Filter-CORS-跨域请求

关键代码：

第一种：使用@WebFilter注解，基本通用

@WebFilter(dispatcherTypes = {
		DispatcherType.REQUEST, 
		DispatcherType.FORWARD, 
		DispatcherType.INCLUDE, 
		DispatcherType.ERROR
	},filterName = "myFilter1", urlPatterns = "/*")
public class CorsFilter implements Filter {
	@Override
	public void init(FilterConfig filterConfig) throws ServletException {}
	@Override
	public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain)
		throws IOException, ServletException {
		//测试过滤器时用
		System.out.println("经过了此过滤器");
		HttpServletRequest request = (HttpServletRequest)req;
		HttpServletResponse response = (HttpServletResponse)resp;
		//设置允许跨域
		// 过滤器应用在SpringBoot时，前端若为vue普通项目则"Access-Control-Allow-Origin"可以写成"*"，若为脚手架，则不能写成"*"
		response.setHeader("Access-Control-Allow-Origin", request.getHeader("Origin"));
		response.setHeader("Access-Control-Allow-Methods","*");
		//设置开启Cookie
		response.setHeader("Access-Control-Allow-Credentials", "true"); 
		chain.doFilter(req, resp);    
	}
	@Override
	public void destroy() {}
}

比较全面一点的

@Slf4j
@WebFilter(urlPatterns = "/*", filterName = "CorsFilter")
public class CorsFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
    }
    @Override
    public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)
            throws IOException, ServletException {

        HttpServletResponse response = (HttpServletResponse) res;
        HttpServletRequest request = (HttpServletRequest) req;
        log.debug(">>>>>>>>>>>>>>>>>跨域》》》》》》》》》》》》》》》》"+request.getHeader("Origin"));
        if(StringUtils.isBlank(request.getHeader("Origin"))){
            response.setHeader("Access-Control-Allow-Origin", "*");
        }else{
            response.setHeader("Access-Control-Allow-Origin", request.getHeader("Origin"));
        }
//        response.setHeader("Access-Control-Allow-Headers", "access-control-allow-origin, authority, content-type, version-info, X-Requested-With");
        response.setHeader("Access-Control-Allow-Headers", "*");
//        response.setHeader("Access-Control-Expose-Headers", "*");
        response.setHeader("Access-Control-Allow-Methods", "*");
        response.setHeader("Access-Control-Max-Age", "3600");
        //response.setHeader("Access-Control-Allow-Credentials", "true");
        if ("OPTIONS".equals(request.getMethod())) {
            response.setStatus(HttpServletResponse.SC_OK);
            return;
        }
        chain.doFilter(request, response);
    }

    @Override
    public void destroy() {
    }
}

解释dispatcherTypes

关于此处内容原文连接:https://www.cnblogs.com/hoobey/p/6699989.html

1. REQUEST
   只要发起的操作是一次HTTP请求，比如请求某个URL发起了一个GET请求、表单提交方式为POST时提交表单则发起了一个POST请求、表单提交方式为GET时提交表单则发起了一次GET请求、一次重定向则前后相当于发起了两次请求，这些情况下有几次请求就会走几次指定过滤器

2. FOWARD
   只有当当前页面是通过请求转发转发过来的场景，才会走指定的过滤器

3. INCLUDE
   只要是通过<jsp:include page="xxx.jsp" />，嵌入进来的页面，每嵌入的一个页面，都会走一次指定的过滤器

4. ERROR
   这个可能开发者不是很熟悉，意思是当触发了一次error的时候，就会走一次指定的过滤器。

<error-page>
    <error-code>400</error-code>
    <location>/filter/error.jsp</location>
</error-page>
<error-page>
    <error-code>404</error-code>
    <location>/filter/error.jsp</location>
</error-page>
<error-page>
    <error-code>500</error-code>
    <location>/filter/error.jsp</location>
</error-page>