Java Http发送GET、POST请求

public class HttpRequest {
/**
* 向指定链接发送Get请求
*/
public static String sendGet(String url, String param) {
String result     = "";
BufferedReader in = null;

try {
String urlNameString = url + "?" + param;
URL realUrl = new URL(urlNameString);
// 打开和URL之间的连接
URLConnection connection = realUrl.openConnection();
// 设置通用的请求属性
connection.setRequestProperty("accept", "*/*");
connection.setRequestProperty("connection", "Keep-Alive");
connection.setRequestProperty("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");

// 建立实际的连接
connection.connect();

// 获取所有响应头字段
Map<String, List<String>> map = connection.getHeaderFields();

// 遍历所有的响应头字段
for(String key : map.keySet()) {
System.out.println(key + "--->" + map.get(key));
}

// 定义BufferedReader输入流来读取URL的响应
in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
String line;
while(null != (line = in.readLine())) {
result += line;
}
} catch(Exception e) {
System.out.println("发送GET请求出现异常！" + e);
e.printStackTrace();
} finally {
try {
if(null != in) {
in.close();
}
} catch(Exception e2) {
e2.printStackTrace();
}
}

return result;
}

/**
* 向指定URL发送POST方法的请求
* @param url
* @param param
* @return
*/
public static String sendPost(String url, String param) {
PrintWriter   out = null;
BufferedReader in = null;
String result     = "";

try {
URL realUrl = new URL(url);
URLConnection conn = realUrl.openConnection();

// 设置通用的请求属性
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
conn.setDoOutput(true);
conn.setDoInput(true);

// 获取URLConnection对象对应的输出流
out = new PrintWriter(conn.getOutputStream());
// 发送请求参数
out.print(param);
// flush输出流的缓冲
out.flush();
in = new BufferedReader(new InputStreamReader(conn.getInputStream()));
String line;
while(null != (line = in.readLine())) {
result += line;
}
} catch(Exception e) {
System.out.println("发送POST请求出现异常！" + e.getLocalizedMessage());
e.printStackTrace();
} finally {
try {
if(null != out) {
out.close();
}

if(null != in) {
in.close();
}
} catch(IOException ex) {
ex.printStackTrace();
}
}

return result;
}
}