restTemplate.exchange() 方法有什么用?

问题描述

restTemplate.exchange() 方法实际上是做什么的?

Actually what does the restTemplate.exchange() method do?

@RequestMapping(value = "/getphoto", method = RequestMethod.GET)
public void getPhoto(@RequestParam("id") Long id, HttpServletResponse response) {

    logger.debug("Retrieve photo with id: " + id);

    // Prepare acceptable media type
    List<MediaType> acceptableMediaTypes = new ArrayList<MediaType>();
    acceptableMediaTypes.add(MediaType.IMAGE_JPEG);

    // Prepare header
    HttpHeaders headers = new HttpHeaders();
    headers.setAccept(acceptableMediaTypes);
    HttpEntity<String> entity = new HttpEntity<String>(headers);

    // Send the request as GET
    ResponseEntity<byte[]> result =
        restTemplate.exchange("http://localhost:7070/spring-rest-provider/krams/person/{id}",
                              HttpMethod.GET, entity, byte[].class, id);

    // Display the image
    Writer.write(response, result.getBody());
}

推荐答案

方法文档非常简单:

对给定的URI模板执行HTTP方法，将给定的请求实体写入请求，返回响应为ResponseEntity.

使用给定的 URI 变量扩展 URI 模板变量(如果有).

URI Template variables are expanded using the given URI variables, if any.

考虑从您自己的问题中提取的以下代码:

---

Consider the following code extracted from your own question:

ResponseEntity<byte[]> result =
    restTemplate.exchange("http://localhost:7070/spring-rest-provider/krams/person/{id}",
                          HttpMethod.GET, entity, byte[].class, id);

我们有以下几点:

• GET 请求将是对给定的 URL 执行发送包含在 HttpEntity 实例.
• 给定的 URL 包含一个模板变量 ({id}).它将被替换为最后一个方法参数 (id) 中给出的值.
• 响应实体将作为 byte[] 包装到 ResponseEntity 实例.

• A GET request will be performed to the given URL sending the HTTP headers that are wrapped in the HttpEntity instance.
• The given URL contains a template variable ({id}). It will be replaced with the value given in the last method parameter (id).
• The response entity will be returned​ as a byte[] wrapped into a ResponseEntity instance.

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