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[�W�记]事务处理

Duran's technical life — Fri, 09 Sep 2005 05:09:00 GMT

@title [�W�记]事务处理

#1 Transaction Propagation Behavior
Required:Excute within a current tx, create a new one if none exists.
Supports: Excute within a current tx, execute without a tx if none exsits.
Mandatory: Excute within a current tx, throw an exception if none exists.
Requires New: Create a new tx and excute within the tx, suspend the current tx if one exists.
Not Supported: Excute without a tx, suspend the current tx if none exsits.
Never: Excute without a tx, throw an exception if a tx exsits.

#2 Transaction Isolation Level[1]
#2.1 Concurrent Problem
Dirty Reads: 脏读�Q�脏数据指已更新�Q�还没提交的数据�Q�。事务T1��d��C��务T2中的脏数据�?/FONT>

Unrepeatable Reads: 不可重复诅R��事务T1��索到某行后，事务T2更新�q�提交了该行�Q�若事务T2再次��索该行，则会看到不一��L��l�果�?/FONT>

Phantom Reads: 虚读。事务T1��索到�W�合某条件的行集后，事务T2插入�q�提交了满��该条件的新行�Q�若事务T2再次按该条�g��索，则会看到以前不存在的行“Phantom”�?/FONT>

#2.2 Isolation Level
+---------------+-------+------------------+-----------+
|Isolation Level|Phantom|Unrepeatable Reads|Dirty Reads|
+---------------+-------+------------------+-----------+
|Read Uncommited|   Y   |         Y        |     Y     |
+---------------+-------+------------------+-----------+
|Read Commited |   Y   |         Y        |     N     |
+---------------+-------+------------------+-----------+
|Repeatable Read|   Y   |         N        |     N     |
+---------------+-------+------------------+-----------+
|Serializable   |   N   |         N        |     N     |
+---------------+-------+------------------+-----------+

#3 Timeout

#4 ReadOnly Transaction
只读事务保证了多条查询SQL的在事务�U�别的读一致性。JDBC和数据库会对只读事务做一些优化�?/FONT>

[1] C.J.Date, An Introduction to Database Systems 7th.

Duran's technical life 2005-09-09 13:09 发表评论

Duran's technical life — Wed, 07 Sep 2005 13:49:00 GMT

iteration::two Cairngorm 0.99 开发指�?BR>@author sakis
@version 0.1

#0
MXML优点�Q��用方便，XML代码��z�易�?BR>�~�点�Q�事件、函数、界面描混在一赗��程序规模大了难于开发维护�?/FONT>

#1
Cairngorm框架是iterationtwo推出的号�U�基于JEE Best Practice的Flex�E�序开发的light-weight framework�?�?light-weight�q�个词还真是��行�?。目前最新版本�ؓ0.99�?/FONT>

Cairngorm的结构如下：
org
└─nevis
    └─cairngorm
        ├─application
        �?nbsp;     CairngormApplication.as
        �?BR>        ├─business
        �?nbsp;     Responder.as
        �?nbsp;     ServiceLocator.as
        �?BR>        ├─commands
        �?nbsp;     Command.as
        �?nbsp;     SequenceCommand.as
        �?BR>        ├─control
        �?nbsp;     Event.as
        �?nbsp;     EventBroadcaster.as
        �?nbsp;     FrontController.as
        �?BR>        ├─model
        �?nbsp;     ModelLocator.as
        �?BR>        ├─view
        �?nbsp;     ViewHelper.as
        �?nbsp;     ViewLocator.as
        �?BR>        └─vo
                ValueObject.as

#2
下面�l�大家简单介�l�Cairngorm的实现思�\�?/FONT>

#2.1
Command/FrontController��Event与Viwe分离�?BR>FrontController实现Singleton模式(以下��写�ؓSP)。所有自定义的Command在要在FrontController构造函��C��实例化�ƈ以关联数�l�的方式注册FrontController#addCommand(eventType:String, commandInstance:Command)。EventBroadcaster实现SP。Event�cȝ��l�构为{type:eventType, data:eventData}。我们通过EventBroadcaster#broadcastEvent(eventType:String, eventData:Object)发布Event。Event发布�?与eventType对应的command instance执行Command#execute(event:Event)�?/FONT>

BTW�Q�在Cairngorm的源码中�Q�eventType、commandName、eventName��L��Q�我�l�一用eventType�?/FONT>

