[Java] Java发送post方法详解

/**
   * post请求（用于请求json格式的参数）
   *
   * @param url  地址
   * @param params json格式的参数
   * @return
   */
  public static string dopost(string url, string params) throws exception {
 
  closeablehttpclient httpclient = httpclients.createdefault();
  httppost httppost = new httppost( url );// 创建httppost
  httppost.setheader( "accept", "application/json" );
  httppost.setheader( "content-type", "application/json" );
  string charset = "utf-8";
  stringentity entity = new stringentity( params, charset );
  httppost.setentity( entity );
  closeablehttpresponse response = null;
 
  try {
 
    response = httpclient.execute( httppost );
    statusline status = response.getstatusline();
    int state = status.getstatuscode();
    if (state == httpstatus.sc_ok) {
    httpentity responseentity = response.getentity();
    string jsonstring = entityutils.tostring( responseentity );
    return jsonstring;
    } else {
    logger.error( "请求返回:" + state + "(" + url + ")" );
    }
  } finally {
    if (response != null) {
    try {
      response.close();
    } catch (ioexception e) {
      e.printstacktrace();
    }
    }
    try {
    httpclient.close();
    } catch (ioexception e) {
    e.printstacktrace();
    }
  }
  return null;
  }

/**
   * post请求(用于key-value格式的参数)
   *
   * @param url
   * @param params
   * @return
   */
  public static string dopost(string url, map params) {
 
  bufferedreader in = null;
  try {
    // 定义httpclient
    httpclient client = new defaulthttpclient();
    // 实例化http方法
    httppost request = new httppost();
    request.seturi( new uri( url ) );
 
    //设置参数
    list<namevaluepair> nvps = new arraylist<namevaluepair>();
    for (iterator iter = params.keyset().iterator(); iter.hasnext(); ) {
    string name = (string) iter.next();
    string value = string.valueof( params.get( name ) );
    nvps.add( new basicnamevaluepair( name, value ) );
 
    //system.out.println(name +"-"+value);
    }
    request.setentity( new urlencodedformentity( nvps, http.utf_8 ) );
 
    httpresponse response = client.execute( request );
    int code = response.getstatusline().getstatuscode();
    if (code == 200) {  //请求成功
    in = new bufferedreader( new inputstreamreader( response.getentity()
      .getcontent(), "utf-8" ) );
    stringbuffer sb = new stringbuffer( "" );
    string line = "";
    string nl = system.getproperty( "line.separator" );
    while ((line = in.readline()) != null) {
      sb.append( line + nl );
    }
    in.close();
 
    return sb.tostring();
    } else {  //
    system.out.println( "状态码：" + code );
    return null;
    }
  } catch (exception e) {
    e.printstacktrace();
    return null;
  }
  }

/**
   * get请求
   *
   * @return
   */
  public static string doget(string url) {
  try {
    httpclient client = new defaulthttpclient();
    //发送get请求
    httpget request = new httpget( url );
    httpresponse response = client.execute( request );
    /**请求发送成功，并得到响应**/
    if (response.getstatusline().getstatuscode() == httpstatus.sc_ok) {
    /**读取服务器返回过来的json字符串数据**/
    string strresult = entityutils.tostring( response.getentity() );
    return strresult;
    }
  } catch (ioexception e) {
    e.printstacktrace();
  }
 
  return null;
  }