使用Hibernate 注解
Posted 专注改变人生。
tags:
篇首语:本文由小常识网(cha138.com)小编为大家整理,主要介绍了 使用Hibernate 注解相关的知识,希望对你有一定的参考价值。
- Hibernate里有两种注解 :
- Hibernate 注解
- JPA注解
案例一: 用注解对非复合主键的表生成配置文件
package bean; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.GenerationType; import javax.persistence.Id; import javax.persistence.Table; import org.hibernate.annotations.GenericGenerator; @Entity // 表明这个类是一个实体类,所谓实体类就是该类对应数据库中的表 @Table(name = "user") // 该实体类对应着数据库中的user表 public class UserBean { @Id @GeneratedValue(generator="a") @GenericGenerator(name="a",strategy="assigned") //设置主键增长机制,assigned为程序中定义,这也是默认方式。 private Integer userid; private String username; private String password; private String sex; @Column(name = "is_admin") // 表示idAdmin这个属性对应着数据库中的is_admin这个字段 private String isAdmin; public UserBean() { } public UserBean(Integer userid, String username, String password, String sex, String isAdmin) { super(); this.userid = userid; this.username = username; this.password = password; this.sex = sex; this.isAdmin = isAdmin; } public Integer getUserid() { return userid; } public void setUserid(Integer userid) { this.userid = userid; } public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } public String getSex() { return sex; } public void setSex(String sex) { this.sex = sex; } public String getIsAdmin() { return isAdmin; } public void setIsAdmin(String isAdmin) { this.isAdmin = isAdmin; } }
- 更新总配置文件
<mapping class="bean.UserBean"/>
案例二: 用注解对含有复合主键的表生成配置文件
package bean; import javax.persistence.EmbeddedId; import javax.persistence.Entity; import javax.persistence.Id; import javax.persistence.Table; /** * Score entity. @author MyEclipse Persistence Tools */ @Entity @Table(name="score") public class Score implements java.io.Serializable { // Fields @Id @EmbeddedId // 表示主键是一个复合主键 private ScoreId id; private Integer score; // Constructors /** default constructor */ public Score() { } /** minimal constructor */ public Score(ScoreId id) { this.id = id; } /** full constructor */ public Score(ScoreId id, Integer score) { this.id = id; this.score = score; } // Property accessors public ScoreId getId() { return this.id; } public void setId(ScoreId id) { this.id = id; } public Integer getScore() { return this.score; } public void setScore(Integer score) { this.score = score; } }
- ScoreId.java
package bean; import javax.persistence.Embeddable; /** * ScoreId entity. @author MyEclipse Persistence Tools */ @Embeddable //表示该类可被其他类嵌入 public class ScoreId implements java.io.Serializable { // Fields private Integer userid; private String subject; // Constructors /** default constructor */ public ScoreId() { } /** full constructor */ public ScoreId(Integer userid, String subject) { this.userid = userid; this.subject = subject; } // Property accessors public Integer getUserid() { return this.userid; } public void setUserid(Integer userid) { this.userid = userid; } public String getSubject() { return this.subject; } public void setSubject(String subject) { this.subject = subject; } public boolean equals(Object other) { if ((this == other)) return true; if ((other == null)) return false; if (!(other instanceof ScoreId)) return false; ScoreId castOther = (ScoreId) other; return ((this.getUserid() == castOther.getUserid()) || (this .getUserid() != null && castOther.getUserid() != null && this .getUserid().equals(castOther.getUserid()))) && ((this.getSubject() == castOther.getSubject()) || (this .getSubject() != null && castOther.getSubject() != null && this .getSubject().equals(castOther.getSubject()))); } public int hashCode() { int result = 17; result = 37 * result + (getUserid() == null ? 0 : this.getUserid().hashCode()); result = 37 * result + (getSubject() == null ? 0 : this.getSubject().hashCode()); return result; } }
- 更新总配置文件
<mapping class="bean.Score"/>
使用注解方式配置bean的时候,Hibernate默认把bean中的所有成员属性都与数据库中的字段相关联,如果有些成员属性并不是数据库中的字段的时候,此时就会报错,
则这时在这些属性前添加 @Transient 注解, 表明这个属性不是数据库的字段。
以上是关于 使用Hibernate 注解的主要内容,如果未能解决你的问题,请参考以下文章
Hibernate——主键生成策略CRUD 基础API区别的总结 和 注解的使用