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