Spring boot Ajax 跨域问题

之前做的api大多都是移动端在用，接口的调用也不会出现什么问题

但是web端调用会出现ajax跨域的请求出错的问题，之前只有个把个接口，所以用jsonp处理的（此处就不解释什么事jsonp了），这次的项目web端调用的比较多，所以就找一些其它的方法解决

首先在网上找了这么一段代码

import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletResponse;
import org.springframework.stereotype.Component;
@Component
public class SimpleCORSFilter implements Filter {
  public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
    HttpServletResponse response = (HttpServletResponse) res;
    response.setHeader("Access-Control-Allow-Origin", "*");
    response.setHeader("Access-Control-Allow-Methods", "POST, GET, OPTIONS, DELETE");
    response.setHeader("Access-Control-Max-Age", "3600");
    response.setHeader("Access-Control-Allow-Headers", "x-requested-with");
    chain.doFilter(req, res);
  }
  public void init(FilterConfig filterConfig) {}
  public void destroy() {}
}

这个是用的annotation加载一个过滤器，配上这个之后在请求进来的时候日志会打印过滤器加载进来了，但是测了一下，只有get请求才能跨域，而post请求还是被拒绝的。

那这个方法就不可取，换一个方法继续试，突然在网上看见了这么一个东西

@CrossOrigin(origins = "http://localhost:9000")
@RequestMapping("/greeting")
public @ResponseBody Greeting greeting(@RequestParam(required=false, defaultValue="World") String name) {
        System.out.println("==== in greeting ====");
        return new Greeting(counter.incrementAndGet(), String.format(template, name));
    }

This @CrossOrigin annotation enables cross-origin requests only for this specific method. By default, its allows all origins, all headers, the HTTP methods specified in the @RequestMappingannotation and a maxAge of 30 minutes is used. You can customize this behavior by specifying the value of one of the annotation attributes: origins, methods, allowedHeaders,exposedHeaders, allowCredentials or maxAge. In this example, we only allowhttp://localhost:8080 to send cross-origin requests.

我这一下子就开心了，以前从没关注过的 @CrossOrigin Annotation瞬间就让我看见了解决的希望。

它不是把ajax请求拒绝了么，查了一下资料，如果不写默认是不允许跨域了。那现在好我直接在 @RestController 的前面加一个Annotation

@CrossOrigin(origins = "*")
@RequestMapping("/test)
@RestController
@Api(tags = "test", description = "testoperation")
public class UserController {
}

这下Controller就把ajax跨域的请求放进来了，测试了一下，ajax跨域成功！