前情提要
这个其实是很早的时候在做本科毕设的时候实现的, 当时因为权限结构简单, 懒得上一个类似于Spring Security这么重的框架, 以及主要是想尝试一下自己实现注解就简单做了一下基于方法注解的权限控制.
设计思路
因为整个系统只有管理员/登录用户/未登录用户三种不同的角色, 并同时考虑到有些接口(比如修改/删除数据)只有作者才能访问, 所以一共设计了@AdminOnly, @CreatorOnly和@LoginOnly三种不同的注解.
注解部分实现
注解的实现代码很简单, 主要是注意需要标记@Retention(RetentionPolicy.RUNTIME)才能在运行时通过反射访问到这个注解:
package weplay.annotation;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
* Created by sl on 17/4/18.
* check the accessor is admin
*/
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.METHOD, ElementType.TYPE})
public @interface AdminOnly {
/**
* exclude method's name when mark class
*/
String[] exclude() default {};
/**
* indicate the check is valid
*/
boolean isValid() default true;
}
因为需要@AdminOnly的方法很多, 为了简单所以除了方法注解以外也设置了类注解, 添加exclude属性以排除某一个类中不需要使用该注解过滤的方法, isValid是为了临时禁用该注解, 方便调试.
package weplay.annotation;
import weplay.enums.EntityType;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
* Created by sl on 17/4/18.
* check the accessor is creator
*/
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.METHOD})
public @interface CreatorOnly {
/**
* indicate EntityType of Entity
*/
EntityType type();
/**
* indicate the position of EntityId in URI
*/
int position();
/**
* indicate the check is valid
*/
boolean isValid() default true;
/**
* indicate admin can access this handler
*/
boolean allowAdmin() default true;
}
这里的设计比较纠结, 因为我需要验证当前用户对当前访问的数据条目有没有权限, 所以需要使用type来获得访问数据条目的业务类型, 以及需要通过position来知道具体的数据条目的id, 这样我才能查询到当前访问的数据条目的创建者, 从而判断是否允许访问, allowAdmin表示除了创建者管理员是否也能访问该接口.
package weplay.annotation;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
* Created by sl on 17/4/22.
*/
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.METHOD})
public @interface LoginOnly {
/**
* indicate the check is valid
*/
boolean isValid() default true;
}
这个表示是否只有登录用户才能访问该接口.
注解解析实现
注解的解析放在SpringMVC的Interceptor中, 因为HandlerInterceptor是单例需要可重入, 所以使用了HandlerInterceptor封装RequestContextHolder.currentRequestAttributes()在当前请求的上下文中临时保存值.
fetchInfo()用于从请求中读取后续解析需要的数据, processAdminOnly(), processCreateOnly()和processLoginOnly()分别解析三个不同的注解, 这里可以考虑做一个公共接口, 然后不同的注解做不同的实现.
在preHandle()中, 通过handlerMethod.getBeanType().getAnnotations()和handlerMethod.getMethod().getAnnotations()分别获取类注解和方法注解, 这里使用了Spring提供的HandlerMethod类, 如果直接使用反射的话, 可以通过class.getAnnotations()和class.getMethod(name, parameterTypes).getAnnotations()分别获取到类注解和方法注解.
获取到注解对象以后, 可以通过直接之前定义的方法来获取到注解配置时设置的值, 比如adminOnly.exclude(), 然后根据业务需要判断是否放行还是抛出异常中止请求响应.
package weplay.aop;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;
import weplay.annotation.AdminOnly;
import weplay.annotation.CreatorOnly;
import weplay.annotation.LoginOnly;
import weplay.enums.AccountState;
import weplay.enums.AccountType;
import weplay.enums.EntityType;
import weplay.enums.ErrorCode;
import weplay.exception.CustomException;
import weplay.helperBean.viewBean.UserInfo;
import weplay.resource.Settings;
import weplay.service.IActivityService;
import weplay.service.IAuthService;
import weplay.service.IEntityService;
import weplay.service.IUserService;
import weplay.utils.RequestContextUtil;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.lang.annotation.Annotation;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
/**
* Created by sl on 17/4/18.
*/
public class AuthorityInterceptor implements HandlerInterceptor {
private IAuthService authService;
private IUserService userService;
private IActivityService activityService;
private IEntityService entityService;
/**
* fetch basic info from request
*/
private void fetchInfo(HttpServletRequest req) throws CustomException {
String uri = req.getRequestURI();
String token = req.getHeader("token");
Integer currentUid;
AccountType accountType;
UserInfo userInfo;
if (token != null) {
currentUid = authService.readUidByToken(token);
if (currentUid == Settings.ROOT_ADMIN_ID) {
accountType = AccountType.ADMIN;
} else {
accountType = AccountType.NORMAL;
}
userInfo = userService.readUserInfoByUid(currentUid);
} else {
token = "";
currentUid = -1;
accountType = AccountType.TOURISM;
userInfo = new UserInfo();
}
// save to RequestContextUtil
RequestContextUtil.setAttribute("uri", uri);
RequestContextUtil.setAttribute("token", token);
RequestContextUtil.setAttribute("uid", currentUid);
RequestContextUtil.setAttribute("accountType", accountType);
RequestContextUtil.setAttribute("userInfo", userInfo);
}
/**
* process @AdminOnly
*/
private void processAdminOnly(Annotation annotation, HandlerMethod handlerMethod) throws CustomException {
AccountType accountType = (AccountType) RequestContextUtil.getAttribute("accountType");
if (annotation instanceof weplay.annotation.AdminOnly) {
AdminOnly adminOnly = (AdminOnly) annotation;
// check isValid
if (!adminOnly.isValid()) {
return;
}
// check exclude method
for (String s : adminOnly.exclude()) {
if (s.equals(handlerMethod.getMethod().getName())) {
return;
}
}
// check current user is admin
if (accountType != AccountType.ADMIN) {
throw new CustomException(ErrorCode.NO_PERMISSION, "ADMIN ONLY");
}
}
}
/**
* process @CreateOnly
*/
private void processCreateOnly(Annotation annotation) throws CustomException {
String uri = (String) RequestContextUtil.getAttribute("uri");
Integer currentUid = (Integer) RequestContextUtil.getAttribute("uid");
AccountType accountType = (AccountType) RequestContextUtil.getAttribute("accountType");
if (annotation instanceof CreatorOnly) {
CreatorOnly creatorOnly = (CreatorOnly) annotation;
// read EntityType and EntityId
String[] uriPartition = uri.split("/");
String entityIdStr = uriPartition[creatorOnly.position()];
Integer entityId;
if (entityIdStr.contains(".")) {
entityId = Integer.valueOf(entityIdStr.split("\\.")[0]);
} else {
entityId = Integer.valueOf(entityIdStr);
}
EntityType entityType = creatorOnly.type();
// read CreatorId
Integer creatorId = -1;
switch (entityType) {
case ACTIVITY:
creatorId = activityService.readActivityById(entityId).getCreator();
break;
case NOTIFICATION:
creatorId = entityService.readNotificationById(entityId).getCreator();
break;
case PHOTO:
creatorId = entityService.readPhotoById(entityId).getCreator();
break;
}
// update accountType
if (currentUid.equals(creatorId)) {
accountType = AccountType.CREATOR;
RequestContextUtil.setAttribute("accountType", accountType);
}
// check current User is creator or admin if admin allow access
if (creatorOnly.isValid() && accountType != AccountType.CREATOR &&
!(creatorOnly.allowAdmin() && accountType == AccountType.ADMIN)) {
throw new CustomException(ErrorCode.NO_PERMISSION, "CREATOR ONLY");
