Question

我尝试更新现有实体，但在使用Ref.create时，会使用缓存值。客户端对象是：

public class RealEstatePropertyAPI {
    private Long id;
    private String name;
    private AddressAPI address;
}

public class AddressAPI {
    private Long id;
    private String street;
    private String city;
    private String state;
    private String zip;
    private String country;
}

服务器端的相应对象：

@Entity
public class RealEstateProperty {
    @Id
    private Long id;
    @Parent
    private Ref<Owner> owner;
    private String name;
    @Load
    private Ref<Address> address;
}

@Entity
public class Address {
    @Id
    private Long id;
    private String street;
    private String city;
    private String state;
    private String zip;
    private String country;
}

我有一种方法可以从客户端对象转换为服务器对象：

public static RealEstateProperty fromAPI(RealEstatePropertyAPI api,
        Owner owner) {
    RealEstateProperty property = new RealEstateProperty();
    property.setId(api.getId());
    property.setName(api.getName());
    property.setOwner(owner);
    if (api.getAddress() != null) {
        Address address = AddressConverter.fromAPI(api.getAddress());
        String x = address.getStreet();
        property.setAddress(address);
        String y = property.getAddress().getStreet();
        System.out.println(x.equals(y));
    }
    return property;
}

public static Address fromAPI(AddressAPI api) {
    Address address = new Address();
    address.setId(api.getId());
    address.setStreet(api.getStreet());
    address.setCity(api.getCity());
    address.setState(api.getState());
    address.setZip(api.getZip());
    address.setCountry(api.getCountry());
    return address;
}

问题出在RealEstateProperty.fromAPI，property.setAddress(address);应该设置新的Address，但事实并非如此。为什么x.equals(y)返回false？

方法：

public void setAddress(Address value) {
    this.address = Ref.create(value);
}

有关更新实体的相关问题。以下调用是否同时更新了RealEstateProperty及其子Address？

public void update(RealEstateProperty property) {
    ofy().save().entity(property);
}

Answer 1

阅读本文档参考部分的“其他注意事项”：

https://code.google.com/p/objectify-appengine/wiki/Entities

参考不持有实体价值;他们只需按住键，然后直接将值加载到会话中（如果不在会话中，则加载数据存储区）。如果要保留新版本的地址，则需要明确地保存（）。

另外：Refs没有级联的save（），因为Refs不包含实体对象！它们只是“指针”。

用objectify更新现有实体

1 个答案: