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  • hibernate —— 树状存储

     1 package com.pt.treeStrut;
     2 
     3 import java.util.Set;
     4 
     5 import javax.persistence.CascadeType;
     6 import javax.persistence.Entity;
     7 import javax.persistence.GeneratedValue;
     8 import javax.persistence.Id;
     9 import javax.persistence.JoinColumn;
    10 import javax.persistence.ManyToOne;
    11 import javax.persistence.OneToMany;
    12 
    13 @Entity
    14 public class ArticleTree {
    15     int id;
    16     String title;
    17     String content;
    18     ArticleTree p_article;
    19     
    20     Set<ArticleTree> sons;
    21     
    22     @OneToMany(mappedBy="p_article",cascade=CascadeType.ALL)
    23     public Set<ArticleTree> getSons() {
    24         return sons;
    25     }
    26     
    27     
    28     public void setSons(Set<ArticleTree> sons) {
    29         this.sons = sons;
    30     }
    31     public ArticleTree(){
    32         
    33     }
    34     public ArticleTree(int id, String title, String content){
    35         setId(id);
    36         setTitle(title);
    37         setContent(content);
    38     }
    39     @Id
    40     //@GeneratedValue
    41     public int getId() {
    42         return id;
    43     }
    44     public void setId(int id) {
    45         this.id = id;
    46     }
    47     public String getTitle() {
    48         return title;
    49     }
    50     public void setTitle(String title) {
    51         this.title = title;
    52     }
    53     public String getContent() {
    54         return content;
    55     }
    56     public void setContent(String content) {
    57         this.content = content;
    58     }
    59     
    60     @ManyToOne(cascade=CascadeType.ALL)
    61     @JoinColumn(name="parent_id")
    62     public ArticleTree getP_article() {
    63         return p_article;
    64     }
    65     public void setP_article(ArticleTree p_article) {
    66         this.p_article = p_article;
    67     }
    68 
    69 
    70     @Override
    71     public String toString() {
    72         // TODO Auto-generated method stub
    73         return title + "  " + content;
    74     }
    75     
    76     
    77 }
    ArticleTree.java
     1 import java.sql.Connection;
     2 import java.util.HashSet;
     3 import java.util.Set;
     4 
     5 import org.hibernate.Session;
     6 import org.hibernate.SessionFactory;
     7 import org.hibernate.cfg.Configuration;
     8 
     9 import com.pt.hibernate.Student;
    10 import com.pt.hibernate.Teacher;
    11 import com.pt.treeStrut.ArticleTree;
    12 
    13 
    14 public class Test {
    15     public static void main(String[] arges){
    16         Configuration cfg = new Configuration();
    17         SessionFactory factory = cfg.configure().buildSessionFactory();
    18         //Session ss=factory.openSession();
    19         Session ss= factory.getCurrentSession();
    20 //        Teacher hong = new Teacher();
    21 //        hong.setName("gaolihong");
    22 //        hong.setCourese("english");
    23 //        
    24 //        Set<Student> students=new HashSet<Student>();
    25 //        Student student = new Student();
    26 //        student.setId(2);
    27 //        student.setSchoolName("DuYangGang2");
    28 //        students.add(student);
    29 //        hong.setMyStudents(students);
    30         ss.beginTransaction();
    31 //        ss.save(hong);
    32 //        ss.getTransaction().commit();
    33         ArticleTree a_p = new ArticleTree(1000,"第一章","导论");
    34         ArticleTree a_s1 = new ArticleTree(1001,"第一节","导论——1");
    35         ArticleTree a_s2 = new ArticleTree(1002,"第二节","导论——2");
    36         
    37         ArticleTree a_p1 = new ArticleTree(2000,"第二章","光学");
    38         ArticleTree a_s11 = new ArticleTree(2001,"第一节","光学——1");
    39         ArticleTree a_s12 = new ArticleTree(2002,"第二节","光学——2");
    40         
    41         a_s11.setP_article(a_p1);
    42         a_s12.setP_article(a_p1);
    43         a_p1.setSons(new HashSet<ArticleTree>());    //否则会报空指针异常
    44         a_p1.getSons().add(a_s11);
    45         a_p1.getSons().add(a_s12);
    46         
    47         
    48         a_s1.setP_article(a_p);
    49         a_s2.setP_article(a_p);
    50         a_p.setSons(new HashSet<ArticleTree>());
    51         a_p.getSons().add(a_s1);
    52         a_p.getSons().add(a_s2);
    53         
    54         ArticleTree all = new ArticleTree(1,"物理","物理");
    55         a_p1.setP_article(all);
    56         a_p.setP_article(all);
    57         all.setSons(new HashSet<ArticleTree>());    //否则会报空指针异常
    58         all.getSons().add(a_p);
    59         all.getSons().add(a_p1);
    60         
    61         //ss.save(all);    //由于设置了cascade,存储一个,整个树都会存储进去
    62         
    63         //ss.save(a_s1);
    64         ss.save(a_s1);    //由于设置了cascade,存储一个,整个树都会存储进去
    65         ss.getTransaction().commit();
    66         //ss.close();        //getsession  不用close
    67         
    68         /****取出树来,并打印*******/
    69         Session ss2= factory.getCurrentSession();
    70         ss2.beginTransaction();
    71         ArticleTree getAll = ss2.load(ArticleTree.class, 1);  //取出父节点
    72         printTree(getAll,0);
    73         ss2.getTransaction().commit();
    74         factory.close();
    75     }
    76     
    77     public static void printTree(ArticleTree parent,int level){
    78         for(int i = 0; i< level; i++){
    79             System.out.print("--");
    80         }
    81         System.out.println(parent);
    82         for(ArticleTree article : parent.getSons()){
    83             printTree(article, level + 1);
    84         }
    85     }
    86 }
    test

    PS:开发过程中写的bug:

      1、commit的时候提示没有session   原因:session没有beginTransion

      2、提示set<sons>  字段找不到匹配的数据库字段类型,  原因:@oneTomany 写在了get上

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  • 原文地址:https://www.cnblogs.com/tengpan-cn/p/5585483.html
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