1, Introduction
The mainstream communication protocols for microservices include RPC,Http, and SpringCloud, which are based on the Http Restful style. There are many ways to initiate an Http request in Java, such as Apache's HttpClient, OKHttp, and so on. Spring encapsulates a Restful based and very simple Http client tool RestTemplate. We use it to implement the communication between order service and user service. It should be noted that RestTemplate itself does not have the functions of service discovery and load balancer. The case in this chapter only demonstrates how to use RestTemplate to initiate calls to user services based on ip and port in order services, that is, do not go to the registry and do not use service discovery.
2, Spring cloud uses RestTemplate
1, Register BEAN
// If you configure a bean, you can't configure dependency injection later, just as you used to configure dependency injection during ssm integration,
// Dependency injection is not allowed in code until the configuration file is configured
// The current file is the spring configuration file
@Bean
@LoadBalanced //Let this RestTemplate have the ability of client load balancing when requesting
public RestTemplate getRestTemplate() {
return new RestTemplate();
}
2, GET request
RestTemplate can send HTTP GET requests. Two methods are often used:
- getForObject()
- getForEntity()
The main difference between the two is that the return value of getForObject() is the response body of HTTP protocol. getForEntity() returns ResponseEntity, which is the encapsulation of HTTP response. In addition to the response body, it also contains HTTP status code, contentType, contentLength, Header and other information.
1. getForObject() accepts the result data in the form of String
@GetMapping("/payment/get/{id}")
public String getPayment_String(@PathVariable("id") Long id) {
return restTemplate.getForObject(PAYMENT_URL + "/payment/get/" + id, String.class);
}
2. getForObject() accepts the result data as an object
@GetMapping("/payment/get/{id}")
public CommonResult<Payment> getPayment(@PathVariable("id") Long id) {
return restTemplate.getForObject(PAYMENT_URL + "/payment/get/" + id, CommonResult.class);
}
3. getForObject() receives the request result in an array
@GetMapping("/payment/get/{id}")
public CommonResult<Payment>[] getPayment_array(@PathVariable("id") Long id) {
CommonResult[] commonResults = restTemplate.getForObject(PAYMENT_URL + "/payment/get/" + id, CommonResult[].class);
return commonResults;
}
4. getForEntity() method
Getforebject request parameter passing method and getForEntity can be used, and the use methods are almost the same, except for a slight difference when the returned results are received. Use ResponseEntity responseEntity to receive response results. Use responseentity Getbody() gets the response body. The response content is consistent with the result returned by the getForObject method. The rest of the response information is the more content of getForEntity than getforebject.
HttpStatus statusCode = responseEntity.getStatusCode(); Get the overall response status information int statusCodeValue = responseEntity.getStatusCodeValue(); Get response code value HttpHeaders headers = responseEntity.getHeaders(); Get response header
@GetMapping("/payment/getForEntity/{id}")
public CommonResult<Payment> getPayment2(@PathVariable("id") Long id) {
ResponseEntity<CommonResult> entity = restTemplate.getForEntity(PAYMENT_URL + "/payment/get/" + id, CommonResult.class);
entity.getStatusCode();//Get the overall response status information
entity.getStatusCodeValue();//Get response code value
entity.getHeaders();//Get response header
if (entity.getStatusCode().is2xxSuccessful()) {
return entity.getBody();
} else {
return new CommonResult<>(444, "operation failed");
}
}
3, POST request
The POST request method is similar to the GET request method. The POST request of RestTemplate also contains two main methods:
- postForObject()
- postForEntity()
The main difference between the two is that the return value of postForObject() is the response body of HTTP protocol. postForEntity() returns ResponseEntity, which is the encapsulation of HTTP response. In addition to the response body, it also contains HTTP status code, contentType, contentLength, Header and other information.
1. Send JSON format request to postForObject
@PostMapping("/payment/create")
public CommonResult<Payment> create(@RequestBody Payment payment) {
return restTemplate.postForObject(PAYMENT_URL + "/payment/create", payment, CommonResult.class);
}
2. postForObject simulates form data submission
public void testForm() {
// Request address
String url = "http://jsonplaceholder.typicode.com/posts";
// Request header setting, data in x-www-form-urlencoded format
HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED);
//Submit parameter settings
MultiValueMap<String, String> map = new LinkedMultiValueMap<>();
map.add("title", "zimug Publish the second article");
map.add("body", "zimug Release the second test content of the article");
// Assembly request body
HttpEntity<MultiValueMap<String, String>> request =
new HttpEntity<MultiValueMap<String, String>>(map, headers);
// Send the post request, print the result, and receive the response result JSON String as String type
String result = restTemplate.postForObject(url, request, String.class);
System.out.println(result);
}
3. postForEntity() method
The postforebject request parameter transfer method and postForEntity can be used, and the use methods are almost the same, except for a slight difference when the return result is received. Use ResponseEntity responseEntity to receive response results. Use responseentity Getbody() gets the response body. The response volume is consistent with the result returned by the postForObject method. The rest of the response information is the more content of postForEntity than postforebject.
HttpStatus statusCode = responseEntity.getStatusCode();Get the overall response status information int statusCodeValue = responseEntity.getStatusCodeValue(); Get response code value HttpHeaders headers = responseEntity.getHeaders();Get response header
@Test
public void testEntityPoJo() {
// Request address
String url = "http://jsonplaceholder.typicode.com/posts";
// Data object to send
PostDTO postDTO = new PostDTO();
postDTO.setUserId(110);
postDTO.setTitle("zimug Publish articles");
postDTO.setBody("zimug Post test content");
// Send a post request and output the result
ResponseEntity<String> responseEntity
= restTemplate.postForEntity(url, postDTO, String.class);
String body = responseEntity.getBody(); // Get response body
System.out.println("HTTP response body: " + postDTO.toString());
//The following is more about postForEntity than postforebject
HttpStatus statusCode = responseEntity.getStatusCode(); // Get response code
int statusCodeValue = responseEntity.getStatusCodeValue(); // Get response code value
HttpHeaders headers = responseEntity.getHeaders(); // Get response header
System.out.println("HTTP Response status:" + statusCode);
System.out.println("HTTP Response status code:" + statusCodeValue);
System.out.println("HTTP Headers Information:" + headers);
}
4. Use of the postForLocation() method
The type, number and usage of parameters passed by postForLocation are basically the same as those of postforebject() or postForEntity(). The only difference from the first two is that the return value is a URI. The returned value of the URI reflects the page Jump after data submission, or the next data operation URI after data submission.
@Test
public void testURI() {
// Request address
String url = "http://jsonplaceholder.typicode.com/posts";
PostDTO postDTO = new PostDTO();
postDTO.setUserId(110);
postDTO.setTitle("zimug Publish articles");
postDTO.setBody("zimug Post test content");
// Send a post request and output the result
URI uri = restTemplate.postForLocation(url,postDTO);
System.out.println(uri);
}