#2.2
ServiceLocator��Remote Service声明与View分离�?BR>ServiceLocator实现SP。在Cairngorm的demo中，又通过Delegate对象解除Command/Responder和ServiceLocator之间的依赖。这个Delegate做的事情其实意义不大�Q�就是调用ServiceLocator中的Method�Q�设�|�莫个Responder为相应远�E�方法的handler。个��得无谓地增加了代码量�Q�而且Delegate对象也没实现SP�Q�也��是说我们每�ơ调用一�ơRemote Service中的Method�Q�都要new一个Delegate对象�Q�实在浪贏V�?/FONT>

#2.3
ViewLocator/ViewHelper��View�Q�MXML�Q�中�Ҏ��的function与View分离�?BR>ViewHelper有点意思，当一个ViewHelper在某个MXML��面中声明时�Q�如。ViewHelper能自动取得所在MXML对象的引用，�q��过ViewLocator#register(id, this:ViewHelper)��自�w�注册到ViewLocator中。ViewLocator实现SP。借助ViewLocator/ViewHelper,我们��可以方便的调用不同MXML��面中的�Ҏ��?/FONT>

#2.4
ModelLocator是一个marker interface�Q�程序中Model可以攑֜�某个ModelLocator方便调用�?/FONT>

#2.5
ValueObject也是一个marker interface, 基本不需要�?/FONT>

#3
Cairngorm.99�l�我们开发Flex�E�序提供了很不错的架构模�?M/V/C/Remote之间可以做到完全解构。但在实际开发时没有必要��L��,代码�l�构清晰有活力就好�?/FONT>

Duran's technical life 2005-09-07 21:49 发表评论

Hibernate一对一兌��实用介绍

Duran's technical life — Tue, 06 Sep 2005 05:16:00 GMT

Hibernate一对一兌��实用介绍

#0
书和文档上写的都不是�Ҏ��楚的。自��p��下来�?/FONT>

#1 Using a PK association

#1.1 POJO with XDolclet annotation
public class Customer {
/**
* @return Returns the shoppingCart.
* @hibernate.many-to-one cascade="delete" column="shopping_cart_id"
* unique="true" foreign-key="FK_SHOPPING_CART__CUSTOMER"
*/
public ShoppingCart getShoppingCart() {
return shoppingCart;
}
}

public class ShoppingCart {
/**
* @return Returns the customer.
* @hibernate.one-to-one property-ref="shoppingCart"
*/
public Customer getCustomer() {
return customer;
}
}

property-ref="shoppingCart" 告诉Hibernate ShoppingCart#customer和Customer#shoppingCart是反向的关系。所以Hibernate知道如何从ShoppingCart#getCustomer中检索到相应的customer对象。取出某个Customer对象�Ӟ��Hibernate会生成DEBUG SQL:324 - 3中的SQL语句�?/FONT>

#1.2 HBM
Customer.hbm.xml
    name="shoppingCart"
    class="ShoppingCart"
    cascade="delete"
    outer-join="auto"
    foreign-key="FK_SHOPPING_CART__CUSTOMER"
    column="shopping_cart_id"
/>

ShoppingCart.hbm.xml
    name="customer"
    class="Customer"
    cascade="none"
    outer-join="auto"
    constrained="false"
    property-ref="shoppingCart"
/>

#1.3 SCHEMA SQL
create table CUSTOMER (
    ID bigint generated by default as identity (start with 1),
    SHOPPING_CART_ID bigint,
    primary key (ID)
)

create table SHOPPING_CART (
ID bigint generated by default as identity (start with 1)
primary key (ID)
)

alter table CUSTOMER
    add constraint FK_SHOPPING_CART__CUSTOMER
    foreign key (SHOPPING_CART_ID)
    references SHOPPING_CART

#1.4 Query SQL
DEBUG SQL:324 - 1
select customer0_.ID as ID, customer0_.SHOPPING_CART_ID as SHOPPING2_3_, customer0_.USERNAME as USERNAME3_, customer0_.PWD as PWD3_
from CUSTOMER customer0_
where customer0_.USERNAME=? and customer0_.PWD=?

DEBUG SQL:324 - 2
select shoppingca0_.ID as ID0_, shoppingca0_.TOTAL as TOTAL8_0_
from SHOPPING_CART shoppingca0_
where shoppingca0_.ID=?

DEBUG SQL:324 - 3
select customer0_.ID as ID1_, customer0_.SHOPPING_CART_ID as SHOPPING2_3_1_, customer0_.USERNAME as USERNAME3_1_, customer0_.PWD as PWD3_1_, shoppingca1_.ID as ID0_, shoppingca1_.TOTAL as TOTAL8_0_
from
CUSTOMER customer0_
left outer join
SHOPPING_CART shoppingca1_
on customer0_.SHOPPING_CART_ID=shoppingca1_.ID
where customer0_.SHOPPING_CART_ID=?

#2 Using a FK association

#2.1 POJO with XDolclet annotation
public class Customer {
/**
* @return Returns the shoppingCart.
* @hibernate.one-to-one cascade="delete"
*/
public ShoppingCart getShoppingCart() {
return shoppingCart;
}
}

public class ShoppingCart {
/**
* @return Returns the id.
* @hibernate.id generator-class="foreign"
* @hibernate.generator-param name="property" value="customer"
*/
public Long getId() {
return id();
}

/**
* @return Returns the customer.
* @hibernate.one-to-one constrained="true" foreign-key="FK_CUSTOMER__SHOPPING_CART"
*/
public Customer getCustomer() {
return customer;
}
}

constrained="true" 告诉Hibernate ShoppingCart的PK�q�应该是一个FK�Q�这个FK引用Customer的PK。还需要多做一点工作，声明ShoppingCart的PK生成�{�略是foreign�Q�对应ShoppingCart#customer。这和上面一句话不是一个意思嘛�Q�FT~~

#2.2 HBM
Customer.hbm.xml
    name="shoppingCart"
    class="ShoppingCart"
    cascade="delete"
    outer-join="auto"
    constrained="false"
/>

ShoppingCart.hbm.xml
    name="id"
    column="id"
    type="java.lang.Long"
>

customer

    name="customer"
    class="Customer"
    cascade="none"
    outer-join="auto"
    constrained="true"
/>

#2.3 SCHEMA SQL
create table CUSTOMER (
ID bigint generated by default as identity (start with 1),
primary key (ID)
)

create table SHOPPING_CART (
    ID bigint not null,
    TOTAL integer,
    primary key (ID)
)

alter table SHOPPING_CART
    add constraint FK_CUSTOMER__SHOPPING_CART
    foreign key (ID)
    references CUSTOMER

#2.4 Query SQL
DEBUG SQL:324 -
select customer0_.ID as ID, customer0_.USERNAME as USERNAME3_, customer0_.PWD as PWD3_
from CUSTOMER customer0_
where customer0_.USERNAME=? and customer0_.PWD=?

DEBUG SQL:324 -
select shoppingca0_.ID as ID0_, shoppingca0_.TOTAL as TOTAL8_0_
from SHOPPING_CART shoppingca0_
where shoppingca0_.ID=?

�q�个“真正”的one-to-one的好处是��条兌��SQL语句�Q�看��C��吗？

Duran's technical life 2005-09-06 13:16 发表评论

Avoid tomcat "out of memory" error

Duran's technical life — Fri, 12 Aug 2005 09:38:00 GMT

1 Open the Apache Tomcat configuration app in sys tray, and on the "Java" tab, bump up the initial memory pool size and the maximum memory pool size to 512 Initial and 768 Max, click Ok.
2 In \Program Files\Apache software Foundation\Tomcat 5.0\bin\catalina.bat, in the last section immediately after "rem Execute Java with the applicable properties", insert this line, set CATALINA_OPTS=-mx1024m. Save the file.

Duran's technical life 2005-08-12 17:38 发表评论

HelloWorld

Duran's technical life — Tue, 09 Aug 2005 01:38:00 GMT

在google里敲了“HelloWolrd”，再点“手气不错”，出来了这样一个页面：http://www2.latech.edu/~acm/HelloWorld.shtml

Hello World!

Welcome to the ACM "Hello World" project. Everyone has seen the Hello World program used as a first exposure to a new language or environment. We are attempting to collect examples for as many languages and related programming environments (shells etc.) as possible.

