持久性實體不能序列

Question

我收到以下錯誤：

SEVERE: null 
javax.jms.MessageFormatException: [C4017]: Invalid message format. 
at com.sun.messaging.jmq.jmsclient.MapMessageImpl.checkValidObjectType(MapMessageImpl.java:653) 
at com.sun.messaging.jmq.jmsclient.MapMessageImpl.setObject(MapMessageImpl.java:632) 
at buyer.Main.sendCart(Main.java:287) 

後，我嘗試通過在MapMessage消息JMS系統發送持久性對象。我不太確定爲什麼會發生這種情況，因爲MapMessage僅接受可序列化的對象以獲取值，而持久性實體是可序列化的。我將不勝感激任何幫助！我的Java代碼如下。

package entities; 

import java.io.Serializable; 
import java.util.List; 
import java.util.Objects; 
import javax.persistence.CascadeType; 
import javax.persistence.Column; 
import javax.persistence.Entity; 
import javax.persistence.FetchType; 
import javax.persistence.GeneratedValue; 
import javax.persistence.GenerationType; 
import javax.persistence.Id; 
import javax.persistence.ManyToOne; 
import javax.persistence.NamedQuery; 
import javax.persistence.OneToMany; 
import javax.persistence.PrimaryKeyJoinColumn; 
import javax.persistence.Table; 

@Entity 
@Table(name = "carts") 
@NamedQuery(
    name = "carts.findAll", 
    query = "select c from Cart c" 
) 
public class Cart implements Serializable { 

private static final long serialVersionUID = 1L; 
@Id 
@GeneratedValue(strategy = GenerationType.IDENTITY) 
@Column(name = "id") 
private Long id; 

@Column(name = "buyer_id") 
private Long buyerId; 

@Column(name = "card_id") 
private Long cardId; 

@Column(name = "successful") 
private boolean successful; 

@ManyToOne(cascade = CascadeType.REFRESH, fetch = FetchType.EAGER) 
@PrimaryKeyJoinColumn(name = "buyer_id") 
private Buyer buyer; 

@ManyToOne(cascade = CascadeType.REFRESH, fetch = FetchType.EAGER) 
@PrimaryKeyJoinColumn(name = "card_id") 
private Card card; 

@OneToMany(mappedBy = "cart", cascade = CascadeType.REFRESH, fetch = FetchType.EAGER) 
private List<CartItem> cartItems; 

public Cart() { 
} 

public Cart(Long buyerId, Long cardId, boolean successful) { 
    this.buyerId = buyerId; 
    this.cardId = cardId; 
    this.successful = successful; 
} 

public Long getId() { 
    return id; 
} 

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

public Long getBuyerId() { 
    return buyerId; 
} 

public void setBuyerId(Long buyerId) { 
    this.buyerId = buyerId; 
} 

public Long getCardId() { 
    return cardId; 
} 

public void setCardId(Long cardId) { 
    this.cardId = cardId; 
} 

public boolean isSuccessful() { 
    return successful; 
} 

public void setSuccessful(boolean successful) { 
    this.successful = successful; 
} 

public Buyer getBuyer() { 
    return buyer; 
} 

public void setBuyer(Buyer buyer) { 
    this.buyer = buyer; 
} 

public Card getCard() { 
    return card; 
} 

public void setCard(Card card) { 
    this.card = card; 
} 

public List<CartItem> getCartItems() { 
    return cartItems; 
} 

public void setCartItems(List<CartItem> cartItems) { 
    this.cartItems = cartItems; 
} 

@Override 
public int hashCode() { 
    int hash = 7; 
    hash = 53 * hash + Objects.hashCode(this.id); 
    hash = 53 * hash + Objects.hashCode(this.buyerId); 
    hash = 53 * hash + Objects.hashCode(this.cardId); 
    hash = 53 * hash + (this.successful ? 1 : 0); 
    return hash; 
} 

@Override 
public boolean equals(Object obj) { 
    if (this == obj) { 
     return true; 
    } 
    if (obj == null) { 
     return false; 
    } 
    if (getClass() != obj.getClass()) { 
     return false; 
    } 
    final Cart other = (Cart) obj; 
    if (this.successful != other.successful) { 
     return false; 
    } 
    if (!Objects.equals(this.id, other.id)) { 
     return false; 
    } 
    if (!Objects.equals(this.buyerId, other.buyerId)) { 
     return false; 
    } 
    if (!Objects.equals(this.cardId, other.cardId)) { 
     return false; 
    } 
    return true; 
} 

@Override 
public String toString() { 
    return "Cart{" + "id=" + id + ", buyerId=" + buyerId + ", cardId=" + cardId + ", successful=" + successful + '}'; 
} 
} 

發送消息的相關方法。

private static Buyer sendCart(Cart cart, String tempId, Buyer buyer) { 
    JMSContext context = connectionFactory.createContext(2); 

    try { 
     Destination queue = context.createQueue("mediator"); 
     JMSProducer producer = context.createProducer(); 

     MapMessage message = context.createMapMessage(); 

     message.setObject("data", cart); 
     message.setObject("tempid", tempId); 
     message.setObject("type", MessageType.BUYER_SENDING_CART); 

     producer.send(queue, message); 

    } catch (JMSException ex) { 
     Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex); 
    } 
} 

Answer 1

問題是MapMessage。據JavaDoc：

A MapMessage object is used to send a set of name-value pairs. The names are String objects, and the values are primitive data types in the Java programming language. The names must have a value that is not null, and not an empty string. The entries can be accessed sequentially or randomly by name. The order of the entries is undefined. MapMessage inherits from the Message interface and adds a message body that contains a Map.

和：

They may also be read or written generically as objects.

所以，即使提供MapMessage消息的 「的setObject」 方法，使用的必須是原始類型的參數。

要通過非原始類型使用ObjectMessage