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Create Struts 2 Application in Eclipse : HTTP Status 500

九宝 — Fri, 20 Apr 2012 18:41:00 GMT

http://viralpatel.net/blogs/2009/12/tutorial-create-struts-2-application-eclipse-example.html

problem:

HTTP Status 500

java.lang.NullPointerException 	
org.apache.struts2.impl.StrutsActionProxy.getErrorMessage(StrutsActionProxy.java:69) 	
com.opensymphony.xwork2.DefaultActionProxy.prepare(DefaultActionProxy.java:185)

resolve problem:
1. struts.xml should under src
2. in struts.xml:
excute"

class="net.viralpatel.struts2.LoginAction">

九宝 2012-04-21 02:41 发表评论

How to check file properties through WMI command line (fw)

九宝 — Wed, 07 Dec 2011 14:29:00 GMT

How to check file properties through WMI command line

24.Sep.2009 | by Gusac | Filed in: Articles, Tutorials

With the lack of Graphical Interface on Windows 2008 Core server there comes a need of performing a lot of task through command line. One of which is checking file properties like file version, path, product verision etc. Luckily we have a command that makes this task simple. On a side note, We can also run the same command on other operating systems like Windows Xp, 2003, vista.

Here is the command:
wmic datafile where name='c:\\windows\\system32\\notepad.exe'

Click here to view the enlarged screenshot

Notice that we have used two backslashes \\ in the file path. Also, notice that the path is enclosed in the single quotes.
The output will be confusing to read in command prompt window. To read and understand it better, we can take the output in text format and read it in notepad.

While doing so, please do NOT wrap the text.
wmic datafile where name='c:\\windows\\system32\\notepad.exe' > out.txt

Click here to view the enlarged screenshot

The output will reveal the file properties like Hidden, Path, Drive, Version Caption, Access rights etc.

To get one particular property of a file we need to modify the command a little bit. We need to use the GET Alias injunction to the command mentioned above. Let's say we want to check the version for the file notepad.exe. The command that is used for this is:
wmic datafile where name='c:\\windows\\system32\\notepad.exe' get version

Similarily, there is a list of properties that can be fetched through this command line. They are:

Access Rights
Caption
Class Name
Compressed
Compression Method
Computer System Class Name
Computer System Name
Creation Date
Current File Open Count
Description
Drive
Eight Dot Three File Name
Encrypted
Encryption Method
File Extension
File Name
File System Class Name
File System Name
File Type
Hidden
Install Date
Last Accessed
Last Modified
Manufacturer
Name
Path
Readable
Should Be Archived
Size
Status
System File
Version
Writeable

九宝 2011-12-07 22:29 发表评论

Windows Authentication

九宝 — Fri, 16 Sep 2011 13:46:00 GMT

from http://www.iis.net/ConfigReference/system.webServer/security/authentication/windowsAuthentication

Overview

The element defines configuration settings for the Internet Information Services (IIS) 7 Windows authentication module. You can use Windows authentication when your IIS 7 server runs on a corporate network that is using Microsoft Active Directory service domain identities or other Windows accounts to identify users. Because of this, you can use Windows authentication whether or not your server is a member of an Active Directory domain.

Windows authentication (formerly named NTLM, and also referred to as Windows NT Challenge/Response authentication) is a secure form of authentication because the user name and password are hashed before being sent across the network. When you enable Windows authentication, the client browser sends a strongly hashed version of the password in a cryptographic exchange with your Web server.

Windows authentication supports two authentication protocols, Kerberos and NTLM, which are defined in the element. When you install and enable Windows authentication on IIS 7, the default protocol is Kerberos. The element can also contain a useKernelMode attribute that configures whether to use the kernel mode authentication feature that is new to Windows Server 2008.

Windows authentication is best suited for an intranet environment for the following reasons:

Client computers and Web servers are in the same domain.
Administrators can make sure that every client browser is Internet Explorer 2.0 or later.
HTTP proxy connections, which are not supported by NTLM, are not required.
Kerberos version 5 requires a connection to Active Directory, which is not feasible in an Internet environment.

New in IIS 7.5

The element was introduced in IIS 7.5, which allows you to configure the settings for the new extended protection features that have been integrated into Windows authentication.

Compatibility

Version	Notes
IIS 7.5	The element was added in IIS 7.5.
IIS 7.0	The element was introduced in IIS 7.0.
IIS 6.0	The element replaces portions of the IIS 6.0 AuthType and AuthFlags metabase properties.

Setup

The default installation of IIS 7 does not include the Windows authentication role service. To use Windows authentication on IIS, you must install the role service, disable Anonymous authentication for your Web site or application, and then enable Windows authentication for the site or application.

Note: After you install the role service, IIS 7 commits the following configuration settings to the ApplicationHost.config file.

Windows Server 2008 or Windows Server 2008 R2

On the taskbar, click Start, point to Administrative Tools, and then click Server Manager.
In the Server Manager hierarchy pane, expand Roles, and then click Web Server (IIS).
In the Web Server (IIS) pane, scroll to the Role Services section, and then click Add Role Services.
On the Select Role Services page of the Add Role Services Wizard, select Windows Authentication, and then click Next.
On the Confirm Installation Selections page, click Install.
On the Results page, click Close.

