how to resolve the question?

msgsnd 2004-06-10 02:04:57
int *test(){
int *a=NULL;
a=malloc(sizeof(a));
*a=200;
return a;
}

void main(){
int *a=NULL;
int b=0;
a=test();
b=(*a)++;
printf("%d",a);
free(a);
}
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leonchew 2004-06-10
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//你可能是这个意思吧
#include <stdio.h>

int *test(){
int *a=NULL;
a=(int*)malloc(sizeof(a));//加强制类型转换int*
*a=200;
return a;
}

void main(){
int *a=NULL;
int b=0;
a=test();
b=++(*a);// ++ 在前面,b才能是 *a+1了,否则 结果是200
printf("%d\n",b);//是 b
free(a);
return;
}

结果: 201

junnyfeng 2004-06-10
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有什么问题
CurrPorts v2.10 Copyright (c) 2004 - 2013 Nir Sofer Web site: http://www.nirsoft.net Description =========== CurrPorts displays the list of all currently opened TCP/IP and UDP ports on your local computer. For each port in the list, information about the process that opened the port is also displayed, including the process name, full path of the process, version information of the process (product name, file description, and so on), the time that the process was created, and the user that created it. In addition, CurrPorts allows you to close unwanted TCP connections, kill the process that opened the ports, and save the TCP/UDP ports information to HTML file , XML file, or to tab-delimited text file. CurrPorts also automatically mark with pink color suspicious TCP/UDP ports owned by unidentified applications (Applications without version information and icons) Versions History ================ * Version 2.10: o When saving the opened ports from command-line, CurrPorts now uses the same columns order saved in the .cfg file. * Version 2.09: o Fixed bug from version 2.08: Some filters stopped working... * Version 2.08: o Added support for filtering by process ID (In Advanced Filters window), for example: include:process:327 * Version 2.07: o Fixed the flickering on automatic refresh. * Version 2.06: o Fixed issue: The properties dialog-box and other windows opened in the wrong monitor, on multi-monitors system. * Version 2.05: o Added support for GeoLite City database. You can now download the GeoLite City database (GeoLiteCity.dat.gz), put it in the same folder of cports.exe, and CurrPorts will automatically use it to get the country/city information for every remote IP address. * Version 2.02: o CurrPorts now displays a simple error message if it fails to close one or more TCP connections. * Version 2.01: o The 'Remote Address' and 'Local Address' columns are now sorted by the IP address numerically. (In previous versions they were sorted alphabetically) * Version 2.00: o Added optional fifth parameter to the /close command-line option, which allows you to specify a process name (e.g: firefox.exe) * Version 1.97: o The 'Use DNS Cache For Host Names' option is now turned off by default, because it seems that reading the DNS cache causes a memory leak on some Windows 7/x64 systems. * Version 1.96: o Fixed bug: CurrPorts randomly failed to display remote port numbers of IPv6 connections. * Version 1.95: o Added 'Use DNS Cache For Host Names' option. When it's turned on, CurrPorts uses the DNS cache of Windows to resolve remote IP addresses. * Version 1.94: o Added 'Custom' AutoRefresh option under Options -> Auto Refresh. The number of seconds for the Custom AutoRefresh can be set in the Advanced Options window (Ctrl+O) o Fixed the problem with sending the data to stdout (when the filename is empty string). * Version 1.93: o Updated the internal country names (added more 14 countries) that are used for displaying the country name in the 'Remote IP Country' column. * Version 1.92: o When choosing 'Clear Log File' option, CurrPorts now asks you whether you want to clear the log, in order to avoid from clearing the log file by mistake. * Version 1.91: o Added 'Beep On New Ports' option. * Version 1.90: o Added 'Tray Balloon On New Ports' option. When both this option and 'Put Icon On Tray' option are turned on, every new port detected by CurrPorts will be displayed in a tray balloon. (If the TCP/UDP port is filtered by the other CurrPorts options and it's not displayed in the main window, it won't be displayed in the tray balloon.) * Version 1.87: o Improved the 'User Name' column. If you run CurrPorts as administrator, this column will display the user name for all processes. (In previous versions, CurrPorts failed to detect processes created by other users, even when you run it as Administrator) * Version 1.86: o Added 'Mark Odd/Even Rows' option, under the View menu. When it's turned on, the odd and even rows are displayed in different color, to make it easier to read a single line. * Version 1.85: o Added command-line options to control the settings under the Options and View menus: /MarkPorts, /DisplayUdpPorts, /DisplayTcpPorts, /DisplayClosedPorts, and more... * Version 1.83: o Added 'Add Header Line To CSV/Tab-Delimited File' option. When this option is turned on, the column names are