使用Java内置类HttpUrlConnection实现HTTP请求(2)

if (status == HttpURLConnection.HTTP_MOVED_TEMP
  || status == HttpURLConnection.HTTP_MOVED_PERM) {
    String location = con.getHeaderField("Location");
    URL newUrl = new URL(location);
    con = (HttpURLConnection) newUrl.openConnection();
 }

9. 读取响应

通过读取HttpUrlConnection实例的InputStream流来读取响应。

读取响应常用方法有getResponseCode(), connect(), getInputStream() or getOutputStream() 。

比如，读取响应状态码：

int status = con.getResponseCode();

比如，读取响应头：

String contentType = con.getHeaderField("Content-Type");

比如，读取响应文本：

BufferedReader in = new BufferedReader(
  new InputStreamReader(con.getInputStream()));
String inputLine;
StringBuffer content = new StringBuffer();
while ((inputLine = in.readLine()) != null) {
    content.append(inputLine);
}
in.close();

关闭连接：

con.disconnect();

结论

在这篇文章中，我们展示了如何通过HttpUrlConnection类来时间Http请求。以下代码可以直接拷贝使用。由于太简单，就不传github了。

package com.linuxidc.utils;

import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder;
import java.util.HashMap;
import java.util.Map;

public class HttpUtil {

private static String POST = "POST";
    private static String GET = "GET";
    private static String CONTENT_TYPE_URLENCODED = "application/x-www-form-urlencoded";
    private static String CONTENT_TYPE_JSON = "application/json";

private static String httpRequest(String method, String contentType, String urlStr, HashMap<String,String> paras)
            throws IOException {
        URL url = new URL(urlStr);
        HttpURLConnection con = (HttpURLConnection) url.openConnection();
        con.setConnectTimeout(5000);
        con.setReadTimeout(5000);
        con.setRequestMethod("POST");
        con.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");

if(paras != null && !paras.isEmpty()){
            con.setDoOutput(true);
            DataOutputStream out = new DataOutputStream(con.getOutputStream());
            out.writeBytes(ParameterStringBuilder.getParamsString(paras));
            out.flush();
            out.close();
        }
       

BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream()));
        String inputLine;
        StringBuffer content = new StringBuffer();
        while ((inputLine = in.readLine()) != null) {
            content.append(inputLine);
        }
        in.close();
        con.disconnect();
        return content.toString();
    }

private static class ParameterStringBuilder {
        public static String getParamsString(Map<String, String> params)
                throws UnsupportedEncodingException {
            StringBuilder result = new StringBuilder();

for (Map.Entry<String, String> entry : params.entrySet()) {
                result.append(URLEncoder.encode(entry.getKey(), "UTF-8"));
                result.append("=");
                result.append(URLEncoder.encode(entry.getValue(), "UTF-8"));
                result.append("&");
            }

String resultString = result.toString();
            return resultString.length() > 0
                    ? resultString.substring(0, resultString.length() - 1)
                    : resultString;
        }
    }