Windows Vista or Windows 7

On the taskbar, click Start, and then click Control Panel.
In Control Panel, click Programs and Features, and then click Turn Windows Features on or off.
Expand Internet Information Services, then World Wide Web Services, then Security.
Select Windows Authentication, and then click OK.

How To

How to enable Windows authentication for a Web site, Web application, or Web service

Open Internet Information Services (IIS) Manager:
- If you are using Windows Server 2008 or Windows Server 2008 R2:
  - On the taskbar, click Start, point to Administrative Tools, and then click Internet Information Services (IIS) Manager.
- If you are using Windows Vista or Windows 7:
  - On the taskbar, click Start, and then click Control Panel.
  - Double-click Administrative Tools, and then double-click Internet Information Services (IIS) Manager.
In the Connections pane, expand the server name, expand Sites, and then the site, application, or Web service for which you want to enable Windows authentication.
Scroll to the Security section in the Home pane, and then double-click Authentication.
In the Authentication pane, select Windows Authentication, and then click Enable in the Actions pane.

How to enable Extended Protection for Windows authentication

Open Internet Information Services (IIS) Manager:
- If you are using Windows Server 2008 or Windows Server 2008 R2:
  - On the taskbar, click Start, point to Administrative Tools, and then click Internet Information Services (IIS) Manager.
- If you are using Windows Vista or Windows 7:
  - On the taskbar, click Start, and then click Control Panel.
  - Double-click Administrative Tools, and then double-click Internet Information Services (IIS) Manager.
In the Connections pane, expand the server name, expand Sites, and then the site, application, or Web service for which you want to enable Extended Protection for Windows authentication.
Scroll to the Security section in the Home pane, and then double-click Authentication.
In the Authentication pane, select Windows Authentication.
Click Enable in the Actions pane.
Click Advanced Settings in the Actions pane.
When the Advanced Settings dialog box appears, select one of the following options in the Extended Protection drop-down menu:
- Select Accept if you want to enable extended protection while providing down-level support for clients that do not support extended protection.
- Select Required if you want to enable extended protection without providing down-level support.
Click OK to close the Advanced Settings dialog box.

Configuration

The element is configurable at the site, application, or virtual directory level in the ApplicationHost.config file.

Attributes

Attribute	Description
`authPersistNonNTLM`	Optional Boolean attribute. Specifies whether IIS automatically reauthenticates every non-NTLM (for example, Kerberos) request, even those on the same connection. False enables multiple authentications for the same connections. Note: A setting of true means that the client will be authenticated only once on the same connection. IIS will cache a token or ticket on the server for a TCP session that stays established. The default is `false`.
`authPersistSingleRequest`	Optional Boolean attribute. Setting this flag to true specifies that authentication persists only for a single request on a connection. IIS resets the authentication at the end of each request, and forces reauthentication on the next request of the session. The default value is `false`.
`enabled`	Required Boolean attribute. Specifies whether Windows authentication is enabled. The default value is `false`.
`useKernelMode`	Optional Boolean attribute. Specifies whether Windows authentication is done in kernel mode. True specifies that Windows authentication uses kernel mode. Kernel-mode authentication may improve authentication performance and prevent authentication problems with application pools that are configured to use a custom identity. As a best practice, do not disable this setting if you use Kerberos authentication and have a custom identity on the application pool. The default is `true`.

Child Elements

Element	Description
`extendedProtection`	Optional element. Specifies extended protection options for Windows authentication. Note: This element was added in IIS 7.5.
`providers`	Optional element. Specifies security support providers used for Windows authentication.

Configuration Sample

The following default element is configured at the root ApplicationHost.config file in IIS 7.0, and disables Windows authentication by default. It also defines the two Windows authentication providers for IIS 7.0.

The following example enables Windows authentication and disables Anonymous authentication for a Web site named Contoso.

Sample Code

The following examples disable Anonymous authentication for a site named Contoso, then enable Windows authentication for the site.

AppCmd.exe

appcmd.exe set config "Contoso" -section:system.webServer/security/authentication/anonymousAuthentication /enabled:"False" /commit:apphost

appcmd.exe set config "Contoso" -section:system.webServer/security/authentication/windowsAuthentication /enabled:"True" /commit:apphost

Note: You must be sure to set the commit parameter to apphost when you use AppCmd.exe to configure these settings. This commits the configuration settings to the appropriate location section in the ApplicationHost.config file.

C#

using System;
using System.Text;
using Microsoft.Web.Administration;

internal static class Sample {

   private static void Main() {

      using(ServerManager serverManager = new ServerManager()) { 
         Configuration config = serverManager.GetApplicationHostConfiguration();

         ConfigurationSection anonymousAuthenticationSection = config.GetSection("system.webServer/security/authentication/anonymousAuthentication", "Contoso");
         anonymousAuthenticationSection["enabled"] = false;

         ConfigurationSection windowsAuthenticationSection = config.GetSection("system.webServer/security/authentication/windowsAuthentication", "Contoso");
         windowsAuthenticationSection["enabled"] = true;

         serverManager.CommitChanges();
      }
   }
}

VB.NET

Imports System
Imports System.Text
Imports Microsoft.Web.Administration

Module Sample
   Sub Main()
      Dim serverManager As ServerManager = New ServerManager
      Dim config As Configuration = serverManager.GetApplicationHostConfiguration

