转：Hibernate实现无限子结点的树形目录

我们只需要一个表就可以很好的实现无限子结点的树型目录结构了
//1.持久类实现

public class Catalog implements Serializable {
 
 private Long id;
 
 private Long parentId;
 
 private String name;
 
 private Catalog parent;
 
 private Set children;
 
 public Catalog() {
  super();
 }

 /**
  * @return
  */
 public Set getChildren() {
  return children;
 }

 /**
  * @return
  */
 public Long getId() {
  return id;
 }

 /**
  * @return
  */
 public String getName() {
  return name;
 }

 /**
  * @return
  */
 public Catalog getParent() {
  return parent;
 }

 /**
  * @param set
  */
 public void setChildren(Set set) {
  children = set;
 }

 /**
  * @param l
  */
 public void setId(Long l) {
  id = l;
 }

 /**
  * @param string
  */
 public void setName(String string) {
  name = string;
 }

 /**
  * @param catalog
  */
 public void setParent(Catalog catalog) {
  parent = catalog;
 }
 
 public String toString() {
  return new ToStringBuilder(this)
   .append("customerId", getId())
   .toString();
 }

 public boolean equals(Object other) {
  if ( !(other instanceof Catalog) ) return false;
  Catalog castOther = (Catalog) other;
  return new EqualsBuilder()
   .append(this.getId(), castOther.getId())
   .isEquals();
 }

 public int hashCode() {
  return new HashCodeBuilder()
   .append(getId())
   .toHashCode();
 }

 /**
  * @return
  */
 public Long getParentId() {
  return parentId;
 }

 /**
  * @param long1
  */
 public void setParentId(Long long1) {
  parentId = long1;
 }

}

//2.配置

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
 "-//Hibernate/Hibernate Mapping DTD//EN"
 "http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">
<hibernate-mapping>
 <!-- com.kbarol.persistence.Catalog root -->
 <class name=“net.huisky.test.po.Catalog" table="catalog">
  <id name="id" type="long" column="id">
   <generator class="native"/>
  </id>
  <property name="name" column="name" type="string"/>
  <property name="parentId" column="parent_id" type="long"/>
 
  <set name="children"
       table="catalog"
       lazy="false"
       >
   <key column="parent_id"/>
   <one-to-many class="net.huisky.test.po.Catalog"/>
  </set>
 
  <many-to-one name="parent"
               insert="false"
                     update="false"
                     column="id"
                     class="net.huisky.test.po.Catalog"/>
 </class>
</hibernate-mapping>

//3.数据库表设计

 CREATE TABLE `catalog` (`id` INT (5) NOT NULL AUTO_INCREMENT, `name` VARCHAR (10) NOT NULL, `parent_id` INT (5) UNSIGNED DEFAULT '0' NOT NULL, PRIMARY KEY(`id`), UNIQUE(`id`), INDEX(`id`));

//4.相关测试代码

  String hql="select catalog from Catalog as catalog where catalog.parentId=:id";
  Session session=null;
  List list=new ArrayList();
  try {
   session=super.openSession(false);
   Query q=session.createQuery(hql);
   q.setParameter("id",new Long(0));//查找所有根结点
   list=q.list();
for(int i=0;i<parent.size();i++){
  Catalog catalog=(Catalog)parent.get(i);
  out.println("-"+catalog.getName()+"<br>");
  Iterator it=catalog.getChildren().iterator();
        while(it.hasNext()){//这里只是循环到第二层目录，可以利用递归方法再循环下去，把下面无限制级的子目录查找出来
   Catalog c=(Catalog)it.next();
   out.println("-----"+c.getName()+"<br>");
   Iterator ii=c.getChildren().iterator();
   }
    }

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