ssm項目如何解決跨域

如何解決跨域

1、為什么出現跨域

出於瀏覽器的同源策略限制。同源策略（Sameoriginpolicy）是一種約定，它是瀏覽器最核心也最基本的安全功能，如果缺少了同源策略，則瀏覽器的正常功能可能都會受到影響。可以說Web是構建在同源策略基礎之上的，瀏覽器只是針對同源策略的一種實現。同源策略會阻止一個域的javascript腳本和另外一個域的內容進行交互。所謂同源（即指在同一個域）就是兩個頁面具有相同的協議（protocol），主機（host）和端口號（port）

2、什么是跨域

當一個請求url的協議、域名、端口三者之間任意一個與當前頁面url不同即為跨域

3、跨域解決方法

第一種：JSONP解決跨域

package com.ruben.controller.interceptor;


import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@Component
public class CrossOriginIntercept implements HandlerInterceptor {

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        response.setHeader("Access-Control-Allow-Origin", request.getHeader("Origin"));
        response.setHeader("Access-Control-Allow-Methods", "GET,POST,OPTIONS,PUT,DELETE");
        response.setHeader("Access-Control-Allow-Headers", ((HttpServletRequest) request).getHeader("Access-Control-Request-Headers"));
        //跨域時首先會發送一個option請求,這里我們給option請求直接返回正常狀態
        if (request.getMethod().equals(RequestMethod.OPTIONS.name())) {
            response.setStatus(HttpStatus.OK.value());
            return false;
        }
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {

    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {

    }
}

如果是springboot項目，需要寫個webconfig引入一下

@EnableWebMvc
@Configuration
public class WebConfig implements WebMvcConfigurer {

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(crossOriginIntercept).addPathPatterns("/**").excludePathPatterns("/static/**");
    }

}

如果是spring項目，需要在springmvc.xml中引入

<!-- 攔截器3  跨域問題 -->
    <mvc:interceptors>
        <mvc:interceptor>
            <mvc:mapping path="/**"/>
            <bean class="com.ruben.controller.interceptor.CrossOriginIntercept"></bean>
        </mvc:interceptor>
    </mvc:interceptors>

來自：https://vampireachao.gitee.io/2020/06/16/攔截器解決跨域問題/

第二種：@CrossOrigin

在Controller加上@CrossOrigin,但我們知道，在企業開發中，會有很多個controller，controller數量多也便於維護和查找控制層代碼

第三種：第三方依賴

//導入jar包
 <dependency>
            <groupId>com.thetransactioncompany</groupId>
            <artifactId>cors-filter</artifactId>
            <version>2.5</version>
 </dependency>

在web.xml加入以下內容：

 <filter>
        <filter-name>CORS</filter-name>
        <filter-class>com.thetransactioncompany.cors.CORSFilter</filter-class>
        <init-param>
            <param-name>cors.allowOrigin</param-name>
            <param-value>*</param-value>
        </init-param>
        <init-param>
            <param-name>cors.supportedMethods</param-name>
            <param-value>GET, POST, HEAD, PUT, DELETE</param-value>
        </init-param>
        <init-param>
            <param-name>cors.supportedHeaders</param-name>
            <param-value>Authorization,Content-Type,Depth,User-Agent,X-File-Size,X-Requested-With,X-Requested-By,If-Modified-Since,X-File-Name,X-File-Type,Cache-Control,Origin,Accept</param-value>
        </init-param>
        <init-param>
            <param-name>cors.exposedHeaders</param-name>
            <param-value>Set-Cookie</param-value>
        </init-param>
        <init-param>
            <param-name>cors.supportsCredentials</param-name>
            <param-value>true</param-value>
        </init-param>
        <init-param>
            <param-name>cors.maxAge</param-name>
            <param-value>3600</param-value>
        </init-param>
    </filter>
    <filter-mapping>
        <filter-name>CORS</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

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