1.使用@CrossOrigin注解

1.1 假设项目二的端口号为8081，项目一的端口号为8080，项目二想要访问项目一的接口，可以在项目一中使用注解解决跨域问题

1.2 @CrossOrigin既可以加在单个方法上也可以加在类上面

package com.yl.cors01.controller;

import org.springframework.web.bind.annotation.CrossOrigin;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class HelloController {

   @CrossOrigin(value = "http://localhost:8081",maxAge = 1500)
    @GetMapping("/hello")
    public String hello() {
        return "hello corso1";
    }
}

2.实现WebMvcConfigurer接口重写addCorsMappings方法

package com.yl.cors01.config;

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

@Configuration
public class WebMvcConfig implements WebMvcConfigurer {
    @Override
    public void addCorsMappings(CorsRegistry registry) {
        registry.addMapping("/**")
                .allowedHeaders("*")
                .allowedMethods("*")
                .allowedOrigins("http://localhost:8081")
                .maxAge(1900);
    }
}

3.提供一个CorsFilter实例并且注册到容器中

package com.yl.cors01.config;

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

@Configuration
public class WebMvcConfig implements WebMvcConfigurer {
// @Override
// public void addCorsMappings(CorsRegistry registry) {
// registry.addMapping("/**")
// .allowedHeaders("*")
// .allowedMethods("*")
// .allowedOrigins("http://localhost:8081")
// .maxAge(1900);
// }

    @Bean
    CorsFilter corsFilter() {
        UrlBasedCorsConfigurationSource source = new UrlBasedCorsConfigurationSource();
        CorsConfiguration config = new CorsConfiguration();
        config.addAllowedOrigin("http://localhost:8081");
        config.addAllowedMethod("*");
        source.registerCorsConfiguration("/**",config);
        return new CorsFilter(source);
    }
}