Question

我是JPA（eclipselink）的新手，我正在尝试使用ManyToOne unidirectional mapping，我有superclass Student和subclass Book，当我尝试保存对象时我最终会遇到异常，细节如下所示

学生是家长班

@Entity
@Table(name="STUDENT")
@TableGenerator(name="student_s", initialValue=1)
public class Student {
    @Id 
    @Column(name="student_id")
    @GeneratedValue(strategy=GenerationType.TABLE ,generator="student_s")
    private int studentID;

    @Column(name="full_name",nullable=false)
    private String student_name;

    public int getStudentID() {
        return studentID;
    }

    public void setStudentID(int studentID) {
        this.studentID = studentID;
    }

    public String getStudent_name() {
        return student_name;
    }

    public void setStudent_name(String student_name) {
        this.student_name = student_name;
    }

}

Book是Child Class

@Entity
@Table(name="BOOK")
@TableGenerator(name="book_s", initialValue=1)
public class Book {
    @Id 
    @Column(name="book_id")
    @GeneratedValue(strategy=GenerationType.TABLE ,generator="book_s")
    private int bookID;

    @Column(name="book_name")
    private String bookName;

    @Column(name="student_id")
    private String studentID;

    @ManyToOne(cascade=CascadeType.ALL)
    @JoinColumn(name="student_id",referencedColumnName="student_id",insertable=false,updatable=false)
    private Student student;

    public int getBookID() {
        return bookID;
    }

    public void setBookID(int bookID) {
        this.bookID = bookID;
    }

    public String getBookName() {
        return bookName;
    }

    public void setBookName(String bookName) {
        this.bookName = bookName;
    }

    public String getStudentID() {
        return studentID;
    }

    public void setStudentID(String studentID) {
        this.studentID = studentID;
    }

    public Student getStudent() {
        return student;
    }

    public void setStudent(Student student) {
        this.student = student;
    }


}

执行持久化操作的Main Class，在执行persist时抛出未知列异常。

public class Main {
    public static void main(String args[]){     
        Student student = new Student();
        student.setStudent_name("Prem");

        Book book = new Book();
        book.setBookName("The Best Laid Plan");
        book.setStudent(student);

        EntityManagerFactory emf=Persistence.createEntityManagerFactory("premjpaeclipselink");
        EntityManager em = emf.createEntityManager();
        em.getTransaction().begin();
        em.persist(book);
        em.getTransaction().commit();
        em.close();
        emf.close();
    }
}

例外：

]: sql: Connection(635083092)--INSERT INTO BOOK (book_id, book_name, student_id) VALUES (?, ?, ?)
    bind => [351, The Best Laid Plan, null]
[EL Fine]: sql: SELECT 1
[EL Warning]: Exception [EclipseLink-4002] (Eclipse Persistence Services - 2.5.2.v20140319-9ad6abd): org.eclipse.persistence.exceptions.DatabaseException
Internal Exception: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Unknown column 'book_name' in 'field list'
Error Code: 1054
Call: INSERT INTO BOOK (book_id, book_name, student_id) VALUES (?, ?, ?)
    bind => [351, The Best Laid Plan, null]
Exception in thread "main" javax.persistence.RollbackException: Exception [EclipseLink-4002] (Eclipse Persistence Services - 2.5.2.v20140319-9ad6abd): org.eclipse.persistence.exceptions.DatabaseException
Internal Exception: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Unknown column 'book_name' in 'field list'
Error Code: 1054
Call: INSERT INTO BOOK (book_id, book_name, student_id) VALUES (?, ?, ?)
    bind => [351, The Best Laid Plan, null]
    at org.eclipse.persistence.internal.jpa.transaction.EntityTransactionImpl.commit(EntityTransactionImpl.java:157)
    at org.prem.jpa.eclipselink.Main.main(Main.java:31)
Caused by: Exception [EclipseLink-4002] (Eclipse Persistence Services - 2.5.2.v20140319-9ad6abd): org.eclipse.persistence.exceptions.DatabaseException
Internal Exception: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Unknown column 'book_name' in 'field list'
Error Code: 1054
Call: INSERT INTO BOOK (book_id, book_name, student_id) VALUES (?, ?, ?)
    bind => [351, The Best Laid Plan, null]
    at org.eclipse.persistence.exceptions.DatabaseException.sqlException(DatabaseException.java:331)
    at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.executeDirectNoSelect(DatabaseAccessor.java:900)
    at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.executeNoSelect(DatabaseAccessor.java:962)
    at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.basicExecuteCall(DatabaseAccessor.java:631)
    at org.eclipse.persistence.internal.databaseaccess.ParameterizedSQLBatchWritingMechanism.executeBatch(ParameterizedSQLBatchWritingMechanism.java:149)
    at org.eclipse.persistence.internal.databaseaccess.ParameterizedSQLBatchWritingMechanism.executeBatchedStatements(ParameterizedSQLBatchWritingMechanism.java:134)
    at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.writesCompleted(DatabaseAccessor.java:1836)
    at org.eclipse.persistence.internal.sessions.AbstractSession.writesCompleted(AbstractSession.java:4244)
    at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.writesCompleted(UnitOfWorkImpl.java:5594)
    at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.acquireWriteLocks(UnitOfWorkImpl.java:1646)
    at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.commitTransactionAfterWriteChanges(UnitOfWorkImpl.java:1614)
    at org.eclipse.persistence.internal.sessions.RepeatableWriteUnitOfWork.commitRootUnitOfWork(RepeatableWriteUnitOfWork.java:284)
    at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.commitAndResume(UnitOfWorkImpl.java:1169)
    at org.eclipse.persistence.internal.jpa.transaction.EntityTransactionImpl.commit(EntityTransactionImpl.java:132)
    ... 1 more
Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Unknown column 'book_name' in 'field list'
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
    at java.lang.reflect.Constructor.newInstance(Unknown Source)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
    at com.mysql.jdbc.Util.getInstance(Util.java:386)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1053)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4096)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4028)
    at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2490)
    at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2651)
    at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2734)
    at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2155)
    at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2458)
    at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2375)
    at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2359)
    at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.executeDirectNoSelect(DatabaseAccessor.java:890)
    ... 13 more

Answer 1

我可以从您的异常堆栈跟踪中看到这一行：

<强> Unknown column 'book_name' in 'field list“

确保BOOK表中的“book_name”列在数据库中是正确的

我希望它有所帮助!!!

Answer 2

将Book类中的private String studentID;更改为private int studentID;，并同时更改相应的getter和setter。

Answer 3

实体运作良好。这是列名的问题。要确保您的DDL，您可以使用

<property name="eclipselink.ddl-generation" value="drop-and-create-tables"/>。

正如@Sanket Pipariya所说，你不需要

@Column(name="student_id")
private String studentID;

因为您已经拥有学生对象（Book表中的＆＃39; student_id＆＃39;列）。您正在Book Class中的Student属性中使用insertable=false，这样当您将Book对象与Student属性一起保留时，Book表中的student_id列将为null。

Answer 4

在书籍和学生的数据库中创建表时，将删除此异常。然后将插入记录。

Eclipselink JPA ManyToOne映射问题

4 个答案: