REST访问(RestTemplate)

https://www.cnblogs.com/softidea/p/6910198.html

经常需要发送一个GET/POST请求到其他系统(REST API)，通过JDK自带的HttpURLConnection、Apache HttpClient、Netty 4、OkHTTP 2/3都可以实现。

HttpClient的使用：http://rensanning.iteye.com/blog/1550436

Spring的RestTemplate封装了这些库的实现，使用起来更简洁。

RestTemplate包含以下几个部分：
HttpMessageConverter 对象转换器
ClientHttpRequestFactory 默认是JDK的HttpURLConnection
ResponseErrorHandler 异常处理
ClientHttpRequestInterceptor 请求拦截器

@Service
public class AccountService {  @Autowired  private RestTemplate restTemplate;  // ...  

}

（1）发送GET请求（getForObject()、getForEntity()、exchange()）

// 1-getForObject()
User user1 = this.restTemplate.getForObject(uri, User.class);  // 2-getForEntity()
ResponseEntity<User> responseEntity1 = this.restTemplate.getForEntity(uri, User.class);
HttpStatus statusCode = responseEntity1.getStatusCode();
HttpHeaders header = responseEntity1.getHeaders();
User user2 = responseEntity1.getBody();  // 3-exchange()
RequestEntity requestEntity = RequestEntity.get(new URI(uri)).build();
ResponseEntity<User> responseEntity2 = this.restTemplate.exchange(requestEntity, User.class);
User user3 = responseEntity2.getBody();

（2）发送POST请求（postForObject()、postForEntity()、exchange()）

// 1-postForObject()
User user1 = this.restTemplate.postForObject(uri, user, User.class);  // 2-postForEntity()
ResponseEntity<User> responseEntity1 = this.restTemplate.postForEntity(uri, user, User.class);  // 3-exchange()
RequestEntity<User> requestEntity = RequestEntity.post(new URI(uri)).body(user);
ResponseEntity<User> responseEntity2 = this.restTemplate.exchange(requestEntity, User.class);

（3）设置HTTP Header信息

// 1-Content-Type
RequestEntity<User> requestEntity = RequestEntity  .post(new URI(uri))  .contentType(MediaType.APPLICATION_JSON)  .body(user);  // 2-Accept
RequestEntity<User> requestEntity = RequestEntity  .post(new URI(uri))  .accept(MediaType.APPLICATION_JSON)  .body(user);  // 3-Other
RequestEntity<User> requestEntity = RequestEntity  .post(new URI(uri))  .header("Authorization", "Basic " + base64Credentials)  .body(user);

（4）异常处理

捕获HttpServerErrorException

int retryCount = 0;
while (true) {  try {  responseEntity = restTemplate.exchange(requestEntity, String.class);  break;  } catch (HttpServerErrorException e) {  if (retryCount == 3) {  throw e;  }  retryCount++;  }
}

自定义异常处理

public class CustomErrorHandler extends DefaultResponseErrorHandler {  @Override  public void handleError(ClientHttpResponse response) throws IOException {  }  }

@Configuration
public class RestClientConfig {  @Bean  public RestTemplate restTemplate() {  RestTemplate restTemplate = new RestTemplate();  restTemplate.setErrorHandler(new CustomErrorHandler());  return restTemplate;  }  }

（5）设置超时时间

@Configuration
public class RestClientConfig {  @Bean  public RestTemplate restTemplate() {  return new RestTemplate(clientHttpRequestFactory());  }  private ClientHttpRequestFactory clientHttpRequestFactory() {  HttpComponentsClientHttpRequestFactory factory = new HttpComponentsClientHttpRequestFactory();  factory.setReadTimeout(2000);  factory.setConnectTimeout(2000);  return factory;  }
}

（6）设置连接池

@Configuration
public class RestClientConfig {  @Bean  public ClientHttpRequestFactory httpRequestFactory() {  return new HttpComponentsClientHttpRequestFactory(httpClient());  }  @Bean  public RestTemplate restTemplate() {  return new RestTemplate(httpRequestFactory());  }  @Bean  public HttpClient httpClient() {  Registry<ConnectionSocketFactory> registry = RegistryBuilder.<ConnectionSocketFactory> create()  .register("http", PlainConnectionSocketFactory.getSocketFactory())  .register("https", SSLConnectionSocketFactory.getSocketFactory())  .build();  PoolingHttpClientConnectionManager connectionManager = new PoolingHttpClientConnectionManager(registry);  connectionManager.setMaxTotal(5);  connectionManager.setDefaultMaxPerRoute(5);  RequestConfig requestConfig = RequestConfig.custom()  .setSocketTimeout(8000)  .setConnectTimeout(8000)  .setConnectionRequestTimeout(8000)  .build();  return HttpClientBuilder.create()  .setDefaultRequestConfig(requestConfig)  .setConnectionManager(connectionManager)  .build();  }  }

（7）发送文件

MultiValueMap<String, Object> multiPartBody = new LinkedMultiValueMap<>();
multiPartBody.add("file", new ClassPathResource("/tmp/user.txt"));
RequestEntity<MultiValueMap<String, Object>> requestEntity = RequestEntity  .post(uri)  .contentType(MediaType.MULTIPART_FORM_DATA)  .body(multiPartBody);

（8）下载文件

// 小文件
RequestEntity requestEntity = RequestEntity.get(uri).build();
ResponseEntity<byte[]> responseEntity = restTemplate.exchange(requestEntity, byte[].class);
byte[] downloadContent = responseEntity.getBody();  // 大文件
ResponseExtractor<ResponseEntity<File>> responseExtractor = new ResponseExtractor<ResponseEntity<File>>() {  @Override  public ResponseEntity<File> extractData(ClientHttpResponse response) throws IOException {  File rcvFile = File.createTempFile("rcvFile", "zip");  FileCopyUtils.copy(response.getBody(), new FileOutputStream(rcvFile));  return ResponseEntity.status(response.getStatusCode()).headers(response.getHeaders()).body(rcvFile);  }
};
File getFile = this.restTemplate.execute(targetUri, HttpMethod.GET, null, responseExtractor);

（9）Spring Boot的RestTemplateBuilder

全局设置

@Component
public class CustomRestTemplateCustomizer implements RestTemplateCustomizer {  @Override  public void customize(RestTemplate restTemplate) {  new RestTemplateBuilder()  .detectRequestFactory(false)  .basicAuthorization("username", "password")  .uriTemplateHandler(new OkHttp3ClientHttpRequestFactory())  .errorHandler(new CustomResponseErrorHandler())  .configure(restTemplate);  }
}

单独设置

@Service
public class MyRestClientService {  private RestTemplate restTemplate;  public MyRestClientService(RestTemplateBuilder restTemplateBuilder) {  this.restTemplate = restTemplateBuilder  .basicAuthorization("username", "password")  .setConnectTimeout(3000)  .setReadTimeout(5000)  .rootUri("http://api.example.com/")  .errorHandler(new CustomResponseErrorHandler())  .additionalMessageConverters(new CustomHttpMessageConverter())  .uriTemplateHandler(new OkHttp3ClientHttpRequestFactory())  .build();  }  public String site() {  return this.restTemplate.getForObject("http://rensanning.iteye.com/", String.class);  }  }

http://rensanning.iteye.com/blog/2362105

转载于:https://www.cnblogs.com/softidea/p/9438783.html

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