原因：java.sql.SQLException:Column'；id'；找不到

我想获取一些字段，然后将其设置为Test.entity。我的SQL查询：

                query = "SELECT t.id as tId, t.test_name, t.duration, q.id as qId, " +
                    "q.question as question, q.is_multichoice as is_multichoice, " +
                    "q.is_open as is_open, a.id as aId, a.answer_text as answer_text  FROM result r " +
                    "JOIN test t ON r.test_id = t.id " +
                    "JOIN user u ON r.user_id = u.id " +
                    "JOIN question q ON t.id = q.test_id JOIN answer a ON q.id = a.question_id " +
                    "WHERE t.id = :testId AND u.id = :userId AND r.permission = :permissionId " +
                    "AND q.archived = false AND a.archived = false", resultClass = com.bionic.entities.Test.class)

测试实体：

public class Test {
@Id
@Column(name = "id")
@GeneratedValue(strategy = GenerationType.AUTO)
private long id;
@Column(name = "duration", nullable = false)
private int duration;
@Column(name = "test_name", nullable = false, unique = true)
private String testName;
@Column(name = "archived", nullable = false)
private boolean archived;
@OneToMany(mappedBy = "test", fetch = FetchType.EAGER)
private Set<Question> questions;
@ManyToMany(mappedBy = "tests")
private Set<User> users;

    public Test getCurrentTest(long id, long testId, long permissionId) {
    Query query = em.createNamedQuery("getCurrentTestById");
    query.setParameter("userId", id);
    query.setParameter("testId", testId);
    query.setParameter("permissionId", permissionId);
    return (Test) query.getSingleResult();
}

但是，在执行此查询后，我得到了以下验证：

Caused by: java.sql.SQLException: Column 'id' not found.

DAO.class:

public class Test {
@Id
@Column(name = "id")
@GeneratedValue(strategy = GenerationType.AUTO)
private long id;
@Column(name = "duration", nullable = false)
private int duration;
@Column(name = "test_name", nullable = false, unique = true)
private String testName;
@Column(name = "archived", nullable = false)
private boolean archived;
@OneToMany(mappedBy = "test", fetch = FetchType.EAGER)
private Set<Question> questions;
@ManyToMany(mappedBy = "tests")
private Set<User> users;

    public Test getCurrentTest(long id, long testId, long permissionId) {
    Query query = em.createNamedQuery("getCurrentTestById");
    query.setParameter("userId", id);
    query.setParameter("testId", testId);
    query.setParameter("permissionId", permissionId);
    return (Test) query.getSingleResult();
}

---

我做错了什么？

您的查询没有返回名为

id

的字段。它的字段名为

aId、qId和tId

---

您需要在实体中使用正确的列名。例如，在您的测试实体中，您声明了一个名为id的列。除了您的查询不返回名为id的列外，它还返回一个名为tId的列。有关需要更改的内容的示例，请参见下文

public class Test {
@tId
@Column(name = "tId")
@GeneratedValue(strategy = GenerationType.AUTO)
private long tId;
 .... 

---

请确保您的所有表都有名为id的列。我如何将其映射到实体中的id字段？我的意思是，我有3个名为id（test、question、aswer）的字段，但我无法通过SQL查询获得3个同名“id”的字段。我明白这一点。这就是为什么你给这3个字段一个别名。从而更改字段的名称，使其唯一。但这也意味着您的代码看不到名为id的字段。您需要通过其新别名引用该字段。如果我应该使用SqlResultSetMappings，我应该使用SqlResultSetMappings还是重命名每个实体中的字段（我不喜欢此变体），我如何为答案和问题设置字段，因为它们是子实体。您需要在实体中使用正确的列名。例如，在测试实体中，您声明了一个名为

id

的列。除了查询不返回名为

id

的列外，它还返回名为

tId

的列。