many-to-one与one-to-many映射文件关于外键的问题

爱被打了一巴掌 2023-10-17 11:36 7阅读 0赞

### many-to-one与one-to-many映射文件 ###

**有两个实体——城市与国家，关系为n：1，欲实现关联关系的双向关联**

### 城市（City.java） ###

package com.hibernate.beans;
    /**
     *  城市实体
     * @author 浪丶荡
     *
     */
    public class City {
        
    
        //域属性
        private Integer cityId;
        private String cityName;
        //关联属性
        private Country country;
        public City() {
            super();
        }
        public City(String cityName) {
            super();
            this.cityName = cityName;
        }
        public Integer getCityId() {
            return cityId;
        }
        public void setCityId(Integer cityId) {
            this.cityId = cityId;
        }
        public String getCityName() {
            return cityName;
        }
        public void setCityName(String cityName) {
            this.cityName = cityName;
        }
        public Country getCountry() {
            return country;
        }
        public void setCountry(Country country) {
            this.country = country;
        }
        @Override
        public String toString() {
            return "City [cityId=" + cityId + ", cityName=" + cityName + "]";
        }
    
    
    }

### 国家（Country.java） ###

package com.hibernate.beans;
    
    import java.util.HashSet;
    import java.util.Set;
    
    /**
     *  国家实体
     * @author 浪丶荡
     *
     */
    public class Country {
        
    
        //域属性
        private Integer countryId;
        private String countryName;
        //关联属性
        private Set<City> citys;
        public Country() {
            citys = new HashSet<City>();
        }
        public Country(String countryName) {
            this();
            this.countryName = countryName;
        }
        public Integer getCountryId() {
            return countryId;
        }
        public void setCountryId(Integer countryId) {
            this.countryId = countryId;
        }
        public String getCountryName() {
            return countryName;
        }
        public void setCountryName(String countryName) {
            this.countryName = countryName;
        }
        public Set<City> getCitys() {
            return citys;
        }
        public void setCitys(Set<City> citys) {
            this.citys = citys;
        }
        @Override
        public String toString() {
            return "Country [countryId=" + countryId + ", countryName="
                    + countryName + ", citys=" + citys + "]";
        }
    
    }

### 映射文件（Country.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">
     <hibernate-mapping package="com.hibernate.beans">
         <class name="Country" table="t_country">
            <id name="countryId" column="t_countryId">
                <generator class="native"/>
            </id>
            <property name="countryName" column="t_countryName"></property>
            <set name="citys" cascade="save-update">
                
                <key column="t_countryId"></key>
                <one-to-many class="City"/>
            </set>
         </class>
     </hibernate-mapping>

### 映射文件（City.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">
     <hibernate-mapping package="com.hibernate.beans">
        <class name="City" table="t_city">
            <id name="cityId" column="t_cityId">
            <generator class="native"></generator>
            </id>
            <property name="cityName" column="t_cityName"/>
            <many-to-one name="country" cascade="save-update" class="Country">
                
                <column name="t_countryId"></column>
            </many-to-one>
        </class>
     </hibernate-mapping>