前後端分離時可能遇到跨域的問題。
如：在前端地址http://www.aaa.com/index.html中通過ajax請求地址：http://www.bbb.com/service/getUsers，就會報跨域錯誤。

一種簡單的解決辦法是：在後臺程式碼中增加過濾器，如下：

AccessFilter.java

import javax.servlet.*;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.ResourceBundle;

/**
 * Created by dq on 2017/1/21.
 */
 

public class AccessFilter implements Filter {

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        HttpServletResponse httpResponse = (HttpServletResponse) servletResponse;
        httpResponse.setHeader("Access-Control-Allow-Origin"
 
, "*");
        httpResponse.setHeader("Access-Control-Allow-Headers","Origin, X-Requested-With, Content-Type, Accept");
        httpResponse.setHeader("Access-Control-Allow-Credentials", "true");
        filterChain.doFilter(servletRequest, httpResponse);
    }

    @Override
    public void destroy
 
() {

    }
}

web.xml

    <!-- 解決跨域 -->
    <filter>
        <filter-name>accessFilter</filter-name>
        <filter-class>com.xxx.filter.AccessFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>accessFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>