java模擬http的get和post請求

如題，使用Java模擬GET和POST請求。使用GET可以實現網頁抓取，使用POST可以實現 對某些網站登錄的暴力破解。 不過僅是練習，實際意義不大。

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 {
    /**
     * 請求類型： GET
     */
    public final static String GET = "GET";
    /**
     * 請求類型： POST
     */
    public final static String POST = "POST";
    
    /**
     * 模擬Http Get請求
     * @param urlStr
     *             請求路徑
     * @param paramMap
     *             請求參數
     * @return
     * @throws Exception
     */
    public static String get(String urlStr, Map<String, String> paramMap) throws Exception{
        urlStr = urlStr + "?" + getParamString(paramMap);
        HttpURLConnection conn = null;
        try{
            //創建URL對象
            URL url = new URL(urlStr);
            //獲取URL連接
            conn = (HttpURLConnection) url.openConnection();
            //設置通用的請求屬性
            setHttpUrlConnection(conn, GET);
            //建立實際的連接
            conn.connect();
            //獲取響應的內容
            return readResponseContent(conn.getInputStream());
        }finally{
            if(null!=conn) conn.disconnect();
        }
    }
    
    /**
     * 模擬Http Post請求
     * @param urlStr
     *             請求路徑
     * @param paramMap
     *             請求參數
     * @return
     * @throws Exception 
     */
    public static String post(String urlStr, Map<String, String> paramMap) throws Exception{
        HttpURLConnection conn = null;
        PrintWriter writer = null;
        try{
            //創建URL對象
            URL url = new URL(urlStr);
            //獲取請求參數
            String param = getParamString(paramMap);
            //獲取URL連接
            conn = (HttpURLConnection) url.openConnection();
            //設置通用請求屬性
            setHttpUrlConnection(conn, POST);
            //建立實際的連接
            conn.connect();
            //將請求參數寫入請求字符流中
            writer = new PrintWriter(conn.getOutputStream());
            writer.print(param);
            writer.flush();
            //讀取響應的內容
            return readResponseContent(conn.getInputStream());
        }finally{
            if(null!=conn) conn.disconnect();
            if(null!=writer) writer.close();
        }
    }
    
    /**
     * 讀取響應字節流並將之轉為字符串
     * @param in
     *         要讀取的字節流
     * @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();
        }
    }
    
    /**
     * 設置Http連接屬性 
     * @param conn
     *             http連接
     * @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);
        }
    }
    
    /**
     * 將參數轉為路徑字符串
     * @param params
     *             參數
     * @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();
        }
    }
}