java模拟http的get和post请求

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.io.Reader;
import java.net.HttpURLConnection;
import java.net.ProtocolException;
import java.net.URL;
import java.util.Map;

/**
* HTTP工具
* @author robinzhang
*
*/
public class HttpUtil {
/**
* 请求类型： GET
*/
public final static String GET = "GET";
/**
* 请求类型： POST
*/
public final static String POST = "POST";

/**
* 模拟Http Get请求
* @param urlStr
*             请求路径
* @param paramMap
*             请求参数
* @return
* @throws Exception
*/
public static String get(String urlStr, Map<String, String> paramMap) throws Exception{
urlStr = urlStr + "?" + getParamString(paramMap);
HttpURLConnection conn = null;
try{
//创建URL对象
URL url = new URL(urlStr);
//获取URL连接
conn = (HttpURLConnection) url.openConnection();
//设置通用的请求属性
setHttpUrlConnection(conn, GET);
//建立实际的连接
conn.connect();
//获取响应的内容
return readResponseContent(conn.getInputStream());
}finally{
if(null!=conn) conn.disconnect();
}
}

/**
* 模拟Http Post请求
* @param urlStr
*             请求路径
* @param paramMap
*             请求参数
* @return
* @throws Exception
*/
public static String post(String urlStr, Map<String, String> paramMap) throws Exception{
HttpURLConnection conn = null;
PrintWriter writer = null;
try{
//创建URL对象
URL url = new URL(urlStr);
//获取请求参数
String param = getParamString(paramMap);
//获取URL连接
conn = (HttpURLConnection) url.openConnection();
//设置通用请求属性
setHttpUrlConnection(conn, POST);
//建立实际的连接
conn.connect();
//将请求参数写入请求字符流中
writer = new PrintWriter(conn.getOutputStream());
writer.print(param);
writer.flush();
//读取响应的内容
return readResponseContent(conn.getInputStream());
}finally{
if(null!=conn) conn.disconnect();
if(null!=writer) writer.close();
}
}

/**
* 读取响应字节流并将之转为字符串
* @param in
*         要读取的字节流
* @return
* @throws IOException
*/
private static String readResponseContent(InputStream in) throws IOException{
Reader reader = null;
StringBuilder content = new StringBuilder();
try{
reader = new InputStreamReader(in);
char[] buffer = new char[1024];
int head = 0;
while( (head=reader.read(buffer))>0 ){
content.append(new String(buffer, 0, head));
}
return content.toString();
}finally{
if(null!=in) in.close();
if(null!=reader) reader.close();
}
}

/**
* 设置Http连接属性
* @param conn
*             http连接
* @return
* @throws ProtocolException
* @throws Exception
*/
private static void setHttpUrlConnection(HttpURLConnection conn, String requestMethod) throws ProtocolException{
conn.setRequestMethod(requestMethod);
conn.setRequestProperty("accept", "*/*");
conn.setRequestProperty("Accept-Language", "zh-CN");
conn.setRequestProperty("User-Agent", "Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; WOW64; Trident/5.0)");
conn.setRequestProperty("Proxy-Connection", "Keep-Alive");
if(null!=requestMethod && POST.equals(requestMethod)){
conn.setDoOutput(true);
conn.setDoInput(true);
}
}

/**
* 将参数转为路径字符串
* @param params
*             参数
* @return
*/
private static String getParamString(Map<String, String> paramMap){
if(null==paramMap || paramMap.isEmpty()){
return "";
}
StringBuilder builder = new StringBuilder();
for(String key : paramMap.keySet() ){
builder.append("&")
.append(key).append("=").append(paramMap.get(key));
}
return builder.deleteCharAt(0).toString();
}

public static void main(String[] args){
try {
System.out.println( get("http://127.0.0.1/crazy_java.pdf", null) );
} catch (Exception e) {
e.printStackTrace();
}
}
}