Hibernate中，基於Annotation的簡單樹形結構的實現

在系統設計中，常常用到遞歸性質的樹形結果，好比菜單、多級分類等，通常是在同一個表中定義父子關係實現這種結構。

下面是在Hibernate中，基於Annotation的簡單樹形結構的實現：

第一步：建立Entity類，並添加註解實現關聯關係

　   ps: 主要是利用@ManyToOne 和 @OneToMany 配置在同一個Entity類中實現樹形遞歸的結構。hibernate註解形式比在xml配置更加簡潔

TreeNode.java

 1 package com.hfut.hibernate;
 2 
 3 import java.util.HashSet;
 4 import java.util.Set;
 5 
 6 import javax.persistence.CascadeType;
 7 import javax.persistence.Entity;
 8 import javax.persistence.FetchType;
 9 import javax.persistence.GeneratedValue;
10 import javax.persistence.Id;
11 import javax.persistence.JoinColumn;
12 import javax.persistence.ManyToOne;
13 import javax.persistence.OneToMany;
14 
15 @Entity
16 public class Node {    
17     private int id;
18     private String name;
19     private Node parent;
20     private Set<Node> children = new HashSet<Node>();
21 
22     @Id
23     @GeneratedValue
24     public int getId() {
25         return id;
26     }
27     public void setId(int id) {
28         this.id = id;
29     }
30     public String getName() {
31         return name;
32     }
33     public void setName(String name) {
34         this.name = name;
35     }
36     @ManyToOne(cascade=CascadeType.ALL)
37     @JoinColumn(name="nodeId")
38     public Node getParent() {
39         return parent;
40     }
41     public void setParent(Node parent) {
42         this.parent = parent;
43     }
44     @OneToMany(mappedBy="parent", cascade=CascadeType.ALL,fetch=FetchType.EAGER)
45     public Set<Node> getChildren() {
46         return children;
47     }
48     public void setChildren(Set<Node> children) {
49         this.children = children;
50     }
51 }

第二步：建立hibernate默認配置文件：

hibernate.cfg.xml

 1 <?xml version='1.0' encoding='utf-8'?>
 2 <!DOCTYPE hibernate-configuration PUBLIC
 3         "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
 4         "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
 5 
 6 <hibernate-configuration>
 7 
 8     <session-factory>
 9 
10          
11         <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
12         <property name="connection.url">jdbc:mysql://localhost/testone</property>
13         <property name="connection.username">root</property>
14         <property name="connection.password">123456</property>
15         <property name="dialect">org.hibernate.dialect.MySQLDialect</property>
16        <!--
17         <property name="connection.driver_class">oracle.jdbc.driver.OracleDriver</property>
18         <property name="connection.url">jdbc:oracle:thin:@localhost:1521:SXT</property>
19         <property name="connection.username">scott</property>
20         <property name="connection.password">tiger</property>
21           <property name="dialect">org.hibernate.dialect.OracleDialect</property>
22        -->
23 
24         <!-- JDBC connection pool (use the built-in) -->
25         <property name="connection.pool_size">1</property>
26 
27         
28 
29         <!-- Enable Hibernate's automatic session context management -->
30         <property name="current_session_context_class">thread</property>
31 
32         <!-- Disable the second-level cache  -->
33         <property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>
34 
35         <!-- Echo all executed SQL to stdout -->
36         <property name="show_sql">true</property>
37         <property name="format_sql">true</property>
38 
39         <!-- Drop and re-create the database schema on startup
40         <property name="hbm2ddl.auto">update</property>
41          -->
42     <mapping class="com.hfut.hibernate.Node"/>
43 
44     </session-factory>
45 
46 </hibernate-configuration>

第三步：建立測試文件：

TreeNodeTest.java

 1 package com.hfut.hibernate;
 2 
 3 import org.hibernate.Session;
 4 import org.hibernate.SessionFactory;
 5 import org.hibernate.cfg.AnnotationConfiguration;
 6 import org.hibernate.tool.hbm2ddl.SchemaExport;
 7 import org.junit.AfterClass;
 8 import org.junit.BeforeClass;
 9 import org.junit.Test;
10 
11 import com.hfut.hibernate.TreeNode;
12 
13 public class TreeNodeTest {
14     
15     private static SessionFactory sessionFactory;
16     
17     @BeforeClass
18     public static void beforeClass() {
19         new SchemaExport(new AnnotationConfiguration().configure()).create(false, true);
20         sessionFactory = new AnnotationConfiguration().configure().buildSessionFactory();
21     }
22     
23     @AfterClass
24     public static void afterClass() {
25         sessionFactory.close();
26     }
27 
28     public void testSave() {
29         Session session = sessionFactory.openSession();
30         TreeNode node0 = new TreeNode();
31         node0.setName("父親");
32         TreeNode node1 = new TreeNode();
33         node1.setName("大兒子");
34         TreeNode node2 = new TreeNode();
35         node2.setName("小兒子");
36         TreeNode node3 = new TreeNode();
37         node3.setName("大兒子的大兒子");
38         TreeNode node4 = new TreeNode();
39         node4.setName("大兒子的小兒子");
40         TreeNode node5 = new TreeNode();
41         node5.setName("小兒子的大兒子");
42         TreeNode node6 = new TreeNode();
43         node6.setName("小兒子的小兒子");
44         
45         node0.getChildren().add(node1);
46         node0.getChildren().add(node2);
47         node1.getChildren().add(node3);
48         node1.getChildren().add(node4);
49         node1.setParent(node0);
50         node2.getChildren().add(node5);
51         node2.getChildren().add(node6);
52         node2.setParent(node0);
53         node3.setParent(node1);
54         node4.setParent(node1);
55         node5.setParent(node2);
56         node6.setParent(node2);
57         
58         session.beginTransaction();
59         session.save(node0);
60         session.getTransaction().commit();
61         session.close();
62     }
63     @Test
64     public void testLoad() {
65         testSave();
66         Session session = sessionFactory.openSession();
67         session.beginTransaction();
68         TreeNode node = (TreeNode)session.load(TreeNode.class, 1);
69         print(node,0);
70         session.getTransaction().commit();
71         session.close();
72     }
73 
74     private void print(TreeNode node,int level) {
75         String preStr = "";
76         for(int i=0;i<level;i++){
77             preStr +="----";
78         }
79         System.out.println(preStr+node.getName());
80         for(TreeNode children:node.getChildren()){
81             print(children,level+1);
82         }    
83     }
84 }

 

[四]、測試結果

測試結果以下：

父親----小兒子--------小兒子的大兒子--------小兒子的小兒子----大兒子--------大兒子的小兒子--------大兒子的大兒子