Hibernate中联合主键映射时有一个也是外键的一种解决方法
昨天遇到一个联合主键的问题，困扰了我很久，最后发现《Hibernate in Action》里有讲到，因为在实际环境中老是报错，也不知配置的对不对，然后回家写了一个DEMO，发现可以保存。
表结构大致如下：
ITEM(ID,NAME)其中id是PK
CATEGORY(ID,NAME)，其中ID是PK
CATEGORY_ITEM(ITEM_ID,CATEGORY_ID,THIRD_ID,ADDED_DATE),其中ITEM_ID,CATEGORY_ID分别是ITEM和CATEGORY的外键，而他们与THIRD_ID一起组成CATETORY_ITEM表的联合主键。
下面给出具体实现：
一、Item.java
/** * @author Terrence * */public class Item implements Serializable {/** * */private static final long serialVersionUID = 1L;private Integer id;private String name;private Set<CategorizedItem> categorizedItems = new HashSet<CategorizedItem>();/** * */public Item() {super();}/** * @return the id */public Integer getId() {return id;}/** * @param id the id to set */public void setId(Integer id) {this.id = id;}/** * @return the name */public String getName() {return name;}/** * @param name the name to set */public void setName(String name) {this.name = name;}/** * @return the categorizedItems */public Set<CategorizedItem> getCategorizedItems() {return categorizedItems;}/** * @param categorizedItems the categorizedItems to set */public void setCategorizedItems(Set<CategorizedItem> categorizedItems) {this.categorizedItems = categorizedItems;}}二、Category.java
/** * @author Terrence * */public class Category implements Serializable {/** * */private static final long serialVersionUID = 1L;private Integer id;private String name;private Set<CategorizedItem> categorizedItems = new HashSet<CategorizedItem>();public Category() {super();}/** * @return the id */public Integer getId() {return id;}/** * @param id the id to set */public void setId(Integer id) {this.id = id;}/** * @return the name */public String getName() {return name;}/** * @param name the name to set */public void setName(String name) {this.name = name;}/** * @return the categorizedItems */public Set<CategorizedItem> getCategorizedItems() {return categorizedItems;}/** * @param categorizedItems the categorizedItems to set */public void setCategorizedItems(Set<CategorizedItem> categorizedItems) {this.categorizedItems = categorizedItems;}}三、CategorizedItem.java
/** * @author Terrence * */public class CategorizedItem implements Serializable {/** * */private static final long serialVersionUID = 1L;public static class Id implements Serializable {/** * */private static final long serialVersionUID = 1L;private Integer thirdId;private Integer categoryId;private Integer itemId;/** * */public Id() {super();}/** * @return the thirdId */public Integer getThirdId() {return thirdId;}/** * @param thirdId the thirdId to set */public void setThirdId(Integer thirdId) {this.thirdId = thirdId;}/** * @return the categoryId */public Integer getCategoryId() {return categoryId;}/** * @param categoryId the categoryId to set */public void setCategoryId(Integer categoryId) {this.categoryId = categoryId;}/** * @return the itemId */public Integer getItemId() {return itemId;}/** * @param itemId the itemId to set */public void setItemId(Integer itemId) {this.itemId = itemId;}/* (non-Javadoc) * @see java.lang.Object#hashCode() */@Overridepublic int hashCode() {return this.categoryId.hashCode()+this.itemId.hashCode();}/* (non-Javadoc) * @see java.lang.Object#equals(java.lang.Object) */@Overridepublic boolean equals(Object obj) {if(obj!=null&&obj instanceof Id){Id that = (Id)obj;return this.categoryId.equals(that.categoryId)&&this.itemId.equals(that.itemId);}else{return false;}}}private Id id = new Id();private Date dateAdded;private Item item;private Category category;/** * */public CategorizedItem() {super();}/** * @return the id */public Id getId() {return id;}/** * @param id the id to set */public void setId(Id id) {this.id = id;}/** * @return the dateAdded */public Date getDateAdded() {return dateAdded;}/** * @param dateAdded the dateAdded to set */public void setDateAdded(Date dateAdded) {this.dateAdded = dateAdded;}/** * @return the item */public Item getItem() {return item;}/** * @param item the item to set */public void setItem(Item item) {this.item = item;this.id.itemId = item.getId();item.getCategorizedItems().add(this);}/** * @return the category */public Category getCategory() {return category;}/** * @param category the category to set */public void setCategory(Category category) {this.category = category;this.id.categoryId = category.getId();category.getCategorizedItems().add(this);}/** * @return the thirdId */public Integer getThirdId() {return this.id.getThirdId();}/** * @param thirdId the thirdId to set */public void setThirdId(Integer thirdId) {this.id.thirdId = thirdId;}}四、*.hbm.xml,这里节省时间空间写在了一起
