SpringBoot使用RestTemplate

RestTemplate 是由 Spring 提供的一个 HTTP 请求工具，它提供了常见的REST请求方案的模版，例如 GET 请求、POST 请求、PUT 请求、DELETE 请求以及一些通用的请求执行方法 exchange 以及 execute。RestTemplate 继承自 InterceptingHttpAccessor 并且实现了 RestOperations 接口，其中 RestOperations 接口定义了基本的 RESTful 操作，这些操作在 RestTemplate 中都得到了实现。

POST请求 postForObject

1、使用LinkedMultiValueMap作为参数（Form表单提交）

RestTemplate template = new RestTemplate();
String url = "http://127.0.0.1:8800/product/update";

MultiValueMap paramMap = new LinkedMultiValueMap();
paramMap.add("id", "123");
paramMap.add("name", "张三");
String result = template.postForObject(url, paramMap, String.class);
System.out.println("result:" + result);

2、使用Object作为参数（JSON提交）

RestTemplate template = new RestTemplate();
String url = "http://127.0.0.1:8800/product/update";

User user = new User(123, "张三");
String result = template.postForObject(url, user, String.class);
System.out.println("result:" + result);

3、使用JSONObject作为参数（JSON提交）

RestTemplate template = new RestTemplate();
String url = "http://127.0.0.1:8800/product/update";

JSONObject obj = new JSONObject();
obj.put("id", "123");
obj.put("name", "张三");
String result = template.postForObject(url, obj, String.class);
System.out.println("result:" + result);

postForEntity

1、使用LinkedMultiValueMap作为参数（Form表单提交）

RestTemplate template = new RestTemplate();
String url = "http://127.0.0.1:8800/product/update";

HttpHeaders headers = new HttpHeaders();
headers.set("token", "asdf");

MultiValueMap paramMap = new LinkedMultiValueMap();
paramMap.add("id", "123");
paramMap.add("name", "张三");

HttpEntity httpEntity = new HttpEntity(paramMap, headers);
ResponseEntity response = template.postForEntity(url, httpEntity, String.class);
System.out.println("result:" + response.getBody());

2、使用Object作为参数（JSON提交）

RestTemplate template = new RestTemplate();
String url = "http://127.0.0.1:8800/product/update";

HttpHeaders headers = new HttpHeaders();

User user = new User(123, "张三");
HttpEntity httpEntity = new HttpEntity(user, headers);
ResponseEntity response = template.postForEntity(url, httpEntity, String.class);
System.out.println("result:" + response.getBody());

3、使用JSONObject为参数（JSON提交）

RestTemplate template = new RestTemplate();
String url = "http://127.0.0.1:8800/product/update";

HttpHeaders headers = new HttpHeaders();

JSONObject obj = new JSONObject();
obj.put("id", "123");
obj.put("name", "张三");
HttpEntity httpEntity = new HttpEntity(obj, headers);
ResponseEntity response = template.postForEntity(url, httpEntity, String.class);
System.out.println("result:" + response.getBody());

exchange

RestTemplate template = new RestTemplate();
String url = "http://127.0.0.1:8800/product/productDetail";

HttpHeaders headers = new HttpHeaders();
MultiValueMap paramMap = new LinkedMultiValueMap();
paramMap.add("id", "123");

HttpEntity httpEntity = new HttpEntity(paramMap, headers);
ResponseEntity response = template.exchange(url, HttpMethod.POST, httpEntity, String.class);
System.out.println("result:" + response.getBody());

postForObject和postForEntity方法的区别主要在于可以在postForEntity方法中设置header的属性，当需要指定header的属性值的时候，使用postForEntity方法。

exchange方法和postForEntity类似，但是更灵活，exchange还可以调用get、put、delete请求。

GET请求 getForObject

RestTemplate template = new RestTemplate();
String url = "http://127.0.0.1:8800/product/detail?id={id}";

Map paramMap = new HashMap();
paramMap.put("id", "123");

String result = template.getForObject(url, String.class, paramMap);
System.out.println("result:" + result);

getForEntity 

RestTemplate template = new RestTemplate();
String url = "http://127.0.0.1:8800/product/detail?id={id}";

Map paramMap = new HashMap();
paramMap.put("id", "123");

ResponseEntity response1 = template.getForEntity(url, String.class, paramMap);
System.out.println("result:" + response1.getBody());

exchange

RestTemplate template = new RestTemplate();
String url = "http://127.0.0.1:8800/product/productDetail";

HttpHeaders headers = new HttpHeaders();
headers.set("token", "asdf");

HttpEntity httpEntity = new HttpEntity(null, headers);
ResponseEntity response = template.exchange(url, HttpMethod.GET, httpEntity, String.class,paramMap);
System.out.println("result:" + response.getBody());