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  • (十) 使用Hibernate 注解

    • Hibernate里有两种注解 : 
    1. Hibernate 注解
    2. 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。

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  • 原文地址:https://www.cnblogs.com/shyroke/p/6850753.html
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