<hibernate-mapping package="org.terrence.hrsystem.model"><class name="Item" table="ITEM"> <id name="id" type="integer" column="ITEM_ID"> <generator /> </id> <property name="name" type="string" not-null="true" update="false" column="ITEM_NAME" /> <set name="categorizedItems" cascade="all, delete-orphan" inverse="true" lazy="false"> <key column="ITEM_ID" not-null="true" /> <one-to-many /> </set> </class><class name="Category" table="CATEGORY"> <id name="id" type="integer" column="CATEGORY_ID"> <generator /> </id> <property name="name" type="string" column="CATEGORY_NAME" not-null="true"/> <set name="categorizedItems" cascade="all, delete-orphan" inverse="true" lazy="false"> <key column="CATEGORY_ID" not-null="true" /> <one-to-many /> </set> </class><class name="Category" table="CATEGORY"> <id name="id" type="integer" column="CATEGORY_ID"> <generator /> </id> <class name="CategorizedItem" table="CATEGORIZED_ITEM" mutable="false"><composite-id name="id" column="THIRD_ID" type="integer"/><key-property name="categoryId" column="CATEGORY_ID"type="integer" /><key-property name="itemId" column="ITEM_ID" type="integer" /></composite-id><property name="dateAdded" column="ADDED_ON" type="timestamp"not-null="true" /><many-to-one name="item" column="ITEM_ID"not-null="true" insert="false" update="false" /><many-to-one name="category" column="CATEGORY_ID"not-null="true" insert="false" update="false" /></class></hibernate-mapping>
五、测试代码
/** * @Title: TestDao.java * @Package test * @Description: TODO(用一句话描述该文件做什么) * @author Terrence.zhung chguxing@163.com * @date 2011-3-29 上午02:45:05 * @version V1.0 */ package test;import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;import org.terrence.hrsystem.dao.CategorizedItemDao;import org.terrence.hrsystem.dao.CategoryDao;import org.terrence.hrsystem.dao.ItemDao;import org.terrence.hrsystem.model.CategorizedItem;import org.terrence.hrsystem.model.Category;import org.terrence.hrsystem.model.Item;/** * @author Terrence * */public class TestDao {/** * @param args */private static ItemDao itemDao;private static CategoryDao categoryDao;private static CategorizedItemDao categorizedItemDao;private static ApplicationContext ctx;public static void init(){if(ctx==null){ctx = new ClassPathXmlApplicationContext(new String[]{"classpath:applicationContext.xml","classpath:daoContext.xml"});}itemDao = (ItemDao)ctx.getBean("itemDao");categoryDao = (CategoryDao)ctx.getBean("categoryDao");categorizedItemDao = (CategorizedItemDao)ctx.getBean("categorizedItemDao");}public static void main(String[] args) throws Exception {init();saveItem();saveCategory();saveCategoryItem();}public static void saveItem() throws Exception{Item item = new Item();item.setName("item2");itemDao.save(item);}public static void saveCategory() throws Exception{Category category = new Category();category.setName("category2");categoryDao.save(category);}public static void saveCategoryItem() throws Exception{Item item = itemDao.get(1);Category category = categoryDao.get(1);CategorizedItem categorizedItem = new CategorizedItem();categorizedItem.setItem(item);categorizedItem.setCategory(category);categorizedItem.setDateAdded(new java.util.Date());categorizedItem.setThirdId(5);categorizedItemDao.save(categorizedItem);}}六、说明
因为用了spring，在配置文件配好环境，表可以用hibernate直接生成，不用写SQL语句。
1 楼 168_ccxx 2011-10-30 CategorizedItem 的配置文件貌似没看到啊.. 2 楼 zhongrf 2011-11-07 168_ccxx 写道CategorizedItem 的配置文件貌似没看到啊..
不好意思,贴错了,现在补上了,谢谢哈 3 楼 abcd880129 2011-11-07 是不是写错了，应该是Item的主键、Category的主键是CategorizedItem的外键，然后又和thirdId组成CategorizedItem的联合主键，看标题让我兴奋了一下，原来不是