      Dim anonymousAuthenticationSection As ConfigurationSection = config.GetSection("system.webServer/security/authentication/anonymousAuthentication", "Contoso")
      anonymousAuthenticationSection("enabled") = False

      Dim windowsAuthenticationSection As ConfigurationSection = config.GetSection("system.webServer/security/authentication/windowsAuthentication", "Contoso")
      windowsAuthenticationSection("enabled") = True

      serverManager.CommitChanges()
   End Sub
End Module

JavaScript

var adminManager = new ActiveXObject('Microsoft.ApplicationHost.WritableAdminManager');
adminManager.CommitPath = "MACHINE/WEBROOT/APPHOST";

var anonymousAuthenticationSection = adminManager.GetAdminSection("system.webServer/security/authentication/anonymousAuthentication", "MACHINE/WEBROOT/APPHOST/Contoso");
anonymousAuthenticationSection.Properties.Item("enabled").Value = false;

var windowsAuthenticationSection = adminManager.GetAdminSection("system.webServer/security/authentication/windowsAuthentication", "MACHINE/WEBROOT/APPHOST/Contoso");
windowsAuthenticationSection.Properties.Item("enabled").Value = true;

adminManager.CommitChanges();

VBScript

Set adminManager = CreateObject("Microsoft.ApplicationHost.WritableAdminManager")
adminManager.CommitPath = "MACHINE/WEBROOT/APPHOST"

Set anonymousAuthenticationSection = adminManager.GetAdminSection("system.webServer/security/authentication/anonymousAuthentication", "MACHINE/WEBROOT/APPHOST/Contoso")
anonymousAuthenticationSection.Properties.Item("enabled").Value = False

Set windowsAuthenticationSection = adminManager.GetAdminSection("system.webServer/security/authentication/windowsAuthentication", "MACHINE/WEBROOT/APPHOST/Contoso")
windowsAuthenticationSection.Properties.Item("enabled").Value = True

adminManager.CommitChanges()

九宝 2011-09-16 21:46 发表评论

How To Determine if Your Computer Is 32-Bit or 64-Bit(forward)

九宝 — Thu, 15 Sep 2011 19:34:00 GMT

how to check window version

run: Winver

Here's How:

Open the System Information

Open the Start menu, and click on Programs -> Accessories -> System Tools -> System Information
Look in the System Summary

The System Information tool will display detailed information about your Windows operating system. Once opened it will show the "System Summary" – it’s an overview of your computer and operating system.
Look for the System Type Item

On the right hand side of the window you will see a list of items. Look for the item called "System Type".

The value of this item will tell you whether your computer is 32-bit or 64-bit:
- x86-based PC: It’s a 32-bit computer.
- x64-based PC: It’s a 64-bit computer.

九宝 2011-09-16 03:34 发表评论

ContentProvider分析

九宝 — Fri, 18 Feb 2011 06:51:00 GMT

摘要: ContentProvider何时创徏呢？�q�是一个值得深思的问题�Q?nbsp; 据我�q�两天的了解是在你要用到的时候才会调用ContentProvider的onCreate函数�q�行创徏。你��׃��什么时候叫要用到的时候呢�Q�比如你要查询或删除修改数据库的时候通过ContentResolver的quire或delete来操�U�|��据时��׃��调用ContentProvider的onCreate函数�Q�若已经创徏了数... 阅读全文

九宝 2011-02-18 14:51 发表评论

GestureDetector手势识别�c?(�?

九宝 — Wed, 16 Feb 2011 07:03:00 GMT

View是在onTouchEvent(MotionEvent event)里对用户的动作做了一定的分析�Q�从而通知我们是发生了点击�q�是长按�{�事件�?/span>

我们需要创��Z��?/span>GestureDetector的对象，传入listener对象�Q�view接收到的onTouchEvent中将event传给GestureDetector�q�行分析�Q?/span>listener会回调给我们相应的动作。其�?/span>GestureDetector.SimpleOnGestureListener�Q?/span>Framework帮我们简化了�Q�是实现了上面提到的OnGestureListener�?/span>OnDoubleTapListener两个接口的类�Q�我们只需要��承它�q��写其中我们关心的回调卛_��?/span>

�Q�那么，�q�个�c�d��何��用呢�Q�以下是使用该类的一个范例：

private GestureDetector mGestureDetector;

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

mGestureDetector = new GestureDetector(this, new MyGestureListener());

}

@Override

public boolean onTouchEvent(MotionEvent event) {

return mGestureDetector.onTouchEvent(event);

/* 有关上面�?onTouchEvent�Ҏ��Q�我们可以直接判断MotionEvent的类型，

对于手势�U�d��仅仅捕获ACTION_MOVE卛_��Q?/p>

我们通过参数MotionEvent e1, MotionEvent e2,float distanceX, float distanceY可以获取操作变化�?/p>

比如 distanceX > 0 向右边移动，distanceX < 0 则向左边�Q�distanceY > 0 向上滚动�Q?distanceY < 0 向下滚动�?/span>

}

class MyGestureListener extends GestureDetector.SimpleOnGestureListener{

@Override

public boolean onSingleTapUp(MotionEvent ev) {

Log.d("onSingleTapUp",ev.toString());

return true;

}

@Override

public void onShowPress(MotionEvent ev) {

Log.d("onShowPress",ev.toString());

}

@Override

public void onLongPress(MotionEvent ev) {

Log.d("onLongPress",ev.toString());

}

更多的回调消息，方便的对用户的动作进行响�?/span>

public interface OnGestureListener {

// Touch down时触�?/span>, e�?/span>down时的MotionEvent

boolean onDown(MotionEvent e);

// �?/span>Touch down之后一定时��_��115ms�Q�触发，e�?/span>down时的MotionEvent

void onShowPress(MotionEvent e);

// Touch up时触发，e�?/span>up时的MotionEvent

boolean onSingleTapUp(MotionEvent e);

// 滑动时触发，e1�?/span>down时的MotionEvent�Q?/span>e2�?/span>move时的MotionEvent

boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY);

// �?/span>Touch down之后一定时��_��500ms�Q�触发，e�?/span>down时的MotionEvent

void onLongPress(MotionEvent e);

// 滑动一�D�距��，up时触发，e1�?/span>down时的MotionEvent�Q?/span>e2�?/span>up时的MotionEvent

boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY);

}

public interface OnDoubleTapListener {

// 完成一�ơ单击，�q�确定没有二��M��件后触发�Q?/span>300ms�Q�，e�?/span>down时的MotionEvent

boolean onSingleTapConfirmed(MotionEvent e);

// �W�二�ơ单�?/span>down时触发，e为第一��?/span>down时的MotionEvent

boolean onDoubleTap(MotionEvent e);

// �W�二�ơ单�?/span>down,move�?/span>up旉��触发�Q?/span>e��Z��同时��Z��?/span>MotionEvent

boolean onDoubleTapEvent(MotionEvent e);

}

boolean onDoubleTap(MotionEvent e)

解释�Q�双�ȝ��W�二下Touch down时触�?/div>

boolean onDoubleTapEvent(MotionEvent e)

解释�Q�双�ȝ��W�二下Touch down和up都会触发�Q�可用e.getAction()区分�?/div>

boolean onDown(MotionEvent e)

解释�Q�Touch down时触�?/div>

boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY)

解释�Q�Touch了滑动一点距��d��Q�up时触发�?/div>

void onLongPress(MotionEvent e)

解释�Q�Touch了不�U�d��一直Touch down时触�?/div>

boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY)

解释�Q�Touch了滑动时触发�?/div>

void onShowPress(MotionEvent e)

解释�Q�Touch了还没有滑动时触�?/div>

�Q�与onDown�Q�onLongPress比较,onDown只要Touch down一定立刻触发。而Touchdown后过一会没有滑动先触发onShowPress再是onLongPress�?/div>

所以Touchdown后一直不滑动�Q�onDown->onShowPress->onLongPress�q�个��序触发�?/div>

boolean onSingleTapConfirmed(MotionEvent e)

boolean onSingleTapUp(MotionEvent e)

解释�Q�上面这两个函数都是在touch down后又没有滑动�Q�onScroll�Q�，又没有长按（onLongPress�Q�，然后Touchup时触发�?/div>

点击一下非常快的（不滑动）Touchup�Q?/div>

onDown->onSingleTapUp->onSingleTapConfirmed

点击一下稍微慢点的�Q�不滑动�Q�Touchup�Q?/div>

onDown->onShowPress->onSingleTapUp->onSingleTapConfirmed

九宝 2011-02-16 15:03 发表评论

九宝 — Mon, 14 Feb 2011 03:18:00 GMT

protected void onNewIntent (Intent intent)

Since: API Level 1

This is called for activities that set launchMode to "singleTop" in their package, or if a client used theFLAG_ACTIVITY_SINGLE_TOP flag when calling startActivity(Intent). In either case, when the activity is re-launched while at the top of the activity stack instead of a new instance of the activity being started, onNewIntent() will be called on the existing instance with the Intent that was used to re-launch it.

An activity will always be paused before receiving a new intent, so you can count on onResume() being called after this method.

Note that getIntent() still returns the original Intent. You can use setIntent(Intent) to update it to this new Intent.

在IntentActivity中重写下列方法：onCreate onStart onRestart onResume onPause onStop onDestroy onNewIntent
一、其他应用发Intent�Q�执行下列方法：
I/@@@philn(12410): onCreate
I/@@@philn(12410): onStart
I/@@@philn(12410): onResume

发Intent的方�?
Uri uri = Uri.parse("philn://blog.163.com");
Intent it = new Intent(Intent.ACTION_VIEW, uri);
startActivity(it);

二、接收Intent声明�Q?br style="line-height: 22px; " />                 android:label="@string/testname">

三、如果IntentActivity处于��d��栈的��端�Q�也��是说之前打开�q�的Activity�Q�现在处�?br style="line-height: 22px; " /> I/@@@philn(12410): onPause
I/@@@philn(12410): onStop 状态的�?br style="line-height: 22px; " /> 其他应用再发送Intent的话�Q�执行顺序�ؓ�Q?br style="line-height: 22px; " /> I/@@@philn(12410): onNewIntent
I/@@@philn(12410): onRestart
I/@@@philn(12410): onStart
I/@@@philn(12410): onResume

九宝 2011-02-14 11:18 发表评论

Observer模式在J2EE中的实现 [http://35java.com/zhibo/forum.php?mod=viewthread&tid=108&extra=page%3D3]

九宝 — Sun, 13 Feb 2011 11:24:00 GMT

引言�Q?/span>
         设计模式是经验的文档化。它是对被用来在特定场景下解决一般设计问题的�c�d��怺�通信的对象的描述。更通俗的来��_��它是一个问�?解决�Ҏ��寏V��一旦我们掌握了设计模式�Q�就�{�于拥有了一支强有力的专安��伍。它甚至能够佉K��向对象的新手利用前�h的经验找��责明��的�c�d��对象�Q�从而获得优雅的解决�Ҏ��。由于设计模式也是重构的目标�Q�如果在设计的初期适当地引入设计模式，可以减少重构的工作量�?/span>
   但是�Q�我们也不能陷入模式的陷阱，��Z��使用模式而去套模式，那样会陷入�Ş式主义。我们在使用模式的时候，一定要注意模式的意图（intent�Q�，而不要过多的��d��注模式的实现�l�节�Q�因��些实现细节在特定情况下，可能会发生一些改变。不要顽固地认�ؓ设计模式一书中的类图或实现代码��׃��表了模式本��n�?/span>
   下面�Q�我们来讨论一下�ؓ什么要在分布式、多层系�l�中使用Observer模式�?/span>

多层体系�l�构�Q�multi-tier architecture�Q�：
三层体系�l�构是多层体�pȝ��构中最��单的一�U�，它一般包括：

表示�?presentation)�Q�窗口、报�?
业务逻辑�?business logic)�Q�管理业务过�E�的��d��和规则。它又可以细分�ؓ领域对象层（代表领域概念�Q�和服务层（提供数据库交互、安全性、打印报表）�?/li>
存储�?storage)�Q�持久化存储机制。如数据库服务器�{��?br style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; word-wrap: break-word; " />

图一�Q�三层体�pȝ��?/strong>

   而Java 2�q�_��企业版（J2EE�Q�是一�U�利用Java 2�q�_��来简化诸多与多��企业解决�Ҏ��的开发、部�|�和��理相关的复杂问题的体系�l�构。它是开攄��、基于标准的�q�_��Q�用以开发、部�|�和��理N层结构、面向Web的，以服务器��Z��心的企业�U�应用�?/span>
   ��Z��支持领域对象的复用，�q�且佉K��域对象的接口变更所带来的媄响最��化。我们将领域层（模型�Q�和表示层（视图�Q�相分离�?/span>
   采用模型�Q�视图模式的意义在于�Q?/span>


支持聚合度更高的模型定义�Q��模型的定义可以集中在领域�q�程的定义，而不是图形界面上�?/li>
允许��模型和用户界面�q�行开发�?/li>
使用��L��面的需求变化对领域层所造成的媄响最��化�?/li>
允许建立与一个现有的领域层对象相�q�接的新视图�Q�同时不影响领域层�?/li>
允许一个模型同时有多个视图�Q�例如��用SVG和表根{�?/li>
允许模型层独立于用户界面层执行�?br style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; word-wrap: break-word; " />

   而这恰恰与Observer模式的意囄��d��。因此我们有必要跨层来实现Observer模式�?/span>
   其实�Q�在应用中更多的是采用MVC框架来架构整个企业应用的。在MVC框架中，Model和View之间存在着依赖关系�Q�是Observer模式的典型应用。当然MVC框架�q�包括其它模式如Composite模式和Strategy模式。在J2EE�q�_��中，我们可以把Web Tier�Q�包括Jsp和servelet和JavaBean�Q�看作是表示层，EJB Tier看作是领域层。而controller可能跨距Web Tier�?EJB Tier�?/span>
   在Java�c�d��中采用Java.util.Observable�c�d��Java.util.Observer接口来实现Observer模式�Q�它们在单个的Java VM.中运行的很好�Q�但如果惛_��EJB中��用它们就会有一些问题。这正如我们引言中提到的�Q�模式的具体实现在特定情况下�Q�可能会发生一些改变�?/span>


��g��递还是远�E�引用传递？
                  ��g��递：
在Java RMI中要求所有的参数和返回类型是JAVA的基本类型或实现Java.io.Serilizable的对象。串行化对象通过��g��递（又名拯��传递）�Q�而不是引用传递，�q�意味着在某一层中串行化对象的更�ƈ不自动媄响到其它的对象�?nbsp;
            �q�程引用传递：
对于EJB对象而言�Q�它�׃��个接口（home接口和remote接口�Q�和一个类�l�成。容器会�Ҏ��ejb规范来生成实��C��面两个接口的�c�（我们分别�U�CؓxxxEJBHome对象和xxxEjbObject对象�Q�。在较多的容器的实现�Ҏ��中，xxxEJBHome对象使用了factory模式来创建xxxEjbObject对象�Q�xxxEjbObject对象则采用proxy模式�Q�作为xxxBean的代理类。在生成以上两个对象的同�Ӟ��容器会从部��v文�g中读取关于安全、事务、持久性等服务�q�在xxxEjbObject对象和xxxEJBHome对象中添加以上服务的代码。而且xxxEJBHome对象和xxxEjbObject对象都是分布式对象，我们在此只讨论xxxEjbObject对象。所谓分布式对象�Q�从本质上来�Ԍ��分�ؓ3个部分：object server、skeleton、stub。其中object server和skeleton位于服务器端�Q�而stub位于客户端。Object server负责实现业务逻辑�Q�skeleton负责marshal和unmarshal�Ҏ��{�֐��?nbsp;

图二�Q�分布式对象

   昄��Q�EJB的客��P��调用EJB的对象）可以是�Q何对象，包括EJB和一般的Java�cȝ��x��用�Q何语�a�写的corba客户端�?/span>
   从EJB的客戯��角来看的话，我们只能看到一个home接口、一个remote接口�Q�对于实体bean的话�Q�还可以看见一个主键类�Q�而bean�c�d��客户是不可见的）。但我们从上面的��Q�我们可以知道，对于remote接口中地�Ҏ��调用�Q�实际上是多态地调用XXX_Stub�c�R��即XXX_Stub对象对客户具有可见性（但这�U�可见性是透明的，卛_��户不知道�q�种可见性的存在�Q�。由于，XXX_Stub对象和Object Server实现了相同的接口�Q��ƈ且Object server真正实现了业务逻辑。所以，当在客户端调用XXX_Stub对象的方法时候，XXX_Stub对象通过socket通信机制��方法签名传�l�XXX_Skeleton对象�Q�XXX_Skeleton对象在去委托Object Server完成业务处理逻辑。因此，Object Server本��n发生了改变。我们称XXX_Stub对象是Object Server对象的远�E�引用，�q�认为当分布式对象作为参��C��递的时候，是通过引用传递的�Q�会产生副作�?/span>

九宝 2011-02-13 19:24 发表评论

RMI的定�?�?http://blog.csdn.net/ocean181/archive/2010/09/02/5857273.aspx

九宝 — Sun, 13 Feb 2011 10:46:00 GMT

RMI的定�?/h2>
Java RMI �Q�Remote Method Invocation �q�程�Ҏ��调用�Q�是用Java�?a class="channel_keylink" target="_blank" style="text-decoration: none; color: #336601; ">JDK1.1中实现的�Q�它大大增强了Java开发分布式应用的能力。Java作�ؓ一�U�风靡一时的�|�络开发语�a��Q�其巨大的威力就体现在它强大的开发分布式�|�络应用的能力上�Q�而RMI��是开发百分之癄��Java的网�l�分布式应用�pȝ��的核心解��x��案之一。其实它可以被看作是RPC的Java版本。但是传�l?a class="channel_keylink" target="_blank" style="text-decoration: none; color: #336601; ">RPC�q�不能很好地应用于分布式对象�pȝ��。而Java RMI 则支持存储于不同地址�I�间�?a class="channel_keylink" target="_blank" style="text-decoration: none; color: #336601; ">�E�序�U�对象之间彼此进行通信�Q�实现远�E�对象之间的无缝�q�程调用�?/p>
RMI目前使用Java�q�程消息交换协议JRMP�Q�Java Remote Messaging Protocol�Q�进行通信。JRMP是专为Java的远�E�对象制定的协议。因此，Java RMI��h��Java�?#8220;Write Once,Run Anywhere”的优点，是分布式应用�pȝ��的百分之癄��Java解决�Ҏ��。用Java RMI开发的应用�pȝ��可以部��v在�Q何支�?a class="channel_keylink" target="_blank" style="text-decoration: none; color: #336601; ">JRE�Q�Java Run Environment Java�Q�运�?a class="channel_keylink" target="_blank" style="text-decoration: none; color: #336601; ">环境�Q�的�q�_��上。但�׃��JRMP是专为Java对象制定的，因此�Q�RMI对于用非Java语言开发的应用�pȝ��的支持不��뀂不能与用非Java语言书写的对象进行通信�?/p>
RMI�?a class="channel_keylink" target="_blank" style="text-decoration: none; color: #336601; ">CORBA的关�p?/h2>
RMI 和CORBA常被视�ؓ�怺�竞争�?a class="channel_keylink" target="_blank" style="text-decoration: none; color: #336601; ">技�?/a>�Q�因��Z��者都提供对远�E�分布式对象的透明讉K��。但�q�两�U�技术实际上是相互补充的�Q�一者的长处正好可以弥补另一者的短处。RMI �?CORBA 的结合��生了 RMI-IIOP�Q�RMI-IIOP 是企�?a class="channel_keylink" target="_blank" style="text-decoration: none; color: #336601; ">服务�?/a>�?Java 开发的基础

1997 �q�_��IBM �?Sun Microsystems启动了一��Ҏ��在促�q?Java 作�ؓ企业开发技术的发展的合作计划。两家公司特别着力于如何��?Java 用作服务器端语言�Q�生成可以结合进现有体系�l�构的企业��代码。所需要的��是一�U�远�E�传输技术，它兼�?Java �?RMI�Q�Remote Method Invocation�Q�远�E�方法调用）较少�?a class="channel_keylink" target="_blank" style="text-decoration: none; color: #336601; ">资源占用量和更成熟的 CORBA�Q�Common Object Request Broker Architecture�Q�公共对象请求代理体�pȝ��构）技术的健壮性。出于这一需要，RMI-IIOP问世了，它帮助将 Java 语言推向了目前服务器端企业开发的��L��语言的领先地位�?/p>
RMI的组�?/h2>
一个正常工作的RMI�pȝ��׃��面几个部分组成：

1、远�E�服务的接口定义

2、远�E�服务接口的具体实现

3、桩�Q�Stub�Q�和框架�Q�Skeleton�Q�文�?/p>
4、一个运行远�E�服务的服务�?/p>
5、一个RMI命名服务�Q�它允许客户端去发现�q�个�q�程服务

6、类文�g的提供者（一个HTTP或者FTP服务器）

7、一个需要这个远�E�服务的客户端程�?/p>
RMI的实�?/h2>
下面我们一步一步徏立一个简单的RMI�pȝ��。首先在你的机器里徏立一个新的文件夹�Q�以便放�|�我们创建的文�g�Q��ؓ了简单�v见，我们只��用一个文件夹存放客户端和服务端代码，�q�且在同一个目录下�q�行服务端和客户端�?br />
如果所有的RMI文�g都已�l�设计好了，那么你需要下面的几个步骤�ȝ��成你的系�l�：

1�?nbsp; �~�写�q�且�~�译接口的Java代码
2�?nbsp; �~�写�q�且�~�译接口实现的Java代码
3�?nbsp; 从接口实现类中生�?Stub �?Skeleton �c�L��?br /> 4�?nbsp; �~�写�q�程服务的主�q�行�E�序
5�?nbsp; �~�写RMI的客��L��E�序
6�?nbsp; 安装�q�且�q�行RMI�pȝ��

1、接�?br />
�W�一步就是徏立和�~�译服务接口的Java代码。这个接口定义了所有的提供�q�程服务的功能，下面是源�E�序�Q?br />
   1. //Calculator.java
   2. //define the interface
   3. import java.rmi.Remote;
   4.
   5. public interface Calculator extends Remote
   6. {
   7.     public long add(long a, long b)
   8.         throws java.rmi.RemoteException;
   9.
10.     public long sub(long a, long b)
11.         throws java.rmi.RemoteException;
12.
13.     public long mul(long a, long b)
14.         throws java.rmi.RemoteException;
15.
16.     public long div(long a, long b)
17.         throws java.rmi.RemoteException;
18. }

注意�Q�这个接口��承自Remote�Q�每一个定义的�Ҏ��都必��L��Z��个RemoteException异常对象�?br />
建立�q�个文�g�Q�把它存攑֜�刚才的目录下�Q��ƈ且编译�?br />
>javac Calculator.java

2、接口的具体实现

下一步，我们��p��写远�E�服务的具体实现�Q�这是一个CalculatorImpl�c�L��Ӟ��

   1. //CalculatorImpl.java
   2. //Implementation
   3. import java.rmi.server.UnicastRemoteObject;
   4.
   5. public class CalculatorImpl extends UnicastRemoteObject implements Calculator
   6. {
   7.
   8.     // �q�个实现必须有一个显式的构造函敎ͼ��q�且要抛��Z��个RemoteException异常
   9.     public CalculatorImpl()
10.         throws java.rmi.RemoteException {
11.         super();
12.      }
13.
14.     public long add(long a, long b)
15.         throws java.rmi.RemoteException {
16.         return a + b;
17.      }
18.
19.     public long sub(long a, long b)
20.         throws java.rmi.RemoteException {
21.         return a - b;
22.      }
23.
24.     public long mul(long a, long b)
25.         throws java.rmi.RemoteException {
26.         return a * b;
27.      }
28.
29.     public long div(long a, long b)
30.         throws java.rmi.RemoteException {
31.         return a / b;
32.      }
33. }

同样的，把这个文件保存在你的目录里然后编译他�?br />
�q�个实现�c�M��用了UnicastRemoteObject去联接RMI�pȝ��。在我们的例子中�Q�我们是直接的从UnicastRemoteObject �q�个�c�M��l�承的，事实上�ƈ不一定要�q�样做，如果一个类不是从UnicastRmeoteObject上��承，那必��M��用它的exportObject() �Ҏ��去联接到RMI�?br />
如果一个类�l�承自UnicastRemoteObject�Q�那么它必须提供一个构造函数�ƈ且声明抛��Z��个RemoteException对象。当�q�个构造函数调用了super()�Q�它久激�z�UnicastRemoteObject中的代码完成RMI的连接和�q�程对象的初始化�?br />
3、Stubs 和Skeletons

下一步就是要使用RMI�~�译器rmic来生成桩和框架文�Ӟ��q�个�~�译�q�行在远�E�服务实现类文�g上�?br />
>rmic CalculatorImpl

在你的目录下�q�行上面的命令，成功执行完上面的命��o你可以发��C��个Calculator_stub.class文�g�Q�如果你是��用的Java2SDK�Q�那么你�q�可以发现Calculator_Skel.class文�g�?br />
4、主机服务器

