前言
在 spring boot 应用程式开发的时候,在对 service 层加入缓存支持的过程中,遇到了处理分页缓存的难题,在摸索了多个解决方式后,找到了比较适合,特此记录
问题描述
在程序中存在 User与 Note 实体。假设用户此时需要从服务器获得 Note 数据,在大部分情况下,用户不需要一次性获取所有的 Note 数据,我们会使用 Page 来减少带宽压力的,同时使用缓存来减少对数据库的访问。
在缓存流程中,在对数据进行查找时候,需要先查找缓存中是否存在相应 key 的数据,如果没有,则触发一次数据库访问并把查询到的结果存入缓存中,这在 Spring Boot 中以注解的方式很容易实现,我们可以这样子使用:
1 @Transactional(readOnly = true)
2 @Cacheable(
3 key = "'user_'+#user.id+':'+#pageable.pageSize+'_'+#pageable.pageNumber",
4 condition = "#user!=null && #pageable!=null",
5 unless = "#result==null",
6 cacheNames = "note"
7 )
8 @Nonnull
9 @Override
10 public Page<Note> findAllByUserAndPageable(@Nonnull User user, @Nonnull Pageable pageable) throws IllegalArgumentException {
但是当用户对其中一个 Note 进行更改时,缓存的更新就成了一大难题,试想有一个方法如下:
1 @Nonnull
2 @Override
3 public Note addOne(@Nonnull Note toAdd) throws IllegalArgumentException {...
我们新增了一个 Note,现在程序需要清除与之有关联的缓存数据,比如 分页,Spring Cache 提供了 @CacheEvict ,现在我们使用它来清除缓存,很自然的,对应产生缓存的方式,我们在 @CacheEvict 的数据中加入 key = "'user_'+#user.id+':'#pageable.pageSize+'_'+#pageable.pageNumber"。很不幸,这是个错误的使用方式,在这里,我们获取不到 pageable 对象。
@CacheEvict 里边有个 allEntries 选项,把它设置为 true 清空 当前 cacheNames 下的所有缓存如何?同样的,这不是一个好的处理方式。如果这么做了,当前缓存中的所有 缓存,包括那些没有被修改的数据,比如单个的 Note 缓存同样被删的一干二净。但是,其中的涉及小细节给了我们一些 hint。
解决思路
在上面的问题中,我们发现使用 allEntries 并不适用,它会导致缓存 cacheNames 下的所有数据被清空,请注意是指定的 cacheNames 下的所有数据,那么我们是否可以将分页数据单独放入对应 User 的 cacheName 下,当发生缓存更改时,直接删除只包含分页缓存的 cacheName 下的缓存? 比如 cacheNames="#principle.username" ?
如果通读过 Spring-doc 的 Cache 章节,会发现,cacheNames 属性并不支持 SpEL 表达式,所以以上的设置并不行得通。似乎山穷水尽,其实不然。仔细观察 @Cache... 的通用属性,会发现 cacheResolver 的注释是这样的。
The bean name of the custom {@link org.springframework.cache.interceptor.CacheResolver} to use.
可以使用 bean ,至少有一丝曙光,点进去 CacheResolver,他只规定了一个方法 resolveCaches,查看它的 Hierarchy 视图,所幸类试图并不复杂,
让我们查看 CacheResolverAdapter 的源码与注释。
Spring's {@link CacheResolver} implementation that delegates to a standard
JSR-107 {@link javax.cache.annotation.CacheResolver}.
Used internally to invoke user-based JSR-107 cache resolvers.
使用JCacheCache 的 JCache (JSR-107)实现, pass
查看 AbstractCacheResolver 的源码与注释。
A base {@link CacheResolver} implementation that requires the concrete
implementation to provide the collection of cache name(s) based on the
invocation context.
很幸运,我们很快发现了候选。但是我们需要参考 spring 的默认实现 SimpleCacheResolver。
A simple {@link CacheResolver} that resolves the {@link Cache} instance(s)
based on a configurable {@link CacheManager} and the name of the
cache(s) as provided by {@link BasicOperation#getCacheNames() getCacheNames()}.
