java - 带有 JPA 和规范的 Spring Cache
问题描述
我使用 Spring Boot 2.2、Spring Data REST、Hibernate、Spring Redis 创建了一个 REST 应用程序。
我配置了一个 Redis 服务器,我想在其中缓存我所做的一些查询。我已经做了我能做的所有优化,但这是一个分布式应用程序,我需要通过集中缓存来提高性能。一切正常,但是当我使用 Spring 存储库的方法时,我看不到如何创建方便的密钥
@Cacheable(cacheNames = "contacts")
@Override
Page findAll(Specification specification, Pageable pageable);
这是我的 Redis 配置:
@Configuration
@EnableCaching
public class RedisCacheConfig extends CachingConfigurerSupport implements CachingConfigurer {
@Override
public CacheErrorHandler errorHandler() {
return new RedisCacheErrorHandler();
}
@Override
@Bean("customKeyGenerator")
public KeyGenerator keyGenerator() {
return new CustomKeyGenerator();
}
}
和我的密钥生成器:
public class CustomKeyGenerator implements KeyGenerator {
public CustomKeyGenerator() {
}
@Override
public Object generate(Object target, Method method, Object... params) {
List<Object> listParams = new ArrayList<>(Arrays.asList(params));
listParams.add(TenantContext.getCurrentTenantId());//Add tenantId as parameter
if (StoreContext.getCurrentStoreId() != null)
listParams.add(StoreContext.getCurrentStoreId());//Add storeId as parameter
return generateKey(listParams.toArray());
}
public static Object generateKey(Object... params) {
if (params.length == 0) {
return SimpleKey.EMPTY;
} else {
if (params.length == 1) {
Object param = params[0];
if (param != null && !param.getClass().isArray()) {
return param;
}
}
return new SimpleKey(params);
}
}
}
当我调用Page findAll(Specification specification, Pageable pageable);
时,我会在我的参数中CustomKeyGenerator
获取参数,但我会收到一个SpecificationComposition
(它是一个 Spring 助手类)来代替Specification
. 每次我调用该方法时,它的哈希码都是不同的,即使“它的内容是相同的”。
就像每次(PageRequest
类)都以相同方式散列的 Pageable 一样,我想这样做Specification
以获取 Spring 缓存机制的优势。
你有什么提示可以告诉我正确的方法吗?
解决方案
经过一番挣扎后,我发布了我的个人解决方案。我不假装它是正确的或“最佳实践”,所以请照原样接受。我想分享,因为也许可以帮助有同样需要的人。
这是密钥生成器:
@Log4j2
public class CustomKeyGenerator implements KeyGenerator {
private static SpecificationService specificationService;
public CustomKeyGenerator() {
specificationService = SpringBeansLoadUtils.getBean(SpecificationService.class);
}
@Override
public Object generate(Object target, Method method, Object... params) {
//********************************************************************
// GET GENERICS IN CASE
// For methods like Page<Document> findAll(Specification specification, Pageable pageable);
// get the Generics type needed to
//********************************************************************
Class returnClass = method.getReturnType();
Class realClass = null;
if (Collection.class.isAssignableFrom(returnClass) || Page.class.isAssignableFrom(returnClass)) {
Type returnType = method.getGenericReturnType();
if (returnType instanceof ParameterizedType) {
ParameterizedType paramType = (ParameterizedType) returnType;
Type[] argTypes = paramType.getActualTypeArguments();
if (argTypes.length > 0) {
realClass = (Class) argTypes[0];
}
}
}
List<Object> listParams = new ArrayList<>(Arrays.asList(params));
listParams.add(TenantContext.getCurrentTenantId());//Add tenantId as parameter
if (StoreContext.getCurrentStoreId() != null)
listParams.add(StoreContext.getCurrentStoreId());//Add storeId as parameter
return generateKey(realClass, listParams.toArray());
}
public static Object generateKey(Class clazz, Object... params) {
if (params.length == 0) {
return SimpleKey.EMPTY;
} else {
if (params.length == 1) {
Object param = params[0];
if (param != null && !param.getClass().isArray()) {
return param;
}
}
HashCodeBuilder builder = new HashCodeBuilder();
for (Object p : params) {
if (p != null && p.getClass().getSimpleName().contains("SpecificationComposition")) {
builder.append(specificationService.hashCode(clazz, (Specification) p));
} else {
builder.append(Arrays.deepHashCode(new Object[]{p}));
}
}
log.info("Hash {}", builder.hashCode());
return builder.hashCode();
}
}
}
这是完成这项工作的服务:
@Service
@Transactional
@PreAuthorize("isAuthenticated()")
@Log4j2
public class SpecificationService {
@PersistenceContext(unitName = "optixPU")
private EntityManager entityManager;
/**
* Generate an hashCode of the given specification
*
* @param clazz
* @param spec
* @return
*/
public Integer hashCode(Class clazz, @Nullable Specification spec) {
try {
CriteriaBuilder builder = entityManager.getCriteriaBuilder();
CriteriaQuery query = builder.createQuery(clazz);
Root root = query.from(clazz);
Predicate predicate = spec.toPredicate(root, query, builder);
String hash = analyzePredicate(predicate);
return hash.hashCode();
} catch (Exception e) {
log.warn("", e);
}
return null;
}
private String analyzePredicate(Predicate predicate) {
String stringRepresentation = "";
for (Expression<Boolean> e : predicate.getExpressions()) {
if (e instanceof CompoundPredicate) {
stringRepresentation += analyzePredicate((CompoundPredicate) e);
} else {
if (e instanceof InPredicate) {
InPredicate inPredicate = (InPredicate) e;
for (Object ex : inPredicate.getValues()) {
stringRepresentation += analyzeExpression((Expression) ex);
}
} else if (e instanceof LikePredicate) {
LikePredicate likePredicate = (LikePredicate) e;
String hashExpression = analyzeExpression(likePredicate.getMatchExpression());
String hashPattern = analyzeExpression(likePredicate.getPattern());
stringRepresentation += hashExpression + hashPattern;
} else if (e instanceof ComparisonPredicate) {
String operator = ((ComparisonPredicate) e).getComparisonOperator().toString();
String leftHand = analyzeExpression(((ComparisonPredicate) e).getLeftHandOperand());
String rightHand = analyzeExpression(((ComparisonPredicate) e).getRightHandOperand());
stringRepresentation += operator + leftHand + rightHand;
} else {
log.warn("Predicate not identified: {}", e);
}
}
}
return stringRepresentation;
}
private String analyzeExpression(Expression expression) {
if (expression instanceof SingularAttributePath) {
SingularAttributePath singularAttributePath = (SingularAttributePath) expression;
return singularAttributePath.getAttribute().getName();
} else if (expression instanceof LikeExpression) {
LiteralExpression likeExpression = (LiteralExpression) expression;
return likeExpression.getLiteral().toString();
}
if (expression instanceof LiteralExpression) {
return ((LiteralExpression) expression).getLiteral().toString();
} else if (expression instanceof ConcatExpression) {
ConcatExpression concatExpression = (ConcatExpression) expression;
String code1 = analyzeExpression(concatExpression.getString1());
String code2 = analyzeExpression(concatExpression.getString2());
return code1 + code2;
} else {
log.warn("Expression {} not identified", expression);
}
return null;
}
}
该服务不处理所有Predicate
/Expression
案例,但它会在不处理时发出警告。
基本上,这个想法是Predicate
从中创建一个Specification
并分析它以生成其值的字符串,然后创建一个 hashCode。
使用此代码,生成的密钥看起来很稳定,现在我可以缓存我的查询 Page findAll(Specification specification, Pageable pageable);
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