java http工具类

Java提供了很多http工具类，其中比较常用的是`HttpURLConnection`和`HttpClient`。

1. HttpURLConnection：

URL url = new URL(urlStr);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();

// 设置请求方式和超时时间
conn.setRequestMethod("GET");
conn.setConnectTimeout(5000);
conn.setReadTimeout(5000);

// 发送请求
int responseCode = conn.getResponseCode();

if (responseCode == 200) {
    // 读取响应流
    InputStream inputStream = conn.getInputStream();
    BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
    String line;
    StringBuilder response = new StringBuilder();
    while ((line = bufferedReader.readLine()) != null) {
        response.append(line);
    }
    inputStream.close();
    conn.disconnect();
    return response.toString();
} else {
    conn.disconnect();
    return null;
}

2. HttpClient：

CloseableHttpClient httpClient = HttpClients.createDefault();
HttpGet httpGet = new HttpGet(urlStr);

// 设置请求参数
RequestConfig requestConfig = RequestConfig.custom()
        .setConnectTimeout(5000)
        .setConnectionRequestTimeout(5000)
        .setSocketTimeout(5000)
        .build();
httpGet.setConfig(requestConfig);

// 发送请求
HttpResponse response = httpClient.execute(httpGet);

if (response.getStatusLine().getStatusCode() == 200) {
    // 读取响应流
    HttpEntity entity = response.getEntity();
    String result = EntityUtils.toString(entity, "utf-8");
    EntityUtils.consume(entity);
    httpClient.close();
    return result;
} else {
    httpClient.close();
    return null;
}

以上代码仅供参考，实际应用中需要根据具体需求进行适当的修改。