新增-后端跨域

前端程序

  login:function(){
    this.$axios.post("http://localhost:8081/javawebstudy/loginServlet")
    .then(res=>{
      console.log(res)
    })
    .catch(error=>{
      console.log(error)
    })


  }

后端程序

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    //指定请求的编码方式为utf-8
    request.setCharacterEncoding("utf-8");
    //指定响应的编码方式为utf-8
    response.setCharacterEncoding("utf-8");
    System.out.println(name);
    System.out.println(password);
    //指定内容格式为html
    response.setContentType("text/html");
    response.getWriter().append("<h1>成功</h1>");
}

现在请求无法，到达需要解决跨域问题

每个servlet单独做跨域设置

     response.setHeader("Access-Control-Allow-Origin", "http://localhost:8082");

跨域过滤器

public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
    // TODO Auto-generated method stub
    // place your code here
    HttpServletResponse resp=(HttpServletResponse) response;
    
    // 允许跨域的主机地址，允许任意domain访问 
    //坑：前台axios设置withCredentials: true后，Access-Control-Allow-Origin的值不可以为*
    resp.setHeader("Access-Control-Allow-Origin", "http://localhost:8082");// 前端地址
    /* 允许跨域的请求头 */
    resp.setHeader("Access-Control-Allow-Headers", "*");
    /* 允许跨域的请求方法GET, POST, HEAD 等 */
    resp.setHeader("Access-Control-Allow-Methods", "PUT,POST,GET,DELETE,OPTIONS");
    /* 重新预检验跨域的缓存时间 (s) */
    resp.setHeader("Access-Control-Max-Age", time + "");
    /* 是否携带cookie,session支持  同步的需要前端做一些配置*/
    resp.setHeader("Access-Control-Allow-Credentials", "true");  
    chain.doFilter(request, resp);
    
}

private final int time = 20 * 24 * 60 * 60;