java - 仅更新更改的实体字段并检查 EJB 中其他用户的更改

Question

在 EJB 类中，我有两个带有远程接口(interface)的方法:

Class MyBean {
    public CustomerEntity getCustomer(String id) {......}
    public void updateCustomer(CustomerEntity newValues, CustomerEntity oldValues) {......}
}

客户实体由一些带有 getter 和 setter 的字段组成。

@Entity 
public class Customer {
    @ID private String id;
    @Column private String name;
    @Column private String phone;
    // Getters and setters 
    .
    .
}

客户端应用程序执行以下操作:

Customer customer myBeanRemoteInterface.getCustomer("some id");
Customer oldCustomer = customer;    //Save original customer data
displayCustomerFormAndAcceptChanges(customer);
myBeanRemoteInterface.updateCustomer(customer, oldCustomer);

EJB updateCustomer 现在应该更新服务器上的客户。为了避免覆盖其他用户对其他字段所做的任何更改，只应提交该用户已更改的字段。就像下面这样:

public void updateCustomer(CustomerEntity newValues, CustomerEntity oldValues) {
    Customer customer = entityManager.find(Customer.class, oldValues.getId());
    if (!newValues.getName().equals(oldValues.getName()) { // Value updated
        // If the value fetched by entityManager.find is different from what was originally fetched that indicates that the value has been updated by another user.
        if (!customer.getName().equals(oldValues.getName()) throw new CustomerUpdatedByOtherUserException();
        else customer.setName(newValues.getName());
    }
    // repeat the code block for every field in Customer class
    entityManager.flush();
}

现在的问题是 updateCustomer 中的代码块需要为 Customer 类中的每个字段重复一次。如果将新字段插入到 Customer 类中，则 EJB 也需要更新。

如果向 Customer 类添加更多字段，我需要一个无需更新 EJB 即可工作的解决方案。

有什么建议吗？

Answer 1

使用 Java 反射:

     Method[] methods = Customer.class.getDeclaredMethods();
     Class<?>[] methodParams = null;
     Object[] paramValue = new Object[1];

     for (Method method : methods) {

       if(method.getName().contains("set")) //This is for set methods. 
       {
           methodParams = method.getParameterTypes();
           if(methodParams[0].equals(String.class))
           {
               paramValue[0] = "some string"; // Assigning some value to method parameter
           }

           method.invoke(customer, paramValues); // customer is your object you are executing your methods on.
       }
    }