RestTemplate调用POST和GET请求示例详解

postForObject/postForEntity(String url, Object request, Class<T> responseType, Object... uriVariables)
eg：
void fun() {
    HttpHeaders headers = new HttpHeaders(); 
    headers.setContentType(MediaType.APPLICATION_JSON);
    MultiValueMap<String, Object> params = new LinkedMultiValueMap<>();
    HttpEntity<String> httpEntity = new HttpEntity<>(params, headers);
    // 注意，如果想要使用可变参数来拼接url，那这里的url一定要使用占位符{}替换，并且名称要和可变参数名称一样才能在运行时将占位符位置替换成传入动态参数【可变参数也可以不传，那么这里的url就不需要占位符拼接】
    String url = "http://www.sea.com?uid={uid}&username={username}";
    String uid = "123";
    String username = "sea";
    // 因为responseType用的是String类型，所以返回的是一个String类型字符串
    String result = restTemplate.postForObject(url, httpEntity, String.class, uid, username);
}
postForObject/postForEntity(String url, Object request, Class<T> responseType, Map<String, ?> uriVariables)
eg：
void fun() {
    HttpHeaders headers = new HttpHeaders(); 
    headers.setContentType(MediaType.APPLICATION_jsON);
    MultiValueMap<String, Object> params = new LinkedMultiValueMap<>();
    HttpEntity<String> httpEntity = new HttpEntity<>(params, headers);
    // 注意，如果想要使用可变参数来拼接url，那这里的url一定要使用占位符{}替换，并且名称要和可变参数名称一样才能在运行时将占位符位置替换成传入动态参数
    String url = "http://www.sea.com?uid={uid}&username={username}";
    Map<String, Object> params = new HashMap<>();
    String uid = "123";
    String username = "sea";
    params.put("uid", uid);
    params.put("username", username)
    // 因为responseType用的是String类型，所以返回的是一个String类型字符串
    String result = restTemplate.postForObject(url, httpEntity, String.class, params);
}
postForObject/postForEntity(URI url, Object request, Class<T> responseType)
eg：
void fun() {
    HttpHeaders headers = new HttpHeaders(); 
    headers.setContentType(MediaType.APPLICATION_JSON);
    MultiValueMap<String, Object> params = new LinkedMultiValueMap<>();
    HttpEntity<String> httpEntity = new HttpEntity<>(params, headers);
    String url = "http://www.sea.com";
    MultiValueMap<String, String> multiValueMap = new LinkedMultiValueMap<>();
    multiValueMap.put("uid", 123);
    multiValueMap.put("username", "sea");
    // 不再使用可变参数绑定url，直接传入绑定后的uri参数
    URI uri = UriComponentsBuilder.fromHttpUrl(url).queryParams(multiValueMap).build().encode().toUri();
    // 因为responseType用的是String类型，所以返回的是一个String类型字符串
    String result = restTemplate.postForObject(uri, httpEntity, String.class);
}
eg: xxforEntity()
void fun() {
    Map<String, Object> map = new HashMap<>();
    map.put("uid", 123);
    map.put("username", "sea");
    HttpHeaders headers = new HttpHeaders();
    headers.setContentType(MediaType.APPLICATION_JSON);
    HttpEntity<HashMap<String, Object>> httpEntity = new HttpEntity<>(map, headers);
    String url = "http://www.sea.com";
    // 使用xxforEntity,返回的是一个ResponseEntity，里面包含了statusCode(状态码)、Headers(响应头)、body(响应体)
    ResponseEntity<String> responseEntity = restTemplate.postForEntity(uri, httpEntity, String.class);
}

getForObject/getForEntity(String url, Class<T> responseType, Object... uriVariables)
getForObject/getForEntity(String url, Class<T> responseType, Map<String, ?> uriVariables)
getForObject/getForEntity(URI url, Class<T> responseType)
在get请求调用中，除了请求参数中少了Object request【请求头和请求体】，其他的参数和方法调用同上面post的方法调用是一样的