HttpClient和RestTemplate发送请求实例

在做后端的时候，我们难免会去请求其他应用获取到我们需要的数据。在Spring框架中一般使用HttpClient发送请求的方式，这种方式新手用起来相对麻烦。在SpringBoot中封装了RestTemplate，这种方式简单易学。本篇博客将用作者工作中的实例介绍这两种方式的用法，希望对大家有帮助。作者能力有限，有错请大牛们指教。不喜勿喷。

一、HttpClient的方式发送请求

1.发送GET请求

    @GetMapping("/doget")
    public String doget() {
        // 创建一个可关闭的http客户端
        CloseableHttpClient httpClient = HttpClients.createDefault();
        // 创建get请求
        HttpGet request = new HttpGet("http://localhost:8080/gets");
        HttpResponse response = null;
        try {
            //执行请求
            response = httpClient.execute(request);
            //得到并返回数据
            return EntityUtils.toString(response.getEntity(), "utf-8");
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }

2.发送POST请求

 @GetMapping("/dopost")
    public String dopost(String pp) throws IOException {
        // 创建一个可关闭的http客户端
        CloseableHttpClient httpClient = HttpClients.createDefault();
        // 创建post请求
        HttpPost post = new HttpPost("http://localhost:8080/posts");
        /**
         * 添加表单数据
         */
//        List<NameValuePair> valuePairs = new ArrayList<>();
//        valuePairs.add(new BasicNameValuePair("po", pp));
//        HttpEntity entity = new UrlEncodedFormEntity(valuePairs, Consts.UTF_8);
//        post.setEntity(entity);
        /**
         * 添加json数据
         */
        JSONObject object=new JSONObject();
        object.put("po",pp);
        post.addHeader("Content-type", "application/json;charset-utf-8");
        post.setEntity(new StringEntity(String.valueOf(object), Charset.forName("UTF-8")));
        // 执行请求
        HttpResponse response = httpClient.execute(post);
		//得到并返回数据
        return EntityUtils.toString(response.getEntity());
    }

二、RestTemplate的方式发送请求

准备工作：为了方便我们会先配置一个bean

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.client.RestTemplate;

@SpringBootApplication
@Configuration
public class HuskyApplication {

	public static void main(String[] args) {
		SpringApplication.run(HuskyApplication.class, args);
	}
	@Bean
	public RestTemplate restTemplate(){
		return new RestTemplate();
	}
}

1.发送GET请求

@RestController
public class RequestController {

    @Autowired
    private RestTemplate template;

    @GetMapping("/doget")
    public String doget() {
        return template.getForObject("http://localhost:8080/gets", String.class);
    }
}

2.发送POST请求
2.1发送表单数据

@RestController
public class RequestController {

    @Autowired
    private RestTemplate template;

    @GetMapping("/dopost")
    public String dopost() {
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.MULTIPART_FORM_DATA);

        MultiValueMap<String, String> map = new LinkedMultiValueMap<>();
        map.add("mchId", mchId);
        map.add("appId", appId);
        map.add("productId", productId);
        map.add("mchOrderNo", mchOrderNo);
        map.add("currency", currency);
        map.add("amount", amount);
        map.add("returnUrl", returnUrl);
        map.add("notifyUrl", notifyUrl);
        map.add("subject", subject);
        map.add("body", body);
        map.add("sign", sign);


        HttpEntity<MultiValueMap> entity = new HttpEntity<>(map, headers);
        ResponseEntity response = template.exchange("https://127.0.0.1:8080/api/pay/create_order", HttpMethod.POST, entity, String.class);
        return String.valueOf(response);
        }
}

2.2发送json数据

@RestController
public class RequestController {

    @Autowired
    private RestTemplate template;

    @GetMapping("/dopost")
    public String dopost() {
            HttpHeaders headers = new HttpHeaders();
            headers.setContentType(MediaType.APPLICATION_JSON);

            JSONObject params = new JSONObject();
            params.put("tradeDate", record.getTradeDate());
            params.put("tradeTime", record.getTradeTime());
            params.put("money", record.getMoney());
            params.put("tradeType", record.getTradeType());
            params.put("remark", record.getRemark());
            params.put("identity", record.getIdentity());
            params.put("bank", record.getBank());
            params.put("bankaccount", record.getBankAccount());// 招行bankaccount 注意a为小写
            log.info("数据："+params);
            HttpEntity<String> requestEntity = new HttpEntity<>(params.toJSONString(), headers);

            ResponseEntity<String> response = null;
            log.info("开始请求！");
            try {
                response = restTemplate.exchange("http://127.0.0.1:8081/alipayNewTransfer/bank", HttpMethod.POST,
                        requestEntity, String.class);
                log.info("结果："+response);
            } catch (Exception e) {
                e.printStackTrace();
            }
            if (response != null && response.getBody().contains("success")) {
                return true;
            }
        }
}