十一、BDB ManyToMany

Bdb JE对复杂数据的存储(四)、ManyToMany关系的存储 
班级类

@Entity
public class Classs {
@PrimaryKey
String cId;

@SecondaryKey(relate=Relationship.MANY_TO_ONE)
String cName;

@SecondaryKey(relate=Relationship.MANY_TO_MANY,relatedEntity=Teacher. class,onRelatedEntityDelete=DeleteAction.NULLIFY)
Set setTeacher= new HashSet();

public Classs(){}

public Classs(String id,String name){
     this.cId=id;
     this.cName=name;
}
}
老师类:

@Entity
public class Teacher {

@PrimaryKey
String tId;

@SecondaryKey(relate=Relationship.MANY_TO_ONE)
String tName;

@SecondaryKey(relate=Relationship.MANY_TO_MANY,relatedEntity=Classs. class,onRelatedEntityDelete=DeleteAction.NULLIFY)
Set setClasss= new HashSet();

public Teacher(){}

public Teacher(String id,String name){
     this.tId=id;
     this.tName=name;
}
}

关系类:
public class Accessor {

PrimaryIndex primaryClassById;
SecondaryIndex classsByName;
SecondaryIndex classsBySetTeacher;

PrimaryIndex primaryTeacherById;
SecondaryIndex teacherByName;
SecondaryIndex teacherByClasss;

Accessor(EntityStore store) throws DatabaseException{
     this.primaryClassById=store.getPrimaryIndex(String. class, Classs. class);
     this.classsByName=store.getSecondaryIndex( this.primaryClassById, String. class, "cName");
     this.classsBySetTeacher=store.getSecondaryIndex( this.primaryClassById, String. class, "setTeacher");
    
     this.primaryTeacherById=store.getPrimaryIndex(String. class, Teacher. class);
     this.teacherByName=store.getSecondaryIndex( this.primaryTeacherById, String. class, "tName");
     this.teacherByClasss=store.getSecondaryIndex( this.primaryTeacherById, String. class, "setClasss");
}
}
测试类:
public class testMany2Many {
public static void main(String[] args) {
    Environment env= null;
    EnvironmentConfig envconfig= new EnvironmentConfig();
    envconfig.setAllowCreate( true);
    envconfig.setTransactional( true);
    StoreConfig storeconfig= new StoreConfig();
    storeconfig.setAllowCreate( true);
    storeconfig.setTransactional( true);
    EntityStore store= null;
     try {
     env= new Environment( new File( "D:/bdb/many2manyje"),envconfig);
     store= new EntityStore(env, "many2manyje",storeconfig);
     Accessor dao= new Accessor(store);
     PrimaryIndex classsById=dao.primaryClassById;
     PrimaryIndex teacherById=dao.primaryTeacherById;
     Transaction txn=env.beginTransaction( null, null);
    
     Classs c1= new Classs( "100001", "三年一班");
     Classs c2= new Classs( "100002", "三年二班");
     Classs c3= new Classs( "100003", "三年三班");
    
     Classs c4= new Classs( "100004", "四年一班");
     Classs c5= new Classs( "100005", "四年二班");
     Classs c6= new Classs( "100006", "四年三班");
    
     Teacher t1= new Teacher( "4200106310001", "张微");
     Teacher t2= new Teacher( "4200106310002", "刘婷");
     Teacher t3= new Teacher( "4200106310003", "许红");
     Teacher t4= new Teacher( "4200106310004", "张珊");
     Teacher t5= new Teacher( "4200106310005", "周燕");
     Teacher t6= new Teacher( "4200106310006", "李蝶");
     Teacher t7= new Teacher( "4200106310007", "徐馨");
     Teacher t8= new Teacher( "4200106310008", "赵君");
     Teacher t9= new Teacher( "4200106310009", "刘可");
    
     Set setT1= new HashSet();
     setT1.add(t1.tId);
     setT1.add(t2.tId);
     setT1.add(t3.tId);
    
     Set setT2= new HashSet();
     setT2.add(t2.tId);
     setT2.add(t3.tId);
     setT2.add(t4.tId);
    
     Set setT3= new HashSet();
     setT3.add(t3.tId);
     setT3.add(t4.tId);
     setT3.add(t5.tId);
    
    
     Set setT4= new HashSet();
     setT4.add(t5.tId);
     setT4.add(t6.tId);
     setT4.add(t7.tId);
    
     Set setT5= new HashSet();
     setT5.add(t7.tId);
     setT5.add(t8.tId);
     setT5.add(t9.tId);
    
     c1.setTeacher=setT1;
     c2.setTeacher=setT2;
     c3.setTeacher=setT1;
     c4.setTeacher=setT3;
     c5.setTeacher=setT4;
     c6.setTeacher=setT5;
    
     teacherById.put(txn,t1);
     teacherById.put(txn,t2);
     teacherById.put(txn,t3);
     teacherById.put(txn,t4);
     teacherById.put(txn,t5);
     teacherById.put(txn,t6);
     teacherById.put(txn,t7);
     teacherById.put(txn,t8);
     teacherById.put(txn,t9);
    
     classsById.put(txn, c1);
     classsById.put(txn, c2);
     classsById.put(txn, c3);
     classsById.put(txn, c4);
     classsById.put(txn, c5);
     classsById.put(txn, c6);
    
    
     EntityCursor ecClasss= null;
     EntityCursor ecTeacher= null;
    
     System.out.println( "---------班级信息-------------------");
     ecClasss=classsById.entities(txn, null);
     for(Classs c:ecClasss){
        Iterator it=c.setTeacher.iterator();
        StringBuffer strbuf= new StringBuffer();
         while(it.hasNext()){
         strbuf.append(teacherById.get(txn, it.next(), LockMode.DEFAULT).tName+ " ");
        }
        System.out.println( "班级ID："+c.cId+ " 班级名称:    "+c.cName+ " 所属该班级的老师: "+strbuf.toString());
     }
     ecClasss.close();
     System.out.println( "---------修改老师的所属班级信息-------------");
     ecTeacher=teacherById.entities(txn, null);
     for(Teacher t:ecTeacher){
        ecClasss=classsById.entities(txn, null);
         for(Classs c:ecClasss){
         if(c.setTeacher.contains(t.tId)){
            t.setClasss.add(c.cId);
         }
        }
        ecTeacher.update(t);
        ecClasss.close();
     }
     ecTeacher.close();
    
     System.out.println( "----------老师信息----------");
     ecTeacher=teacherById.entities(txn, null);
     for(Teacher t:ecTeacher){
        Iterator it=t.setClasss.iterator();
        StringBuffer strbuf= new StringBuffer();
         while(it.hasNext()){
         strbuf.append(classsById.get(txn,it.next(),LockMode.DEFAULT).cName+ " ");
        }
        System.out.println( "老师的ID "+t.tId+ " 老师的名字: "+t.tName+ " 老师所属班级: "+strbuf.toString());
     }
     ecTeacher.close();
     //在提交txn的时候最好有把所有的游标都要关闭
     txn.commit();
     store.close();
     env.cleanLog();
     env.close();
    } catch (EnvironmentLockedException e) {
     e.printStackTrace();
    } catch (DatabaseException e) {
     e.printStackTrace();
    }
}
}