HttpServletResponse返回Json

resp.setCharacterEncoding("utf-8");
resp.setContentType("application/json; charset=utf-8");
PrintWriter writer = resp.getWriter();
JSONObject o = new JSONObject();
o.put("status", "success");
writer.write(o.toString());

这点可以与异常处理相配合，当发生异常时，使用上述方法返回给前端指定信息

try {
    // 判断该请求是不是受保护的请求
    if(isProtectedUrl(request)) {
        // Options请求可以不用校验，其他诸如Get、Post等请求都要校验
        if(!request.getMethod().equals("OPTIONS"))
            // 校验是否带有有效token
            request = JwtUtil.validateTokenAndAddUserIdToHeader(request);
    }
} catch (CustomException e) {
    response.setCharacterEncoding("utf-8");
    response.setContentType("application/json; charset=utf-8");
    PrintWriter writer =response.getWriter();
    JSONObject o = new JSONObject();
    o.put("code", e.getId());
    o.put("message", e.getMessage());
    writer.write(o.toString());
    return;
}