[na:1.8.0_201]
    at sun.net.www.http.HttpClient.New(HttpClient.java:357) ~[na:1.8.0_201]
    at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:1220) ~[na:1.8.0_201]
    at sun.net.www.protocol.http.HttpURLConnection.plainConnect0(HttpURLConnection.java:1156) ~[na:1.8.0_201]
    at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:1050) ~[na:1.8.0_201]
    at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:984) ~[na:1.8.0_201]
    at org.springframework.http.client.SimpleBufferingClientHttpRequest.executeInternal(SimpleBufferingClientHttpRequest.java:76) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.http.client.AbstractBufferingClientHttpRequest.executeInternal(AbstractBufferingClientHttpRequest.java:48) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.http.client.AbstractClientHttpRequest.execute(AbstractClientHttpRequest.java:53) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:735) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:670) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.web.client.RestTemplate.getForEntity(RestTemplate.java:338) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at com.tdl.controller.ToDoNoteController.addUserToNote(ToDoNoteController.java:323) ~[classes/:na]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_201]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_201]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_201]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_201]
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:189) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:102) ~[spring-webmvc-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:895) ~[spring-webmvc-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:800) ~[spring-webmvc-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1038) ~[spring-webmvc-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:942) ~[spring-webmvc-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1005) ~[spring-webmvc-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:908) ~[spring-webmvc-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:660) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:882) ~[spring-webmvc-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.16.jar:9.0.16]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:92) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:93) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:200) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:490) [tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) [tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) [tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) [tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408) [tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:834) [tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1415) [tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.16.jar:9.0.16]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_201]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_201]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.16.jar:9.0.16]
    at java.lang.Thread.run(Thread.java:748) [na:1.8.0_201]

方法本身：

@PostMapping("/todos/{toDoNoteId}/users")
    public ResponseEntity<?> addUserToNote(@RequestBody User user,@PathVariable int toDoNoteId) throws JsonParseException, JsonMappingException, ConnectException, IOException{
        String email = user.getEmail();
        final String uri = "http://friend:5000/users/"+email;
        RestTemplate restTemplate = new RestTemplate();
        ResponseEntity<String> result =null;
        int statusCode=0;
        ObjectMapper mapper = new ObjectMapper();
        //ResponseEntity<String> result = restTemplate.getForEntity(uri, String.class);

        //return null;

        try { // If user exists we will just add it to our ToDoNote

             result = restTemplate.getForEntity(uri, String.class); // exception thrown here

             ResponsePojo pojo = mapper.readValue(result.getBody(), ResponsePojo.class);
             User userToRespond = new User(pojo.getData().getEmail(),pojo.getData().getFirstName(),pojo.getData().getLastName());
             ToDoNote toDoNote = toDoNoteService.getToDoNoteById(toDoNoteId);
             if(toDoNote.checkIfUserExists(userToRespond)==true) {
                    return new ResponseEntity<String>("\"User already in this note\"",HttpStatus.CONFLICT);
             }
                else {
                    toDoNoteService.getToDoNoteById(toDoNoteId).addUser(userToRespond);
                    return new ResponseEntity<User>(userToRespond,HttpStatus.CREATED);
                }

            //System.out.println("result" + result);


        }
        catch(ConnectException ex2) {
            System.out.println(ex2.getCause());
            return new ResponseEntity<String>("\"Coudl not connect\"",HttpStatus.CONFLICT);
        }

        catch (HttpClientErrorException ex) {
            System.out.println("value"+ ex.getStatusCode().value());
            statusCode=ex.getStatusCode().value();     
        }


        try { // If user does not exist by the given email we can POST
            if(statusCode==404) {
                if(user.getEmail()==null || user.getFirstName()==null || user.getLastName()==null) {
                     return new ResponseEntity<String>("\"Required fields are missing( required fields are email,firstName,LastName)\"",HttpStatus.BAD_REQUEST);
                }
                final String uriPost = "http://friend:5000/users";
                result= restTemplate.postForEntity(uriPost, user, String.class);
                System.out.println("result" + result);

