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()
   */
  @Override
  public int hashCode() {
   return this.categoryId.hashCode()+this.itemId.hashCode();
  }
  /* (non-Javadoc)
   * @see java.lang.Object#equals(java.lang.Object)
   */
  @Override
  public 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 class="identity" />
      </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 class="CategorizedItem" />
      </set>
   </class>

<class name="Category" table="CATEGORY">
      <id name="id" type="integer" column="CATEGORY_ID">
         <generator class="identity" />
      </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 class="CategorizedItem" />
      </set>
   </class>

<class name="Category" table="CATEGORY">
      <id name="id" type="integer" column="CATEGORY_ID">
         <generator class="identity" />
      </id>
      <class name="CategorizedItem" table="CATEGORIZED_ITEM" mutable="false">
 <composite-id name="id" class="CategorizedItem$Id">
 <key-property name="thirdId" 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" class="Item" column="ITEM_ID"
   not-null="true" insert="false" update="false" />
 <many-to-one name="category" class="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 
* @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。

Hibernate中联合主键映射时有一个也是外键的一种解决方法

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