解决进行
让我们针对 cache names 细节做一些具体实现:继承这个类,更改 getCacheNames 方法,然后我们就得到了一个具体的实现
1 /**
2 * dynamic generates cache name: findAllByUserAndPageable_${userId}
3 * <br>
4 * use for page<Note> with annotation{@link org.springframework.cache.annotation.CacheEvict}, {@link org.springframework.cache.annotation.Cacheable}
5 */
6 public static class DynamicNotePageCacheNames extends SimpleCacheResolver implements CacheResolver {
7 private final AuthenticationHelper authenticationHelper;
8 public static final String FIND_ALL_BY_USER_AND_PAGEABLE = "findAllByUserAndPageable";
9
10 public DynamicNotePageCacheNames(CacheManager cacheManager, AuthenticationHelper authenticationHelper) {
11 super(cacheManager);
12 log.debug(String.format("using customize CacheResolver: %s , cacheManager: %s",
13 this.getClass().getName(), cacheManager.getClass().getName()));
14 this.authenticationHelper = authenticationHelper;
15 }
16
17 @Override
18 protected Collection<String> getCacheNames(CacheOperationInvocationContext<?> context) {
19
20 Long uId = authenticationHelper.checkAndExtractUserFromAuthentication().getId();
21 String cacheName = String.format("%s_%d", FIND_ALL_BY_USER_AND_PAGEABLE, uId);
22 log.debug(String.format("generate cache name %s for target %s", cacheName, context.getTarget()));
23 return Collections.singleton((String.format("%s_%d", FIND_ALL_BY_USER_AND_PAGEABLE, uId)));
24 }
25 }
这里我从 Security 中获取到当前的登录用户的 id,将 id 与 方法字符串拼接起来作为 cachename 返回。需要注意的是 在方法体中我并没有对 uId 进行空检查是因为在调用 checkAndExtractUserFromAuthentication 方法 尝试获取 user 的时候,如果当前 Authentication 中只存在匿名用户的时候,方法会抛出 AccessDeniedException 错误,直接导致了 403 返回,具体可参考章节附。
让我们使用这个bean,实例化并且改写 service 层
@Bean("dynamicNotePageCacheNames")
public DynamicNotePageCacheNames cacheResolver() {
return new DynamicNotePageCacheNames(cacheManager, authenticationHelper);
}
@Cacheable的使用:
1 @Transactional(readOnly = true)
2 @Cacheable(
3 key = "#pageable.pageSize+'_'+#pageable.pageNumber",
4 condition = "#user!=null && #pageable!=null",
5 unless = "#result==null",
6 cacheResolver = "dynamicNotePageCacheNames"
7 )
8 @Nonnull
9 @Override
10 public Page<Note> findAllByUserAndPageable(@Nonnull User user, @Nonnull Pageable pageable) throws IllegalArgumentException {
@CacheEvict的使用:
@Transactional(rollbackFor = EntityExistsException.class)
@Caching(
evict = {
@CacheEvict(
condition = "#toAdd!=null ",
cacheResolver = "dynamicNotePageCacheNames", allEntries = true),
},
put = @CachePut(key = "'id_'+#result.id",
condition = "#toAdd!=null",
unless = "#result==null", cacheNames = CustomCacheConfig.NOTE)
)
@Nonnull
@Override
public Note addOne(@Nonnull Note toAdd) throws IllegalArgumentException {
需要注意的是,类上的注解 @CacheConfig 会覆盖方法中的设置,参考
附
AuthenticationHelper:
1 /**
2 *
3 *
4 * @author pancc
5 * @version 1.0
6 */
7 @Component
8 public class AuthenticationHelper {
9 private final UserService userService;
10
11 public AuthenticationHelper(UserService userService) {
12 this.userService = userService;
13 }
14
15 /**
16 * extract User From Authentication at current request, at this case it refers to a {@link UsernamePasswordAuthenticationToken}<br>
17 * <br>
18 * <code>anonymousUser</code> filter out anonymous user set by spring security web
19 *
20 * @param authentication if null, will get from current request
21 * @return optional with current user or empty
22 * @see JWTAuthenticationFilter
23 * @see TokenAuthenticationProcessor#getAuthentication(String)
24 * @see AnonymousAuthenticationFilter#AnonymousAuthenticationFilter(java.lang.String)
25 */
26 private Optional<User> extractUserOptionalFromAuthentication(Authentication authentication) {
27 final String anonymous = "anonymousUser";
28 if (authentication == null) {
29 authentication = SecurityContextHolder.getContext().getAuthentication();
30 }
31 if (authentication == null || !authentication.isAuthenticated()) {
32 return Optional.empty();
33 }
34 if ((authentication.getPrincipal().getClass().equals(String.class))) {
35 String username = (String) authentication.getPrincipal();
36 if (username == null || username.contentEquals(anonymous)) {
37 return Optional.empty();
38 }
39 return userService.findByUsername(username);
40 }
41 return Optional.empty();
42 }
43
44 /**
45 * extract User From Authentication at current request, at this case it refers to a {@link UsernamePasswordAuthenticationToken}<br>
46 *
47 * @return optional with current user or empty
48 * @see JWTAuthenticationFilter
49 * @see TokenAuthenticationProcessor#getAuthentication(String)
50 */
51 public Optional<User> extractUserOptionalFromAuthentication() {
52 return this.extractUserOptionalFromAuthentication(null);
53 }
54
55 /**
56 * extract User From Authentication, at this case it points to a {@link UsernamePasswordAuthenticationToken}<br>
57 * this method may throw {@link AccessDeniedException} if not caught, resulting in server response 403 code
58 * <br>
59 * <b>required login</b>
60 *
61 * @param authentication {@link UsernamePasswordAuthenticationToken}
62 * @return current user or throw AccessDeniedException that means 403 Http-code
63 * @throws AccessDeniedException if current Authentication contains bad Credentials
64 * @see ExceptionResolver.AccessDeniedAdvice
65 * @see JWTAuthenticationFilter
66 * @see TokenAuthenticationProcessor#getAuthentication(String)
67 */
68 public User checkAndExtractUserFromAuthentication(Authentication authentication) throws AccessDeniedException {
69 return this.extractUserOptionalFromAuthentication(authentication).orElseThrow(() -> new AccessDeniedException("Access Denied"));
70 }
71
72 /**
73 * extract User From Authentication at current request, at this case it refers to a {@link UsernamePasswordAuthenticationToken}<br>
74 * this method may throw {@link AccessDeniedException} if not caught, resulting in server response 403 code
75 * <br>
76 * <b>required login</b>
77 *
78 * @return current user or throw AccessDeniedException that means 403 Http-code
79 * @throws AccessDeniedException if current Authentication contains bad Credentials
80 * @see ExceptionResolver.AccessDeniedAdvice
81 * @see JWTAuthenticationFilter
82 * @see TokenAuthenticationProcessor#getAuthentication(String)
83 */
84 public User checkAndExtractUserFromAuthentication() throws AccessDeniedException {
85 return this.extractUserOptionalFromAuthentication(null).orElseThrow(() -> new AccessDeniedException("Access Denied"));
86 }
87
88 }