added as the first line when you export to csv or tab-delimited file. * Version 1.82: o Added 'Resize Columns On Every Refresh' option, which allows you to automatically resize the columns according to the text length on every refresh. * Version 1.81: o Added more include/exclude filter options in the context menu of CurrPorts. * Version 1.80: o Added custom log line option (In 'Advanced Options' window), which allows you to set the format of the log line and put in it any column value you like. * Version 1.76: o Added 'One-Click Tray Icon' option. When it's checked and you use the tray icon option, one click on the tray icon with the left mouse button will open CurrPorts. (Without this option, double-click is required) * Version 1.75: o Added 'Exclude Selected Processes In Filters' option in the context menu. o Added accelerator key for 'Include Selected Processes In Filters' option. o Fixed bug 'Include Selected Processes In Filters' option: failed to work on system process. o Added 'Disable All Filters' option to easily toggle between active filter state and no filter state, as an alternative for 'Clear All Filters', which doesn't allow you to return back the filters. * Version 1.70: o Added /sort command-line option for sorting the connections list saved from command-line. * Version 1.66: o Fixed issue: When CurrPorts window is hidden and there is an icon in the taskbar, running CurrPorts again will open the existing instance of CurrPorts, instead of creating another one. * Version 1.65: o Added drag And drop icon in the toolbar that allows to to easily filter by the desired application. Simply drag the target icon into the window of the application, and CurrPorts will display only the opened ports of this application. * Version 1.60: o Added new column: Window Title (The window title of the process) o Added 'Clear All Filters' option. o Added 'Include Selected Processes In Filters' option. Allows you to easily filter by selected processes. * Version 1.56: o Added new option: Ask before any action. (If you uncheck this option, CurrPorts won't ask you any question before closing ports/applications) * Version 1.55: o Added number of remote connections to the status bar. o Added ports information in the tray icon tooltip. * Version 1.51: o Fixed bug: In rare cases, exception window may appear when starting CurrPorts. * Version 1.50: o Added 'Display Port In Address' option. When this option is checked, the addresses will be displayed in 'address:port' format. * Version 1.48: o Fixed the Alt+1 accelerator key. * Version 1.47: o Added AutoRefresh every 1 second. * Version 1.46: o Automatically launch IPNetInfo when it's in the same folder of CurrPorts. * Version 1.45: o Added 'Remote IP Country' column that displays the country name of the remote IP address (requires to download an external file from here) * Version 1.41: o Fixed bug: CurrPorts failed to display the current Auto Refresh status in Menu. * Version 1.40: o Added support for IPv6. * Version 1.37: o Fixed bug: CurrPorts failed to display process information when running under Windows Vista with non-admin user. o Added Module Filename column (works only on XP/SP2) * Version 1.36: o Fixed bug: The main window lost the focus when the user switched to another application and then returned back to CurrPorts. * Version 1.35: o Fixed bug in saving as comma-delimited file when field values contained comma character. * Version 1.34: o New Option: Remember Last Filter (The filter is saved in cports_filter.txt) * Version 1.33: o Added support for saving comma-delimited (.csv) files. o Added new command-line option: /scomma * Version 1.32: o New Option: Start CurrPorts As Hidden (Only when 'Put Icon On Tray' is turned on) o New Option: Copy Remote IP Address (F2). * Version 1.31: o Fixed bug: TCP and UDP ports with the same number and in the same process merged into one item. * Version 1.30: o New column: Added On - Displays the date that the specified connection was added. o New Option: Put Icon On Tray. o New Option: Log File. * Version 1.20: o Added support for filters. o The settings of CurrPorts utility is now saved to cfg file instead of using the Registry. o New command-line options. o You can now send the information to stdout by specifying an empty filename ("") in the command-line. o Added support for x64. * Version 1.11: o Added support for process information in Vista. * Version 1.10: o A tooltip is displayed when a string in a column is longer than the column length. * Version 1.09: o /close command-line parameter - Close a connection from command-line * Version 1.08: o Fixed columns order bug. * Version 1.07: o New option: Resolve the remote IP addresses. * Version 1.06: o New column: Process Attributes - Display the file attributes of the process (H for hidden, R for read-only, and so on) o Added support for working with IPNetInfo utility * Version 1.05: o Fixed bug: identify process path starting with '\??