Hibernate中多种方式解除延迟加载
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问题引发：因为dao使用load（），默认延迟加载的，当在biz关闭session之后，UI层无法获取对象的非id属性值
解决方案：
1.变成get，即时加载
2.用Hibernate.isInitialized(obj)被初始化
3.类级别的lazy属性设为true
4.用final修饰类，因为用final修饰的类不允许有子类。而我们所说的内存中保存的代理对象其实就是该类的子类。此方法从根本上解决了延迟加载
5.在事务提交之前，先调用一下该类的非id属性
1
package
cn.happy.entity;
2
3
public
class
Users {
4
private
Integer id;
5
private
String name;
6
private
String password;
7
private
String telephone;
8
private
String userName;
9
private
String isAdmin;
10
11
12
public
Integer getId() {
13
return
id;
14
}
15
16
public
void
setId(Integer id) {
17
this.id = id;
18 }
1920public String getName() {
21return name;
22 }
2324publicvoid setName(String name) {
25this.name = name;
26 }
2728public String getPassword() {
29return password;
30 }
3132publicvoid setPassword(String password) {
33this.password = password;
34 }
3536public String getTelephone() {
37return telephone;
38 }
3940publicvoid setTelephone(String telephone) {
41this.telephone = telephone;
42 }
4344public String getUserName() {
45return userName;
46 }
4748publicvoid setUserName(String userName) {
49this.userName = userName;
50 }
5152public String getIsAdmin() {
53return isAdmin;
54 }
5556publicvoid setIsAdmin(String isAdmin) {
57this.isAdmin = isAdmin;
58 }
5960 }
1 <?xml version="1.0"?>
2 <!DOCTYPE hibernate-mapping PUBLIC
3 "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
4 "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
5 6 7 <hibernate-mapping package="cn.happy.entity">
8 9 <class name="Users" table="USERS" lazy="false">
10 <id name="id" column="ID">
11 <generator class="native" />
12 </id>
13 <property name="name" type="string" column="NAME" />
14 <property name="password" />
15 <property name="telephone" />
16 <property name="userName" />
17 <property name="isAdmin" />
18 </class>
1920 </hibernate-mapping>
1
package
cn.happy.dao;
2
3
import
java.io.Serializable;
4
5
import
cn.happy.until.HibernateUtil;
6
7
public
class
UsersDao {
8
//
添加用户记录
9
public
Serializable save(Object object){
10
return
HibernateUtil.currentSession().save(object);
11
}
12
//
检索oid
13
public
Object get(Class clazz, Serializable id){
14
return
HibernateUtil.currentSession().load(clazz, id);
15
}
16
17
//
修改用户记录
18
public
void
update(Object object){
19
HibernateUtil.currentSession().update(object);
20
}
21
22 }
1
package
cn.happy.biz;
2
3
import
java.io.Serializable;
4
5
import
org.hibernate.Hibernate;
6
import
org.hibernate.Transaction;
7
8
import
cn.happy.dao.UsersDao;
9
import
cn.happy.until.HibernateUtil;
10
11
public
class
UsersBiz {
12 UsersDao user=new UsersDao();
13//添加用户记录14public Serializable save(Object object){
15 Transaction tx=HibernateUtil.currentSession().beginTransaction();
16 Serializable result=user.save(object);
17 tx.commit();
18return result;
19 }
20//检索oid21public Object get(Class clazz, Serializable id){
22 Transaction tx = HibernateUtil.currentSession().beginTransaction();
23 Object obj=user.get(clazz, id);
24// if(!Hibernate.isInitialized(obj)){
25// Hibernate.initialize(obj);
26// }27 tx.commit();
28 HibernateUtil.closeSession();
29return obj;
30 }
3132//修改用户记录33publicvoid update(Object object){
34 Transaction tx=HibernateUtil.currentSession().beginTransaction();
35 user.update(object);
36 tx.commit();
37 }
38 }
1
package
cn.happy.ui;
2
3
import
org.hibernate.Session;
4
import
org.hibernate.SessionFactory;
5
import
org.hibernate.Transaction;
6
import
org.hibernate.cfg.Configuration;
7
8
import
cn.happy.biz.UsersBiz;
9
import
cn.happy.entity.Users;
10
import
cn.happy.until.HibernateUtil;
11
12
public
