Eclipselink JPA ManyToOne 映射问题

问题描述 投票：0回答：4

我是JPA(eclipselink)的新手，正在尝试使用JPA(eclipselink)。ManyToOne unidirectional mapping，我有 superclass Student 和 subclass Book当我试图保存对象时，我最终出现了异常，详情如下所示

学生是家长的班级

@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;
    }

}

书是孩子的课堂

@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;
    }


}

执行持久化操作的主类，当执行持久化时，会抛出未知列异常。

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();
    }
}

异常。

]: 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
java jpa eclipselink
4个回答
1
投票

我可以从你的异常堆栈跟踪中看到这一行。

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。

我希望它能帮助 !!!

0
投票

变化 private String studentID; 在书类中，以 private int studentID; 并同时改变各自的getter和setter。

0
投票

实体运行良好。这是列名的问题。为了确保你的DDL，你可以用

<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;

因为你已经有了学生对象（书表中的'student_id'列）。insertable=false 的学生属性中，这样当你把书本对象和学生属性一起持久化的时候。student_id 在书表中的列将为空，当你在数据库中同时创建书和学生表时，这个异常将被删除。

0
投票

当你在数据库中同时创建书和学生的表时，这个异常将被删除，然后记录将被插入。

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