                ResponsePojo pojo = mapper.readValue(result.getBody(), ResponsePojo.class);
                User userToRespond = new User(pojo.getData().getEmail(),pojo.getData().getFirstName(),pojo.getData().getLastName());
                toDoNoteService.getToDoNoteById(toDoNoteId).addUser(userToRespond);
                return new ResponseEntity<User>(userToRespond,HttpStatus.CREATED);
            }
        }
            catch (HttpClientErrorException ex) {
                System.out.println("value"+ ex.getStatusCode().value());
                return ResponseEntity.status(ex.getRawStatusCode()).headers(ex.getResponseHeaders())
                        .body(ex.getResponseBodyAsString());
            }
    // istryniau daug tu throws not sure if thats that good

        System.out.println("Rip");
        return null;

    }

@PostMapping（“/todos/{toDoNoteId}/users”）
public ResponseEntity addUserToNote（@RequestBody User User，@PathVariable int toDoNoteId）抛出JsonParseException、JsonMappingException、ConnectException、IOException{
字符串email=user.getEmail（）；
最终字符串uri=”http://friend:5000/users/“+电子邮件；
RestTemplate RestTemplate=新RestTemplate（）；
ResponseEntity结果=空；
int statusCode=0；
ObjectMapper mapper=新的ObjectMapper（）；
//ResponseEntity结果=restemplate.getForEntity（uri，String.class）；
//返回null；
请尝试{//如果用户存在，我们将只将其添加到ToDoNote中
result=restTemplate.getForEntity（uri，String.class）；//此处引发异常
ResponsePojo pojo=mapper.readValue（result.getBody（），ResponsePojo.class）；
User userToRespond=新用户（pojo.getData（）.getEmail（），pojo.getData（）.getFirstName（），pojo.getData（）.getLastName（））；
todonotetodonote=toDoNoteService.getToDoNoteById（toDoNoteId）；
if（toDoNote.checkIfUserExists（userToRespond）=true）{
返回新的ResponseEntity（“\”用户已在此注释中\“”，HttpStatus.CONFLICT）；
}
否则{
toDoNoteService.getToDoNoteById（toDoNoteId）.addUser（userToRespond）；
返回新的ResponseEntity（userToRespond，HttpStatus.CREATED）；
}
//系统输出打印项次（“结果”+结果）；
}
捕获（ConnectException ex2）{
System.out.println（ex2.getCause（））；
返回新的响应属性（“Coudl not connect\”，HttpStatus.CONFLICT）；
}
捕获（HttpClientErrorException-ex）{
System.out.println（“value”+ex.getStatusCode（）.value（））；
statusCode=ex.getStatusCode（）.value（）；
}
如果我们可以发布的给定电子邮件中不存在用户，请尝试{//
如果（状态代码==404）{
if（user.getEmail（）==null | | user.getFirstName（）==null | | | user.getLastName（）==null）{
return new ResponseEntity（“\”必填字段缺失（必填字段为email、firstName、LastName）\”，HttpStatus.BAD\u请求）；
}
最后一个字符串uriPost=”http://friend:5000/users";
结果=restTemplate.postForEntity（uriPost、用户、String.class）；
系统输出打印项次（“结果”+结果）；
ResponsePojo pojo=mapper.readValue（result.getBody（），ResponsePojo.class）；
User userToRespond=新用户（pojo.getData（）.getEmail（），pojo.getData（）.getFirstName（），pojo.getData（）.getLastName（））；
toDoNoteService.getToDoNoteById（toDoNoteId）.addUser（userToRespond）；
返回新的ResponseEntity（userToRespond，HttpStatus.CREATED）；
}
}
捕获（HttpClientErrorException-ex）{
System.out.println（“value”+ex.getStatusCode（）.value（））；
返回ResponseEntity.status（例如getRawStatusCode（））.headers（例如getResponseHeaders（））
.body（例如getResponseBodyAsString（））；
}
//istryniau daug tu不确定这是否好
系统输出打印项次（“Rip”）；
返回null；
}

唯一有效的方法是捕获异常或RestClientException，不过我希望捕获ConnectException本身。有人知道我遗漏了什么吗？

这是关键部分：

嵌套异常是java.net.ConnectException

RestTemplate的

getForEntity

抛出一个RestClientException，它封装了ConnectException。这与引用父类型不同——RestClientException不会扩展ConnectException，因此您不能只是尝试捕获包装的类型

