当浏览器请求访问页面时，页面中请求的ajax地址如果和页面请求的地址域名、端口、协议不同的话，浏览器会采用安全策略，请求能够正常的到达服务器端，但是无法获取响应结果。
跨域问题的遇到场景网站跨域问题的解决方案实际开发中前后端分离
1、响应头设置允许跨域访问，response.setHeader("Access-Control-Allow-Origin","*");*表示允许所有的ip2、使用jsonp解决网站跨域访问。缺点：只支持get请求，本质模拟了script脚本提交3、使用HttpClient实现转发。缺点：需要发送两次请求4、使用Nginx搭建API网关，保持域名和端口一致。配置location位置5、使用微服务中的Zuul网关
方案一（通过设置响应头）
==============A项目(http://127.0.0.1:8080)================$(document).ready(function() { $.ajax({ type : "POST", async : false, url : "http://127.0.0.1:8081/getBInfo", dataType : "json", success : function(data) { alert(data["retCode"]); }, error : function() { alert('fail'); } });});===============B项目(http://127.0.0.1:8081)================@RequestMapping("/getBInfo")public Map
方案二（使用jsonp）
===============A项目(http://127.0.0.1:8080)================$(document).ready(function() { $.ajax({ type : "POST", async : false, url : "http://127.0.0.1:8081/getBInfo", dataType : "jsonp", jsonp:"jsonpCallback", jsonpCallback:"callback", success : function(data) { alert(data["retCode"]); }, error : function() { alert('fail'); } });});===============B项目(http://127.0.0.1:8081)================@RequestMapping("/getBInfo")public void getBInfo(HttpServletResponse response, String jsonpCallback) throws IOException { JSONObject result = new JSONObject(); result.put("retCode", "200"); result.put("retMsg", "登陆成功"); PrintWriter writer = response.getWriter(); writer.println(jsonpCallback + "(" + result.toJSONString() + ")"); writer.close(); // 127.0.0.1:8081?jsonpCallback=256163154 // B项目返回结果集 256163154(jsonObject)}
方案三（通过HttpClient）
===============A项目(http://127.0.0.1:8080)================$(document).ready(function() { $.ajax({ type : "POST", async : false, url : "http://127.0.0.1:8080/forWardB", dataType : "json", success : function(data) { alert(data["retCode"]); }, error : function() { alert('fail'); } });});// 使用HttpClient进行方法B接口，该接口的ip地址为127.0.0.1:8080@RequestMapping("/forWardB")@ResponseBodypublic JSONObject forWardB() { // 中间采用rpc httpClient技术调用接口。服务器与服务器之间不存在跨域问题 JSONObject result = HttpClientUtils.httpGet("http://127.0.0.1:8081/getBInfo"); return result;}===============B项目(http://127.0.0.1:8081)================@RequestMapping("/getBInfo")@ResponseBodypublic Map
public class HttpClientUtils { private static Logger logger = LoggerFactory.getLogger(HttpClientUtils.class); // 日志记录 private static RequestConfig requestConfig = null; static { // 设置请求和传输超时时间 requestConfig = RequestConfig.custom().setSocketTimeout(2000).setConnectTimeout(2000).build(); } public static JSONObject httpPost(String url, JSONObject jsonParam) { // post请求返回结果 CloseableHttpClient httpClient = HttpClients.createDefault(); JSONObject jsonResult = null; HttpPost httpPost = new HttpPost(url); // 设置请求和传输超时时间 httpPost.setConfig(requestConfig); try { if (null != jsonParam) { // 解决中文乱码问题 StringEntity entity = new StringEntity(jsonParam.toString(), "utf-8"); entity.setContentEncoding("UTF-8"); entity.setContentType("application/json"); httpPost.setEntity(entity); } CloseableHttpResponse result = httpClient.execute(httpPost); // 请求发送成功，并得到响应 if (result.getStatusLine().getStatusCode() == HttpStatus.SC_OK) { String str = ""; try { // 读取服务器返回过来的json字符串数据 str = EntityUtils.toString(result.getEntity(), "utf-8"); // 把json字符串转换成json对象 jsonResult = JSONObject.parseObject(str); } catch (Exception e) { logger.error("post请求提交失败:" + url, e); } } } catch (IOException e) { logger.error("post请求提交失败:" + url, e); } finally { httpPost.releaseConnection(); } return jsonResult; } public static JSONObject httpPost(String url, String strParam) { // post请求返回结果 CloseableHttpClient httpClient = HttpClients.createDefault(); JSONObject jsonResult = null; HttpPost httpPost = new HttpPost(url); httpPost.setConfig(requestConfig); try { if (null != strParam) { // 解决中文乱码问题 StringEntity entity = new StringEntity(strParam, "utf-8"); entity.setContentEncoding("UTF-8"); entity.setContentType("application/x-www-form-urlencoded"); httpPost.setEntity(entity); } CloseableHttpResponse result = httpClient.execute(httpPost); // 请求发送成功，并得到响应 if (result.getStatusLine().getStatusCode() == HttpStatus.SC_OK) { String str = ""; try { // 读取服务器返回过来的json字符串数据 str = EntityUtils.toString(result.getEntity(), "utf-8"); // 把json字符串转换成json对象 jsonResult = JSONObject.parseObject(str); } catch (Exception e) { logger.error("post请求提交失败:" + url, e); } } } catch (IOException e) { logger.error("post请求提交失败:" + url, e); } finally { httpPost.releaseConnection(); } return jsonResult; } public static JSONObject httpGet(String url) { // get请求返回结果 JSONObject jsonResult = null; CloseableHttpClient client = HttpClients.createDefault(); // 发送get请求 HttpGet request = new HttpGet(url); request.setConfig(requestConfig); try { CloseableHttpResponse 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 HttpEntity entity = response.getEntity(); String strResult = EntityUtils.toString(entity, "utf-8"); // 把json字符串转换成json对象 jsonResult = JSONObject.parseObject(strResult); } else { logger.error("get请求提交失败:" + url); } } catch (IOException e) { logger.error("get请求提交失败:" + url, e); } finally { request.releaseConnection(); } return jsonResult; }}
方案四（使用Nginx搭建网关）
==================本地计算的host文件=====================127.0.0.01 api.mayikt.com=============Nginx的配置文件conf===============server{ listen 80; server_name localhost; location /mayikt-a/{ proxy_pass http://192.168.18.190:8080/;# 8080后不加/，项目路径中必须有mayikt-a，所以不要省略 index index.html index.htm; } location /mayikt-b/{ proxy_pass http://192.168.18.190:8081/; index index.html index.htm; }}
===============A项目(http://192.168.18.190:8080)================$(document).ready(function() { $.ajax({ type : "POST", async : false, url : "http://api.mayikt.com/mayikt-b/getInfo", dataType : "json", success : function(data) { alert(data["retCode"]); }, error : function() { alert('fail'); } });});===============B项目(http://192.168.18.190:8081)================@RequestMapping("/getBInfo")@ResponseBodypublic Map