web項目跨域

web項目跨域問題： 

環境： JDK 1.8  Tomcat 8

第一步： 先自己寫一個filter 過濾器

package com.yyg.filter;

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

public class SimpleCORSFilter implements Filter {
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        HttpServletResponse res = (HttpServletResponse) servletResponse;
        res.setHeader("Access-Control-Allow-Origin", "*");
        res.setHeader("Access-Control-Allow-Methods", "POST, GET, OPTIONS, DELETE");
        res.setHeader("Access-Control-Max-Age", "3600");
        res.setHeader("Access-Control-Allow-Headers", "x-requested-with");
        filterChain.doFilter(servletRequest, servletResponse);
    }

    public void destroy() {

    }
}

第二步：引入jar包，因爲我用的idea 所以直接放鏈接了。

<!-- json跨域 -->
<filter>
    <filter-name>cors</filter-name>
    <filter-class>com.yyg.filter.SimpleCORSFilter</filter-class>
</filter>
<filter-mapping>
    <filter-name>cors</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>

第三步：將過濾器導入到項目內，在web.xml文件內添加如下代碼 （filter-class 內寫你自己再上一步所寫的filter所在路徑）

<!-- json跨域 -->
<filter>
    <filter-name>cors</filter-name>
    <filter-class>com.yyg.filter.SimpleCORSFilter</filter-class>
</filter>
<filter-mapping>
    <filter-name>cors</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>