http 代替 ajax原理解析

ajax主要用于系统内部方法的发起

用httpClient 后台模拟ajax主要是针对rest接口的数据调用
在一般情况下，如果只是需要Web站点的某个简单页面提交请求并获取服务器响应，HttpURLConnection完全可以胜任。但在绝大部分情况下，Web站点的网页可能没这么简单，这些页面并不是通过一个简单的URL就可访问的，可能需要用户登录而且具有相应的权限才可访问该页面。在这种情况下，就需要涉及Session、Cookie的处理了，如果打算使用HttpURLConnection来处理这些细节，当然也是可能实现的，只是处理起来难度就大了。

HttpClient更方便更强大的解决了HttpURLConnection能做到或者不能做到的事情，HttpClient模块提供的两大类HttpPost和HttpGet实现Http请求：

       HttpPost —— 传送的数据量较大，一般被默认为不受限制。一般用于发送一些表单数据，传输数据更安全

       HttpGet —— 传送的数据量较小，不能大于2KB。一般用于请求获取一些信息，执行效率更高

其中的认证信息就是通过setheader（）；来实现的

                method.setHeader("X-Auth-Token", token);
                // 记录日志需要的参数
                if (isPostInfo) {
                    method.setHeader("Event-Id", UUID.randomUUID().toString());
                    method.setHeader("User-Id", CommonUtil.getUserId());
                }
                method.setHeader("Content-Type", "application/Json");



原理解析：



/**

* POST请求，上传表单

* @param  url  链接地址“http://host:8080/Login.ashx”

* @param  params  上传参数List

* @param  str_agent 标识

* @return 返回获取的数据

*/

public static String postTableData(String url, List<NameValuePair> params,

                                          String str_agent) throws ConnectTimeoutException,ClientProtocolException,

                                          IOException, XmlPullParserException {

              String result = null;HttpClient httpclient = createHttpClient();// 创建一个HttpClient

              HttpPost httppost = new HttpPost(url);// 创建一个POST请求

              httppost.setEntity(new UrlEncodedFormEntity(params, HTTP.UTF_8));// 添加请求参数到请求对象

              httppost.setHeader("User-Agent", str_agent);//在报文头部添加一些字符串标识 ,报文头不是url之后的参数，只是用于表识的东西，类似于action空间名

              HttpResponse response = httpclient.execute(httppost);//发送请求

              HttpEntity resEntity = response.getEntity();//从响应中获取消息实体

              if (resEntity != null) {

                            result = EntityUtils.toString(resEntity);

              }

              httpclient.getConnectionManager().shutdown();//关闭连接

              return result;

}

/**

* Get请求，下载数据

* @param  url  链接地址“http://host:8080/GetList.ashx”

* @param  params  上传参数List

* @param  str_agent 标识

* @return 返回获取的数据

* /

public static String getListData(String url, List<NameValuePair> params,

                                                        String str_agent) throws ConnectTimeoutException,ClientProtocolException,

                                                        IOException, XmlPullParserException {

              // 构建url

              if (params != null) {

                            StringBuffer buf = new StringBuffer();

                            for (int i = 0; i < params.size(); i++) {

                                          buf.append("&").append(params.get(i).getName()).append("=").append(params.get(i).getValue());

                            }

                            if (url.indexOf("?") != -1)// url已经有参数

                             {

                                          url = url + buf.toString();

                            } else {

                                          url = url + "?" + buf.toString();

                            }

              }

              String result = null; HttpClient httpclient = createHttpClient();// 创建一个HttpClient

              HttpGet httpGet = new HttpGet(url);// 创建一个Get请求

              httpGet.setHeader("User-Agent", str_agent);//在报文头部添加一些字符串标识

              HttpResponse response = httpclient.execute(httpGet);//发送请求

              HttpEntity resEntity = response.getEntity();//从响应中获取消息实体

              if (resEntity != null) {

                            result = EntityUtils.toString(resEntity);

              }

              httpclient.getConnectionManager().shutdown();//关闭连接

               return result;

}








//调用代码：
传入的调用对方rest的方法参数
String resultJson = JSONObject.toJSON(instance).toString();
        HttpClientPostRequest postRequest = new HttpClientPostRequest(ConfigFileLoad.getConfContent("NFVO_IP") + "/rest/nsrs/instantiate");
//传入参数，并获取对方接口返回值
        String result = postRequest.processPostEntity(resultJson, true);
        JSONObject jsonObj = JSONObject.parseObject(result);
        ResponseVO resVO = (ResponseVO) JSONObject.toJavaObject(jsonObj, ResponseVO.class);




//具体实现代码：

方式（一）：

HttpClient httpClient = new DefaultHttpClient();
       
        //获取方法类型post get
        HttpPost method = new HttpPost(url);
HttpResponse response = httpClient.execute(method);


/**
     *
     * @Title           函数名称：   processPostEntity
     * @Description     功能描述：   创建实例 需要post一个 entity的json（String）格式
     * @param           参          数：  
     * @return          返  回   值：   String 
     * @throws
     */
    @SuppressWarnings({ "resource", "deprecation" })
    public String processPostEntity(String entityJson, boolean isPostInfo) {
        String token = CommonUtil.getAuthToken();
        StringBuffer result = new StringBuffer();
        HttpClient httpClient = new DefaultHttpClient();
       
        //获取方法类型post get
        HttpPost method = new HttpPost(url);
        if (method != null) {
            try {
                // 添加参数    类似于ajax的参数，传进来的参数已经是json字符串了
                method.setEntity(new StringEntity(entityJson, HTTP.UTF_8));
                method.setHeader("X-Auth-Token", token);
                // 记录日志需要的参数
                if (isPostInfo) {
                    method.setHeader("Event-Id", UUID.randomUUID().toString());
                    method.setHeader("User-Id", CommonUtil.getUserId());
                }
                method.setHeader("Content-Type", "application/Json");
                // 设置编码   模拟浏览器发出http url请求，并转化返回结果的编码方式,执行url中的响应mvc方法，从而调用对方的rest接口
                HttpResponse response = httpClient.execute(method);
               
                //对方返回的另一种实体结果
                InputStream in = response.getEntity().getContent();
                BufferedReader breader = new BufferedReader(new InputStreamReader(in, "utf-8"));
                String st = breader.readLine();
                result.append(st);
                while (st != null) {
                    st = breader.readLine();
                }
                int statusCode = response.getStatusLine().getStatusCode();
                logger.info("statusCode:" + statusCode);
            } catch (IOException e) {
                // 发生网络异常
                logger.error("exception occurred!\n" + ExceptionUtils.getFullStackTrace(e));
            } finally {
                method.abort();
            }
        }
        return result.toString();
    }




方式（二）：



实现原理：
HttpClient httpClient = new HttpClient();


HttpMethod httpMethod = new DeleteMethod(url);
        //  HttpMethod httpMethod = new GetMethod(url);
httpClient.executeMethod(httpMethod);



调用实例：


public ResultModel<List<TplInsVO>> getInsList(int page, int rows, String sortName, String sortType) {
        logger.info("查询实例信息  " + "页码：" + page + "记录数：" + rows + "排序字段：" + sortName + " 排序方式：" + sortType);
        final List<TplInsVO> voList = new ArrayList<TplInsVO>();
        // 调用REST 接口
        String requestUrl = ConfigFileLoad.getConfContent("NFVO_IP") + "/rest/nsrs/";// http://172.16.38.132:8080/nfvo/rest/nsrs
        HttpClientRequest request = new HttpClientGetRequest(requestUrl);
        // 分页信息
        request.addParam("pageSize", page);
        request.addParam("pageNum", rows);
        request.addParam("orderField", sortName == null ? "" : sortName);
        request.addParam("orderType", sortType == null ? "" : sortType);
        try {
            request.process(new HttpClientResponseHandler() {
                @Override
                public void handle(String response, String retCode, String msg) throws HttpClientException {
                    logger.info("getInsList-process-return-response：" + response);
                    JSONObject jsonObj = JSONObject.parseObject(response);// .fromObject(response);
                    logger.debug("查询一组实例信息,返回状态retCode：" + retCode + ",返回信息Msg:" + msg);
                    NsrPageResult result = (NsrPageResult) JSONObject.toJavaObject(jsonObj.getJSONObject("result"), NsrPageResult.class);
                    if (result != null) {
                        String num = result.getSize();
                        List<Nsr> nsrList = result.getNsrList();
                        if (nsrList != null && !nsrList.isEmpty()) {
                            TplInsVO vo;
                            for (Nsr nsr : nsrList) {
                                vo = new TplInsVO();
                                vo.setInsId(nsr.getId());
                                vo.setInsName(nsr.getName());
                                vo.setNsdId(nsr.getNsdId());
                                vo.setInsStatus(changeStatus(nsr.getStatus()));
                                vo.setInsType(nsr.getFlavour() == null ? "" : nsr.getFlavour().getName());
                                vo.setIpAddr(nsr.getIpAddr());
                                voList.add(vo);
                            }
                        }
                    }