Aproximate number of examples:204     <----wow~~~
This page has been accessed 33274 times.
Last updated: January 20, 2005

看看C的，�l�典HelloWorld
#include
main()
{
for(;;)
      {
          printf ("Hello World!\n");
      }
}

�q�也是HelloWolrd�Q�！
a 1986 entry from Bruce Holloway:

#include "stdio.h"
#define e 3
#define g (e/e)
#define h ((g+e)/2)
#define f (e-g-h)
#define j (e*e-g)
#define k (j-h)
#define l(x) tab2[x]/h
#define m(n,a) ((n&(a))==(a))

long tab1[]={ 989L,5L,26L,0L,88319L,123L,0L,9367L };
int tab2[]={ 4,6,10,14,22,26,34,38,46,58,62,74,82,86 };

main(m1,s) char *s; {
    int a,b,c,d,o[k],n=(int)s;
    if(m1==1){ char b[2*j+f-g]; main(l(h+e)+h+e,b); printf(b); }
    else switch(m1-=h){
        case f:
            a=(b=(c=(d=g)<            return(m(n,a|c)|m(n,b)|m(n,a|d)|m(n,c|d));
        case h:
            for(a=f;a=e)for(b=g<            return(o[b-g]%n+k-h);
        default:
            if(m1-=e) main(m1-g+e+h,s+g); else *(s+g)=f;
            for(*s=a=f;a        }
}

曄��最短的HelloWorld�Q?A href="mailto:Jari.Arkko@lmf.eua.ericsson.se">Jari.Arkko@lmf.eua.ericsson.se�Q?BR>jar.1.c
char*_="Hello world.\n";

ln -s /dev/tty jar.1.o
cc -c jar.1.c

现在最短的HelloWorld �Q�Jyrki Holopainen�Q?BR>";main(){puts("Hello World!");}char*C=".c
char*_=__FILE__;

Duran's technical life 2005-08-09 09:38 发表评论

Hibernate MySQL 中文��q��问题

Duran's technical life — Fri, 10 Jun 2005 13:35:00 GMT

环境�Q�Hibernate 2.1.7 + MySQL4.1�Q�MySQL的编码已讄��为utf8�Q?BR>问题�Q�通过Hibernate向MySQL写入中文后，通过Hibernate取回数据�Q�在console中打印java对象昄��正常。但在MySQL Query Browser中看到的是�ؕ码，传给前端的Flex也是��q��?BR>原因�Q�Hibernate的基��q�是JDBC�Q�所以一样需要设�|�characterEncoding�Q?BR>解决�Ҏ���Q?BR>在hibernate.cfg.xml中应该这样写

<property name="connection.url">jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=UTF-8property>

如果用hibernate.properties
#hibernate.connection.url jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=UTF-8

ps�Q�处理中文的话，characterEncoding用GBK一样可以�?BR>但字节编码问题最好的解决�Ҏ��q�是�l�一使用UTF-8�Q�！�Q?/FONT>

Duran's technical life 2005-06-10 21:35 发表评论

Duran's technical life — Thu, 19 May 2005 01:54:00 GMT

摘要: 参考package EDU.oswego.cs.dl.util.concurrent 1public interface Sync {2 public void acquire();3 public void release();4... 阅读全文

Duran's technical life 2005-05-19 09:54 发表评论

[�W�记]Hibernate - Parent/Child relationship & inverse usage

Duran's technical life — Thu, 19 May 2005 01:28:00 GMT

Suppose we start with a simple association from Parent to Child.

1<hibernate-mapping package="org.hibernate.auction.model">
2 <class name="Parent" table="PARENT">
3  <id name="id" column="PARENT_ID" type="long">
4   <generator class="native">generator>
5  id>
6  <set name="children">
7   <key column="MY_PARENT_ID" />
8   <one-to-many class="org.hibernate.auction.model.Child" />
9  set>
10 class>
11 <class name="Child" table="CHILD">
12  <id name="id" column="CHILD_ID" type="long">
13   <generator class="native">generator>
14  id>
15  <property name="name" column="NAME" type="string" />
16 class>
17hibernate-mapping>

If we were to execute the following code

1Parent p = new Parent(new HashSet());
2Child c1 = new Child(new String("c1"));
3
4try {
5    session = sessionFactory.openSession();
6    tx = session.beginTransaction();
7    session.save(p);
8    Long pid = p.getId();
9    tx.commit();
10    session.close();
11
12    session = sessionFactory.openSession();
13    tx = session.beginTransaction();
14    Parent pp = (Parent) session.load(Parent.class, pid);
15    pp.getChildren().add(c1);
16    session.save(c1);
17    session.flush();
18    tx.commit();
19
20} catch (HibernateException e) {
21}

Hibernate would issue two SQL statements:
- an INSERT to create the record for c
- an UPDATE to create the link from p to c

Hibernate: insert into PARENT values ( )
Hibernate: select parent0_.PARENT_ID as PARENT_ID0_ from PARENT parent0_ where parent0_.PARENT_ID=?
Hibernate: select children0_.MY_PARENT_ID as MY_PAREN3___, children0_.CHILD_ID as CHILD_ID__, children0_.CHILD_ID as CHILD_ID0_, children0_.NAME as NAME0_ from CHILD children0_ where children0_.MY_PARENT_ID=?

