? 在實(shí)際程序開發(fā)中，經(jīng)常需要持久化臨時(shí)對(duì)象，比如新建一個(gè)學(xué)生，將加入到一個(gè)存在的班級(jí)中（或者新建的一個(gè)班級(jí)），在這里不妨把引起級(jí)聯(lián)操作的對(duì)象稱為根對(duì)象（本文中所指的就是team對(duì)象）?，而根對(duì)象可能出于transient,persistence,detach三態(tài)，下面分別討論
首先，建立數(shù)據(jù)庫(kù)表：
?
CREATE
?
TABLE
?certificate?(
??id?
varchar
(
100
)?
NOT
?
NULL
?
default
?
''
,
??description?
varchar
(
100
)?
default
?
''
,
??
PRIMARY
?
KEY
??(id)
);
CREATE
?
TABLE
?student?(
??team_id?
varchar
(
100
)?
default
?
''
,
??id?
varchar
(
100
)?
NOT
?
NULL
?
default
?
''
,
??name?
varchar
(
20
)?
default
?
''
,
??cardId?
varchar
(
20
)?
NOT
?
NULL
?
default
?
''
,
??age?
int
(
11
)?
default
?
'
0
'
,
??
PRIMARY
?
KEY
??(id)
);
CREATE
?
TABLE
?team?(
??id?
varchar
(
100
)?
NOT
?
NULL
?
default
?
''
,
??teamName?
varchar
(
100
)?
default
?
''
,
??
PRIMARY
?
KEY
??(id)
);
INSERT
?
INTO
?certificate?
VALUES
?(
'
1
'
,
'
110108
'
);
INSERT
?
INTO
?certificate?
VALUES
?(
'
2
'
,
'
110109
'
);
INSERT
?
INTO
?student?
VALUES
?(
'
1
'
,
'
1
'
,
'
tomclus
'
,
'
2006m
'
,
33
);
INSERT
?
INTO
?student?
VALUES
?(
'
2
'
,
'
2
'
,
'
tom
'
,
'
2007m
'
,
22
);
INSERT
?
INTO
?team?
VALUES
?(
'
1
'
,
'
team1
'
);
?
持久化對(duì)象Pojo
?
package
?Cascade.Relation;
public
?
class
?Certificate?
{
????
private
?String?id;
????
private
?String?description;
????
private
?Student?stu;
????
public
?Student?getStu()?
{
????????
return
?stu;
????}
????
public
?
void
?setStu(Student?stu)?
{
????????
this
.stu?
=
?stu;
????}
????
public
?String?getDescription()?
{
????????
return
?description;
????}
????
public
?
void
?setDescription(String?description)?
{
????????
this
.description?
=
?description;
????}
????
public
?String?getId()?
{
????????
return
?id;
????}
????
public
?
void
?setId(String?id)?
{
????????
this
.id?
=
?id;
????}
}
package
?Cascade.Relation;
public
?
class
?Student?
{
????
private
?String?id;?
//
標(biāo)識(shí)id
????
private
?String?cardId;?
//
學(xué)號(hào)
????
private
?String?name;?
//
學(xué)生姓名
????
private
?
int
?age;?
//
歲數(shù)
????
private
?Certificate?cer;
//
身分證
????
private
?Team?team;
//
班級(jí)
?????
public
?
int
?getAge()?
{
????????
return
?age;
????}
????
public
?String?getName()?
{
????????
return
?name;
????}
????
public
?String?getCardId()?
{
????????
return
?cardId;
????}
????
public
?
void
?setId(String?id)?
{
????????
this
.id?
=
?id;
????}
????
public
?
void
?setAge(
int
?age)?
{
????????
this
.age?
=
?age;
????}
????
public
?
void
?setName(String?stuName)?
{
????????
this
.name?
=
?stuName;
????}
????
public
?
void
?setCardId(String?cardId)?
{
????????
this
.cardId?
=
?cardId;
????}
????
public
?String?getId()?
{
????????
return
?id;
????}
????
public
?Student()?
{?
//
無(wú)參的構(gòu)造函數(shù)
????}
?????
public
?Certificate?getCer()?
{
????????
return
?cer;
????}
????
public
?
void
?setCer(Certificate?pass)?
{
????????
this
.cer?
=
?pass;
????}
????
public
?Team?getTeam()?
{
????????
return
?team;
????}
????
public
?
void
?setTeam(Team?team)?
{
????????
this
.team?
=
?team;
????}
}
package
?Cascade.Relation;
import
?java.util.HashSet;
import
?java.util.Set;
public
?
class
?Team?
{
????
private
?String?id;
????
private
?Set?students
=
new
?HashSet();
????
private
?String?teamName;
????
private
?Set?tests;
??
????
public
?Set?getTests()?
{
????????
return
?tests;
????}
?
????
public
?
void
?setTests(Set?tests)?
{
????????
this
.tests?
=
?tests;
????}
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