CORS是一个W3C标准，全称是"跨域资源共享"（Cross-origin resource sharing）。它允许浏览器向跨源服务器，发出XMLHttpRequest请求，从而克服了AJAX只能同源使用的限制。只要服务器实现了CORS接口，就可以跨源通信。
CORS有两种请求，简单请求和非简单请求。
跨域就等于从百度访问谷歌的资源，URL由协议、域名、端口和路径组成，如果两个URL的协议、域名和端口相同，则表示他们同源。相反，只要协议，域名，端口有任何一个的不同，就被当作是跨域。
浏览器采用同源策略，禁止页面加载或执行与自身来源不同的域的任何脚本。
假设在服务器8080和8088这2个端口同时挂载不同代码
@RequestMapping ("/")
@ResponseBody
public String index(HttpServletResponse response) {
return "跨域内容显示";
}
@RequestMapping("/cors")
public String cors(HttpServletResponse response) {
return "/cors";
}
cors.html
<!DOCTYPE html>
<html lang="zh-CN" xmlns:th="http://www.thymeleaf.org">
<head>
<meta charset="utf-8">
<title></title>
<script th:src="@{js/jquery-1.9.1.min.js}"></script>
</head>
<body>
<button>获取跨域内容</button>
<p id="p1"></p>
</body>
<script>
$(function(){
$("button").click(function(){
$.ajax({
type: "post",
url:"http://localhost:8088/",
success:function(result){
$("#p1").html(result);
}
});
});
});
</script>
</html>
直接访问8088端口的方法时没有任何问题
如果通过8080端口的ajaxa访问8088的方法时，会报错信息如下
Failed to load http://localhost:8088/: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost:8080' is therefore not allowed access.
被调用方需要的解决方案：
public class CorsFilter extends OncePerRequestFilter {
@Override
protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {
if (request.getHeader("Access-Control-Request-Method") != null && "OPTIONS".equals(request.getMethod())) {
// CORS "pre-flight" request
response.addHeader("Access-Control-Allow-Origin", "*");
response.addHeader("Access-Control-Allow-Methods", "GET, POST, PUT, DELETE, OPTIONS");
response.setHeader("Access-Control-Allow-Headers", "x-requested-with");
response.addHeader("Access-Control-Max-Age", "1800");//30 min
}
//This will filter your requests and responses.
filterChain.doFilter(request, response);
}
}
web.xml
<filter>
<filter-name>allowedAccessFilter</filter-name>
<filter-class>aaa.bbb.ccc.ddd.CorsFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>allowedAccessFilter</filter-name>
<url-pattern>/registeryuyue/*</url-pattern>
</filter-mapping>
@SpringBootApplication
@Controller
@CrossOrigin (origins = "http://localhost:8080", maxAge = 3600)
public class DemoApplication {
public static void main(String[] args) {
SpringApplication.run(DemoApplication.class, args);
}
@RequestMapping ("/")
@ResponseBody
public String index(HttpServletResponse response) {
return "跨域内容显示";
}
}
此方法中 CrossOrigin 注解只可以应用于单个controller，而下面全局配置的方式可以应用于整个工程
package com.pzh.cros.demo;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.cors.CorsConfiguration;
import org.springframework.web.cors.UrlBasedCorsConfigurationSource;
import org.springframework.web.filter.CorsFilter;
/**
* 实现基本的跨域请求
*/
@Configuration
public class CorsConfig {
private CorsConfiguration buildConfig() {
CorsConfiguration corsConfiguration = new CorsConfiguration();
corsConfiguration.setMaxAge(3600L); // 表明在3600秒内，不需要再发送预检验请求
corsConfiguration.addAllowedOrigin("http://localhost:8080"); // 允许http://localhost:8080域名使用
corsConfiguration.addAllowedHeader("*"); // 允许任何头
corsConfiguration.addAllowedMethod("*"); // 允许任何方法（post、get等）
return corsConfiguration;
}
@Bean
public CorsFilter corsFilter() {
UrlBasedCorsConfigurationSource source = new UrlBasedCorsConfigurationSource();
source.registerCorsConfiguration("/**", buildConfig()); // 对接口配置跨域设置
return new CorsFilter(source);
}
}
Access-Control-Allow-Origin: http://kbiao.me
Access-Control-Max-Age: 3628800
Access-Control-Allow-methods: GET, PUT, DELETE, POST
Access-Control-Allow-Header: content-type
Access-Control-Allow-Credentail: true
“Access-Control-Allow-Origin"表明它允许” http://kbiao.me "发起跨域请求
"Access-Control-Max-Age"表明在3628800秒内，不需要再发送预检验请求，可以缓存该结果（上面的资料上我们知道CROS协议中，一个AJAX请求被分成了第一步的OPTION预检测请求和正式请求）
"Access-Control-Allow-Methods"表明它允许GET、PUT、DELETE的外域请求
"Access-Control-Allow-Headers"表明它允许跨域请求包含content-type头
"Access-Control-Allow-Credentials"表明它允许cookies