- Hibernate: insert into CHILD (NAME) values (?)
- Hibernate: update CHILD set MY_PARENT_ID=? where CHILD_ID=?

This is not only inefficient, but also violates any NOT NULL constraint on the
MY_PARENT_ID column.

**********1
The underlying cause is that the link (the foreign key parent_id) from p to c is not considered part of the state of the Child object and is therefore not created in the INSERT. So the solution is to make the link part of the Child mapping.
**********1

<many-to-one name="my_parent"
class="org.hibernate.auction.model.Parent" column="MY_PARENT_ID"
not-null="true">
many-to-one>

**********2
Now that the Child entity is managing the state of the link, we tell the collection not to update the link. We use the inverse attribute.
**********2

The following code would be used to add a new Child

1Parent pp = (Parent) session.load(Parent.class, pid);
2pp.getChildren().add(c1);
3c1.setMy_parent(pp); //the link is part of the Child object's state. @see***1
4session.save(c1);

And now, only one SQL INSERT would be issued!
To tighten things up a bit, we could create an addChild() method of Parent.

1public void addChild(Child c) {
2 c.setParent(this);
3 children.add(c);
4}

Now, the code to add a Child looks like

1Parent p = (Parent) session.load(Parent.class, pid);
2Child c = new Child();
3p.addChild(c); // 1.let both side of the association knows each other.
4session.save(c); // 2.save the non-verse side

=========================================================================================
CONCLUSION:
1.The non-inverse(inverse="false") side is responsible to save the in-memory representation (object) to the database .
--- you should save the child: session.save(c);
2.Changes made only to the inverse end of the association are not persisted.
--- you needn't update the parent: //session.update(p);

1session = sessionFactory.openSession();
2tx = session.beginTransaction();
3Parent pp = (Parent) session.load(Parent.class, new Long(1));
4pp.getChildren().add(c1); //the parent(pp) now knowns about the relationship
5c1.setMy_parent(pp); //the child(c1) now knows about the relationship
6
7// when cascade="save-update", update(p) will cause all p's
8// referencing children become persistence(cascade
9// saveOrUpdate() operation to parent's all children).
10// So, it's same as you explicitly call session.save(c1).
11
12// when cascade="none"(default), update(p) will just cause
13// p become persistence.
14// And inverse="true", update(p) just persists p, but not
15// persists the link between p and c1. @see ***2
16session.update(pp);
17//session.save(c1);
18session.flush();
19tx.commit();
20

Hibernate: select parent0_.PARENT_ID as PARENT_ID0_ from PARENT parent0_ where parent0_.PARENT_ID=?
Hibernate: select children0_.MY_PARENT_ID as MY_PAREN3___, children0_.CHILD_ID as CHILD_ID__, children0_.CHILD_ID as CHILD_ID0_, children0_.NAME as NAME0_, children0_.MY_PARENT_ID as MY_PAREN3_0_ from CHILD children0_ where children0_.MY_PARENT_ID=?

1session = sessionFactory.openSession();
2tx = session.beginTransaction();
3Parent pp = (Parent) session.load(Parent.class, new Long(1));
4pp.getChildren().add(c1);
5c1.setMy_parent(pp);
6//session.update(pp);
7
8// when save(c1), because c1 holds a reference to its Parent
9// (my_parent), so p become persistence too.
10session.save(c1); //The relationship will be saved. @see ***1
11session.flush();
12tx.commit();
13

Duran's technical life 2005-05-19 09:28 发表评论

亚洲精品老司机在线观看,亚洲中文字幕乱码熟女在线,亚洲成A∨人片天堂网无码

[�W�记]事务处理

Hibernate一对一兌���实用介绍

Avoid tomcat "out of memory" error

HelloWorld

Hibernate MySQL 中文��q��问题

[�W�记]Hibernate - Parent/Child relationship & inverse usage

Hibernate一对一兌��实用介绍