经过很多努力后，我发布了我的个人解决方案。我不认为这是正确的，也不是“最佳实践”，所以请照原样进行。我想分享一下，因为它可以帮助有同样需求的人。
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;
}
}
该服务无法处理所有Predicate / Expression的情况，但会在未处理时发出警告。
基本上，这个想法是从Predicate创建一个Specification并对其进行分析以生成其值的字符串，然后创建一个hashCode。
使用此代码，生成的键似乎稳定，现在我可以像Page findAll(Specification specification,Pageable pageable);一样缓存我的查询
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