Spring不推荐使用Specifications<T>类型

Question

我正在实现来自链接：Spring Data - Multi-column searches的逻辑，在这里我希望通过FirstName进行搜索。

As链接：https://docs.spring.io/spring-data/jpa/docs/current/api/org/springframework/data/jpa/domain/Specifications.html

EmployeeSpecification.java

public class EmployeeSpecification {
    public static Specification<Employee> textInAllColumns(String text) {
        if (!text.contains("%")) {
            text = "%" + text + "%";
        }
        final String finalText = text;

        return new Specification<Employee>() {
            @Override
            public Predicate toPredicate(Root<Employee> root, CriteriaQuery<Employee> cq, CriteriaBuilder builder) {
                return builder.or(root.getModel().getDeclaredSingularAttributes().stream().filter(a -> {
                    if (a.getJavaType().getSimpleName().equalsIgnoreCase("string")) {
                        return true;
                    } else {
                        return false;
                    }
                }).map(a -> builder.like(root.get(a.getName()), finalText)).toArray(Predicate[]::new));
            }
        };
    }
}

EmployeeRepository.java

public interface EmployeeRepository extends JpaRepository<Employee, Long>{
    List<Employee> findAll(Specification<Employee> spec);
}

EmployeeServiceImpl.java

@Service
@Slf4j
public class EmployeeServiceImpl implements EmployeeService {
    @Autowired
    private EmployeeRepository employeeRepository;

    @Override
    public void findAllCustomersByFirstName(String firstName) {
        employeeRepository.findAll(Specifications.where(EmployeeSpecification.textInAllColumns(firstName)));
    }
}

错误：

这一行中的多个标记-类型规范中的(规格)不适用于参数(规范)的方法-不推荐类型规范

​

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Answer 1

您的回购代码需要像这样扩展JpaSpecificationExecutor：

public interface EmployeeRepository extends JpaRepository<Employee, Long>, 
    JpaSpecificationExecutor<Employee> {
}

JpaSpeficationExecutor有以下方法可以调用：

public interface JpaSpecificationExecutor<T> {
    Optional<T> findOne(@Nullable Specification<T> var1);

    List<T> findAll(@Nullable Specification<T> var1);

    Page<T> findAll(@Nullable Specification<T> var1, Pageable var2);

    List<T> findAll(@Nullable Specification<T> var1, Sort var2);

    long count(@Nullable Specification<T> var1);
}

然后你就可以：

public void findAllCustomersByFirstName(String firstName) {
    employeeRepository.findAll(
            EmployeeSpecification.textInAllColumns(firstName)
    );
}

我更改了您的规范，使用lambdas：

public class EmployeeSpecification {
    public static Specification<Employee> textInAllColumns(String text) {
        if (!text.contains("%")) {
            text = "%" + text + "%";
        }
        final String finalText = text;

        return  (Specification<Employee>) (root, query, builder) -> 
                builder.or(root.getModel().getDeclaredSingularAttributes().stream().filter(a -> {
                if (a.getJavaType().getSimpleName().equalsIgnoreCase("string")) {
                    return true;
                } else {
                    return false;
                }
            }).map(a -> builder.like(root.get(a.getName()), finalText)).toArray(Predicate[]::new));
    }
}

您可以在这里查看您在回答中拥有的代码的更新版本：https://github.com/zifnab87/spring-boot-rest-api-helpers/blob/26501c1d6afcd6afa8ea43c121898db85b4e5dbe/src/main/java/springboot/rest/specifications/CustomSpecifications.java#L172