多种方式实现（jdk原生api实现/httpClient的实现） java 发送http（post/get）请求并携带参数（讲解超详细）

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.URL;
import java.net.URLConnection;

public class DemoPrimary {

public static void main(String[] args) {
PrintWriter out = null;
BufferedReader in = null;
StringBuilder result = new StringBuilder();
String url = "http://www.baidu.com";
String sign = "11f5c83b448383cdb34330d5ddc88209";
try {
URL realUrl = new URL(url);
// 打开和URL之间的连接
URLConnection conn = realUrl.openConnection();

/*
* 设置通用的请求头属性
*
* */
conn.setRequestProperty("accept", "*/*");
conn.setRequestProperty("connection", "Keep-Alive");
conn.setRequestProperty("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");

// 发送POST请求必须设置如下两行   否则会抛异常（java.net.ProtocolException: cannot write to a URLConnection if doOutput=false - call setDoOutput(true)）
conn.setDoOutput(true);
conn.setDoInput(true);

/*
*  获取URLConnection对象对应的输出流并开始发送参数
*
*  */
out = new PrintWriter(conn.getOutputStream());
//下面开始设置参数，下面是随便模拟的两个参数sign和name
out.print("&sign="+sign);//设置一个参数sign
out.print("&name="+"zhangsan");//设置一个参数name
// flush输出流的缓冲
out.flush();

// 定义BufferedReader输入流来读取URL的响应
in = new BufferedReader(new InputStreamReader(conn.getInputStream()));
String line;
while ((line = in.readLine()) != null) {
result.append(line);
}
} catch (Exception e) {
e.printStackTrace();
}finally {// 使用finally块来关闭输出流、输入流
try {
if (out != null) {
out.close();
}
if (in != null) {
in.close();
}
} catch (IOException ex) {
ex.printStackTrace();
}
}
System.out.println(result.toString());
}
}