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我查看了许多示例并尝试了各种 w/&w/o 示例匹配器约束，但是无论我通过示例进行查询都只返回 null。

我能够毫无问题地使 CRUD 存储库数据调用正常工作，但是我将其扩展到 JPA 存储库并添加了 QueryByExampleExecutor 接口。findOne() 似乎不起作用。

使用 Spring Boot 2.2.6.RELEASE、spring-boot-starter-data-jpa 和 mysql 5.7。

使用示例查询时，是否需要完成整个对象才能匹配？换句话说，所有的二传手都需要正确的信息吗？还是只是要匹配的对象数据项？

是的，数据库确实只包含一个我试图匹配的正确字符串。

顾客

@Entity
@Table(name="customer")
public class Customer {
    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    @Column(name="id")
    private long id;

    @Column(name="social_security_number")
    private String socialSecurityNumber;

    //Other data fields are included
}

客户资料库

import org.springframework.data.jpa.repository.JpaRepository;

public interface CustomerRepository extends JpaRepository<Customer, Long> {
}

QueryByExampleExecutor

import java.util.Optional;

import org.springframework.data.domain.Example;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.Pageable;
import org.springframework.data.domain.Sort;

public interface QueryByExampleExecutor<T> {

    <S extends T> Optional<S> findOne(Example<S> example);

    <S extends T> Iterable<S> findAll(Example<S> example);

    <S extends T> Iterable<S> findAll(Example<S> example, Sort sort);

    <S extends T> Page<S> findAll(Example<S> example, Pageable pageable);

    <S extends T> long count(Example<S> example);

    <S extends T> boolean exists(Example<S> example);

}

客户服务

public interface CustomerService {
    public Customer findBySSN(String ssn);
}

CustomerServiceImpl

@Service
public class CustomerServiceImpl implements CustomerService {

private CustomerRepository customerRepository;

    @Autowired
    public CustomerServiceImpl(CustomerRepository theCustomerRepository) {
        customerRepository = theCustomerRepository;
    }

    @Override
    public Customer findBySSN(String ssn) {
        //Create a new object to use as a basis for querying against
        Customer customer = new Customer();
        //Set the parameters for the query
        customer.setSocialSecurityNumber(ssn);
        //Create an example query
        Example<Customer> customerExample = Example.of(customer);

        Optional<Customer> result = customerRepository.findOne(customerExample);

        if (result.isPresent()) { 
            return result.get();
        } else {
            // Didn't find the customer
            throw new ObjectNotFoundException("Customer", "Social Security Number ("+ssn+") not found...");
        }
    }
}

调用方法

    @Autowired
    private CustomerService customerService;


    Customer ssnCustomer = customerService.findBySSN("123456789");
        if(ssnCustomer == null) {
            System.out.println("SSN NOT FOUND WAS NULL");
        } else {
            System.out.println("SSN FOUND "+ssnCustomer.getId());
        }

我错过了什么？先感谢您。

4

1 回答 1

2

将 id 类型从 long 更改为 Long。long 自动将值设置为 0 并使其成为查询的一部分。

私人长ID；

相应地更改 getter 和 Setter

于 2020-06-04T01:54:24.503 回答