                }
            });
        } catch (HttpClientException e) {
            e.printStackTrace();
        }
        int totalSize = voList.size();
        int toRow = (page - 1) * 10 + 10;
        if (toRow > voList.size()) {
            toRow = voList.size();
        }
        List<TplInsVO> newList = voList.subList((page - 1) * 10, toRow);

        // ResultModel<List<TplInsVO>> result = new ResultModel<List<TplInsVO>>(newList);
        ResultModel<List<TplInsVO>> result = new ResultModel<List<TplInsVO>>(voList);
        result.setResult(Constants.RESULT_FLAG.SUCCESS.number());
        result.setTotalSize(totalSize);
        result.setCurrentPageNum(page);
        result.setPageSize(rows);
        result.setStartRowNo(CommonUtil.getStartRowNo(page, rows));
        return result;
    }


   /**
     * 执行请求
     * @throws HttpClientException httpClient请求异常
     */
    @Override
    public int process(HttpClientResponseHandler httpClientResponseHandler) throws HttpClientException {
        String auth_token = null;
        try {
            auth_token = CommonUtil.getAuthToken();
        } catch (Exception e) {
            e.printStackTrace();
        }
        // 获取子类的具体的HttpMethod实现
        HttpMethod httpMethod = this.getHttpMethod();
        // Head 里面塞值 -- modify by renjing
        // --- X-Auth-Token 值取什么？
        logger.info("client auth_token=" + auth_token);
        Header header = new Header("X-Auth-Token", auth_token);
        httpMethod.setRequestHeader(header);
        if (ObjectUtils.isNull(httpMethod))
            throw new NullPointerException("Cannot process request because the httpMethod is null.");

        HttpClient httpClient = new HttpClient();
        httpClient.getParams().setParameter(HttpMethodParams.HTTP_CONTENT_CHARSET, "UTF-8");

        try {
            long start = System.currentTimeMillis();
            logger.info("Begin to visit {}.", httpMethod.getURI());
            httpClient.executeMethod(httpMethod);
            logger.info("End to visit and take: {} ms.", (System.currentTimeMillis() - start));
        } catch (IOException e) {
            throw new HttpClientException(httpMethod.getPath(), e.getMessage());
        }

        // 利用HttpClientResponseHandler处理响应结果
        String retCode = null;
        String msg = null;
        if (ObjectUtils.isNotNull(httpClientResponseHandler))
            try {
                BufferedReader reader = new BufferedReader(new InputStreamReader(httpMethod.getResponseBodyAsStream()));
                StringBuilder builder = new StringBuilder();
                String str = null;
                while ((str = reader.readLine()) != null) {
                    builder.append(str);
                }
                String response = builder.toString();
                // httpClientResponseHandler.handle(response);  把返回的response，作为流的方式读出，作为一个json格式的对象返回（不是实体类的格式）
                JSONObject jsonObj = JSONObject.parseObject(response);// .fromObject(response);
                retCode = jsonObj.getString("retCode");
                msg = jsonObj.getString("msg");
                httpClientResponseHandler.handle(response, retCode, msg);
            } catch (IOException e) {
                logger.error(e.getMessage(), e);
            }

        httpMethod.releaseConnection();
        /* if (retCode == null || !retCode.equals("ok")) {
             throw new RuntimeException(msg);
         } else {
             return 0;
         }*/
        return 0;
    }

