spring boot 跨域访问处理

1. 问题场景：由于项目中使用到跨域访问，今天也得到高人指点，所以写出来分享给大家。可能是考虑到前后端分离，前端后端服务器不在一台机器上，出现这种跨域访问的情况。正常情况下本地访问是没有问题，但是遇到这种非同一台服务器的情况下，就会报错 Access-Control-Allow-Origin 。具体报错内容不记得了。
2. 问题解决方案一：采用添加拦截器的方式对请求添加跨域访问的头，允许跨域访问。

   package com.meicloud.interceptor;
   
   import javax.servlet.http.HttpServletRequest;
   import javax.servlet.http.HttpServletResponse;
   
   import org.apache.log4j.Logger;
   import org.springframework.web.servlet.ModelAndView;
   import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;
   
   public class CommonInterceptor extends HandlerInterceptorAdapter  {
   
       private final static  Logger logger = Logger.getLogger(CommonInterceptor.class);
   
       @Override
       public boolean preHandle(HttpServletRequest request,HttpServletResponse response, Object handler) throws Exception {
           logger.info("添加跨域访问头配置，Access-Control-Allow-Origin:*");
           //跨域访问CORS
           response.addHeader("Access-Control-Allow-Origin", "*");
           response.addHeader("Access-Control-Allow-Methods", "POST,GET,OPTIONS,PUT,DELETE,HEAD");
           response.addHeader("Access-Control-Allow-Headers", "S_ID,content-type");
           response.addHeader("Access-Control-Max-Age", "3600000");
           response.addHeader("Access-Control-Allow-Credentials", "true");
   
           //让请求，不被缓存，
           response.setHeader("Cache-Control", "no-cache");
           response.setHeader("Cache-Control", "no-store");
           response.setHeader("Pragma", "no-cache");
           response.setDateHeader("Expires", 0); 
   
           logger.debug("==================================preHandle");
           return true;
       }
   
       @Override
       public void postHandle(HttpServletRequest request,
               HttpServletResponse response, Object handler,
               ModelAndView modelAndView) throws Exception {
           logger.debug("==================================postHandle");
       }
   
       @Override
       public void afterCompletion(HttpServletRequest request,
               HttpServletResponse response, Object handler, Exception ex)
               throws Exception {
           logger.debug("==================================afterCompletion");
       }
   }

   上面是拦截器内容，下面是对拦截器的配置。

   package com.meicloud.config;
   
   import org.springframework.context.annotation.ComponentScan;
   import org.springframework.context.annotation.Configuration;
   import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
   import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
   import org.springframework.web.servlet.config.annotation.ViewControllerRegistry;
   import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;
   
   import com.meicloud.interceptor.CommonInterceptor;
   
   @ComponentScan
   @Configuration
   public class WebMvcConfig extends WebMvcConfigurerAdapter {
   
       @Override
       public void addInterceptors(InterceptorRegistry registry) {
           // TODO Auto-generated method stub
           registry.addInterceptor(new CommonInterceptor()).addPathPatterns("/getDOC");
       }
   
   }

   然后就可以在controller中使用他了，下面是我的controller

   @ResponseBody
   @RequestMapping(value="/getDOC",method=RequestMethod.POST)
   public BaseReturn getDOC(@RequestBody MailEntity mailEntity, HttpServletRequest request, HttpServletResponse response, HttpSession httpSession){
   log.info("excute controllor HomeController.getDOC");
   BaseReturn baseReturn = new BaseReturn();

   String name = mailEntity.getName();
   String company = mailEntity.getCompany();
   String departments = mailEntity.getDepartments();
   String job = mailEntity.getJob();
   String email = mailEntity.getEmail();
   String phone = mailEntity.getPhone();
   String doc = mailEntity.getDoc();

   try {
   if(name==null||name.equals("")){
   throw new CommenException("姓名不能为空!");
   }
   if(email==null||email.equals("")){
   throw new CommenException("Email不能为空!");
   }
   if(phone==null||phone.equals("")){
   throw new CommenException("电话号码不能为空!");
   }
   if(doc==null||doc.equals("")){
   throw new CommenException("文档不能为空!");
   }
   } catch (Exception e1) {
   baseReturn.setCode(ReturnType.FAIL);
   baseReturn.setMsg(e1.getMessage());
   log.error(e1.getMessage());
   return baseReturn;
   }

