我正在测试Spring Data 1.10.4.RELEASE，按照Spring Data文档中的示例http://docs.spring.io/spring-data/jpa/docs/current/reference/html/#projections进行。
我注意到了一些问题，有两个问题需要解决。
首先，假设我有以下这两个实体：
@Entity
public class Person {
@Id @GeneratedValue
private Long id;
private String firstName, lastName;
@OneToOne
private Address address;
}
@Entity
public class Address {
@Id @GeneratedValue
private Long id;
private String street, state, country;
}
- 问题1：
对于以下的投影：
interface PersonLimited {
String getFirstName();
AddressLimited getAddress();
}
interface AddressLimited {
String getCountry();
}
当我运行findPersonByFirstNameProjectedForLimitedData时
interface PersonRepository extends CrudRepository<Person, Long> {
@Query("select p from Person p where p.firstName = ?1")
PersonLimited findPersonByFirstNameProjectedForLimitedData(String firstName);
}
它返回的正是预期的内容：
{
firstName: 'Homer',
address: {
country: 'USA'
}
}
现在如果我查看生成的 SQL，我得到如下结果：
SELECT person0_.firstName AS col_0_0_,
address1_.id AS id1_13_,
address1_.street AS street2_13_,
address1_.state AS state3_13_,
address1_.country AS country4_13_
FROM person person0_
LEFT OUTER JOIN address address1_
ON person0_.addressId = address1_.id
WHERE person0_.firstName = ?
对于“Person”实体的投影只选择了“fistName”，这是100%正确的，因为在PersonLimited接口中我仅定义了“getFirstName”。
但是对于“Address”实体，它选择了所有字段，这是错误的，因为在AddressLimited接口中我仅定义了“getCountry”，应该只选择“country”。
生成的查询应该类似于：
SELECT person0_.firstName AS col_0_0_,
address1_.country AS country4_13_
FROM person person0_
LEFT OUTER JOIN address address1_
ON person0_.addressId = address1_.id
WHERE person0_.firstName = ?
那么问题是，为什么不仅选择地址“实体”的“国家”字段？为什么需要选择所有字段？这是Spring中的错误吗？
- 问题2：
对于与上面相同的投影，当我运行findAllPersonsProjectedForLimitedData时
interface PersonRepository extends CrudRepository<Person, Long> {
@Query("select p from Person p")
List<PersonLimited> findAllPersonsProjectedForLimitedData();
}
它返回了完全符合预期的内容：
[
{
firstName: 'Homer',
address: {
country: 'USA'
}
},
{
firstName: 'Maggie',
address: {
country: 'USA'
}
}
]
现在如果我查看生成的SQL，我会得到以下结果：
SELECT person0_.id AS id1_18_,
person0_.firstName AS firstName2_18_,
person0_.lastName AS lastName3_18_,
person0_.addressid AS company4_18_
FROM person person0_
SELECT address0_.id AS id1_13_0_,
address0_.street AS street2_13_0_,
address0_.state AS state3_13_0_,
address0_.country AS country4_13_0_
FROM address address0_
WHERE address0_.id = ?
在这里，Person和Address实体的投影选择了所有字段，这是错误的，它应该只选择"firstName"和"country"。
生成的查询应该类似于：
SELECT person0_.firstName AS firstName2_18_
FROM person person0_
SELECT address0_.country AS country4_13_0_
FROM address address0_
WHERE address0_.id = ?
这是正常行为吗？难道我们不应该只选择需要的字段吗？
谢谢，