直接向 DTO 查询结果答案

【问题标题】：Querying results directly to a DTO直接向 DTO 查询结果
【发布时间】：2019-02-17 07:42:06
【问题描述】：

当我尝试直接从 spring 数据查询结果到 DTO 类时，我收到此错误

原因：java.lang.IllegalArgumentException: org.hibernate.QueryException: 无法解析属性：owner_name of: test.dao.bean.Car [SELECT new test.dto.bean.CarOwners(c.owner_name, c. owner_nid, c.owner_phone, c.driver_name, c.driver_nid, c.driver_phone) FROM test.dao.bean.Car c] 在 org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:133) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final] 在 org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:157) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final] 在 org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:164) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final] 在 org.hibernate.internal.AbstractSharedSessionContract.createQuery(AbstractSharedSessionContract.java:670) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final] 在 org.hibernate.internal.AbstractSessionImpl.createQuery(AbstractSessionImpl.java:23) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final] 在 sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_152] 在 sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_152] 在 sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_152] 在 java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_152] 在 org.springframework.orm.jpa.ExtendedEntityManagerCreator$ExtendedEntityManagerInvocationHandler.invoke(ExtendedEntityManagerCreator.java:350) ~[spring-orm-5.0.7.RELEASE.jar:5.0.7.RELEASE] 在 com.sun.proxy.$Proxy123.createQuery(Unknown Source) ~[na:na] 在 org.springframework.data.jpa.repository.query.SimpleJpaQuery.validateQuery(SimpleJpaQuery.java:87) ~[spring-data-jpa-2.0.8.RELEASE.jar:2.0.8.RELEASE] ...省略了76个常用框架

这是我的查询：

@Query("SELECT new test.dto.bean.CarOwners(c.owner_name, c.owner_nid, c.owner_phone, c.driver_name, c.driver_nid, c.driver_phone) FROM car c")
public List<CarOwners> findAllCarOwners();

这是 DTO 类：

test.dto.bean;

public class CarOwners{

private String owner_name;
private Long owner_nid;
private Integer owner_phone;
private String driver_name;
private Long driver_nid;
private Integer driver_phone;

 public CarOwners(String owner_name, Long owner_nid, Integer owner_phone, String driver_name, Long driver_nid, Integer driver_phone) {
        this.owner_name = owner_name;
        this.owner_nid = owner_nid;
        this.owner_phone = owner_phone;
        this.driver_name = driver_name;
        this.driver_nid = driver_nid;
        this.driver_phone = driver_phone;

    }

public String getOwner_name() {
    return owner_name;
}


public void setOwner_name(String owner_name) {
    this.owner_name = owner_name;
}


public Long getOwner_nid() {
    return owner_nid;
}


public void setOwner_nid(Long owner_nid) {
    this.owner_nid = owner_nid;
}


public Integer getOwner_phone() {
    return owner_phone;
}


public void setOwner_phone(Integer owner_phone) {
    this.owner_phone = owner_phone;
}


public String getDriver_name() {
    return driver_name;
}


public void setDriver_name(String driver_name) {
    this.driver_name = driver_name;
}


public Long getDriver_nid() {
    return driver_nid;
}


public void setDriver_nid(Long driver_nid) {
    this.driver_nid = driver_nid;
}


public Integer getDriver_phone() {
    return driver_phone;
}


public void setDriver_phone(Integer driver_phone) {
    this.driver_phone = driver_phone;
}
}

有什么帮助吗？？

【问题讨论】：

标签： java spring-boot spring-data

【解决方案1】：

引起：java.lang.IllegalArgumentException： org.hibernate.QueryException：无法解析属性：owner_name of: test.dao.bean.Car

显然，select 子句中的字段应该引用映射实体 (Car) 的 Java 属性名称，而不是 DTO 中的属性名称。

所以假设汽车是：

@Entity
@Table(name="car")
public class Car{


    @Column(name="owner_name")
    private String ownerName;

}

那么你应该写：

@Query("SELECT new test.dto.bean.CarOwners(c.ownerName) FROM car c")

实际上，DTO 字段的名称与@Query 字符串的写法无关。它只匹配 DTO 构造函数参数和 SELECT NEW 子句中的字段之间的顺序。只要它们的订单和数据类型匹配，您就可以使用任何 DTO 名称。

【讨论】：