function getBuyerCodeByJSON(){
        var sellerCode = document.forms[0].elements['searchCriteria.sellerCode'].value;
        var url = "getBuyerCodeByJSON.do?searchCriteria.sellerCode=" + sellerCode ; //调用URL
        var prop = {
                action: url,
                success: function(obj) {//返回一个success
                    var responseXML = obj.data; //如需获得来自服务器的响应，请使用 XMLHttpRequest 对象的 responseText 或 responseXML 属性。
                    var responses = responseXML.getElementsByTagName( "response" ); //获得响应数据                
                    if (responses != null && responses.length ) {//响应数据不为空
                        var result = responses[0].getAttribute("result");
                        if (result == 'success') {//返回一个success，返回值是一个XML信息
                            var msg = responseXML.getElementsByTagName("cause")[0].childNodes;
                            var buyerCode = msg[0].firstChild.nodeValue;//获取第一个子节点的value值
                              document.forms[0].elements['searchCriteria.buyerCode'].value = buyerCode;//对页面上的HTML进行赋值
                              
                              getprodAndSourchBranchByJSON();
                        }else if(result == 'failure'){
                            
                        } else if (result == 'fail') {
                            
                        }                                
                    }
                }
            };
            JAF.ajaxSend(prop);
        
    }

JAF.ajaxSend = function(prop) {
    var p = {
        action  : location.href,
        method  : "GET",
        contentType :  "application/x-www-form-urlencoded",
        async   : true,
        params  : null,
        dataType: "xml",
        success : null,
        error   : null
    }
    if (prop) {
        p = JAF.merge(prop, p);
    }
    var csrfTokenUrl = p.action;
    if(typeof(addTokenToUrl)!='undefined'){
        csrfTokenUrl = addTokenToUrl(csrfTokenUrl);
    }
    p.action = csrfTokenUrl;
    var regQuery = /?/; // regular expression for query string
    // if params is available, append params to action url for get requests
    if (p.params && p.method === "GET") {
        p.action += (regQuery.test(p.action) ? "&" : "?") + p.params;
    }
    // build the request object
    var xhr = JAF.buildXHR();
    if (!xhr) return;
    xhr.open(p.method, p.action, p.async);
    // set the correct header, if params is being sent
    if (p.params || p.contentType) {
        xhr.setRequestHeader("Content-Type", p.contentType);
    }
    
    // wait for a response to come back
    var onreadystatechange = xhr.onreadystatechange = function( ) {
        if (xhr && xhr.readyState === 4) {
            if (xhr.status === 0 || xhr.status === 200) {
                var data = (p.dataType === "xml") ? xhr.responseXML : xhr.responseText;
                success({
                    data : data
                });
            }
            // stop memory leaks
            if (p.async) xhr = null;
        }
    };
    
    // send params
    try {
        if(p.params)
        xhr.send(p.method === "POST" ? p.params : null);
    } catch(e) {}
    
    /**
     * to be invoked when ajax send success
     * @param obj JSON
     *            data : return data
     */
    function success(obj) {
        // if call-back for sccuss is specified, fire it and pass it an object with return data
        if (p.success) {
            p.success.call(null, obj);
        }
    }
    
    return xhr;
}

responseText ：获得字符串形式的响应数据。

responseXML ：获得 XML 形式的响应数据。

JAVA代码：

　　　　　　　　　CompanyGridForm lookupForm = (CompanyGridForm)form;
                ARSellerBuyerSearchCriteria criteria = lookupForm.getSearchCriteria2();
                if (lookupForm.getFirstTimeOpen().equals(BaseConstants.YES)) {
                    lookupForm.getSearchCriteria().setPageSize(10);
                }
                if(null == lookupForm.getSellerCode()||StringUtil.isEmpty(lookupForm.getSellerCode())){
                     lookupForm.setSellerCode(lookupForm.getSearchCriteria().getSellerCode());
                }
                criteria = PoiExtClsInterface.getARBuyerListBySiteCodeAndSeller(criteria, lookupForm.getSellerCode());
                String buyerCode = "";
                String sellerCode = lookupForm.getSellerCode();
                String importFactor = "";
                VoARProfile voARProfile = null;
                VoARSellerBuyer[] voARSellerBuyers = criteria.getSellerBuyers();
                lookupForm.setSearchCriteria2(criteria);
                String responseXml = null;
                String checkMessage = null;
                    if(voARSellerBuyers != null && voARSellerBuyers.length == 1){//页面需求为，如果每个seller对应的只有一个buyer可选，那么会自动进行页面局部刷新
　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　所以长度为1
                         buyerCode = voARSellerBuyers[0].getBuyerCustCode();   //得到一个buyer
                        checkMessage = ""+buyerCode+"";//组装XML信息
                    }
                    if(!StringUtil.isEmpty(checkMessage)){//如果XML不为空，返回一个success
                        responseXml = ""+checkMessage+"";
                    } else {   　　　　　　　　　　　　　　　　//否则返回failure
                        responseXml = "";
                    }
                    this.printWriterXML(response,responseXml);
                    return null;

private void printWriterXML(final HttpServletResponse response, final String responseXml)
            throws WafException {
            try {
                // response.setCharacterEncoding("UTF-8");
                response.setContentType("text/xml;charset=utf-8");
                response.setHeader("Cache-Control", "no-cache");
                PrintWriter out = response.getWriter();
                out.println(responseXml);
                out.close();
            } catch (IOException e) {
                throw new WafException(e.getMessage());
            }