java - 如何链接两个不同类的对象？

Question

我想为库构建一个 REST API(端点是客户和发票)。其中一项功能是添加发票(带有客户 ID 的 PUT 请求)。首先，我必须检查传递的客户 ID(通过 URL 中的 PUT)是否存在，这意味着检查 customerMap 并查看正在讨论的 id。问题是 customerMap 是 clientService 类中的 HashMap(而不是 invoiceService 类中的)(使用 Map 而不是数据库)。如何获取 map 中存储的数据？代码的相关部分如下:

客户端

public class client {

private static final AtomicLong counter = new AtomicLong();

private final long id;

public client() {
    this.id = counter.getAndIncrement();
}

public long getId() {
    return id;
}
}

客户端服务

public class clientService {
public Map<Long, client> clientMap = new HashMap<>();

public client put(client g) {
    clientMap.put(g.getId(), g);
    return g;
}

public Collection<client> getAll() {
    return clientMap.values();
}
}

发票

invoice  {

private static final AtomicLong counter = new AtomicLong();

private final long id;
private client client;

public invoice() {
    this.id = counter.getAndIncrement();
}

public long getId() {
    return id;
}
}

发票服务

public class invoiceService {
private Map<Long, invoice> invoiceMap = new HashMap<>();

public Rechnung createinvoice(invoice g, long id) {

    if(<!--client exists-->)
    invoicegMap.put(g.getId(), g);
    return g;
}}

Answer 1

首先向您的 ClientService 添加一个方法以通过 id 查找客户端:

public Client getClientById(Long clientId) {
   return clientMap.get(clientId);
}

然后将您的 ClientService 注入(inject)到您的 Invoice Service 中；

public class invoiceService {
private Map<Long, invoice> invoiceMap = new HashMap<>();
private ClientService clientService; // provide a getter or a constructor argument for the service

public Rechnung createinvoice(invoice g, long id) {

    if(clientService.getClientById(id) != null) {
      invoicegMap.put(g.getId(), g);
}
    return g;
}}