SpringBoot CORS前端请求跨域问题解决方案

前言

在前后端分离的项目中，当前后端部署不在同一个地址下的时候，请求服务端接口会出现跨域请求报错的情况，关于浏览器跨域的概念，这里不进行解释，直接给出解决办法。

解决方案

SpringBoot 1.5.x

第一种方法：

import java.util.List;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.format.FormatterRegistry;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.validation.MessageCodesResolver;
import org.springframework.validation.Validator;
import org.springframework.web.method.support.HandlerMethodArgumentResolver;
import org.springframework.web.method.support.HandlerMethodReturnValueHandler;
import org.springframework.web.servlet.HandlerExceptionResolver;
import org.springframework.web.servlet.config.annotation.AsyncSupportConfigurer;
import org.springframework.web.servlet.config.annotation.ContentNegotiationConfigurer;
import org.springframework.web.servlet.config.annotation.CorsRegistry;
import org.springframework.web.servlet.config.annotation.DefaultServletHandlerConfigurer;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.PathMatchConfigurer;
import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
import org.springframework.web.servlet.config.annotation.ViewControllerRegistry;
import org.springframework.web.servlet.config.annotation.ViewResolverRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;


@Configuration
public class CorsConfig {

    @Bean
    public WebMvcConfigurer corsConfigurer() {
        return new WebMvcConfigurer() {
        
			@Override
            //重写父类提供的跨域请求处理的接口
            public void addCorsMappings(CorsRegistry registry) {
                //添加映射路径
                registry.addMapping("/**")
                    //放行哪些原始域
                    .allowedOrigins("*")
                    //是否发送Cookie信息
                    .allowCredentials(true)
                    //放行哪些原始域(请求方式)
                    .allowedMethods("GET","POST", "PUT", "DELETE")
                    //放行哪些原始域(头部信息)
                    .allowedHeaders("*")
                    //暴露哪些头部信息（因为跨域访问默认不能获取全部头部信息）
                    .exposedHeaders("Header1", "Header2");
            }
			
            @Override
            public void configurePathMatch(PathMatchConfigurer configurer) {

            }

            @Override
            public void configureContentNegotiation(ContentNegotiationConfigurer configurer) {

            }

            @Override
            public void configureAsyncSupport(AsyncSupportConfigurer configurer) {

            }

            @Override
            public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {

            }

            @Override
            public void addFormatters(FormatterRegistry registry) {

            }

            @Override
            public void addInterceptors(InterceptorRegistry registry) {

            }

            @Override
            public void addResourceHandlers(ResourceHandlerRegistry registry) {

            }

            @Override
            public void addViewControllers(ViewControllerRegistry registry) {

            }

            @Override
            public void configureViewResolvers(ViewResolverRegistry registry) {

            }

            @Override
            public void addArgumentResolvers(List<HandlerMethodArgumentResolver> argumentResolvers) {

            }

            @Override
            public void addReturnValueHandlers(List<HandlerMethodReturnValueHandler> returnValueHandlers) {

            }

            @Override
            public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {

            }

            @Override
            public void extendMessageConverters(List<HttpMessageConverter<?>> converters) {

            }

            @Override
            public void configureHandlerExceptionResolvers(List<HandlerExceptionResolver> exceptionResolvers) {

            }

            @Override
            public void extendHandlerExceptionResolvers(List<HandlerExceptionResolver> exceptionResolvers) {

            }

            @Override
            public Validator getValidator() {
                return null;
            }

            @Override
            public MessageCodesResolver getMessageCodesResolver() {
                return null;
            }
        };
    }
}

第二种方法：

使用@CrossOrigin注解实现，在需要允许跨域的Controller上加入注解。

@CrossOrigin
@RestController
@RequestMapping("/instance_node")
@Slf4j
public class HelloController {

}

第三种方法：

实现Interceptor，在HttpServletResponse中加入Header。

@Slf4j
public class ControllerInterceptor extends HandlerInterceptorAdapter {

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        log.info("ControllerInterceptor preHandle execute");
        response.addHeader("Access-Control-Allow-Credentials", "true");
        response.addHeader("Access-Control-Allow-Origin", "*");
        response.addHeader("Access-Control-Allow-Methods", "GET, POST, DELETE, PUT");
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        log.info("ControllerInterceptor postHandle execute");
    }
}

验证

<html lang="en">
<head>
    <meta charset="UTF-8"/>
    <title>Page Indextitle>
head>
<body>
<h2>前台系统h2>
<p id="info">p>
body>
<script src="https://ajax.aspnetcdn.com/ajax/jquery/jquery-3.5.1.min.js">script>
<script>
    $.ajax({
        url: 'http://localhost:8080/hello/get',
        type: "GET",
        success: function (data) {
            $("#info").html("跨域访问成功:"+data);
        },
        error: function (data) {
            $("#info").html("跨域失败!!");
        }
    })
script>
html>