跨域

当一台服务器资源从另一台服务器（不同的域名或者端口）请求一个资源或者接口，就会发起一个跨域HTTP请求。

同源：协议、域名、端口都相同
只要一个不同，就是跨域。

例子

请求方	响应方	是否跨域	原因
http://www.baidu.com	http://www.baidu.com/test.html	否	协议/域名/端口相同
http://www.baidu.com	https://www.baidu.com/test.html	是	协议不同
http://www.baidu.com	http://www.hhhh.com/test.html	是	主域名不同
http://www.baidu.com	http://haha.baidu.com/test.html	是	主域名相同、子域名不同
http://www.baidu.com:8080	http://www.baidu.com/8090/test.html	是	端口不同

跨域访问实例

跨域处理

任意一种方式都可。

1.添加跨域配置类

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;

@Configuration
public class GlobalCorsConfig {

    @Bean
    public CorsFilter corsFilter(){
        // 1.添加cors配置信息
        CorsConfiguration config = new CorsConfiguration();
        // 放行哪些原始域名
        config.addAllowedOriginPattern("*");//2.4.0后的写法
        // config.addAllowedOrigin("*");
        // 是否发送Cookie
        config.setAllowCredentials(true);
        // 放行哪些请求方式
        config.addAllowedMethod("*");
        // 放行哪些原始请求头部信息
        config.addAllowedHeader("*");
        // 暴露哪些头部信息
        config.addExposedHeader("*");
        // 2.添加映射路径
        UrlBasedCorsConfigurationSource corsConfigurationSource = new UrlBasedCorsConfigurationSource();
        corsConfigurationSource.registerCorsConfiguration("/**", config);
        // 3.返回新的CorsFilter
        return new CorsFilter(corsConfigurationSource);
    }
}

2.重写WebMvcConfigurer

import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.CorsRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

@Configuration
public class CorsConfig implements WebMvcConfigurer {

    @Override
    public void addCorsMappings(CorsRegistry registry) {
        registry.addMapping("/**")
                // 是否发送Cookie
                .allowCredentials(true)
                // 放行哪些原始域
                //.allowedOrigins("*")
                .allowedOriginPatterns("*") // 2.4.0后的写法
                .allowedMethods(new String[] {"GET", "POST", "PUT", "DELETE"})
                .allowedHeaders("*")
                .exposedHeaders("*");
    }
}

3.注解@CrossOrigin

类上注解

@RestController
@CrossOrigin("*")
public class CorsController {

    @GetMapping("/cors")
    public String hello(){
        return "hello cors";
    }
}

方法上注解
方法可以单独跨域，没有@CrossOrigin(“*”)注解的方法则不行

@RestController
public class CorsController {

    @GetMapping("/cors")
    @CrossOrigin("*")
    public String hello(){
        return "hello cors";
    }

    @GetMapping("/cors2")
    public String hello2(){
        return "hello cors2";
    }
}

4.自定义过滤器

import org.springframework.stereotype.Component;

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;


@Component
public class MyCorsFilter implements Filter {

    @Override
    public void doFilter(ServletRequest req, ServletResponse res,
                         FilterChain chain) throws IOException, ServletException {

        HttpServletResponse response = (HttpServletResponse) res;
        HttpServletRequest httpServletRequest = (HttpServletRequest) req;
        response.setHeader("Access-Control-Allow-Origin", httpServletRequest.getHeader("origin"));
        response.setHeader("Access-Control-Allow-Methods", "POST, GET, OPTIONS, DELETE, HEAD");
        response.setHeader("Access-Control-Max-Age", "3600");
        response.setHeader("Access-Control-Allow-Headers", "access-control-allow-origin, authority, content-type, version-info, X-Requested-With");
        response.setHeader("Access-Control-Allow-Credentials", "true");
        chain.doFilter(req, res);
    }

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        
    }

    @Override
    public void destroy() {

    }
}