Question

我有一名实体学生，我正在使用DB concat方法计算全名。使用名字和姓氏创建全名。但是，当我运行我的应用程序时，它会出错（如下所述）。我正在使用hibernate和DB作为MySql：

@Entity
@Table(name = "students")
public class Student implements Serializable {

    private static final long serialVersionUID = 1L;
    @Id
    @Column(name = "studentId")
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer studentId;
    @Column(name = "fname")
    private String fname;
    @Column(name = "lname")
    private String lname;

    @Generated(value = GenerationTime.ALWAYS)
    @Column(columnDefinition = "AS CONCAT(" + "    COALESCE(fname, ''), "
            + "    COALESCE(' ' + lname, ''), " + ")")
    private String fullName;

    //Getter Setter omitted
}

将学生实体保存如下：

public void addStudent(StudentBean studentBean)
{
    Student student=new Student();

    student.setFname(studentBean.getFname());
    student.setLname(studentBean.getLname());
    studentDAO.saveStudent(student);
}

我得到的错误如下所述：

com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Unknown column 'student_.fullName' in 'field list'
sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
java.lang.reflect.Constructor.newInstance(Unknown Source)
com.mysql.jdbc.Util.handleNewInstance(Util.java:409)
com.mysql.jdbc.Util.getInstance(Util.java:384)
com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1052)
com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4232)
com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4164)
com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2615)
com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2776)
com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2838)
com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2082)
com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:2212)
org.apache.tomcat.dbcp.dbcp2.DelegatingPreparedStatement.executeQuery(DelegatingPreparedStatement.java:82)
org.apache.tomcat.dbcp.dbcp2.DelegatingPreparedStatement.executeQuery(DelegatingPreparedStatement.java:82)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
java.lang.reflect.Method.invoke(Unknown Source)
org.hibernate.engine.jdbc.internal.proxy.AbstractStatementProxyHandler.continueInvocation(AbstractStatementProxyHandler.java:122)
org.hibernate.engine.jdbc.internal.proxy.AbstractProxyHandler.invoke(AbstractProxyHandler.java:81)
com.sun.proxy.$Proxy60.executeQuery(Unknown Source)
org.hibernate.persister.entity.AbstractEntityPersister.processGeneratedProperties(AbstractEntityPersister.java:4365)
org.hibernate.persister.entity.AbstractEntityPersister.processInsertGeneratedProperties(AbstractEntityPersister.java:4338)
org.hibernate.action.internal.EntityIdentityInsertAction.execute(EntityIdentityInsertAction.java:80)
org.hibernate.engine.spi.ActionQueue.execute(ActionQueue.java:272)
org.hibernate.event.internal.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:304)
org.hibernate.event.internal.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:195)
org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:128)
org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:204)

Answer 1

  I think issues happens here

   @Column(columnDefinition = "AS CONCAT(" + "    
     COALESCE(fname, ''), "
            + "    COALESCE(' ' + lname, ''), " + ")")
    private String fullName;

    From exception I identified that there is no reference column with "fullName" in table student......

首先检查数据库表并确认该列的名称为“fullName”

然后将上面的代码块转换为

     @Column(name="fullName",
     columnDefinition = " 
     AS CONCAT(" + "    
     COALESCE(fname, ''), "
            + "    COALESCE(' ' + lname, ''), " + ")")
    private String fullName;

检查数据库并确认其是否完整名称，并将列名称与上述语句一样放置

我希望它能起作用

Hibarnate @Generated注释不起作用

1 个答案: