SpringBoot远程接口调用-RestTemplate使用

　　在web服务中,调度远程url是常见的使用场景,最初多采用原生的HttpClient,现采用Spring整合的RestTemplate工具类进行.实操如下:

　　1. 配置

　　主要用以配置远程链接的相关参数.

@Configuration
public class RestTemplateConfig {

    @Bean
    public RestTemplate restTemplate(ClientHttpRequestFactory factory) {
        return new RestTemplate(factory);
    }

    @Bean
    public ClientHttpRequestFactory simpleClientHttpRequestFactory() {
        SimpleClientHttpRequestFactory factory = new SimpleClientHttpRequestFactory();
        factory.setConnectTimeout(15000);
        factory.setReadTimeout(5000);
        return factory;
    }

}

　　2.实际使用

　　此处以post请求为例,使用RestTemplate时主要有以下三种方式:postForObject/postForEntity/exchange

@Autowired
private RestTemplate template;

        String url = "http://192.168.2.40:8081/channel/channelHourData/getHourNewUserData";
        // 封装参数，千万不要替换为Map与HashMap，否则参数无法传递
        MultiValueMap<String, Object> paramMap = new LinkedMultiValueMap<String, Object>();
        paramMap.add("dt", "20180416");

        // 1、使用postForObject请求接口
        String result = template.postForObject(url, paramMap, String.class);
        System.out.println("result1==================" + result);

        // 2、使用postForEntity请求接口
        HttpHeaders headers = new HttpHeaders();
        HttpEntity<MultiValueMap<String, Object>> httpEntity = new HttpEntity<MultiValueMap<String, Object>>(paramMap,headers);
        ResponseEntity<String> response2 = template.postForEntity(url, httpEntity, String.class);
        System.out.println("result2====================" + response2.getBody());

        // 3、使用exchange请求接口
        ResponseEntity<String> response3 = template.exchange(url, HttpMethod.POST, httpEntity, String.class);
        System.out.println("result3====================" + response3.getBody());   

　　3.实操演示

　　昨日在与其它服务做对接数据时,发现对方实际接收数据有误,换了几种请求方式,要么就是编码有误/要么就是请求体展示有误,随着问题排查的深入,还出现了框架层面报错类转换异常的问题

　　代码如下 :

// 发送请求

String url = callback;

HttpHeaders requestHeaders = new HttpHeaders();
//requestHeaders.add("Content-Type","application/x-www-form-urlencoded");
requestHeaders.add("charset","UTF-8");
requestHeaders.setContentType(MediaType.APPLICATION_FORM_URLENCODED);

LinkedMultiValueMap<String, Object> paramMap = new LinkedMultiValueMap<>();
paramMap.add("message","Ok");
paramMap.add("code","200");
paramMap.add("data",data.toJSONString());

HttpEntity<LinkedMultiValueMap<String,Object>> httpEntity = new HttpEntity<>(paramMap, requestHeaders);

ResponseEntity<String> exchange = restTemplate.postForEntity(url,httpEntity,String.class);

String resultRemote = exchange.getBody();

　　注意事项:

　　1.与接口方约定好请求头信息 , 如 此处的媒体类型值即为 :  application/x-www-form-urlencoded

　　2.在使用HttpEntity时,注意请求体,value需为String类型.原因在于:Spring框架在遍历请求体参数时,会强转为String,故此处code设置为 "200"