问题
遇到问题：在前后端分离跨域访问的项目中shiro进行权限拦截失效 (即使有正确权限的访问也会被拦截) 时造成302重定向错误等问题
报错：response for preflight is invalid (redirect)
1.302原因：使用ajax访问后端项目时无法识别重定向操作
2.shiro拦截失效原因：跨域访问时有一种带预检访问的跨域，即访问时先发出一条methods为OPTIONS的的访问，这种访问不带cookie等信息。造成shiro误判断为无权限访问。
3.一般使用的访问methods都是：get,post,put,delete
解决方案
1.让shiro不对预检访问拦截
2. 改变shiro中无权限，未登录拦截的重定向，这就需要重写几个过滤器
3. 将重写的过滤器进行配置
实现代码
1.重写shiro 登录 过滤器
过滤器运行机制：
（1）shiro是否拦截访问 以 isAccessAllowed返回值为准
（2）如果isAccessAllowed 方法返回false会进入onAccessDenied方法重定向至 登录 or 无权限 页面
package com.yaoxx.base.shiro;
import java.io.PrintWriter;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.lang3.StringUtils;
import org.apache.shiro.web.filter.authc.FormAuthenticationFilter;
import org.apache.shiro.web.util.WebUtils;
import org.springframework.http.HttpStatus;
/**
*
* @version: 1.0
* @since: JDK 1.8.0_91
* @Description:
* 未登录过滤器，重写方法为【跨域的预检访问】放行
*/
public class MyAuthenticationFilter extends FormAuthenticationFilter {
@Override
protected boolean isAccessAllowed(ServletRequest request, ServletResponse response, Object mappedValue) {
boolean allowed = super.isAccessAllowed(request, response, mappedValue);
if (!allowed) {
// 判断请求是否是options请求
String method = WebUtils.toHttp(request).getMethod();
if (StringUtils.equalsIgnoreCase("OPTIONS", method)) {
return true;
}
}
return allowed;
}
@Override
protected boolean onAccessDenied(ServletRequest request, ServletResponse response) throws Exception {
if (isLoginRequest(request, response)) { // 判断是否登录
if (isLoginSubmission(request, response)) { // 判断是否为post访问
return executeLogin(request, response);
} else {
// sessionID已经注册,但是并没有使用post方式提交
return true;
}
} else {
HttpServletRequest req = (HttpServletRequest) request;
HttpServletResponse resp = (HttpServletResponse) response;
/*
* 跨域访问有时会先发起一条不带token，不带cookie的访问。
* 这就需要我们抓取这条访问，然后给他通过，否则只要是跨域的访问都会因为未登录或缺少权限而被拦截
* （如果重写了isAccessAllowed，就无需下面的判断）
*/
// if (req.getMethod().equals(RequestMethod.OPTIONS.name())) {
// resp.setStatus(HttpStatus.OK.value());
// return true;
// }
/*
* 跨域的第二次请求就是普通情况的request了，在这对他进行拦截
*/
String ajaxHeader = req.getHeader(CustomSessionManager.AUTHORIZATION);
if (StringUtils.isNotBlank(ajaxHeader)) {
// 前端Ajax请求，则不会重定向
resp.setHeader("Access-Control-Allow-Origin", req.getHeader("Origin"));
resp.setHeader("Access-Control-Allow-Credentials", "true");
resp.setContentType("application/json; charset=utf-8");
resp.setCharacterEncoding("UTF-8");
resp.setStatus(HttpStatus.UNAUTHORIZED.value());//设置未登录状态码
PrintWriter out = resp.getWriter();
// Map result = new HashMap<>();
// result.put("MESSAGE", "未登录用户");
String result = "{"MESSAGE":"未登录用户"}";
out.println(result);
out.flush();
out.close();
} else {
// == 如果是普通访问重定向至shiro配置的登录页面 == //
saveRequestAndRedirectToLogin(request, response);
}
}
return false;
}
} 2.重写role权限 过滤器
package com.yaoxx.base.shiro;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.lang3.StringUtils;
import org.apache.shiro.web.filter.authz.RolesAuthorizationFilter;
import org.apache.shiro.web.util.WebUtils;
import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.RequestMethod;
/**
*
* @author: yao_x_x
* @since: JDK 1.8.0_91
* @Description: role的过滤器
*/
public class MyAuthorizationFilter extends RolesAuthorizationFilter {
@Override
public boolean isAccessAllowed(ServletRequest request, ServletResponse response, Object mappedValue)
throws IOException {
boolean allowed =super.isAccessAllowed(request, response, mappedValue);
if (!allowed) {
String method = WebUtils.toHttp(request).getMethod();
if (StringUtils.equalsIgnoreCase("OPTIONS", method)) {
return true;
}
}
return allowed;
}
@Override
protected boolean onAccessDenied(ServletRequest request, ServletResponse response) throws IOException {
HttpServletRequest req = (HttpServletRequest) request;
HttpServletResponse resp = (HttpServletResponse) response;
if (req.getMethod().equals(RequestMethod.OPTIONS.name())) {
resp.setStatus(HttpStatus.OK.value());
return true;
}
// 前端Ajax请求时requestHeader里面带一些参数，用于判断是否是前端的请求
String ajaxHeader = req.getHeader(CustomSessionManager.AUTHORIZATION);
if (StringUtils.isNotBlank(ajaxHeader)) {
// 前端Ajax请求，则不会重定向
resp.setHeader("Access-Control-Allow-Origin", req.getHeader("Origin"));
resp.setHeader("Access-Control-Allow-Credentials", "true");
resp.setContentType("application/json; charset=utf-8");
resp.setCharacterEncoding("UTF-8");
PrintWriter out = resp.getWriter();
String result = "{"MESSAGE":"角色，权限不足"}";
out.println(result);
out.flush();
out.close();
return false;
}
return super.onAccessDenied(request, response);
}
}3.配置过滤器
@Configuration
public class ShiroConfiguration {
@Autowired
private RoleService roleService;
@Autowired
private PermissionService permissionService;
@Bean("shiroFilter")
public ShiroFilterFactoryBean shiroFilter(@Qualifier("securityManager")SecurityManager manager) {
ShiroFilterFactoryBean bean = new ShiroFilterFactoryBean();
bean.setSecurityManager(manager);
/* 自定义filter注册 */
Map filters = bean.getFilters();
filters.put("authc", new MyAuthenticationFilter());
filters.put("roles", new MyAuthorizationFilter());
Map filterChainDefinitionMap =new LinkedHashMap<>();
filterChainDefinitionMap.put("/login", "anon");
// filterChainDefinitionMap.put("/*", "authc");
// filterChainDefinitionMap.put("/admin", "authc,roles[ADMIN]");
bean.setFilterChainDefinitionMap(filterChainDefinitionMap);
return bean;
} 
