public String getParametersToString(String prefix) {
        final StringBuilder sb = new StringBuilder();
        getParameters().forEach((k, v) -> {
            if (sb.length() > 0) sb.append('&');
            try {
                sb.append(k).append('=').append(URLEncoder.encode(v, "UTF-8"));
            } catch (IOException ex) {
                throw new RuntimeException(ex);
            }
        });
        return (sb.length() > 0 && prefix != null) ? (prefix + sb) : sb.toString();
    }
public String getParametersToString ( String prefix ) { final StringBuilder sb = new StringBuilder ( ) ; getParameters ( ) . forEach ( ( k , v ) -> { if ( sb . length ( ) > 0 ) sb . append ( '&' ) ; try { sb . append ( k ) . append ( '=' ) . append ( URLEncoder . encode ( v , "UTF-8" ) ) ; } catch ( IOException ex ) { throw new RuntimeException ( ex ) ; } } ) ; return ( sb . length ( ) > 0 && prefix != null ) ? ( prefix + sb ) : sb . toString ( ) ; }
将请求参数转换成String, 字符串格式为: bean1={}&amp;id=13&amp;name=xxx <br>
不会返回null，没有参数返回空字符串

@param prefix 拼接前缀， 如果无参数，返回的字符串不会含有拼接前缀

@return String