我不知道您为什么反对捕获异常或RestClientException。如果我只想拥有处理ConnectException的特定逻辑，我将捕获RestClientException，然后检查内部异常的类型（如果不是ConnectException，则重新调用）

比如说：

试试看{
response=restTemplate.getForEntity（…）；
//为简洁起见省略
}捕获（RestClientException e）{
if（例如，getCause（）instanceof ConnectException）{
//句柄连接异常
返回ResponseEntity.status（HttpStatus.CONFLICT）.body（“无法连接”）；
}
抛出e；//如果不是ConnectException，则重试
}

我明白了。感谢您的解释和关于如何处理异常的建议。：）另外，如果说我需要捕获更多嵌套异常，是否有一种比多个if子句更优雅的方法？您可以在rest模板上设置自己的错误处理程序，默认情况下，它会将400/500响应作为异常抛出，可以在此处查看快速摘要@Darrenforsyth它不会处理ResourceAccessExceptions

@PostMapping("/todos/{toDoNoteId}/users")
    public ResponseEntity<?> addUserToNote(@RequestBody User user,@PathVariable int toDoNoteId) throws JsonParseException, JsonMappingException, ConnectException, IOException{
        String email = user.getEmail();
        final String uri = "http://friend:5000/users/"+email;
        RestTemplate restTemplate = new RestTemplate();
        ResponseEntity<String> result =null;
        int statusCode=0;
        ObjectMapper mapper = new ObjectMapper();
        //ResponseEntity<String> result = restTemplate.getForEntity(uri, String.class);

        //return null;

        try { // If user exists we will just add it to our ToDoNote

             result = restTemplate.getForEntity(uri, String.class); // exception thrown here

             ResponsePojo pojo = mapper.readValue(result.getBody(), ResponsePojo.class);
             User userToRespond = new User(pojo.getData().getEmail(),pojo.getData().getFirstName(),pojo.getData().getLastName());
             ToDoNote toDoNote = toDoNoteService.getToDoNoteById(toDoNoteId);
             if(toDoNote.checkIfUserExists(userToRespond)==true) {
                    return new ResponseEntity<String>("\"User already in this note\"",HttpStatus.CONFLICT);
             }
                else {
                    toDoNoteService.getToDoNoteById(toDoNoteId).addUser(userToRespond);
                    return new ResponseEntity<User>(userToRespond,HttpStatus.CREATED);
                }

            //System.out.println("result" + result);


        }
        catch(ConnectException ex2) {
            System.out.println(ex2.getCause());
            return new ResponseEntity<String>("\"Coudl not connect\"",HttpStatus.CONFLICT);
        }

        catch (HttpClientErrorException ex) {
            System.out.println("value"+ ex.getStatusCode().value());
            statusCode=ex.getStatusCode().value();     
        }


        try { // If user does not exist by the given email we can POST
            if(statusCode==404) {
                if(user.getEmail()==null || user.getFirstName()==null || user.getLastName()==null) {
                     return new ResponseEntity<String>("\"Required fields are missing( required fields are email,firstName,LastName)\"",HttpStatus.BAD_REQUEST);
                }
                final String uriPost = "http://friend:5000/users";
                result= restTemplate.postForEntity(uriPost, user, String.class);
                System.out.println("result" + result);

                ResponsePojo pojo = mapper.readValue(result.getBody(), ResponsePojo.class);
                User userToRespond = new User(pojo.getData().getEmail(),pojo.getData().getFirstName(),pojo.getData().getLastName());
                toDoNoteService.getToDoNoteById(toDoNoteId).addUser(userToRespond);
                return new ResponseEntity<User>(userToRespond,HttpStatus.CREATED);
            }
        }
            catch (HttpClientErrorException ex) {
                System.out.println("value"+ ex.getStatusCode().value());
                return ResponseEntity.status(ex.getRawStatusCode()).headers(ex.getResponseHeaders())
                        .body(ex.getResponseBodyAsString());
            }
    // istryniau daug tu throws not sure if thats that good

        System.out.println("Rip");
        return null;

    }