使用 Spring RestTemplate 调用 rest 服务时自定义请求头（custom HTTP headers）

在 Spring 3.0 中可以通过  HttpEntity 对象自定义请求头信息，如：

private static final String APPLICATION_PDF = "application/pdf";

RestTemplate restTemplate = new RestTemplate();

@Test

public void acceptHeaderUsingHttpEntity() throws Exception {

  HttpHeaders headers = new HttpHeaders();

  headers.setAccept(singletonList(MediaType.valueOf(APPLICATION_PDF)));

  ResponseEntity<byte[]> response = restTemplate.exchange("http://example.com/file/123",

      GET,

      new HttpEntity<byte[]>(headers),

      byte[].class);

  String responseText = PdfTextExtractor.getTextFromPage(new PdfReader(response.getBody()), 1);

  assertEquals("Some text in PDF file", responseText);

}

在 Spring 3.1 中有了一个更强大的替代接口  ClientHttpRequestInterceptor，这个接口只有一个方法： intercept(HttpRequest request, byte[] body,     ClientHttpRequestExecution execution)，下面是一个例子：

private static final String APPLICATION_PDF = "application/pdf";

RestTemplate restTemplate = new RestTemplate();

@Test

public void acceptHeaderUsingHttpRequestInterceptors() throws Exception {

  ClientHttpRequestInterceptor acceptHeaderPdf = new AcceptHeaderHttpRequestInterceptor(

      APPLICATION_PDF);

  restTemplate.setInterceptors(singletonList(acceptHeaderPdf));

  byte[] response = restTemplate.getForObject("http://example.com/file/123", byte[].class);

  String responseText = PdfTextExtractor.getTextFromPage(new PdfReader(response), 1);

  assertEquals("Some text in PDF file", responseText);

}

class AcceptHeaderHttpRequestInterceptor implements ClientHttpRequestInterceptor {

  private final String headerValue;

  public AcceptHeaderHttpRequestInterceptor(String headerValue) {

    this.headerValue = headerValue;

  }

  @Override

  public ClientHttpResponse intercept(HttpRequest request, byte[] body,

      ClientHttpRequestExecution execution) throws IOException {

    HttpRequestWrapper requestWrapper = new HttpRequestWrapper(request);

    requestWrapper.getHeaders().setAccept(singletonList(MediaType.valueOf(headerValue)));

    return execution.execute(requestWrapper, body);

  }

}

原文：http://svenfila.wordpress.com/2012/01/05/resttemplate-with-custom-http-headers/