class
Test {
13
public
static
void
main(String[] args) {
14
get();
15
}
16
//
添加
17
public
static
void
add(){
18 Users user=new Users();
19 user.setName("回青");
20 user.setIsAdmin("yes");
21 user.setPassword("123456");
22 user.setTelephone("18265808945");
23 user.setUserName("户梦艳");
24 UsersBiz usersBiz=new UsersBiz();
25 usersBiz.save(user);
26 System.out.println("ok");
2728 }
29//修改30publicstaticvoid modify(){
31 Session session = HibernateUtil.currentSession();
32 Transaction transaction = session.beginTransaction();
33 Users user = (Users)session.get(Users.class, 6);
34 user.setName("岁月静好");
35 session.update(user);
36 transaction.commit();
37 HibernateUtil.closeSession();
38 }
3940//
41publicstaticvoid get(){
42 UsersBiz ub=new UsersBiz();
43 Users user = (Users)ub.get(Users.class, 6);
44 System.out.println(user.getName());
45 }
46 }
6.用openSessionInView模式
Open Session In View模式的主要思想：在用户的每一次请求过程始终保持 一个Session对象打开着
过滤器：过滤用的。过滤请求和响应。双向过滤
实现步骤：
Until包
1
package
cn.happy.until;
2
3
import
org.hibernate.Session;
4
import
org.hibernate.SessionFactory;
5
import
org.hibernate.cfg.Configuration;
6
7
public
class
HibernateUtil {
8
private
static
final ThreadLocal sessionTL=new ThreadLocal();
9privatestatic Configuration configuration;
10privatefinalstatic SessionFactory sessionFactory;
11static{
12 configuration=new Configuration().configure();
13 sessionFactory=configuration.buildSessionFactory();
14 }
15publicstatic Session currentSession(){
16 Session session=(Session)sessionTL.get();
17//如果session为null，则打开一个新的session18if(session==null){
19 session=sessionFactory.openSession();
20 sessionTL.set(session);
21 }
22return session;
23 }
24publicstaticvoid closeSession(){
25 Session session=(Session)sessionTL.get();
26 sessionTL.set(null);
27 session.close();
28 }
29 }
1
package
cn.happy.entity;
2
3
public
class
Users {
4
private
Integer id;
5
private
String name;
6
private
String password;
7
private
String telephone;
8
private
String userName;
9
private
String isAdmin;
10
11
12
public
Integer getId() {
13
return
id;
14
}
15
16
public
void
setId(Integer id) {
17
this.id = id;
18 }
1920public String getName() {
21return name;
22 }
2324publicvoid setName(String name) {
25this.name = name;
26 }
2728public String getPassword() {
29return password;
30 }
3132publicvoid setPassword(String password) {
33this.password = password;
34 }
3536public String getTelephone() {
37return telephone;
38 }
3940publicvoid setTelephone(String telephone) {
41this.telephone = telephone;
42 }
4344public String getUserName() {
45return userName;
46 }
4748publicvoid setUserName(String userName) {
49this.userName = userName;
50 }
5152public String getIsAdmin() {
53return isAdmin;
54 }
5556publicvoid setIsAdmin(String isAdmin) {
57this.isAdmin = isAdmin;
58 }
5960 }
entity包
1
package
cn.happy.entity;
2
3
public
class
Users {
4
private
Integer id;
5
private
String name;
6
private
String password;
7
private
String telephone;
8
private
String userName;
9
private
String isAdmin;
10
11
12
public
Integer getId() {
13
return
id;
14
}
15
16
public
void
setId(Integer id) {
17
this.id = id;
18 }
1920public String getName() {
21return name;
22 }
2324publicvoid setName(String name) {
25this.name = name;
26 }
2728public String getPassword() {
29return password;
30 }
3132publicvoid setPassword(String password) {
33this.password = password;
34 }
3536public String getTelephone() {
37return telephone;
38 }
3940publicvoid setTelephone(String telephone) {
41this.telephone = telephone;
42 }
4344public String getUserName() {
45return userName;
46 }
4748publicvoid setUserName(String userName) {
