在My Corda项目中，我需要根据状态类的某些特定字段检索特定状态，我为每个状态设置了Unique。在Corda中如何做？执行状态如下：

@BelongsToContract(OfferContract.class)
public class OfferState implements LinearState {
    private final UniqueIdentifier linearID;
    private AnonymousParty sender;
    private AnonymousParty receiver;
    private final String policyID;
    private final double faceValue;
    private double offeredAmount;

    private boolean isActive;

    public OfferState(UniqueIdentifier linearID, AnonymousParty sender, AnonymousParty receiver, String policyID, double faceValue, double offeredAmount, boolean isActive) {
        this.linearID = linearID;
        this.sender = sender;
        this.receiver = receiver;
        this.policyID = policyID;
        this.faceValue = faceValue;
        this.offeredAmount = offeredAmount;
        this.isActive = isActive;
    }

    public UniqueIdentifier getLinearID() {
        return linearID;
    }

    public AnonymousParty getSender() {
        return sender;
    }

    public AnonymousParty getReceiver() {
        return receiver;
    }

    public String getPolicyID() {
        return policyID;
    }

    public double getFaceValue() {
        return faceValue;
    }

    public double getOfferedAmount() {
        return offeredAmount;
    }

    public boolean isActive() {
        return isActive;
    }

    @NotNull
    @Override
    public UniqueIdentifier getLinearId() {
        return linearID;
    }

    @NotNull
    @Override
    public List<AbstractParty> getParticipants() {
        return Arrays.asList(sender,receiver);
    }

    @Override
    public String toString() {
        return super.toString();
    }
}

我正在使用以下代码在API中进行查询，但是，在 Postman 输出中显示了[]之类的空括号。

@GetMapping(value = "/getOfferWithID",headers = "Content-Type=application/x-www-form-urlencoded")
    private List<StateAndRef<OfferState>> getOfferWithID(HttpServletRequest request) throws IllegalArgumentException {
        String s  = request.getParameter("PolicyID");
        return proxy.vaultQuery(OfferState.class).getStates().stream().filter(it->it.getState().getData().getPolicyID().equalsIgnoreCase(s)).collect(Collectors.toList());
    }

你能告诉我，如何在查询时过滤状态，这是怎么回事？是否有任何直接查询方法，以便我可以在rpc调用本身中对其进行过滤，或者我真的需要为此编写流程吗？