Java Post 连接使用 Try 和资源

Question

我想使用 try 和资源来实现处理 POST 请求的代码。

以下是我的代码:

public static String sendPostRequestDummy(String url, String queryString) {
    log.info("Sending 'POST' request to URL : " + url);
    log.info("Data : " + queryString);
    BufferedReader in = null;
    HttpURLConnection con = null;
    StringBuilder response = new StringBuilder();
    try{
        URL obj = new URL(url);
        con = (HttpURLConnection) obj.openConnection();
        // add request header
        con.setRequestMethod("POST");
        con.setRequestProperty("User-Agent", "Mozilla/5.0");
        con.setRequestProperty("Accept-Language", "en-US,en;q=0.5");
        con.setRequestProperty("Content-Type", "application/json");
        // Send post request
        con.setDoOutput(true);
        DataOutputStream wr = new DataOutputStream(con.getOutputStream());
        wr.writeBytes(queryString);
        wr.flush();
        wr.close();
        int responseCode = con.getResponseCode();
        log.info("Response Code : " + responseCode);
        if (responseCode >= 400)
            in = new BufferedReader(new InputStreamReader(con.getErrorStream()));
        else 
            in = new BufferedReader(new InputStreamReader(con.getInputStream()));

        String inputLine;

        while ((inputLine = in.readLine()) != null) {
            response.append(inputLine);
        }
    }catch(Exception e){
        log.error(e.getMessage(), e);
        log.error("Error during posting request");
    }
    finally{
        closeConnectionNoException(in,con);
    }
    return response.toString();
}

我对代码有以下担忧:

1. 针对上述场景，如何在 try 和 resources 中引入条件语句？
2. 有没有办法在尝试资源时传递连接？ (可以使用嵌套的 try-catch block 来完成，因为 URL 和 HTTPConnection 不是 AutoCloseable，这本身不是一个合规的解决方案)
3. 使用 try 和资源来解决上述问题是否是更好的方法？

Answer 1

试试这个。

HttpURLConnection con = (HttpURLConnection) obj.openConnection();
try (AutoCloseable conc = () -> con.disconnect()) {
    // add request headers
    try (DataOutputStream wr = new DataOutputStream(con.getOutputStream())) {
        wr.writeBytes(queryString);
    }
    int responseCode = con.getResponseCode();
    try (InputStream ins = responseCode >= 400 ? con.getErrorStream() : con.getInputStream();
        BufferedReader in = new BufferedReader(new InputStreamReader(ins))) {
        // receive response
    }
}

() -> con.disconnect() 是一个 lambda 表达式，它在 try 语句的最后阶段执行 con.disconnect()。