【Java】RestTemplate下載遠程文件到本地

一、什麼是RestTemplate

RestTemplate 是 Spring 框架提供的一個用於訪問 REST 服務的組件，底層對 HTTP 請求及響應進行了封裝，提供了很多訪問遠程REST服務的方法，可簡化代碼開發。

二、實例化RestTemplate

@Configuration
@ComponentScan(basePackageClasses = RecordingConfig.class)
public class RecordingConfig {

    /**
     * 支持重定向的restTemplate
     *
     * @return
     */
    @Bean
    public RestTemplate restTemplate() {
        final RestTemplate restTemplate = new RestTemplate();
        final HttpComponentsClientHttpRequestFactory factory = new HttpComponentsClientHttpRequestFactory();
        final HttpClient httpClient = HttpClientBuilder.create().setRedirectStrategy(new LaxRedirectStrategy()).build();
        factory.setHttpClient(httpClient);
        restTemplate.setRequestFactory(factory);
        return restTemplate;
    }
}

三、下載遠程文件到本地

@Service
public class Test extends BaseService {

    @Autowired
    private RestTemplate restTemplate;

    public void download(String remoteUrl, String localUrl) {
        File localFile = new File(localUrl);
        if (!localFile.getParentFile().exists()) {
            localFile.getParentFile().mkdirs();
        }

        int reTry = 1;
        while (true) {
            ResponseEntity<File> responseEntity = restTemplate.execute(remoteUrl, HttpMethod.GET, null, response -> {
                if (response.getStatusCode() == HttpStatus.OK) {
                    FileCopyUtils.copy(response.getBody(), new FileOutputStream(localFile));
                    return ResponseEntity.status(response.getStatusCode()).headers(response.getHeaders()).body(localFile);
                } else {
                    return null;
                }
            });

            if (responseEntity != null && responseEntity.getStatusCode() == HttpStatus.OK) {
                break;
            }

            reTry++;
            if (reTry >= 3) {
                logger.error("下載遠程文件失敗！remoteUrl: {}", remoteUrl);
                break;
            }

            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
            }
        }
    }

}

四、測試下載