Hibernate JPA坚持

Question

我有一个实体类。 当我坚持执行时，出现错误：“无法通过反射吸气剂获得字段值”。

请帮我。

我的实体类代码：

    @Entity
    @Table( name = "class" )
    @NamedQueries( {
        @NamedQuery( name = "SchoolClass.findAll", query = "SELECT c FROM SchoolClass c" ),
        @NamedQuery( name = "SchoolClass.findById", query = "SELECT c FROM SchoolClass c WHERE c.id = :id" )
    } )
    public class SchoolClass implements Serializable {

        /**
         * Generated Serial Version ID
         */
        private static final long   serialVersionUID    = 6703663444336018288L;

        @Id
        @Column( nullable = false, updatable = false )
        private Long                id;

        @Column( nullable = false, length = 100 )
        private String              name;

        /**
         * @return The getter method of the 'id' instance variable
         */
        public Long getId() {
            return id;
        }

        /**
         * @param The setter method of the 'id' instance variable
         */
        public void setId( final Long id ) {
            this.id = id;
        }

        /**
         * @return The getter method of the 'name' instance variable
         */
        public String getName() {
            return name;
        }

        /**
         * @param The setter method of the 'name' instance variable
         */
        public void setName( final String name ) {
            this.name = name;
        }

        /* (non-Javadoc)
         * @see java.lang.Object#toString()
         */
        @Override
        public String toString() {
            return "SchoolClass [id=" + id + ", name=" + name + "]";
        }
    }

我的持久性代码：

    try {
            final UserTransaction transaction = ( UserTransaction ) new InitialContext()
                .lookup( "java:comp/UserTransaction" );

            transaction.begin();

            entityManager.persist( schoolClass ); // Exception here
            entityManager.flush();

            transaction.commit();

        } catch ( SecurityException | IllegalStateException | NamingException | NotSupportedException | SystemException
            | RollbackException | HeuristicMixedException | HeuristicRollbackException e ) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

我的例外：

由以下原因引起：javax.persistence.PersistenceException：org.hibernate.PropertyAccessException：无法通过org.hibernate.jpa.spi.AbstractEntityManagerImpl上的com.ilkerkonar.applications.schoolproject.orm.model.SchoolClass.id的反射getter获取字段值。 org.hibernate.jpa.spi上的.convert（AbstractEntityManagerImpl.java:1763）org.org.hibernate.jpa.spi.AbstractEntityManagerImpl.convert（AbstractEntityManagerImpl.java:1677）上的org.hibernate.jpa.spi.AbstractEntityManagerImpl.convert（AbstractEntityManagerImpl.java:1683）上的。 hibernate.jpa.spi.AbstractEntityManagerImpl.persist（AbstractEntityManagerImpl.java:1187）位于com.sun.enterprise.container.common.impl.EntityManagerWrapper.persist（EntityManagerWrapper.java:287）位于com.ilkerkonar.applications.schoolproject.orm。 service.ClassService.addNewClass（ClassService.java:61）

Answer 1

您是否也尝试过添加@GeneratedValue ？ 使ID不可更新，首先不告诉JPA如何生成ID。 它也应该通过删除updatable=false 。