跨域无效问题解决（java后端方案）

通用后端跨域方法

1、@CrossOrigin 注解

在Spring Boot 中给我们提供了一个注解 @CrossOrigin 来实现跨域，这个注解可以实现方法级别的细粒度的跨域控制。我们可以在类或者方添加该注解，如果在类上添加该注解，该类下的所有接口都可以通过跨域访问，如果在方法上添加注解，那么仅仅只限于加注解的方法可以访问。

@Slf4j
@RestController
@RequestMapping(value = AppPath.SERVICE_LOCATION_URL + "/appointment")
@Api(value = "AppointmentController",tags = "预约列表接口")
@CrossOrigin
public class AppointmentController {

    @Autowired
    private LiveAppointmentService appointmentService;
    
    @RequestMapping
    @ApiOperation(value = "预约列表分页查询", response = CsLiveAppointmentDTO.class)
    public JsonResult<PageInfo> getAppointmentList(AppointmentListDTO dto){
        log.info("getAppointmentList vo:{}", JSONUtil.toJsonStr(dto));
        PageInfo<CsLiveAppointmentDTO> appointmentList = appointmentService.getAppointmentList(dto);
        return JsonResult.success(appointmentList);
    }
}

**@CrossOrigin 注解不生效问题**

在Spring框架4.2版本后，Spring给出了注解的方式解决问题。

即在Controller控制器中，在Controller注解上方添加@CrossOrigin注解。

但是使用这种方式后也有可能仍然出现跨域问题，解决方案就是：

**在@RequestMapping注解中没有指定Get、Post方式，或者使用@GetMapping或者@Post Mapping**

**在@CrossOrigin(methods = {RequestMethod.POST})指定方法**

@Slf4j
@RestController
@RequestMapping(value = AppPath.SERVICE_LOCATION_URL + "/appointment")
@Api(value = "AppointmentController",tags = "预约列表接口")
@CrossOrigin
public class AppointmentController {

    @Autowired
    private LiveAppointmentService appointmentService;

    @ApiOperation(value = "预约列表分页查询", response = CsLiveAppointmentDTO.class)
    //@GetMapping("getList")
    @RequestMapping(method = RequestMethod.GET)
    public JsonResult<PageInfo> getAppointmentList(AppointmentListDTO dto){
        log.info("getAppointmentList vo:{}", JSONUtil.toJsonStr(dto));
        PageInfo<CsLiveAppointmentDTO> appointmentList = appointmentService.getAppointmentList(dto);
        return JsonResult.success(appointmentList);
    }
}

2、springboot2.0 实现WebMvcConfigurer 实现跨域

@Configuration
public class WebMvcConfig implements WebMvcConfigurer {
 
    @Override
    public void addCorsMappings(CorsRegistry registry) {
        registry.addMapping("/**")
                .allowedOrigins("*")
                .allowedMethods("POST","GET","OPTIONS")
                .allowedHeaders("*")
                .allowCredentials(false).maxAge(3600);
    }
 
}

3、过滤器实现跨域

@WebFilter(filterName = "CorsFilter")
@Configuration
@Order(Ordered.HIGHEST_PRECEDENCE)
@Slf4j
public class CorsFilter implements Filter {

    @Value("${allow.headers:X-Requested-With,Authorization,Content-Type}")
    private String allowHeaders;

    @Value("${allow.origin:https://xxx.com}")
    private String allowOrigin;

    @Override
    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-Origin", "http://xxx:9091");
        response.setHeader("Access-Control-Allow-Credentials", "true");
        response.setHeader("Access-Control-Allow-Methods", "POST, GET, PATCH,OPTIONS, DELETE, PUT");
        response.setHeader("Access-Control-Max-Age", "3600");
        response.setHeader("Access-Control-Allow-Headers", allowHeaders);
//        response.setHeader("Access-Control-Allow-Headers", "*");
        log.info("CorsFilter res {},{}", response.getHeader("Access-Control-Allow-Origin"), response.containsHeader("Access-Control-Allow-Origin"));
        chain.doFilter(req, res);
    }
}

**跨域不生效问题**

（1）、@Order(Ordered.HIGHEST_PRECEDENCE)如果有登录拦截，要将跨域filter等级提升为最高优先级

（2）、 response.setHeader("Access-Control-Allow-Headers", "*");

Access-Control-Allow-Headers: * 在部分客户端上有兼容问题，MDN中介绍 Access-Control-Allow-Headers: * 有两重意思。

一个是在服务端设置Access-Control-Allow-Credentials: true的时候这个 * 只会被客户端当做字符串 * （我们不希望的，会出错的）。

另一个是没有这个设置则会被当做通配符（我们希望的，不会出错的）。

猜测是客户端对于 * 的实现上有兼容性问题，所以建议不要这样设置，用到什么设置什么最好，例如：Access-Control-Allow-Headers: Content-Type,X-Requested-With,Authorization。

（3）、 response.setHeader("Access-Control-Allow-Origin", "*")

//指定允许其他域名访问

'Access-Control-Allow-Origin:http://172.80.0.206'//一般用法（*，指定域，动态设置），3是因为*不允许携带认证头和cookies

//是否允许后续请求携带认证信息（cookies）,该值只能是true,否则不返回

（4）、 response.setHeader("Access-Control-Allow-Methods", "POST, GET, PATCH,OPTIONS, DELETE, PUT");OPTIONS 在**预检请求**复杂请求中也会使用到

（5）、 如果有spring security结合使用需要添加该过滤器

@Configuration
public class SecurityConfig extends WebSecurityConfigurerAdapter {
 
    @Override
    protected void configure(HttpSecurity security) throws Exception {
        security.csrf().disable();
        security.headers().frameOptions().disable();
        //加入过滤器
        security.addFilterBefore(new CORSFilter(),                              UsernamePasswordAuthenticationFilter.class);
    }
}

4、定制化参数实现跨域

        前面要么是*,实际需求是根据业务参数定制化

@WebFilter(filterName = "corsFilter", urlPatterns = "/*",
        initParams = {@WebInitParam(name = "allowOrigin", value = "*"),
                @WebInitParam(name = "allowMethods", value = "GET,POST,PUT,DELETE,OPTIONS"),
                @WebInitParam(name = "allowCredentials", value = "true"),
                @WebInitParam(name = "allowHeaders", value = "Content-Type,X-Token")})
public class CorsFilter implements Filter {
 
    private String allowOrigin;
    private String allowMethods;
    private String allowCredentials;
    private String allowHeaders;
    private String exposeHeaders;
 
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        allowOrigin = filterConfig.getInitParameter("allowOrigin");
        allowMethods = filterConfig.getInitParameter("allowMethods");
        allowCredentials = filterConfig.getInitParameter("allowCredentials");
        allowHeaders = filterConfig.getInitParameter("allowHeaders");
        exposeHeaders = filterConfig.getInitParameter("exposeHeaders");
    }
 
    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) servletRequest;
        HttpServletResponse response = (HttpServletResponse) servletResponse;
        if (!StringUtils.isEmpty(allowOrigin)) {
            if(allowOrigin.equals("*")){
                // 设置哪个源可以访问
                response.setHeader("Access-Control-Allow-Origin", allowOrigin);
            }else{
                List<String> allowOriginList = Arrays.asList(allowOrigin.split(","));
                if (allowOriginList != null && allowOriginList.size() > 0) {
                    String currentOrigin = request.getHeader("Origin");
                    if (allowOriginList.contains(currentOrigin)) {
                        response.setHeader("Access-Control-Allow-Origin", currentOrigin);
                    }
                }
            }
        }
        if (!StringUtils.isEmpty(allowMethods)) {
            //设置哪个方法可以访问
            response.setHeader("Access-Control-Allow-Methods", allowMethods);
        }
        if (!StringUtils.isEmpty(allowCredentials)) {
            // 允许携带cookie
            response.setHeader("Access-Control-Allow-Credentials", allowCredentials);
        }
        if (!StringUtils.isEmpty(allowHeaders)) {
            // 允许携带哪个头
            response.setHeader("Access-Control-Allow-Headers", allowHeaders);
        }
        if (!StringUtils.isEmpty(exposeHeaders)) {
            // 允许携带哪个头
            response.setHeader("Access-Control-Expose-Headers", exposeHeaders);
        }
        filterChain.doFilter(servletRequest, servletResponse);
    }
 
    @Override
    public void destroy() {
 
    }
}

5、 使用SpringCloud网关GateWay实现跨域

原理和前面类似

@Configuration
public class CorsConfig {
    @Bean
    public CorsWebFilter corsFilter() {
        CorsConfiguration config = new CorsConfiguration();
        config.setAllowCredentials(Boolean.TRUE);//允许Cookie跨域
        config.addAllowedMethod("*");
        config.addAllowedOrigin("*");
        config.addAllowedHeader("*");//不要设置成*,参考前面

        UrlBasedCorsConfigurationSource source = new UrlBasedCorsConfigurationSource(new PathPatternParser());
        source.registerCorsConfiguration("/**", config);

        return new CorsWebFilter(source);
    }
}

注：在下层服务不需要在做任何跨域配置，例如注解@CrossOrigin，否则会由于配置冲突导致依然出现跨域问题

6、nginx配置代理解决跨域问题

server {
        listen       8000;
        server_name  localhost;
        # / 表示匹配路径为/的url
        location / {
           proxy_pass http://需要跨域的域名:5500;
        }
 
        # /user 表示访问以/user 开头 的地址 如/username,/user/find等
        location /user {
           proxy_pass http://需要跨域的域名:3000;
        }
 
    }

7、nginx配置响应头允许跨域

#
# Wide-open CORS config for nginx
#
location / {
    
    #### 对OPTIONS请求，会设置很多的请求头，并返回204
     if ($request_method = 'OPTIONS') {
        add_header 'Access-Control-Allow-Origin' '*';
        add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS';
        #
        # Custom headers and headers various browsers *should* be OK with but aren't
        #
        add_header 'Access-Control-Allow-Headers' 'DNT,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Range';
        #
        # Tell client that this pre-flight info is valid for 20 days
        #
        add_header 'Access-Control-Max-Age' 1728000;
        add_header 'Content-Type' 'text/plain; charset=utf-8';
        add_header 'Content-Length' 0;
        return 204;
     }
     if ($request_method = 'POST') {
        add_header 'Access-Control-Allow-Origin' '*';
        add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS';
        add_header 'Access-Control-Allow-Headers' 'DNT,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Range';
        add_header 'Access-Control-Expose-Headers' 'Content-Length,Content-Range';
     }
     if ($request_method = 'GET') {
        add_header 'Access-Control-Allow-Origin' '*';
        add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS';
        add_header 'Access-Control-Allow-Headers' 'DNT,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Range';
        add_header 'Access-Control-Expose-Headers' 'Content-Length,Content-Range';
     }
}

参考来源如下：

> https://blog.csdn.net/weixin_40910372/article/details/100068498

> https://blog.csdn.net/letterTiger/article/details/105939465

> https://blog.csdn.net/liao0801_123/article/details/103459241

> https://blog.csdn.net/f641385712/article/details/101170214

> https://blog.csdn.net/qq_36155003/article/details/114540029