Introduction to RestTemplate

1. Overview of RestTemplate

2. RestTemplate Configuration Items

• setBufferRequestBody
  Whether or not to buffer the stream to store the request body, default true
• setProxy
  Setting proxy objects
• setChunkSize
  Set the byte length for each transfer, in conjunction with setBufferRequestBody (false)
• setConnectTimeout
  Set connection timeout, default - 1
• setReadTimeout
  Set read content timeout, default - 1
• setOutputStreaming
  Set Connection to Set Output Flow
• setTaskExecutor
  Setting up asynchronous callback actuator

3. RestTemplate request mode

• GET
  Get resources by requesting URI s
• POST
  Used to add new content
• PUT
  Used to modify something, add if it does not exist
• DELETE
  Delete something
• OPTIONS
  Ask what methods can be implemented
• HEAD
  Similar to GET, but without returning body information, it checks whether an object exists and obtains its metadata.
• CONNECT
  Used for proxy transmission, such as using SSL
• TRACE
  Used for remote diagnostic server

II. RestTemplate use

1. Get request mode

• getForEntity()
  Send an HTTP GET request, and the ResponseEntity returned contains the object mapped by the response body.
• getForObject()
  Send an HTTP GET request, and the returned body of the request will be mapped to an object

(1) Requesting Party

@RestController
public class UserRibbonController {
    @Resource
    private RestTemplate restTemplate;
    //No parameters
    @GetMapping("/user")
    public Result select() throws Exception{
    	return restTemplate.getForObject("http://eureka-client1/select/", Result.class);
    }
    //Single parameter
    @GetMapping("/selectById/{uid}")
    public Result selectById(@PathVariable("uid") int uid) throws Exception{
    	return restTemplate.getForObject("http://eureka-client1/selectById/" + uid, Result.class);
    }
    //Multiple parameters
    @GetMapping("/updateById")
    public Result updateById(Users users) throws Exception{
    	return restTemplate.getForObject("http://eureka-client1/updateById/" + users.getPassword() +"/"+ users.getUid(), Result.class);
    }
}

(2) Receiver

@RestController
public class UserClientController {
    @Resource
    private UserService us;
    //No parameters
    @GetMapping("/select")
    public Result select() throws Exception{
    	Result result = new Result();
    	List<Users> list = us.select();
    	if(list.size() > 0) {
    		result.setList(list);
    		result.setCode("success");
    	}else {
    		result.setMessage("error");
    	}
    	return result;
    }
    //Single parameter
    @GetMapping("/selectById/{uid}")
    public Result selectById(@PathVariable("uid") int uid) throws Exception{
    	Result result = new Result();
    	Users users = us.selectById(uid);
    	if(users != null) {
    		result.setObject(users);
    		result.setCode("success");
    	}else {
    		result.setMessage("error");
    	}
    	return result;
    }
    //Multiple parameters
    @GetMapping("/updateById/{password}/{uid}")
    public Result updateById(@PathVariable("password") String password, @PathVariable("uid") int uid) throws Exception{
    	Users users = new Users();
    	users.setUid(uid);
    	users.setPassword(password);
    	Result result = new Result();
    	us.updateById(users);
    	result.setCode("success");
    	return result;
    }
}

2. Post request mode

• postForEntity()
  POST data goes to a URL and returns ResponseEntity containing an object that is mapped from the body of the response.
  Here we are.
• postForObject()
  POST data goes to a URL and returns the object formed by matching the response volume.
• postForLocation()
  POST data goes to a URL and returns the URL of the newly created resource

(1) Requesting Party

@RestController
public class UserClientController {
    @Resource
    private RestTemplate restTemplate;    
 	@GetMapping("/updateById")
    public Result updateById(Users users) throws Exception{
    	Result result = restTemplate.postForObject("http://eureka-client1/updateById", users, Result.class);
    	return result;
    }
}

(2) Receiver

@RestController
public class UserClientController {
    @Resource
    private UserService us;
	@PostMapping("updateById")
	public Result updateById(@RequestBody Users users) throws Exception{
    	System.out.println(users.getUsername());
    	Result result = new Result();
    	us.updateById(users);
    	result.setCode("success");
    	return result;
	}
}

3. Put request mode

• put()
  PUT resource to a specific URL, put request mode does not return parameters

(1) Requesting Party

@RestController
public class UserRibbonController {
    @Resource
    private RestTemplate restTemplate;    
    @GetMapping("/updateById")
    public Result updateById(Users users) throws Exception{
    	restTemplate.put("http://eureka-client1/updateById", users, 11);
    	Result result = new Result();
    	result.setCode("success");
    	return result;
    }
}

(2) Receiver

@RestController
public class UserClientController {
    @Resource
    private UserService us;
    @PutMapping("updateById")
    public void updateById(@RequestBody Users users) throws Exception{
    	us.updateById(users);
    }
}

3. Delete request

• delete()
  Perform HTTP DELETE operations on resources at specific URL s

4. RestTemplate other methods

• exchange()
  Execute a specific HTTP method on the URL and return the ResponseEntity containing the object from the body of the response
  Mapped
• execute()
  Executing a specific HTTP method on the URL returns an object mapped from the response volume
• headForHeaders()
  Send an HTTP HEAD request and return the HTTP header containing a specific resource URL
• optionsForAllow()
  Send an HTTP OPTIONS request, returning the Allow header information for a specific URL