49this.userName = userName;
50 }
5152public String getIsAdmin() {
53return isAdmin;
54 }
5556publicvoid setIsAdmin(String isAdmin) {
57this.isAdmin = isAdmin;
58 }
5960 }
1 <?xml version="1.0"?>
2 <!DOCTYPE hibernate-mapping PUBLIC
3 "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
4 "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
5 6 7 <hibernate-mapping package="cn.happy.entity">
8 9 <class name="Users" table="USERS">
10 <id name="id" column="ID">
11 <generator class="native" />
12 </id>
13 <property name="name" type="string" column="NAME" />
14 <property name="password" />
15 <property name="telephone" />
16 <property name="userName" />
17 <property name="isAdmin" />
18 </class>
1920 </hibernate-mapping>
Dao包
1
package
cn.happy.dao;
2
3
import
java.io.Serializable;
4
5
import
cn.happy.until.HibernateUtil;
6
7
public
class
UsersDao {
8
//
添加用户记录
9
public
Serializable save(Object object){
10
return
HibernateUtil.currentSession().save(object);
11
}
12
//
检索oid
13
public
Object get(Class clazz, Serializable id){
14
return
HibernateUtil.currentSession().load(clazz, id);
15
}
16
17
//
修改用户记录
18
public
void
update(Object object){
19
HibernateUtil.currentSession().update(object);
20
}
21
22 }
Biz包
1
package
cn.happy.biz;
2
3
import
java.io.Serializable;
4
5
import
org.hibernate.Hibernate;
6
import
org.hibernate.Transaction;
7
8
import
cn.happy.dao.UsersDao;
9
import
cn.happy.until.HibernateUtil;
10
11
public
class
UsersBiz {
12 UsersDao user=new UsersDao();
13//添加用户记录14public Serializable save(Object object){
15 Transaction tx=HibernateUtil.currentSession().beginTransaction();
16 Serializable result=user.save(object);
17 tx.commit();
18return result;
19 }
20//检索oid21public Object get(Class clazz, Serializable id){
22//Transaction tx = HibernateUtil.currentSession().beginTransaction();23 Object obj=user.get(clazz, id);
24// if(!Hibernate.isInitialized(obj)){
25// Hibernate.initialize(obj);
26// }
27//tx.commit();
28//HibernateUtil.closeSession();29return obj;
30 }
3132//修改用户记录33publicvoid update(Object object){
34 Transaction tx=HibernateUtil.currentSession().beginTransaction();
35 user.update(object);
36 tx.commit();
37 }
38 }
Filter包
1
package
cn.happy.filter;
2
3
import
java.io.IOException;
4
5
import
javax.servlet.Filter;
6
import
javax.servlet.FilterChain;
7
import
javax.servlet.FilterConfig;
8
import
javax.servlet.ServletException;
9
import
javax.servlet.ServletRequest;
10
import
javax.servlet.ServletResponse;
11
12
import
org.hibernate.HibernateException;
13
import
org.hibernate.Session;
14
import
org.hibernate.Transaction;
15
16
import
cn.happy.until.HibernateUtil;
17
18
public
class OpenSessionInViewFilter implements Filter {
192021publicvoid doFilter(ServletRequest request, ServletResponse response,
22 FilterChain chain) throws IOException, ServletException {
23 request.setCharacterEncoding("utf-8");
24 Session session=null;
25 Transaction tx=null;
26try {
27 session=HibernateUtil.currentSession();
28 System.out.println("filter\t"+session.hashCode());
29 tx=session.beginTransaction();
30//执行请求处理链 双向过滤31 chain.doFilter(request, response);
32//返回响应 提交事务33 tx.commit();
34 } catch (HibernateException e) {
35 e.printStackTrace();
36 tx.rollback();
37 }finally{
38 HibernateUtil.closeSession();
39 }
4041 }
4243publicvoid init(FilterConfig arg0) throws ServletException {
44// TODO Auto-generated method stub4546 }
47publicvoid destroy() {
48// TODO Auto-generated method stub4950 }
515253 }
原文：http://www.cnblogs.com/hmy-1365/p/5773530.html
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