   try {
   // iMailClent.sendMail(mailEntity);
   iMailClent.sendHtmlMail(mailEntity);
   baseReturn.setCode(ReturnType.SUCCESS);
   } catch (Exception e) {
   e.printStackTrace();
   baseReturn.setCode(ReturnType.FAIL);
   baseReturn.setMsg("发送邮件失败！");
   log.error(e.getMessage());
   }

   return baseReturn;
   }

   接下来是前端的调用，前端采用ajax post 请求

   var params = {
                             name:name,
                             company:company,
                             departments:departments,
                             job:job,
                             email:email,
                             phone:phone,
                             doc:'/doc/api.doc'
                     };
   
   var type = 'POST';
   var url = Config.host + url;
   
   $.ajax({
           url : url,
           data : JSON.stringify(params),
           type : type,
           contentType : "application/json",
           async : false,
           success : function(data) {
               //TODO 成功
           },
           error : function(data) {
               //TODO 失败
           }
       });

3. 问题解决方案二：使用 JSONP 来实现跨域访问。直接上代码，前端代码为：

   url = 'http://localhost:9999/getDOC' + '?name=' + params.name
               + '&company=' + params.company
               + '&departments=' + params.departments + '&job=' + params.job
               + '&email=' + params.email + '&phone=' + params.phone + '&doc='
               + params.doc;
   
   $.ajax({
           url : url,
           type : 'get',
           async : false,
           dataType : "jsonp",
           jsonpCallback : "callback",
           success : function(data) {
               //TODO 成功
           },
           error : function(data) {
               //TODO 失败
           }
       });

   限制调用方式为 get ，数据类型为 jsonp。后端也必须响应 JSONPObject 对象。

   @ResponseBody
       @RequestMapping(value="/getDOC",method=RequestMethod.GET)
       public JSONPObject getDOC(HttpServletRequest request,String callback){
   
           BaseReturn baseReturn = new BaseReturn();
   
           String name = request.getParameter("name");
           String company = request.getParameter("company");
           String departments = request.getParameter("departments");
           String job = request.getParameter("job");
           String email = request.getParameter("email");
           String phone = request.getParameter("phone");
           String doc = request.getParameter("doc");
   
           try {
               if(name==null||name.equals("")){
                   throw new CommenException("姓名不能为空!");
               }
               if(email==null||email.equals("")){
                   throw new CommenException("Email不能为空!");
               }
               if(phone==null||phone.equals("")){
                   throw new CommenException("电话号码不能为空!");
               }
               if(doc==null||doc.equals("")){
                   throw new CommenException("文档不能为空!");
               }
           } catch (Exception e1) {
               baseReturn.setCode(ReturnType.FAIL);
               baseReturn.setMsg(e1.getMessage());
               log.error(e1.getMessage());
               return new JSONPObject(callback, baseReturn);
           }
   
           MailEntity mailEntity = new MailEntity();
           mailEntity.setCompany(company);
           mailEntity.setDepartments(departments);
           mailEntity.setDoc(doc);
           mailEntity.setEmail(email);
           mailEntity.setJob(job);
           mailEntity.setName(name);
           mailEntity.setPhone(phone);
   
           try {
                iMailClent.sendHtmlMail(mailEntity);
               baseReturn.setCode(ReturnType.SUCCESS);
           } catch (Exception e) {
               e.printStackTrace();
               baseReturn.setCode(ReturnType.FAIL);
               baseReturn.setMsg("发送邮件失败！");
               log.error(e.getMessage());
           }
   
           return new JSONPObject(callback, baseReturn);
       }
       

4. 今天得到高人指点，原来有一种更加简便的方法，可以实现。不过原理肯定都是一样的，通过给请求添加消息头来设置跨域访问，这点是无疑的。新的解决办法就是给controller或方法添加 @CrossOrigin 注解，具体详情请参考：http://spring.io/blog/2015/06/08/cors-support-in-spring-framework

   @ResponseBody
       @RequestMapping(value="/getDOC",method=RequestMethod.POST)
       @CrossOrigin //使用注解方式添加跨域访问消息头
       public BaseReturn getDOC(@RequestBody MailEntity mailEntity, HttpServletRequest request, HttpServletResponse response, HttpSession httpSession){
           log.info("excute controllor HomeController.getDOC");

   就这么多了吧，在网上看到还有添加过滤器的，当然都是差不多的做法。