    /**
     * 执行请求
     * @throws HttpClientException httpClient请求异常   需要记录日志
     */
    @Override
    public int processAndSaveLog(HttpClientResponseHandler httpClientResponseHandler) throws HttpClientException {
        String auth_token = null;
        try {
            auth_token = CommonUtil.getAuthToken();
        } catch (Exception e) {
            e.printStackTrace();
        }
        // 获取子类的具体的HttpMethod实现
        HttpMethod httpMethod = this.getHttpMethod();
        // Head 里面塞值 -- modify by renjing
        // --- X-Auth-Token 值取什么？
        logger.info("client auth_token=" + auth_token);
        // Header header = new Header("X-Auth-Token", auth_token);
        httpMethod.addRequestHeader("X-Auth-Token", auth_token);

        httpMethod.addRequestHeader("Event-Id", UUID.randomUUID().toString());
        httpMethod.addRequestHeader("User-Id", CommonUtil.getUserId());
        if (ObjectUtils.isNull(httpMethod))
            throw new NullPointerException("Cannot process request because the httpMethod is null.");

        HttpClient httpClient = new HttpClient();
        httpClient.getParams().setParameter(HttpMethodParams.HTTP_CONTENT_CHARSET, "UTF-8");

        try {
            long start = System.currentTimeMillis();
            logger.info("Begin to visit {}.", httpMethod.getURI());
           
           
            //模拟浏览器发出http url 请求，url中有需要调用方法的mvc自此完成方法的执行
            httpClient.executeMethod(httpMethod);
            logger.info("End to visit and take: {} ms.", (System.currentTimeMillis() - start));
        } catch (IOException e) {
            throw new HttpClientException(httpMethod.getPath(), e.getMessage());
        }

        // 利用HttpClientResponseHandler处理响应结果
        String retCode = null;
        String msg = null;
        if (ObjectUtils.isNotNull(httpClientResponseHandler))
            try {
                BufferedReader reader = new BufferedReader(new InputStreamReader(httpMethod.getResponseBodyAsStream()));
                StringBuilder builder = new StringBuilder();
                String str = null;
                while ((str = reader.readLine()) != null) {
                    builder.append(str);
                }
                String response = builder.toString();
                // httpClientResponseHandler.handle(response);
                JSONObject jsonObj = JSONObject.parseObject(response);// .fromObject(response);
                retCode = jsonObj.getString("retCode");
                msg = jsonObj.getString("msg");
                httpClientResponseHandler.handle(response, retCode, msg);
            } catch (IOException e) {
                logger.error(e.getMessage(), e);
            }

        httpMethod.releaseConnection();
        /* if (retCode == null || !retCode.equals("ok")) {
             throw new RuntimeException(msg);
         } else {
             return 0;
         }*/
        return 0;
    }



//对应这个的解析getHttpMethod
  String requestUrl = ConfigFileLoad.getConfContent("NFVO_IP") + "/rest/nsrs/";// http://172.16.38.132:8080/nfvo/rest/nsrs
        HttpClientRequest request = new HttpClientGetRequest(requestUrl);
        // 分页信息
        request.addParam("pageSize", page);
        request.addParam("pageNum", rows);
        request.addParam("orderField", sortName == null ? "" : sortName);
        request.addParam("orderType", sortType == null ? "" : sortType);


========================
@Override
    public HttpMethod getHttpMethod() {
        StringBuilder builder = new StringBuilder();
        for (Entry<String, Object> entry : params.entrySet()) {
            builder.append(entry.getKey()).append("=").append(String.valueOf(entry.getValue())).append("&");
        }
        String param = null;
        if (builder.length() != 0)
            param = builder.deleteCharAt(builder.length() - 1).toString();

        String url = null;
        if (StringUtils.isEmpty(param))
            url = this.url;
        else
            url = this.url + "?" + param;

        HttpMethod httpMethod = new DeleteMethod(url);
        //  HttpMethod httpMethod = new GetMethod(url);
        return httpMethod;
    }