RestTemplate 用法

RestTemplate是Spring框架提供的一个用于发送HTTP请求的客户端工具类。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和execute。

以下是RestTemplate的一些基本用法：

1. 创建RestTemplate实例：

private static RestTemplate restTemplate = new RestTemplate();

2. 发送GET请求：

String url = "http://example.com/api/resource";
ResponseEntity<String> response = restTemplate.getForEntity(url, String.class);

3. 发送POST请求：

String url = "http://example.com/api/resource";
HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_JSON);
JSONObject requestBody = new JSONObject();
requestBody.put("key", "value");
HttpEntity<String> entity = new HttpEntity<>(requestBody.toString(), headers);
ResponseEntity<String> response = restTemplate.postForEntity(url, entity, String.class);

4. 发送PUT请求：

String url = "http://example.com/api/resource";
HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_JSON);
JSONObject requestBody = new JSONObject();
requestBody.put("key", "value");
HttpEntity<String> entity = new HttpEntity<>(requestBody.toString(), headers);
ResponseEntity<String> response = restTemplate.put(url, entity, String.class);

5. 发送DELETE请求：

String url = "http://example.com/api/resource";
ResponseEntity<String> response = restTemplate.delete(url, String.class);

6. 使用exchange方法发送请求：

String url = "http://example.com/api/resource";
HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_JSON);
JSONObject requestBody = new JSONObject();
requestBody.put("key", "value");
HttpEntity<String> entity = new HttpEntity<>(requestBody.toString(), headers);
ResponseEntity<String> response = restTemplate.exchange(url, HttpMethod.POST, entity, String.class);

7. 使用execute方法发送请求：

String url = "http://example.com/api/resource";
HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_JSON);
JSONObject requestBody = new JSONObject();
requestBody.put("key", "value");
HttpEntity<String> entity = new HttpEntity<>(requestBody.toString(), headers);
ResponseEntity<String> response = restTemplate.execute(url, HttpMethod.POST, entity, String.class);