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

經常需要發送一個GET/POST請求到其他系統(REST API)，通過JDK自帶的HttpURLConnection、Apache HttpClient、Netty 4、OkHTTP 2/3都可以實現。

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

Spring的RestTemplate封裝了這些庫的實現，使用起來更簡潔。

RestTemplate包含以下幾個部分：?
HttpMessageConverter 對象轉換器
ClientHttpRequestFactory 默認是JDK的HttpURLConnection
ResponseErrorHandler 異常處理
ClientHttpRequestInterceptor 請求攔截器

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

（1）發送GET請求（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();

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（2）發送POST請求（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);

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（3）設置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);

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（4）異常處理?

捕獲HttpServerErrorException?

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

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自定義異常處理?

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

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

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（5）設置超時時間?

@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; } }

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（6）設置連接池?

@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(); } }

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（7）發送文件?

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);

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（8）下載文件?

// 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);

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（9）Spring Boot的RestTemplateBuilder?

全局設置?

@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); } }

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單獨設置?

@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

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轉載于:https://www.cnblogs.com/softidea/p/9438783.html

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