手动发起get、post请求 -- HttpURLConnection

前言

    现在对接接口数据，都有一些很好用的工具类，例如：RestTemplate，但有些场景还是需要我们自己手动去实现，而且自己实现一遍也有利我们理解。废话不多说了，现在通过HttpURLConnection来发起get、post请求。

Get请求

    @GetMapping("/getMethod")
    public String testGetMethod() {
        String result = "";
        String path = "http://127.0.0.1:8083/device/list?pageNo=1&pageSize=5&deviceType=IPC";
        try {
            URL url = new URL(path);
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            // 设置请求方式
            conn.setRequestMethod(HttpMethod.GET.name());
            // 设置超时时间
            conn.setConnectTimeout(5000);
            conn.setReadTimeout(5000);

            int code = conn.getResponseCode();
            // 2xxx成功 3xxx重定向 4xxx资源错误 5xxx服务器错误
            if (code == 200) {
                InputStream is = conn.getInputStream();
                // 从输入流读取字符串，指定编码格式为UTF-8，不然会出现乱码的问题。
                result = StreamUtils.copyToString(is, Charset.forName("UTF-8"));
            }

        } catch (IOException e) {
            e.printStackTrace();
        }

        return result;
    }

StreamUtils是Spring框架的一个数据流工具类，这边大家也可以自己实现，下面贴一下源码

	/**
	 * Copy the contents of the given InputStream into a String.
	 * Leaves the stream open when done.
	 * @param in the InputStream to copy from (may be {@code null} or empty)
	 * @return the String that has been copied to (possibly empty)
	 * @throws IOException in case of I/O errors
	 */
	public static String copyToString(@Nullable InputStream in, Charset charset) throws IOException {
		if (in == null) {
			return "";
		}

		StringBuilder out = new StringBuilder();
		InputStreamReader reader = new InputStreamReader(in, charset);
		char[] buffer = new char[BUFFER_SIZE];
		int bytesRead = -1;
		while ((bytesRead = reader.read(buffer)) != -1) {
			out.append(buffer, 0, bytesRead);
		}
		return out.toString();
	}

 

Post请求

post请求传参的时候一般有两种方式：RequestParam和RequestBody。

RequestParam

使用类似于get方式的key-value传参方式，Content-Type为application/x-www-form-urlencoded。

    @GetMapping("/postMethod")
    public String testPostMethod() {
        String result = "";
        String path = "http://127.0.0.1:8083/device/query";
        try {
            URL url = new URL(path);
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            // 设置请求方式
            conn.setRequestMethod(HttpMethod.POST.name());
            // 设置传参方式，当服务端通过@RequestParam接受参数时，使用application/x-www-form-urlencoded
            conn.setRequestProperty("Content-Type","application/x-www-form-urlencoded");
            // 设置超时时间
            conn.setConnectTimeout(5000);
            conn.setReadTimeout(5000);

            String param = "pageNo=1&pageSize=5&deviceType=IPC";
            conn.setDoOutput(true);
            conn.getOutputStream().write(param.getBytes(Charset.forName("UTF-8")));

            int code = conn.getResponseCode();
            if (code == 200) {
                InputStream is = conn.getInputStream();
                // 从输入流读取字符串，指定编码格式为UTF-8，不然会出现乱码的问题。
                result = StreamUtils.copyToString(is, Charset.forName("UTF-8"));
            }

        } catch (IOException e) {
            e.printStackTrace();
        }
        return result;
    }

RequestBody

一般使用json格式传递参数，Content-Type为application/json。

    @GetMapping("/postJsonMethod")
    public String testPostJsonMethod() {
        String result = "";
        String path = "http://127.0.0.1:8083/device/create";
        try {
            URL url = new URL(path);
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            // 设置请求方式
            conn.setRequestMethod(HttpMethod.POST.name());
            // 设置传参方式，当服务端通过@RequestBody接受参数时，使用application/json
            conn.setRequestProperty("Content-Type","application/json");
            // 设置超时时间
            conn.setConnectTimeout(5000);
            conn.setReadTimeout(5000);

            JSONObject param = new JSONObject();
            param.put("id", "0019318cac98402e83f3367102360777");
            param.put("deviceType", "IPC");
            param.put("name", "测试");
            param.put("gbid", "31011700041325005777");
            param.put("status", 1);
            param.put("latitude", 0.0);
            param.put("longitude", 0.0);
            conn.setDoOutput(true);
            conn.getOutputStream().write(param.toJSONString().getBytes(Charset.forName("UTF-8")));

            int code = conn.getResponseCode();
            if (code == 200) {
                InputStream is = conn.getInputStream();
                // 从输入流读取字符串，指定编码格式为UTF-8，不然会出现乱码的问题。
                result = StreamUtils.copyToString(is, Charset.forName("UTF-8"));
            }

        } catch (IOException e) {
            e.printStackTrace();
        }
        return result;
    }

 

注：读取数据的时候一定要指定编码格式为UTF-8，不然会出现乱码的问题。