RestTemplate之微服务之间的调用

1.。。。RestTemplate是spring的一个rest客户端，在spring-web这个包下，spring boot的依赖如下

            org.springframework.boot
            spring-boot-starter-web
        

导入json解析依赖 此依赖是发送post请求时将对象转化的

    net.sf.json-lib
    json-lib
    2.4
    jdk15

2.。。。在配置类中配置restTemplate  此处设置了连接超时时间和读取的超时时间

@Bean
public RestTemplate restTemplate() {
    SimpleClientHttpRequestFactory requestFactory = new SimpleClientHttpRequestFactory();
    // 设置超时
    requestFactory.setConnectTimeout(60000);
        requestFactory.setReadTimeout(60000);

    //利用复杂构造器可以实现超时设置，内部实际实现为 HttpClient
    RestTemplate restTemplate = new RestTemplate(requestFactory);
    return restTemplate;
}

3.然后在需要用到的类中注入

@Autowired
private RestTemplate restTemplate;

发送Post请求

//设置请求头的编码格式
 HttpHeaders headers = new HttpHeaders();
 MediaType type = MediaType.parseMediaType("application/json; charset=UTF-8");
 headers.setContentType(type);
 headers.add("Accept", MediaType.APPLICATION_JSON.toString());
//请求的实体
 ClientTokenVM clientTokenVM = new ClientTokenVM();
 clientTokenVM.setToken(publishBean.getToken());
//将实体转换成json对象（好像是必须转的，不转就各种报错啊 一下午）
 JSONObject jsonObj = JSONObject.fromObject(clientTokenVM);
 HttpEntity formEntity = new HttpEntity<>(jsonObj.toString(), headers);
 //调用api接口获取新的token(请求路径加在配置文件中)
 String tokenInfo = restTemplate.postForObject("url", formEntity, String.class);
 JSONObject jsonObject = JSONObject.fromObject(tokenInfo);
 if (jsonObject != null && Boolean.TRUE.equals(jsonObject.get("success"))) {
     //取出新的token
     String newToken = jsonObject.getString("data");
 }

有时候发送post请求可以会传map类型的参数 此时应该 用new LinkedMultiValueMap<>();

HttpHeaders reqHeaders = new HttpHeaders();
reqHeaders.setContentType(MediaType.APPLICATION_FORM_URLENCODED);
MultiValueMap formParams = new LinkedMultiValueMap<>();//此处用这个
formParams.set("grant_type", "client_credentials");
addAuthentication(reqHeaders);
HttpEntity> entity = new HttpEntity<>(formParams, reqHeaders);
log.debug("contacting OAuth2 token endpoint to authenticate internal service.");
ResponseEntity responseEntity = restTemplate.postForEntity(tokenUrl, entity,
        OAuth2AccessToken.class);
if (responseEntity.getStatusCode() != HttpStatus.OK) {
    log.debug("failed to authenticate user with OAuth2 token endpoint, status: {}",
            responseEntity.getStatusCodeValue());
    throw new HttpClientErrorException(responseEntity.getStatusCode());
}
OAuth2AccessToken accessToken = responseEntity.getBody();

GET请求

String jsonResult = restTemplate.getForEntity(url, String.class).getBody();
//将返回结果搞成json 然后从json中取数据
JSONObject jsonObject = JSONObject.fromObject(jsonResult);

exchange请求（推荐）

利用此请求可以轻松在post和get请求间切换

HttpHeaders headers = new HttpHeaders();
        headers.add(AUTHORIZATION_HEADER, String.format("%s %s", BEARER_TOKEN_TYPE, accessToken.getValue()));
        MediaType type = MediaType.parseMediaType("application/json; charset=UTF-8");
        headers.setContentType(type);
        headers.add("Accept", MediaType.APPLICATION_JSON.toString());
        SearchNameVM searchNameVM = new SearchNameVM(name);
        JSONObject jsonObj = JSONObject.fromObject(searchNameVM);
        HttpEntity requestEntity = new HttpEntity<>(jsonObj.toString(), headers);
        //3.请求base接口获取数据baseUrl + BASE_URI
        ResponseEntity response = restTemplate.exchange(baseUrl, HttpMethod.POST, requestEntity, List.class);
        if (response.getStatusCode().is2xxSuccessful()) {
 List body = response.getBody();
            //4.将租户id和名称组装返回
            List resultList = Lists.newArrayList();
            body.stream().forEach(e -> {
                TanentInfoViewEntity tanentInfoViewEntity = new TanentInfoViewEntity((String) e.get("tenantId"), (String) e.get("tenantName"));
                resultList.add(tanentInfoViewEntity);

            });
            return resultList;
        }

此例子是我从另一个微服务发送post请求返回的list数据里边放的是map类型 将其取出来 放到新对象 将对象装进集合的操作

 

4.其他相关-异步调用（AsyncRestTemplate）：

在很多场景中我们需要异步调用，我们使用RestTemplate的兄弟类AsyncRestTemplate。 AsyncRestTemplate是在Spring4.0中对RestTemplate进行扩展产生的新类，其为客户端提供了异步http请求处理的一种机制，通过返回ListenableFuture对象生成回调机制，以达到异步非阻塞发送http请求。

public String asyncReq(){  
        String url = "http://localhost:8080/jsonAsync";  
        ListenableFuture> future = asyncRestTemplate.getForEntity(url, JSONObject.class);  
        future.addCallback(new SuccessCallback>() {  
            public void onSuccess(ResponseEntity result) {  
                System.out.println(result.getBody().toJSONString());  
            }  
        }, new FailureCallback() {  
            public void onFailure(Throwable ex) {  
                System.out.println("onFailure:"+ex);  
            }  
        });  
        return "this is async sample";  
}