\' * Version 1.04: o Added more accelerator keys. o Added support for Windows XP visual styles. * Version 1.03: o New Option: Display Listening o New Option: Display Established o New Option: Display Items With Unknown State o New Option: Display Items Without Remote Address * Version 1.02: o Fixed bug: "Exception C0000005" message when running CurrPorts on Windows NT/2000 without administrator rights. o New column: "Process Services" - Displays the list of services of a process. * Version 1.01: o The 'Copy Selected Items' option now copies the ports data in tab-delimited format, so you can instantly paste the data into your Excel worksheet. o Improvment in ports to process binding under Windows 2000. Process information is now also displayed under Windows NT. * Version 1.00: First release. System Requirements =================== This utility works perfectly under Windows NT, Windows 2000, Windows XP, Windows Server 2003, Windows Server 2008, Windows Vista, and Windows 7. There is also a separated download of CurrPorts for x64 versions of Windows. If you want to use this utility on Windows NT, you should install psapi.dll in your system32 directory. You can also use this utility on older versions of Windows (Windows 98/ME), but in these versions of Windows, the process information for each port won't be displayed. Using CurrPorts =============== CurrPorts utility is a standalone executable, and it doesn't require any installation process or additional DLLs. In order to start using it, just copy the executable file (cports.exe) to any folder you like, and run it. The main window of CurrPorts displays the list of all currently opened TCP and UDP ports. You can select one or more items, and then close the selected connections, copy the ports information to the clipboard, or save it to HTML/XML/Text file. If you don't want to view all available columns, or you want to change the order of the columns on the screen and in the files you save, select 'Choose Column' from the View menu, and select the desired columns and their order. In order to sort the list by specific column, click on the header of the desired column. The Options Menu ================ The following options are available under the Options menu: * Display Listening: If this option is enabled, all listening ports are displayed. * Display Established: If this option is enabled, all established connections are displayed. * Display Closed: If this option is enabled, closed ports (with 'Time Wait', 'Close Wait', or 'Closed' state) are displayed. * Display Items With Unknown State: If this option is enabled, items with unknown state (the state column is empty) are displayed. * Display Items Without Remote Address: If this option is enabled, disconnected ports with no remote address are displayed. * Display TCP Ports: If this option is disabled, TCP ports won't be displayed in the ports list. * Display UDP Ports: If this option is disabled, UDP ports won't be displayed in the ports list. * Mark Ports Of Unidentified Applications: If this option is enabled, all TCP/UDP ports that opened by applications with no version information and with no icons, are automatically marked with pink color. If you have on your system one or more ports marked with pink color, you should deeply check the processes that created these ports. It could be only an innocent application that simply doesn't contain any icons and version information (For example: the executables of MySQL and Oracle servers don't contain any icons or version info, so if you have MySQL/Oracle servers on your system, the ports they open will be marked.) , but it can also be a trojan or other unwanted application that infiltrated into your system. * Mark New/Modified Ports: If this option is enabled, each time the ports list is refreshed, all newly added ports and existing ports with changes are marked with green color. * Auto Refresh: Allows you to automatically refresh the opened ports list each 2, 4, 6, 8, or 10 seconds. * Sort On Auto Refresh If this option is enabled, the entire ports list is sorted each time that the list is refreshed automatically. Otherwise, new/modified ports are added to the bottom of the list. The 'Remote IP Country' column ============================== In order to watch the countries of the remote IP addresses, you have to download the latest IP To Country file from here. You have the put the 'IpToCountry.csv' file in the same folder of cports.exe You can also use the GeoLite City database. Simply download the GeoLite City in Binary / gzip (GeoLiteCity.dat.gz) and put it in the same folder of cports.exe If you want to get faster loading process, extract the GeoLiteCity.dat from the GeoLiteCity.dat.gz and put it in the same folder of cports.exe Using Filters ============= Starting from version 1.20, you can monitor only the opened ports that you need, by using the "Advanced Filters" option (Options -> Advanced Filters). In the filters dialog-box, you can add one or more filter strings (separated by spaces, semicolon, or CRLF) in the following syntax: [include | exclude] : [local | remote | both | process] : [tcp | udp | tcpudp] : [IP Range | Ports Range] Here's some examples that demonstrate how to create a filter string: * Display only packets with remote tcp port 80 (Web sites): include:remote:tcp:80 * Display only packets with remote tcp port 80 (Web sites) and udp port 53 (DNS): include:remote:tcp:80 include:remote:udp:53 * Display only packets originated from the following IP address range: 192.168.0.1 192.168.0.100: include:remote:tcpudp:192.168.0.1-192.168.0.100 * Display only TCP and UDP packets that use the following port range: 53 - 139: include:both:tcpudp:53-139 * Filter most BitTorrent packets (port 6881): exclude:both:tcpupd:6881 * Display only the opened ports of FireFox browser: include:process:firefox.exe Integration with IPNetInfo utility ================================== If you want to get more information about the remote IP address displayed in CurrPorts utility, you can utilize the Integration with IPNetInfo utility in order to easily view the IP address information from WHOIS servers: 1. Download and run the latest version of IPNetInfo utility. (If you have IPNetInfo with version prior to v1.06, you must download the newer version.) 2. Select the desired connections, and then choose "IPNetInfo" from the File menu (or simply click Ctrl+I). 3. IPNetInfo will retrieve the information about remove IP addresses of the selected connections. Log File ======== Starting from version 1.30, CurrPorts allows you to save all changes (added and removed connections) into a log file. In order to start writing to the log file, check the 'Log Changes' option under the File menu. By default, the log file is saved as 'cports.log' in the same folder that cports.exe is located. You can change the default log filename by setting the 'LogFilename' entry in cports.cfg file. Be aware that the log file is updated only when you refresh the ports list manually, or when the 'Auto Refresh' option is turned on. Custom Log Line =============== Starting from version 1.80, you can set the format of the lines in the log file according to your needs. In order to use this feature, go to 'Advanced Options' window (Ctrl+O), check the custom log line option, type the desired format string. In the format string, you can use the following variables: %Process_Name% %Protocol% %Local_Port% %Local_Address% %Remote_Port% %Remote_Address% %Process_Path% %Process_ID% %State% %Product_Name% %File_Description% %File_Version% %Company% %Process_Created_On% %Local_Port_Name% %Remote_Port_Name% %User_Name% %Process_Services% %Process_Attributes% %Remote_Host_Name% %Added_On% %Module_Filename% %Remote_IP Country% %Window_Title% You can also set the minimum number of characters for the column value, for example: %Process_Name.25% (Fill with spaces - up to 25 characters) Notice: %Remote_Host_Name% variable is not displayed on newly added connections, because the IP address resolving is asynchronous operation, and the host name is still not available when the log line is added. Command-Line Options ==================== /stext Save the list of all opened TCP/UDP ports into a regular text file. /stab Save the list of all opened TCP/UDP ports into a tab-delimited text file. /scomma Save the list of all opened TCP/UDP ports into a comma-delimited text file. /stabular Save the list of all opened TCP/UDP ports into a tabular text file. /shtml Save the list of all opened TCP/UDP ports into HTML file (Horizontal). /sverhtml Save the list of all opened TCP/UDP ports into HTML file (Vertical). /sxml Save the list of all opened TCP/UDP ports to XML file. /sort This command-line option can be used with other save options for sorting by the desired column. If you don't specify this option, the list is sorted according to the last sort that you made from the user interface. The parameter can specify the column index (0 for the first column, 1 for the second column, and so on) or the name of the column, like "Remote Port" and "Remote Address". You can specify the '~' prefix character (e.g: "~Remote Address") if you want to sort in descending order. You can put multiple /sort in the command-line if you want to sort by multiple columns. Examples: cports.exe /shtml "f:\temp\1.html" /sort 2 /sort ~1 cports.exe /shtml "f:\temp\1.html" /sort "Protocol" /sort "~Remote Address" /nosort When you specify this command-line option, the list will be saved without any sorting. /filter Start CurrPorts with the specified filters. If you want to specify more than one filter, use the ';' character as a delimiter. /cfg Start CurrPorts with the specified config file. /MarkPorts /DisplayUdpPorts /DisplayTcpPorts /DisplayClosedPorts /MarkNewModifiedPorts /SortOnAutoRefresh /AlwaysOnTop /AskBefore /DisplayIPv6Ports /DisplayListening /DisplayEstablished /DisplayNoState /DisplayNoRemoteIP /ResolveAddresses /RememberLastFilter /DisplayPortInAddress /AutoRefresh, /ShowInfoTip /TrayIcon /TrayIconOneClick /StartAsHidden /LogChanges /LogFilename /DisabledFilters /AddExportHeaderLine You can use all