}
}
}
/**
* process @CreateOnly
*/
private void processLoginOnly(Annotation annotation) throws CustomException {
AccountType accountType = (AccountType) RequestContextUtil.getAttribute("accountType");
UserInfo userInfo = (UserInfo) RequestContextUtil.getAttribute("userInfo");
if (annotation instanceof LoginOnly) {
LoginOnly loginOnly = (LoginOnly) annotation;
// check isValid
if (!loginOnly.isValid()) {
return;
}
if (accountType == AccountType.TOURISM) {
throw new CustomException(ErrorCode.NO_PERMISSION, "LOGIN USER ONLY");
}
}
}
public boolean preHandle(HttpServletRequest req, HttpServletResponse res, Object o) throws Exception {
// static resource handler
if (!(o instanceof HandlerMethod)) {
return true;
}
// convert handler into current Type
HandlerMethod handlerMethod = (HandlerMethod) o;
// fetch basic info
this.fetchInfo(req);
// process Annotations
List<Annotation> annotations = new ArrayList<Annotation>();
annotations.addAll(Arrays.asList(handlerMethod.getBeanType().getAnnotations()));
annotations.addAll(Arrays.asList(handlerMethod.getMethod().getAnnotations()));
for (Annotation a : annotations) {
this.processAdminOnly(a, handlerMethod);
this.processCreateOnly(a);
this.processLoginOnly(a);
}
return true;
}
}
package weplay.utils;
import org.springframework.web.context.request.RequestAttributes;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Created by sl on 17/4/22.
* Utils for wrapping RequestContextHolder
*/
public class RequestContextUtil {
/**
* prefix for user custom Attribute
*/
private static String prefix = "u_";
/**
* set Attribute to Context
*/
public static void setAttribute(String key, Object obj) {
RequestContextHolder.currentRequestAttributes().setAttribute(prefix + key, obj, RequestAttributes.SCOPE_REQUEST);
}
/**
* get Attribute from Context
*/
public static Object getAttribute(String key) {
return RequestContextHolder.currentRequestAttributes().getAttribute(prefix + key, RequestAttributes.SCOPE_REQUEST);
}
/**
* remove Attribute at Context
*/
public static void removeAttribute(String key) {
RequestContextHolder.currentRequestAttributes().removeAttribute(prefix + key, RequestAttributes.SCOPE_REQUEST);
}
/**
* get Current Request
*/
public HttpServletRequest currentRequest() {
return ((ServletRequestAttributes) RequestContextHolder.currentRequestAttributes()).getRequest();
}
/**
* get Current Response
*/
public HttpServletResponse currentResponse() {
return ((ServletRequestAttributes) RequestContextHolder.currentRequestAttributes()).getResponse();
}
}
注解的使用
配置好注解类并在拦截器中处理注解以后, 那么只需要在相应的地方进行注解标注就可以了, 如同使用Java自带或Spring提供的注解一样. 例如:
@RestController
@AdminOnly(exclude = {"createReport"})
public class AdminController {
\\...
}
@CreatorOnly(type = EntityType.NOTIFICATION, position = 2)
@RequestMapping(path = "/notification/{id:[0-9]+}", method = RequestMethod.DELETE)
public ResponseEntity<String> deleteNotification(@PathVariable("id") Integer id) throws CustomException {
\\...
}
总结与回顾
总的来说, 注解本质上相当于只是给类或者方法打了一个标记, 具体想要知道一个类或者一个方法是否有这个标记需要通过反射来获得, 并进行对应的处理.
通过反射对于类进行操作, 总体来说是比较慢的, 目前各大框架的配置逐渐从XML形式转变为注解形式, 这一过程是否会造成比较大的性能损失是一个需要思考的问题.
在这一次的例子中, 每一次请求都对其所有的注解进行遍历是比较慢而且进行了很多操作, 可以考虑增加一个HashMap用于记录一个类/方法对应了哪几个注解, 这样下次访问同一个类/方法时直接查表就可以而不用再通过反射来获取. 或者考虑倒排索引的形式, 记录每一个注解都对应哪些方法, 从而避免重复的查询和处理.