�q�程RMI服务必须是在一个服务器中运行的。CalculatorServer�c�L��一个非常简单的服务器�?br />
   1. //CalculatorServer.java
   2. import java.rmi.Naming;
   3.
   4. public class CalculatorServer {
   5.
   6.    public CalculatorServer() {
   7.      try {
   8.         Calculator c = new CalculatorImpl();
   9.        Naming.rebind("rmi://localhost:1099/CalculatorService", c);
10.       } catch (Exception e) {
11.        System.out.println("Trouble: " + e);
12.       }
13.     }
14.
15.    public static void main(String args[]) {
16.      new CalculatorServer();
17.     }
18. }

建立�q�个服务器程序，然后保存��C��的目录下�Q��ƈ且编译它�?br />
5、客��L��

客户端源代码如下�Q?br />
   //CalculatorClient.java

    import java.rmi.Naming;
    import java.rmi.RemoteException;
    import java.net.MalformedURLException;
   import java.rmi.NotBoundException;

   public class CalculatorClient {

       public static void main(String[] args) {
         try {
             Calculator c = (Calculator)
                              Naming.lookup(
                    "rmi://localhost
                            /CalculatorService");
               System.out.println( c.sub(4, 3) );
            System.out.println( c.add(4, 5) );
               System.out.println( c.mul(3, 6) );
              System.out.println( c.div(9, 3) );
            }
           catch (MalformedURLException murle) {
               System.out.println();
              System.out.println(
                 "MalformedURLException");
               System.out.println(murle);
            }
           catch (RemoteException re) {
              System.out.println();
               System.out.println(
                          "RemoteException");
               System.out.println(re);
           }
          catch (NotBoundException nbe) {
              System.out.println();
               System.out.println(
                          "NotBoundException");
               System.out.println(nbe);
            }
           catch (
               java.lang.ArithmeticException
                                         ae) {
              System.out.println();
              System.out.println(
               "java.lang.ArithmeticException");
             System.out.println(ae);
            }
       }
   }

保存�q�个客户端程序到你的目录下（注意�q�个目录是一开始徏立那个，所有的我们的文仉��在那个目录下�Q�，�q�且�~�译他�?br />
6、运行RMI�pȝ��

现在我们建立了所有运行这个简单RMI�pȝ��所需的文�Ӟ��现在我们�l�于可以�q�行�q�个RMI�pȝ��啦！来��n受吧�?br />
我们是在命��o控制��C��q�行�q�个�pȝ��的，你必��d��启三个控制台�H�口�Q�一个运行服务器�Q�一个运行客��L��Q�还有一个运行RMIRegistry�?br />
首先�q�行注册�E�序RMIRegistry�Q�你必须在包含你刚写的类的那么目录下�q�行�q�个注册�E�序�?br />
>rmiregistry

好，�q�个命��o成功的话�Q�注册程序已�l�开始运行了�Q�不要管他，现在切换到另外一个控制台�Q�在�W�二个控制台里，我们�q�行服务器CalculatorService�Q�因为RMI的安全机制将在服务端发生作用,所以你必须增加一条安全策略。以下是对应安全�{�略的例�?br /> grant {
permission java.security.AllPermission "", "";
};

注意:�q�是一条最��单的安全�{�略,它允�怓Q何�h做�Q何事,对于你的更加关键性的应用,你必��L��定更加详�l�安全策略�?br />
现在��Z��q�行服务端，你需要除客户�c?CalculatorClient.class)之外的所有的�c�L��件。确认安全策略在policy.txt文�g之后,使用如下命��o来运行服务器�?br />
> java -Djava.security.policy=policy.txt CalculatorServer

�q�个服务器就开始工作了�Q�把接口的实现加载到内存�{�待客户端的联接。好现在切换到第三个控制収ͼ�启动我们的客��L��?br />
��Z��在其他的机器�q�行客户端程序你需要一个远�E�接�?Calculator.class) 和一个stub(CalculatorImpl_Stub.class)�?使用如下命��o�q�行客户�?br />
> java -Djava.security.policy=policy.txt CalculatorClient

如果所有的�q�些都成功运行，你应该看��C��面的输出�Q?br /> 1
9
18
3

如果你看��C��上面的输出，恭喜你，你成功了�Q�你已经成功的创��Z��一个RMI�pȝ��Q��ƈ且��他正��工作了。即使你�q�行在同一个计��机上，RMI�q�是使用了你的网�l�堆栈和TCP/IP去进行通讯�Q��ƈ且是�q�行在三个不同的Java虚拟��Z��。这已经是一个完整的RMI�pȝ��?/p>

九宝 2011-02-13 18:46 发表评论

JavaBean PropertyChange 之设计模式Observer(�?

九宝 — Sun, 13 Feb 2011 10:26:00 GMT
     摘要: java语言里包含了许多对设计模式的直接支持�Q�如command模式�Q�agent模式�Q�observer模式�{�。虽然java提供的对�q�些模式的支持很��单，不能满��比较复杂的应用。但在简单的场景下，使用�q�些�c�d��往能够得到立杆见媄的效果。所以，如果没有什么特�D�需求，�q�是最好利用java的这些类�?        Observ...  阅读全文

九宝 2011-02-13 18:26 发表评论