these parameters to control the options that are available under the Options and View menus. For example, if you want to start CurrPorts with 'Display UDP Ports' turned off and 'Display Closed' turned on: cports.exe /DisplayUdpPorts 0 /DisplayClosedPorts 1 You can also use these parameters in conjunction with all save parameters. For example: If you want to save into tab-delimited file only the UDP ports: cports.exe /DisplayUdpPorts 1 /DisplayTcpPorts 0 /stab "c:\temp\udp.txt" Here's some examples: * Save all opened TCP/IP ports created by Internet Explorer browser to HTML file: cports.exe /filter "include:process:iexplore" /shtml "c:\temp\ports.html" * Add all opened ports information to ports.txt (as tab-delimited text file). This example only works when running it from a command-prompt window. cports.exe /stab "" >> c:\temp\cports1.txt * Start CurrPorts with filter that will only display the opened ports of Internet Explorer and FireFox: cports.exe /filter "include:process:firefox;include:process:iexplore" Closing a Connection From Command-Line ====================================== Starting from version 1.09, you can close one or more connections from command-line, by using /close parameter. The syntax of /close command: /close {Process Name} For each parameter, you can specify "*" in order to include all ports or addresses. The process name is an optional parameter. If you specify a process, only the ports of the specified process will be closed. Examples: * Close all connections with remote port 80 and remote address 192.168.1.10: /close * * 192.168.1.10 80 * Close all connections with remote port 80 (for all remote addresses): /close * * * 80 * Close all connections to remote address 192.168.20.30: /close * * 192.168.20.30 * * Close all connections with local port 80: /close * 80 * * * Close all connections of Firefox with remote port 80: /close * * * 80 firefox.exe Translating CurrPorts To Another Language ========================================= CurrPorts allows you to easily translate all menus, dialog-boxes, and other strings to other languages. In order to do that, follow the instructions below: 1. Run CurrPorts with /savelangfile parameter: cports.exe /savelangfile A file named cports_lng.ini will be created in the folder of CurrPorts utility. 2. Open the created language file in Notepad or in any other text editor. 3. Translate all menus, dialog-boxes, and string entries to the desired language. 4. After you finish the translation, Run CurrPorts, and all translated strings will be loaded from the language file. If you want to run CurrPorts without the translation, simply rename the language file, or move it to another folder. License ======= This utility is released as freeware. You are allowed to freely distribute this utility via floppy disk, CD-ROM, Internet, or in any other way, as long as you don't charge anything for this. If you distribute this utility, you must include all files in the distribution package, without any modification ! Disclaimer ========== The software is provided "AS IS" without any warranty, either expressed or implied, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose. The author will not be liable for any special, incidental, consequential or indirect damages due to loss of data or any other reason. Feedback ======== If you have any problem, suggestion, comment, or you found a bug in my utility, you can send a message to nirsofer@yahoo.com
1:外文原文 Struts——an open-source MVC implementation This article introduces Struts, a Model-View-Controller implementation that uses servlets and JavaServer Pages (JSP) technology. Struts can help you control change in your Web project and promote specialization. Even if you never implement a system with Struts, you may get some ideas for your future servlets and JSP page implementation. Introduction Kids in grade school put HTML pages on the Internet. However, there is a monumental difference between a grade school page and a professionally developed Web site. The page designer (or HTML developer) must understand colors, the customer, product flow, page layout, browser compatibility, image creation, JavaScript, and more. Putting a great looking site together takes a lot of work, and most Java developers are more interested in creating a great looking object interface than a user interface. JavaServer Pages (JSP) technology provides the glue between the page designer and the Java developer. If you have worked on a large-scale Web application, you understand the term change. Model-View-Controller (MVC) is a design pattern put together to help control change. MVC decouples interface from business logic and data. Struts is an MVC implementation that uses Servlets 2.2 and JSP 1.1 tags, from the J2EE specifications, as part of the implementation. You may never implement a system with Struts, but looking at Struts may give you some ideas on your future Servlets and JSP implementations. Model-View-Controller (MVC) JSP tags solved only part of our problem. We still have issues with validation, flow control, and updating the state of the application. This is where MVC comes to the rescue. MVC helps resolve some of the issues with the single module approach by dividing the problem into three categories: • Model The model contains the core of the application's functionality. The model encapsulates the state of the application. Sometimes the only functionality it contains is state. It knows nothing about the view or controller. • View The view provides the presentation of the model. It is the look of the application. The view can access the model getters, but it has no knowledge of the setters. In addition, it knows nothing about the controller. The view should be notified when changes to the model occur. • Controller The controller reacts to the user input. It creates and sets the model. MVC Model 2 The Web brought some unique challenges to software developers, most notably the stateless connection between the client and the server. This stateless behavior made it difficult for the model to notify the view of changes. On the Web, the browser has to re-query the server to discover modification to the state of the application. Another noticeable change is that the view uses different technology for implementation than the model or controller. Of course, we could use Java (or PERL, C/C++ or what ever) code to generate HTML. There are several disadvantages to that approach: • Java programmers should develop services, not HTML. • Changes to layout would require changes to code. • Customers of the service should be able to create pages to meet their specific needs. • The page designer isn't able to have direct involvement in page development. • HTML embedded into code is ugly. For the Web, the classical form of MVC needed to change. Figure 4 displays the Web adaptation of MVC, also commonly known as MVC Model 2 or MVC 2. The ActionServlet class Do you remember the days of function mappings? You would map some input event to a pointer to a function. If you where slick, you would place the configuration information into a file and load the file at run time. Function pointer arrays were the good old days of structured programming in C. Life is better now that we have Java technology, XML, J2EE, and all that. The Struts Controller is a servlet that maps events (an event generally being an HTTP post) to classes. And guess what -- the Controller uses a configuration file so you don_t have to hard-code the values. Life changes, but stays the same. ActionServlet is the Command part of the MVC implementation and is the core of the Framework. ActionServlet (Command) creates and uses Action, an ActionForm, and ActionForward. As mentioned earlier, the struts-config.xml file configures the Command. During the creation of the Web project, Action and ActionForm are extended to solve the specific problem space. The file struts-config.xml instructs ActionServlet on how to use the extended classes. There are several advantages to this approach: • The entire logical flow of the application is in a hierarchical text file. This makes it easier to view and understand, especially with large applications. • The page designer does not have to wade through Java code to understand the flow of the application. • The Java developer does not need to recompile code when making flow changes. Command functionality can be added by extending ActionServlet. The ActionForm class ActionForm maintains the session state for the Web application. ActionForm is an abstract class that is sub-classed for each input form model. When I say input form model, I am saying ActionForm represents a general concept of data that is set or updated by a HTML form. For instance, you may have a UserActionForm that is set by an HTML Form. The Struts framework will: • Check to see if a UserActionForm exists; if not, it will create an instance of the class. • Struts will set the state of the UserActionForm using corresponding fields from the HttpServletRequest. No more dreadful request.getParameter() calls. For instance, the Struts framework will take fname from request stream and call UserActionForm.setFname(). • The Struts framework updates the state of the UserActionForm before passing it to the business wrapper UserAction. • Before passing it to the Action class, Struts will also conduct form state validation by calling the validation() method on UserActionForm. Note: This is not always wise to do. There might be ways of using UserActionForm in other pages or business objects, where the validation might be different. Validation of the state might be better in the UserAction class. • The UserActionForm can be maintained at a session level. Notes: • The struts-config.xml file controls which HTML form request maps to which ActionForm. • Multiple requests can be mapped UserActionForm. • UserActionForm can be mapped over multiple pages for things such as wizards. The Action class The Action class is a wrapper around the business logic. The purpose of Action class is to translate