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  • (十三)Hibernate中的多表操作(3):单向多对多

    • 多对多的处理方式是,有一张中间表,中间表保存两个多方之间的关系。首先来看实际应用场景:在之前开发的系统中,应用了基于角色的控制访问,也就是RBAC模型,一个用户可能存在多种角色,一种角色也可能有多个用户,所以用户和角色之间是一个多对多的关系。

    案例一:  使用注解方式实现多对多关系

    • RoleBean.java
    package bean;
    
    import java.io.Serializable;
    import java.util.HashSet;
    import java.util.Set;
    
    import javax.persistence.Entity;
    import javax.persistence.Id;
    import javax.persistence.JoinColumn;
    import javax.persistence.JoinColumns;
    import javax.persistence.JoinTable;
    import javax.persistence.ManyToMany;
    import javax.persistence.Table;
    
    @Entity
    @Table(name = "role")
    public class RoleBean implements Serializable {
    
        @Id
        private Integer role_id;
        private String role_name;
        private String role_remark;
    
        @ManyToMany
        @JoinTable(name = "role_menu",    // //name=”role_menu”中间表的名称是“role_menu”
        joinColumns = { @JoinColumn(name = "roleid") },    //设置当前实体在中间表中的映射,也就是说在中间表中有一个字段叫roleid,使它指向当前表的主键这里是role_id
        inverseJoinColumns = { @JoinColumn(name = "menu_id") })  //设置对方实体在中间中的映射,也就是说在中间表中有一个字段menu_id,使它指向对方表(menu表)的主键。
        private Set<MenuBean> menuSet = new HashSet<MenuBean>();
    
        public RoleBean(Integer role_id, String role_name, String role_remark) {
            super();
            this.role_id = role_id;
            this.role_name = role_name;
            this.role_remark = role_remark;
        }
    
        public RoleBean() {
        }
    
        public Integer getRole_id() {
            return role_id;
        }
    
        public void setRole_id(Integer role_id) {
            this.role_id = role_id;
        }
    
        public String getRole_name() {
            return role_name;
        }
    
        public void setRole_name(String role_name) {
            this.role_name = role_name;
        }
    
        public String getRole_remark() {
            return role_remark;
        }
    
        public void setRole_remark(String role_remark) {
            this.role_remark = role_remark;
        }
    
        public Set<MenuBean> getMenuSet() {
            return menuSet;
        }
    
        public void setMenuSet(Set<MenuBean> menuSet) {
            this.menuSet = menuSet;
        }
    
    }
    • MenuBean.java
    package bean;
    
    import java.io.Serializable;
    
    import javax.persistence.Entity;
    import javax.persistence.Id;
    import javax.persistence.Table;
    
    @Entity
    @Table(name = "menu")
    public class MenuBean implements Serializable {
        @Id
        private Integer menuid;
        private String menuname;
    
        public MenuBean() {
        }
    
        public MenuBean(Integer menuid, String menuname) {
            super();
            this.menuid = menuid;
            this.menuname = menuname;
        }
    
        public Integer getMenuid() {
            return menuid;
        }
    
        public void setMenuid(Integer menuid) {
            this.menuid = menuid;
        }
    
        public String getMenuname() {
            return menuname;
        }
    
        public void setMenuname(String menuname) {
            this.menuname = menuname;
        }
    
    }

    • 把两个含有注解的bean文件添加到总配置文件里即可实现。



     

    案例二:使用xml配置文件实现单向多对多

    • 创建实体类  Role.java
    package bean;
    
    import java.util.HashSet;
    import java.util.Set;
    
    /**
     * Role entity. @author MyEclipse Persistence Tools
     */
    
    public class Role implements java.io.Serializable {
    
        // Fields
    
        private Integer roleId;
        private String roleName;
        private String roleRemark;
    
        private Set<MenuBean> menuSet=new HashSet<MenuBean>();
        // Constructors
    
        /** default constructor */
        public Role() {
        }
    
        /** minimal constructor */
        public Role(Integer roleId) {
            this.roleId = roleId;
        }
    
        /** full constructor */
        public Role(Integer roleId, String roleName, String roleRemark) {
            this.roleId = roleId;
            this.roleName = roleName;
            this.roleRemark = roleRemark;
        }
    
        // Property accessors
    
        public Integer getRoleId() {
            return this.roleId;
        }
    
        public void setRoleId(Integer roleId) {
            this.roleId = roleId;
        }
    
        public String getRoleName() {
            return this.roleName;
        }
    
        public void setRoleName(String roleName) {
            this.roleName = roleName;
        }
    
        public String getRoleRemark() {
            return this.roleRemark;
        }
    
        public void setRoleRemark(String roleRemark) {
            this.roleRemark = roleRemark;
        }
    
        public Set<MenuBean> getMenuSet() {
            return menuSet;
        }
    
        public void setMenuSet(Set<MenuBean> menuSet) {
            this.menuSet = menuSet;
        }
        
    }
    • 创建实体类 MenuBean.java
    package bean;
    
    /**
     * MenuBean entity. @author MyEclipse Persistence Tools
     */
    
    public class MenuBean implements java.io.Serializable {
    
        // Fields
    
        private Integer menuid;
        private String menuname;
    
        /** default constructor */
        public MenuBean() {
        }
    
        /** minimal constructor */
        public MenuBean(Integer menuid) {
            this.menuid = menuid;
        }
    
        /** full constructor */
        public MenuBean(Integer menuid, String menuname) {
            this.menuid = menuid;
            this.menuname = menuname;
        }
    
        // Property accessors
    
        public Integer getMenuid() {
            return this.menuid;
        }
    
        public void setMenuid(Integer menuid) {
            this.menuid = menuid;
        }
    
        public String getMenuname() {
            return this.menuname;
        }
    
        public void setMenuname(String menuname) {
            this.menuname = menuname;
        }
    
    }
    • 把创建实体类的映射文件 Role.hbm.xml
    <?xml version="1.0" encoding="utf-8"?>
    <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
    <!-- Mapping file autogenerated by MyEclipse Persistence Tools -->
    <hibernate-mapping>
        <class name="bean.Role" table="role" catalog="test">
            <id name="roleId" type="java.lang.Integer">
                <column name="role_id" />
                <generator class="assigned"></generator>
            </id>
            <property name="roleName" type="java.lang.String">
                <column name="role_name" />
            </property>
            <property name="roleRemark" type="java.lang.String">
                <column name="role_remark" />
            </property>
     <!-- 单向多对多 -->
            <set name="menuSet" table="role_menu">
                <key column="roleid"></key>     <!-- 表示当前类映射到关系表中的列 -->
                <many-to-many   column="menu_id"  class="bean.MenuBean" ></many-to-many>   <!-- 所对应的另一方在关系表中的列 -->
            </set>
    
        </class>
    </hibernate-mapping>
    • MenuBean.hbm.xml
    <?xml version="1.0" encoding="utf-8"?>
    <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
    <!-- 
        Mapping file autogenerated by MyEclipse Persistence Tools
    -->
    <hibernate-mapping>
        <class name="bean.MenuBean" table="menu" catalog="test">
            <id name="menuid" type="java.lang.Integer">
                <column name="menuid" />
                <generator class="assigned"></generator>
            </id>
            <property name="menuname" type="java.lang.String">
                <column name="menuname" />
            </property>
        </class>
    </hibernate-mapping>
    • 把两个映射文件添加到总配置文件里即可实现。
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  • 原文地址:https://www.cnblogs.com/shyroke/p/6900125.html
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