使用RestTemplate时出现消息“不支持HTTP协议”的异常

Question

I'm trying to hit a URL using GET request using RestTemplate. It is giving an exception stating http protocol is not supported.

I'm able to get the expected response using plain old HttpURLConnection method to hit the endpoint. But I'm unable to do so using the rest template. I'm not using any kind of VPN or proxy while trying this out.

Following is the code I'm using. I'll be replacing the actual ip and port used with ip:port.

final String url = "http://ip:port/h2h.php?channelid=acrs&posid=1";
final HttpHeaders httpHeaders = new HttpHeaders();
httpHeaders.setContentType(MediaType.APPLICATION_XML);
httpHeaders.set(HttpHeaders.ACCEPT, MediaType.APPLICATION_XML_VALUE);
final HttpEntity<String> httpEntity = new HttpEntity<>("", httpHeaders)
restTemplate.exchange(url, HttpMethod.GET, httpEntity, String.class);

Exception Trace

org.springframework.web.client.ResourceAccessException: I/O error on GET request for "http://ip:port/h2h.php": http protocol is not supported; nested exception is org.apache.http.conn.UnsupportedSchemeException: http protocol is not supported
    at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:673) ~[spring-web-4.3.13.RELEASE.jar:4.3.13.RELEASE]
    at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:620) ~[spring-web-4.3.13.RELEASE.jar:4.3.13.RELEASE]
    at org.springframework.web.client.RestTemplate.exchange(RestTemplate.java:538) ~[spring-web-4.3.13.RELEASE.jar:4.3.13.RELEASE]
    at org.springframework.web.client.RestTemplate$$FastClassBySpringCGLIB$$aa4e9ed0.invoke(<generated>) ~[spring-web-4.3.13.RELEASE.jar:4.3.13.RELEASE]
    at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204) ~[spring-core-4.3.13.RELEASE.jar:4.3.13.RELEASE]
    at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:738) ~[spring-aop-4.3.13.RELEASE.jar:4.3.13.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157) ~[spring-aop-4.3.13.RELEASE.jar:4.3.13.RELEASE]
    at org.springframework.aop.aspectj.MethodInvocationProceedingJoinPoint.proceed(MethodInvocationProceedingJoinPoint.java:85) ~[spring-aop-4.3.13.RELEASE.jar:4.3.13.RELEASE]
    at org.springframework.cloud.netflix.metrics.RestTemplateUrlTemplateCapturingAspect.captureUrlTemplate(RestTemplateUrlTemplateCapturingAspect.java:33) ~[spring-cloud-netflix-core-1.4.3.RELEASE.jar:1.4.3.RELEASE]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_191]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_191]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_191]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_191]
    at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethodWithGivenArgs(AbstractAspectJAdvice.java:629) ~[spring-aop-4.3.13.RELEASE.jar:4.3.13.RELEASE]
    at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethod(AbstractAspectJAdvice.java:618) ~[spring-aop-4.3.13.RELEASE.jar:4.3.13.RELEASE]
    at org.springframework.aop.aspectj.AspectJAroundAdvice.invoke(AspectJAroundAdvice.java:70) ~[spring-aop-4.3.13.RELEASE.jar:4.3.13.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) ~[spring-aop-4.3.13.RELEASE.jar:4.3.13.RELEASE]
    at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92) ~[spring-aop-4.3.13.RELEASE.jar:4.3.13.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) ~[spring-aop-4.3.13.RELEASE.jar:4.3.13.RELEASE]
    at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:673) ~[spring-aop-4.3.13.RELEASE.jar:4.3.13.RELEASE]
    at org.springframework.web.client.RestTemplate$$EnhancerBySpringCGLIB$$8fab6610.exchange(<generated>) ~[spring-web-4.3.13.RELEASE.jar:4.3.13.RELEASE]
    at com.gdn.x.pulsa.service.impl.TransactionServiceImpl.getTransactionResult(MobileTransactionServiceImpl.java:118) ~[classes/:na]

Any help will be appreciated.

Thank you.

EDIT: Code with HttpUrlConnection

try {
      URL obj = new URL(url);
      HttpURLConnection con = (HttpURLConnection) obj.openConnection();
      con.setRequestMethod("GET");
      con.setRequestProperty("User-Agent", "Mozilla/5.0");
      int responseCode = con.getResponseCode();
      System.out.println("\nSending 'GET' request to URL : " + url);
      System.out.println("Response Code : " + responseCode);
      BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream()));
      String inputLine;
      StringBuffer response = new StringBuffer();
      while ((inputLine = in.readLine()) != null) {
        response.append(inputLine);
      }
      in.close();
      System.out.println(response.toString());
    } catch (Exception e) {

    }

Answer 1

try using a closebale httpclient 
   CloseableHttpClient httpClient = HttpClients.custom()
            .setSSLHostnameVerifier(new NoopHostnameVerifier())
            .build();
    HttpComponentsClientHttpRequestFactory requestFactory
            = new HttpComponentsClientHttpRequestFactory();
    requestFactory.setHttpClient(httpClient);

    ResponseEntity<String> response
            = new RestTemplate(requestFactory).exchange(
            url, HttpMethod.GET, httpEntity, String.class);

Answer 2

This is how I use RestTemplate :

String payload = "something";
HttpHeaders headers = new HttpHeaders();
headers.setAccept(Collections.singletonList(MediaType.APPLICATION_JSON));
headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED);
RestTemplate restTemplate = new RestTemplate();
restTemplate.postForObject(url, new HttpEntity<>(payload, headers), String.class);