Question

我为每个新实体类的所有实体创建一个基类来扩展它。在基类中，我使用orm的注释，代码如下：

public class BaseEntity<I> implements IBaseEntity<I> {

@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name = "ID", nullable = false)
private I id;


public I getId() {
return id;
}

public void setId(I id) {
this.id = id;
}}

然后我创建一个类如下：

@SuppressWarnings("serial")
@Entity
@Table(name = FoodEntity.TABLE_NAME, schema = "public")
public class FoodEntity extends BaseEntity<Long> {

public static final String TABLE_NAME = "T_Food";

@Column(name = "NAME", unique = true, nullable = false, length = 500)
private String name;

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}}

但是，当我执行一个示例来测试我的类时，我得到以下异常：

    Initial SessionFactory creation failed.org.hibernate.AnnotationException: No identifier specified for entity: FoodEntity
Exception in thread "main" java.lang.ExceptionInInitializerError
at ir.msr.projects.crawler.HibernateUtil.buildSessionFactory(HibernateUtil.java:31)
at ir.msr.projects.crawler.HibernateUtil.<clinit>(HibernateUtil.java:14)
Caused by: org.hibernate.AnnotationException: No identifier specified for entity: FoodEntity
at org.hibernate.cfg.InheritanceState.determineDefaultAccessType(InheritanceState.java:266)
at org.hibernate.cfg.InheritanceState.getElementsToProcess(InheritanceState.java:211)
at org.hibernate.cfg.AnnotationBinder.bindClass(AnnotationBinder.java:731)
at org.hibernate.boot.model.source.internal.annotations.AnnotationMetadataSourceProcessorImpl.processEntityHierarchies(AnnotationMetadataSourceProcessorImpl.java:249)
at org.hibernate.boot.model.process.spi.MetadataBuildingProcess$1.processEntityHierarchies(MetadataBuildingProcess.java:222)
at org.hibernate.boot.model.process.spi.MetadataBuildingProcess.complete(MetadataBuildingProcess.java:265)
at org.hibernate.boot.model.process.spi.MetadataBuildingProcess.build(MetadataBuildingProcess.java:83)
at org.hibernate.boot.internal.MetadataBuilderImpl.build(MetadataBuilderImpl.java:418)
at org.hibernate.boot.internal.MetadataBuilderImpl.build(MetadataBuilderImpl.java:87)
at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:691)

Answer 1

我找到了答案，我必须使用@MappedSuperclass作为BaseEntity Class（父类）。

Answer 2

尝试创建BaseEntity抽象和anotated Id放入主类，或使用注释@MappedSuperclass

public class HighScoreScreenSlide extends FragmentActivity {
    /**
     * The number of pages (wizard steps) to show in this demo.
     */
    private static final int NUM_PAGES = 3;

    /**
     * The pager widget, which handles animation and allows swiping horizontally to access previous
     * and next wizard steps.
     */
    private ViewPager mPager;
    private int countDownInd;
    Bundle bundle;
    /**
     * The pager adapter, which provides the pages to the view pager widget.
     */
    private PagerAdapter mPagerAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.high_score_view_pager);
        countDownInd = getIntent().getIntExtra("gameType", 0);
        // Instantiate a ViewPager and a PagerAdapter.
        mPager = (ViewPager) findViewById(R.id.pager);
        mPagerAdapter = new ScreenSlidePagerAdapter(getSupportFragmentManager());
        mPager.setAdapter(mPagerAdapter);
        mPager.setCurrentItem(countDownInd);
        InkPageIndicator inkPageIndicator = (InkPageIndicator) findViewById(R.id.indicator);
        inkPageIndicator.setViewPager(mPager);

    }

    @Override
    public void onBackPressed() {
        if (mPager.getCurrentItem() == 0) {
            // If the user is currently looking at the first step, allow the system to handle the
            // Back button. This calls finish() on this activity and pops the back stack.
            super.onBackPressed();
        } else {
            // Otherwise, select the previous step.
            mPager.setCurrentItem(mPager.getCurrentItem() - 1);
        }
    }

    /**
     * A simple pager adapter that represents 5 ScreenSlidePageFragment objects, in
     * sequence.
     */
    private class ScreenSlidePagerAdapter extends FragmentStatePagerAdapter {

        public ScreenSlidePagerAdapter( FragmentManager fm) {

            super(fm);
        }

        @Override
        public Fragment getItem(int position) { //use position
            HighScoreFragment fragment = new HighScoreFragment();
            bundle=new Bundle();
            bundle.putInt("gameType",position);
            fragment.setArguments(bundle);
            return fragment;

                        }

        @Override
        public int getCount() {
            return NUM_PAGES;
        }
    }
}

或

@MappedSuperclass
public class BaseEntity<I> implements IBaseEntity<I> {

   @Id    
   @GeneratedValue(strategy = GenerationType.AUTO)
   @Column(name = "ID", nullable = false)
   private I id;

   public I getId() {
      return id;
   }

   public void setId(I id) {
      this.id = id;
   }
}

}

hibernate无法在注释方法中指定通用属性标识符

2 个答案: