使用Spring Data Mongo时，@ DBRef不会提取数据

Question

我使用了以下代码：Error creating bean with name 'personRepository': Invocation of init method failed; nested exception is com.mongodb.util.JSONParseException:，现在试着打电话

Person p = personRepository.findByAddresses_City("London NW1");
System.out.println("PERSON FOR ADDRESS = "+p);

我得到空响应。

此外，下面的查询不会拉任何东西。

Query query = new Query(Criteria.where("address.$id").is(2L));
List<Person> l = mongoTemplate.find(query, Person.class);
System.out.println(l);

这里：

db.getCollection（ '地址'）。找到（{}）

/* 1 */
{
    "_id" : NumberLong(1),
    "address" : "221b Baker Street",
    "city" : "London NW1",
    "state" : "London",
    "zipcode" : NumberLong(12345),
    "_class" : "com.example.demo.model.Address"
}

和db.getCollection('person').find({})

/* 1 */
{
    "_id" : NumberLong(1),
    "name" : "Achilles",
    "age" : 0,
    "addresses" : [],
    "_class" : "com.example.demo.model.Person"
}

/* 2 */
{
    "_id" : NumberLong(2),
    "name" : "Hektor",
    "age" : 0,
    "addresses" : [ 
        {
            "$ref" : "address",
            "$id" : NumberLong(1),
            "$db" : "address"
        }
    ],
    "_class" : "com.example.demo.model.Person"
}

如何解决这个错误？

@Document(collection = "address")
public class Address {

    @Id
    private long addressId;
    private String address;
    private String city;
    private String state;
    private long zipcode;

    public Address() {
        System.out.println("CAlling default cons");
    }

    @PersistenceConstructor
    public Address(long addressId, String address, String city, String state, long zipcode) {
        this.addressId = addressId;
        this.address = address;
        this.city = city;
        this.state = state;
        this.zipcode = zipcode;
    }
    // setter and getter... toString()..
}

和

@Document
public class Person {
    @Id
    private Long personId;

    private String name;

    private int age;

    @DBRef(db = "address")
    private List<Address> addresses = new ArrayList<>();

    public Person() {
    }

    @PersistenceConstructor
    public Person(Long personId, String name, int age) {
        super();
        this.personId = personId;
        this.name = name;
        this.age = age;
    }
    // setter, getter and toString
}

Answer 1

这按设计工作。 MongoDB不允许通过查询进行应用程序级别连接，您需要使用聚合框架来进行更复杂的查询。因此，存储库查询只允许通过完整值（即Address对象）或标识符来查找DBRef。

如果您将where子句修复为address.addressId，则第二个示例应该有效。

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