休眠：只需使用@EmbeddedId作为主键保存一个实体

Question

当我使用复合主键的@EmbeddedId注释向表中添加条目时，我想学习休眠基础知识并且不理解为什么我的应用程序不起作用：

代表PK的类：

@Embeddable
public class OHLCVKey implements Serializable{

    private static final long serialVersionUID = -3996067621138883817L;

    @Column(name="Symbol")
    protected String symbol;

    @Column(name="Currency")
    protected String currency;

    @Column(name="Datum")
    protected java.sql.Date datum;

    public OHLCVKey() {}

    public OHLCVKey(String symbol, String currency, Date datum) {
        super();
        this.symbol = symbol;
        this.currency = currency;
        this.datum = datum;
    }



    public String getSymbol() {
        return symbol;
    }

    public void setSymbol(String symbol) {
        this.symbol = symbol;
    }

    public String getCurrency() {
        return currency;
    }

    public void setCurrency(String currency) {
        this.currency = currency;
    }

    public java.sql.Date getDatum() {
        return datum;
    }

    public void setDatum(java.sql.Date endTime) {
        this.datum = endTime;
    }

    @Override
    public String toString() {
        return String.format("OHLCKey: {%s %s %s}", symbol, currency, datum);
    }

    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + (symbol == null ? 0 : symbol.hashCode());
        result = prime * result + (currency == null ? 0 : currency.hashCode());
        result = prime * result + (datum == null ? 0 : datum.hashCode());
        return result;
    }

    @Override
    public boolean equals(Object obj) {
        if(obj != null || !(obj instanceof OHLCVKey)) {
            OHLCVKey other = (OHLCVKey) obj;
            boolean sameSymbol = this.symbol.equals(other.symbol);
            boolean sameCurrency = this.currency.equals(other.currency);
            boolean endTime = this.datum.equals(other.datum);
            return sameSymbol && sameCurrency && endTime;
        }
        return false;
    }
}

持久班：

@Entity
@Table(name = "ohlcv_data")
public class OHLCV implements Serializable {

    /**
     * 
     */
    private static final long serialVersionUID = -742762046516249869L;

    @EmbeddedId
    protected OHLCVKey key;

    @Column(name = "Exchange")
    private String exchange;

    @Column(name = "Open")
    private double open;

    @Column(name = "High")
    private double high;

    @Column(name = "Low")
    private double low;

    @Column(name = "Close")
    private double close;

    @Column(name = "Volume")
    private long volume;

    public OHLCV() {};

    public OHLCV(OHLCVKey key) {
        super();
        this.key = key;
    }

    public OHLCV(OHLCVKey key, String exchange, double open, double high, double low, double close, long volume) {
        super();
        this.key = key;
        this.exchange = exchange;
        this.open = open;
        this.high = high;
        this.low = low;
        this.close = close;
        this.volume = volume;
    }

    public OHLCVKey getKey() {
        return key;
    }

    public void setKey(OHLCVKey key) {
        this.key = key;
    }

    public String getExchange() {
        return exchange;
    }

    public void setExchange(String exchange) {
        this.exchange = exchange;
    }

    public double getOpen() {
        return open;
    }

    public void setOpen(double open) {
        this.open = open;
    }

    public double getHigh() {
        return high;
    }

    public void setHigh(double high) {
        this.high = high;
    }

    public double getLow() {
        return low;
    }

    public void setLow(double low) {
        this.low = low;
    }

    public double getClose() {
        return close;
    }

    public void setClose(double close) {
        this.close = close;
    }

    public long getVolume() {
        return volume;
    }

    public void setVolume(long volume) {
        this.volume = volume;
    }
}

我假设在创建OHLC实例之后，可以使用以下函数（在名为OHLCVDataManager的类中）将其数据添加到数据库表中：

public void addOHLCV(OHLCV ohlcv) { // line 50
    Session session = factory.openSession();
    Transaction tx = null;
    try {
        tx = session.beginTransaction();
        session.save(ohlcv); // line 55
        tx.commit();
        log.info("Added {} to database!", key.toString());
    } catch(Exception e) {
        if(tx != null) {
            tx.rollback();
        }
        e.printStackTrace();
    } finally {
        session.close();
        System.exit(2); //TODO remove, exit Spring application
    }
}

