跨域及session失效

 跨域问题

response.setHeader(“Access-Control-Allow-Origin”, “*”);
response.setHeader(“Access-Control-Allow-Methods”, “POST, GET, OPTIONS, DELETE”);
response.setHeader(“Access-Control-Allow-Headers”, “x-requested-with”);

在服务器端加上以上代码就可以了，主要是第一行允许其它域名的访问。

后台设置代码与拦截器

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class AuthFilter implements Filter {
	
	private String localLoginUrl;

	@Override
	public void init(FilterConfig filterConfig) throws ServletException {
		this.localLoginUrl = filterConfig.getInitParameter("localLoginUrl");
	}
	
	public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
		HttpServletRequest httpRequest = (HttpServletRequest) request;
		HttpServletResponse httpResponse = (HttpServletResponse) response;

		request.setCharacterEncoding(localLoginUrl);
		httpResponse.setContentType("text/html;charset="+localLoginUrl);
		httpResponse.setHeader("Pragma","No-cache");
		httpResponse.setHeader("Cache-Control","no-cache");
		httpResponse.setDateHeader("Expires", 0);
		httpResponse.setHeader("Access-Control-Allow-Origin", httpRequest.getHeader("Origin"));
		httpResponse.setHeader("Access-Control-Allow-Methods", "POST, GET, OPTIONS, DELETE");
		httpResponse.setHeader("Access-Control-Max-Age", "3600");
		httpResponse.setHeader("Access-Control-Allow-Headers", "x-requested-with");
		httpResponse.setHeader("Access-Control-Allow-Credentials","true");

		chain.doFilter(request, response);
	}

	public void destroy() {}
}

同时客户端请求代码中添加 

如 Angular 中

app.config(function ($httpProvider) {
    $httpProvider.defaults.withCredentials = true;
});

session失效问题：

在我们每一次的数据请求中，浏览器都会向后台发送一个JSession，后台会根据这个值自动查找Id为JSession的那个session对象。但是当跨域时，JSession的值每次都会改变，后台就会以为是新的一个会话打开，于是又去创建了一个新的Session对象，而原来的Session对象就找不到了。

当我们登录成功后保存一个token到session中去，下一个请求来的时候又会重建一个session，原来的session就取不到了，于是还是未登录状态。解决这个问题只要加上这句就可以了：

response.setHeader(“Access-Control-Allow-Credentials”,”true”); //是否支持cookie跨域 

配置了allow-credentials之后，如果allow-origin设为*，跨域时会报错说因为允许credentials，origin不能设为通配*，那么就设置为当前domain。

response.setHeader(“Access-Control-Allow-Origin”, request.getHeader(“Origin”));