Hibernate自增列保存失败的问题

author： hiu

最近由ibatis转用Hibernate，期间遇到了一系列的问题，今天又遇到了个问题，是因为自增列的问题导致保存时报错，现在记录下来，以便日后忘记时查看

这个问题其实是使用myEclipse生成表的实体类时，自增列的注解错误导致的。

问题原因：利用myEclipse的Hibernate Reverse Engineening生成的实体类自增列注解设置了在主键keyjobno上，而不是对应的 id 列上

解决办法 ：将自增列注解设置在对应的 自增列id上

数据库employee表：

这里主要列出了部分字段，关键在于id和keyjobno，id设置了是自增列，keyjobno设置为主键

利用myEclipse的Hibernate Reverse Engineening生成实体类

生成后的实体类Employee，只贴出了keyjobno,id的，其它的没贴出来

@Entity
@Table(name = "employee", catalog = "union_ssh", uniqueConstraints = @UniqueConstraint(columnNames = "id"))
public class Employee implements java.io.Serializable {

	// Fields

	private String keyjobno;
	private Integer id;	
		
		
		
	@Id
	@GeneratedValue(strategy = IDENTITY)
	@Column(name = "keyjobno", unique = true, nullable = false, length = 20)
	public String getKeyjobno() {
		return this.keyjobno;
	}

	public void setKeyjobno(String keyjobno) {
		this.keyjobno = keyjobno;
	}

	@Column(name = "id", unique = true, nullable = false)
	public Integer getId() {
		return this.id;
	}

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

service层

public Employee save(Employee employee) throws SQLException {

      employee.setKeyjobno("K8888");

      employeeDao.save(employee);

      return employee;
}

dao层

@Override
public Serializable save(T o) {
     return this.getCurrentSession().save(o);
}

2014-07-04 14:10:50 [org.hibernate.SQL]-[DEBUG] 
    insert 
    into
        union_ssh.employee
        (born_boon, borndate, company, createdate, dept, getborn_date, getmarry_date, id, identitycard, ifout, interest, jobno, lodging, marry, marry_boon, name, nativename, operator, phone, politicsface, sex) 
    values
        (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
Hibernate: 
    insert 
    into
        union_ssh.employee
        (born_boon, borndate, company, createdate, dept, getborn_date, getmarry_date, id, identitycard, ifout, interest, jobno, lodging, marry, marry_boon, name, nativename, operator, phone, politicsface, sex) 
    values
        (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
2014-07-04 14:10:50 [org.hibernate.engine.jdbc.spi.SqlExceptionHelper]-[DEBUG] Field 'keyjobno' doesn't have a default value [n/a]
<span style="color:#ff0000;"><strong>java.sql.SQLException: Field 'keyjobno' doesn't have a default value</strong></span>

employee.setKeyjobno("K8888");

明明已经为keyjobno设置值了，居然还说我没有默认值。再看一下打出来的sql语句，里面有id，但是没有keyjobno，按理说id在数据库表中设置了自增，这里不应该也插入的，但keyjobno明明是已经设置了值的，却没有显示在插入的sql中，这是因为注解时将keyjobno设置为了自增列了。

现在再来看看实体类中的注解：

@Id
@GeneratedValue(strategy = IDENTITY)
@Column(name = "keyjobno", unique = true, nullable = false, length = 20)
public String getKeyjobno() {
<span style="white-space:pre">	</span>return this.keyjobno;
}

@Id —— 注解声明了该实体bean的标识属性（对应表中的主键）。

@GeneratedValue —— 注解声明了主键的生成策略。该注解有如下属性   

strategy 指定生成的策略（JPA定义的），这是一个GenerationType。默认是GenerationType. AUTO   
   GenerationType.AUTO 主键由程序控制  

GenerationType.IDENTITY 主键由数据库自动生成（主要是自动增长类型）

看到注解说明，大家应该就明白了，我在数据库表中设置的是id自增列，但是生成的实体类的自增列却是keyjobno，这就是导致保存失败的原因了，将实体类改为以下形式，主要是将keyjobno的自增注解剪切到id列中

@Entity
@Table(name = "employee", catalog = "union_ssh", uniqueConstraints = @UniqueConstraint(columnNames = "id"))
public class Employee implements java.io.Serializable {

	private String keyjobno;
	private Integer id;	

	@Column(name = "keyjobno", unique = true, nullable = false, length = 20)
	public String getKeyjobno() {
		return this.keyjobno;
	}

	public void setKeyjobno(String keyjobno) {
		this.keyjobno = keyjobno;
	}

	<strong>@Id
	@GeneratedValue(strategy = IDENTITY)</strong>
	@Column(name = "id", unique = true, nullable = false)
	public Integer getId() {
		return this.id;
	}

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

2014-07-04 14:30:21 [org.hibernate.SQL]-[DEBUG] 
    insert 
    into
        union_ssh.employee
        (born_boon, borndate, company, createdate, dept, getborn_date, getmarry_date, identitycard, ifout, interest, jobno, keyjobno, lodging, marry, marry_boon, name, nativename, operator, phone, politicsface, sex) 
    values
        (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
Hibernate: 
    insert 
    into
        union_ssh.employee
        (born_boon, borndate, company, createdate, dept, getborn_date, getmarry_date, identitycard, ifout, interest, jobno, keyjobno, lodging, marry, marry_boon, name, nativename, operator, phone, politicsface, sex) 
    values
        (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
2014-07-04 14:30:21 [org.hibernate.id.IdentifierGeneratorHelper]-[DEBUG] Natively generated identity: 557

总结：注解地方的错误是因为使用myEclipse生成实体类时引致的注解设置地方错误，所以有时也不要太过依赖自动生成实体类。个人猜测原因，是因为我将id设为是自增的，但keyjobno列设置为主键，也即是说，这两列都是唯一的，myEclipse在生成实体类是可能不能区分，就将自增列的注解设置了在主键的列上了，没仔细研究，大家有兴趣的话，可以去研究下。

Hibernate自增列保存失败的问题,古老的榕树,5-wow.com