如何使用Annotations在Hibernate中表示组合键？ [英] How to Represent Composite keys in Hibernate using Annotations?

问题描述

所以我从我的数据库中反向设计了一些表格，当我尝试将我的对象保存到数据库时，出现以下错误：

初始SessionFactory创建失败.hibernate.AnnotationException：引用com.mycode.Account中的com.mycode.Block的外键具有错误的列号。应该是2
线程main中的异常java.lang.ExceptionInInitializerError

域对象是包含多个Account对象的Block：

  @OneToMany（fetch = FetchType.LAZY，mappedBy =Block）
 public Set< EAccount> getAccounts（）{
返回this.Accounts; 
} 
  

账户具有Id和Role的组合键。这已经在一个单独的类中设置：

  @Embeddable 
 public class BlockAccountId implements java.io.Serializable {
 
私人长块blockOid; 
私人字符串accountRole; 
 $ b $ public BlockAccountId（）{
} 
 
 public BlockAccountId（long blockOid，String accountRole）{
 this.blockOid = blockOid; 
 this.accountRole = accountRole; 
 
 $ b @Column（name =BLOCK_OID，nullable = false）
 public long getBlockOid（）{
 return this.blockOid; 
} 
 
 public void setBlockOid（long blockOid）{
 this.blockOid = blockOid; 
 
 $ b @Column（name =ACCOUNT_ROLE，nullable = false，length = 10）
 public String getAccountRole（）{
 return this.accountRole; 
} 
 
 public void setAccountRole（String accountRole）{
 this.accountRole = accountRole; 
} 
  

所以我想知道。我如何链接blockOid上的表格和帐户，但仍确保帐户表格同时具有blockOid和accountRole作为组合键。

任何示例都将不胜感激！

注意：这是一个帐户（多个）关系。

谢谢 解决方案

直接在嵌入式ID组件中。

Hibernate参考文档

• 第5.1.2.1节0.1 。 id）作为使用组件类型的属性（）

示例（仅编写重要的getter（）和setter（））

  @Entity 
 public class Block {
 
 @Id 
 @GeneratedValue（strategy = GenerationType.IDENTITY）
 @Column（name =BLOCK_OID）
 long blockOid; 
 
 @OneToMany（fetch = FetchType.LAZY，mappedBy =id.block，cascade = CascadeType.ALL）
 Set< Account> accounts = new HashSet< Account>（）; 
} 
 
 @Entity 
公共类帐户{
 
 @EmbeddedId BlockAccountId id; 
 
 public Account（）
 {
 this.id = new BlockAccountId（）; 
} 
 
 public void setBlock（Block pBlock）{
 this.id.setBlock（pBlock）; 
} 
 
 public Block getBlock（）{
 return this.id.getBlock（）; 
} 
 
 public String getAccountRole（）{
 return this.id.getAccountRole（）; 
} 
 
 public void setAccountRole（String accountRole）{
 this.id.setAccountRole（accountRole）; 
 
 
 
 
 @Embeddable 
 public class BlockAccountId implements java.io.Serializable {
 
 @ManyToOne（可选= false）
私有块块; 
 
 @Column（name =ACCOUNT_ROLE，nullable = false，length = 10）
 private String accountRole; 
 $ b $ public BlockAccountId（）{
 
} 
 
 //实现equals和hashcode 
} 
 
  
  
 
 CREATE TABLE block（
 BLOCK_OID bigint（20）NOT NULL auto_increment，
 PRIMARY KEY（`BLOCK_OID`）
）
 
 
 CREATE TABLE account（
 ACCOUNT_ROLE varchar（10）NOT NULL，
 block_BLOCK_OID bigint（20）NOT NULL，
 PRIMARY KEY（`ACCOUNT_ROLE`，`block_BLOCK_OID`），
 KEY`FK_block_OID`（`block_BLOCK_OID ``），
 CONSTRAINT`FK_block_OID` FOREIGN KEY（`block_BLOCK_OID`）参考`block`（`BLOCK_OID`）
）
  
 
So I reverse engineered some tables from my db and when I try to save my object to the db I get the following  error:


Initial SessionFactory creation failed.org.hibernate.AnnotationException: A Foreign key refering com.mycode.Block from com.mycode.Account has the wrong number of column. should be 2
Exception in thread "main" java.lang.ExceptionInInitializerError

The Domain objects Are Block which contains a number of Account Objects:
    @OneToMany(fetch = FetchType.LAZY, mappedBy = "Block")
public Set<EAccount> getAccounts() {
    return this.Accounts;
}
Account has a Composite key of Id and Role. This has been setup in a seperate Class:
@Embeddable
public class BlockAccountId implements java.io.Serializable {

private long blockOid;
private String accountRole;

public BlockAccountId() {
}

public BlockAccountId(long blockOid, String accountRole) {
    this.blockOid = blockOid;
    this.accountRole = accountRole;
}

@Column(name = "BLOCK_OID", nullable = false)
public long getBlockOid() {
    return this.blockOid;
}

public void setBlockOid(long blockOid) {
    this.blockOid = blockOid;
}

@Column(name = "ACCOUNT_ROLE", nullable = false, length = 10)
public String getAccountRole() {
    return this.accountRole;
}

public void setAccountRole(String accountRole) {
    this.accountRole = accountRole;
}
So I want to know. How can I Link the tables Block and account on blockOid but still ensure the account table has both blockOid and accountRole as a composite key. 

Any examples would be greatly appreciated!

N.B this is a Block (One) to Account (Many) relationship.

Thanks
解决方案
The easiest is to place your association directly in the embedded id component. 

  
Hibernate reference documentation  
  
  

  
Section 5.1.2.1.1. id as a property using a component type ()
  
Example (Only write the important getter() and setter())
@Entity
public class Block {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name="BLOCK_OID")
    long blockOid;

    @OneToMany(fetch = FetchType.LAZY, mappedBy = "id.block", cascade=CascadeType.ALL)
    Set<Account> accounts = new HashSet<Account>();
}

@Entity
public class Account {

    @EmbeddedId BlockAccountId id;

    public Account()
    {
        this.id = new BlockAccountId();
    }

    public void setBlock(Block pBlock) {        
        this.id.setBlock(pBlock);
    }

    public Block getBlock() {
        return this.id.getBlock();
    }

    public String getAccountRole() {    
        return this.id.getAccountRole();
    }

    public void setAccountRole(String accountRole) { 
        this.id.setAccountRole(accountRole);
    }
}


@Embeddable
public class BlockAccountId implements java.io.Serializable {

    @ManyToOne(optional = false)    
    private Block block;

    @Column(name = "ACCOUNT_ROLE", nullable = false, length = 10)
    private String accountRole;

    public BlockAccountId() {

    }

    //Implement equals and hashcode
}
The corresponding database table are :
CREATE TABLE  block (
  BLOCK_OID bigint(20) NOT NULL auto_increment,
  PRIMARY KEY  (`BLOCK_OID`)
) 


CREATE TABLE  account (
  ACCOUNT_ROLE varchar(10) NOT NULL,
  block_BLOCK_OID bigint(20) NOT NULL,
  PRIMARY KEY  (`ACCOUNT_ROLE`,`block_BLOCK_OID`),
  KEY `FK_block_OID` (`block_BLOCK_OID`),
  CONSTRAINT `FK_block_OID` FOREIGN KEY (`block_BLOCK_OID`) REFERENCES `block` (`BLOCK_OID`)
)


                        
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