但是我得到了带有堆栈跟踪的以下PropertyAccessException / IllegalArgumentException：

org.hibernate.property.access.spi.PropertyAccessException: Error accessing field [protected OHLCVKey OHLCV.key] by reflection for persistent property [OHLCV#key] : OHLCV@46479254
2018-11-03 18:43:57.567  INFO 18384 --- [       Thread-9] ConfigServletWebServerApplicationContext : Closing org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext@7582b66f: startup date [Sat Nov 03 18:43:53 CET 2018]; root of context hierarchy
    at org.hibernate.property.access.spi.GetterFieldImpl.get(GetterFieldImpl.java:75)
    at org.hibernate.tuple.entity.AbstractEntityTuplizer.getIdentifier(AbstractEntityTuplizer.java:224)
    at org.hibernate.persister.entity.AbstractEntityPersister.getIdentifier(AbstractEntityPersister.java:4931)
    at org.hibernate.mapping.Component$StandardGenerationContextLocator.locateGenerationContext(Component.java:480)
    at org.hibernate.id.CompositeNestedGeneratedValueGenerator.generate(CompositeNestedGeneratedValueGenerator.java:93)
    at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:123)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:192)
    at org.hibernate.event.internal.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:38)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:177)
    at org.hibernate.event.internal.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:32)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:73)
    at org.hibernate.internal.SessionImpl.fireSave(SessionImpl.java:709)
    at org.hibernate.internal.SessionImpl.save(SessionImpl.java:701)
    at org.hibernate.internal.SessionImpl.save(SessionImpl.java:696)
    at OHLCVDataManager.addOHLCV(OHLCVDataManager.java:55)
    at OHLCVDataManager.addOHLCV(OHLCVDataManager.java:70)
    at ServerApplication.main(ServerApplication.java:16)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.springframework.boot.devtools.restart.RestartLauncher.run(RestartLauncher.java:49)
Caused by: java.lang.IllegalArgumentException: Can not set OHLCVKey field OHLCV
    at sun.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:167)
    at sun.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:171)
    at sun.reflect.UnsafeFieldAccessorImpl.ensureObj(UnsafeFieldAccessorImpl.java:58)
    at sun.reflect.UnsafeObjectFieldAccessorImpl.get(UnsafeObjectFieldAccessorImpl.java:36)
    at java.lang.reflect.Field.get(Field.java:393)
    at org.hibernate.property.access.spi.GetterFieldImpl.get(GetterFieldImpl.java:71)

EDIT1：

ohlcvDataManager.addOHLCV("TEST", "USD", new java.sql.Date(2018, 1, 1), "TEST", 1, 1, 1, 1, 1);

// OHLCDataManager#addOHLCV call:    
public void addOHLCV(String symbol, String currency, java.sql.Date date, 
String exchange, double open, double high, double low, double close, long volume) {
    addOHLCV(new OHLCV(new OHLCVKey(symbol,currency, date),exchange, open, high, low, close, volume));
}

EDIT2： 我有带有Java 1.8的testet hibernate-core版本5.3.7和5.4

EDIT2： 我的类路径中只有一个OHLCV类和一个OHLCVKey类，我还尝试过重命名这些类。

Answer 1

我认为您在用Hibernate 5.0和5.1中映射为EmbededID的复合键遇到了一个bug，应该在5.1.1中已修复 https://hibernate.atlassian.net/browse/HHH-10618

尝试更改休眠版本。我也可以在评论之一中看到@ K.Nicholas在说相同的代码对他有效。这就是为什么我更倾向于认为您遇到了这个错误。

Answer 2

降级到版本

  

4.3.11。最终

工作...

Answer 3

自从我进入休眠状态以来已经有一段时间了，但是从错误中看来它无法访问 [protected OHLCVKey OHLCV.key]此字段。为了缩小范围，我建议两件事。首先，查看是否可以删除此行OHLCVKey key = (OHLCVKey) session.save(ohlcv); // line 55中的转换并将其转换为session.save(ohlcv)，只是为了确定是导致转换的转换还是保存本身。其次，尽管没有多大意义，请尝试将此处的访问修饰符更改为私有。

 @EmbeddedId
    protected OHLCVKey key;

如果这两个方法都不能解决问题，请尝试使用HQL并查看。

Answer 4

get(req: Request, res: Response) {
    const mongo = new MongoDb();
    mongo.connect().then(() => {

      const db = mongo.getDb();
      const collection = db.collection('todo', (error, collection) => {
          if (error) {
              res.json(error);
              res.statusCode = HttpStatus.BAD_REQUEST
              return;
          }

          collection.find().toArray((error, result) => {
              if (error) {
                  res.json(error);
                  res.statusCode = HttpStatus.BAD_REQUEST
              }

              res.json(result);
              res.statusCode = HttpStatus.OK;
          })

      });

      mongo.close();
    });
} 

和平的堆栈跟踪意味着Hibernate尝试为某个对象设置字段值，但是它们的类不兼容：

Caused by: java.lang.IllegalArgumentException: Can not set OHLCVKey field OHLCV
    at sun.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:167)
    at sun.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:171)
    at sun.reflect.UnsafeFieldAccessorImpl.ensureObj(UnsafeFieldAccessorImpl.java:58)
    at sun.reflect.UnsafeObjectFieldAccessorImpl.get(UnsafeObjectFieldAccessorImpl.java:36)
    at java.lang.reflect.Field.get(Field.java:393)
    at org.hibernate.property.access.spi.GetterFieldImpl.get(GetterFieldImpl.java:71)

这意味着Hibernate从不同的类而不是您要保存的对象的类中加载了元数据。请检查您的应用程序的类路径中是否只有一个OHLCV类，因为您提供的示例效果很好。