hibernate-annotations——@Column

今天看了下Hibernate的@Column注解

@Column(
    name="columnName";                         1
    boolean unique() default false;              2
    boolean nullable() default true;              3
    boolean insertable() default true;           4
    boolean updatable() default true;           5
    String columnDefinition() default "";      6
    String table() default "";                        7
    int length() default 255;                        8
    int precision() default 0;                        9

    int scale() default 0;                             10

)

除了7、9、10，其他都容易理解。

其中9和10是设置decimal的精度，开始定义了Float和Double类型的字段，然后在这两种类型的字段上使用@Column注解，结果9和10不起作用。最后发现在使用BigDecimal类型时，9和10才起作用。如果自己使用columnDefinition定义类型(@Column(columnDefinition="decimal"))，则需要自己定义精度，9和10是不起作用的，同理，使用Double和Float类型时MySQL中生成的是double和float，于是也不会起作用。

而7要和@SecondaryTable注解一起使用。

import java.math.BigDecimal;
import java.util.Date;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Lob;
import javax.persistence.SecondaryTable;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;

/**
 * @author lan 2010-8-23
 */
@Entity
@Table(name="student")
@SecondaryTable(name="SName")
public class Student {

    private Integer id;
    private String name;
    private Integer age;
    private Date birthday;
    private String resume;
    private BigDecimal height;
    private Double weight;

    @Id
    @GeneratedValue
    public Integer getId() {
        return id;
    }

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

    @Column(table="SName")
    public String getName() {
        return name;
    }

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

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    @Temporal(TemporalType.DATE)
    public Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    @Lob
    @Column(insertable=false)
    public String getResume() {
        return resume;
    }

    public void setResume(String resume) {
        this.resume = resume;
    }

    @Column(precision=5,scale=2)
    public BigDecimal getHeight() {
        return height;
    }
    
    public void setHeight(BigDecimal height) {
        this.height = height;
    }
  

    @Column(precision=5,scale=2)
    public Double getWeight() {
        return weight;
    }


    public void setWeight(Double weight) {
        this.weight = weight;
    }

    @Override
    public String toString() {
        return "Student [id=" + id + ", name=" + name + ", age=" + age + ", birthday=" + birthday + ", resume="
                + resume + ", height=" + height + ", weight=" + weight + "]";
    }

}

 

本文只是作为自己的备忘录，本人对于hibernate的了解还很粗浅，欢迎各位大牛指教。

 

评论

1 楼 laijavatoo 2011-08-01  

我想问问oracle 小数类型应该怎么映射 和生命精度呢