the HttpServletRequest to the business logic. To use Action, subclass and overwrite the process() method. The ActionServlet (Command) passes the parameterized classes to ActionForm using the perform() method. Again, no more dreadful request.getParameter() calls. By the time the event gets here, the input form data (or HTML form data) has already been translated out of the request stream and into an ActionForm class. Struts, an MVC 2 implementation Struts is a set of cooperating classes, servlets, and JSP tags that make up a reusable MVC 2 design. This definition implies that Struts is a framework, rather than a library, but Struts also contains an extensive tag library and utility classes that work independently of the framework. Figure 5 displays an overview of Struts. Struts overview • Client browser An HTTP request from the client browser creates an event. The Web container will respond with an HTTP response. • Controller The Controller receives the request from the browser, and makes the decision where to send the request. With Struts, the Controller is a command design pattern implemented as a servlet. The struts-config.xml file configures the Controller. • Business logic The business logic updates the state of the model and helps control the flow of the application. With Struts this is done with an Action class as a thin wrapper to the actual business logic. • Model state The model represents the state of the application. The business objects update the application state. ActionForm bean represents the Model state at a session or request level, and not at a persistent level. The JSP file reads information from the ActionForm bean using JSP tags. • View The view is simply a JSP file. There is no flow logic, no business logic, and no model information -- just tags. Tags are one of the things that make Struts unique compared to other frameworks like Velocity. Note: "Think thin" when extending the Action class. The Action class should control the flow and not the logic of the application. By placing the business logic in a separate package or EJB, we allow flexibility and reuse. Another way of thinking about Action class is as the Adapter design pattern. The purpose of the Action is to "Convert the interface of a class into another interface the clients expect. Adapter lets classes work together that couldn_t otherwise because of incompatibility interface" (from Design Patterns - Elements of Reusable OO Software by Gof). The client in this instance is the ActionServlet that knows nothing about our specific business class interface. Therefore, Struts provides a business interface it does understand, Action. By extending the Action, we make our business interface compatible with Struts business interface. (An interesting observation is that Action is a class and not an interface. Action started as an interface and changed into a class over time. Nothing's perfect.) The Error classes The UML diagram also included ActionError and ActionErrors. ActionError encapsulates an individual error message. ActionErrors is a container of ActionError classes that the View can access using tags. ActionErrors is Struts way of keeping up with a list of errors. The ActionMapping class An incoming event is normally in the form of an HTTP request, which the servlet Container turns into an HttpServletRequest. The Controller looks at the incoming event and dispatches the request to an Action class. The struts-config.xml determines what Action class the Controller calls. The struts-config.xml configuration information is translated into a set of ActionMapping, which are put into container of ActionMappings. (If you have not noticed it, classes that end with s are containers) The ActionMapping contains the knowledge of how a specific event maps to specific Actions. The ActionServlet (Command) passes the ActionMapping to the Action class via the perform() method. This allows Action to access the information to control flow. ActionMappings ActionMappings is a collection of ActionMapping objects. Struts pros • Use of JSP tag mechanism The tag feature promotes reusable code and abstracts Java code from the JSP file. This feature allows nice integration into JSP-based development tools that allow authoring with tags. • Tag library Why re-invent the wheel, or a tag library? If you cannot find something you need in the library, contribute. In addition, Struts provides a starting point if you are learning JSP tag technology. • Open source You have all the advantages of open source, such as being able to see the code and having everyone else using the library reviewing the code. Many eyes make for great code review. • Sample MVC implementation Struts offers some insight if you want to create your own MVC implementation. • Manage the problem space Divide and conquer is a nice way of solving the problem and making the problem manageable. Of course, the sword cuts both ways. The problem is more complex and needs more management. Struts cons • Youth Struts development is still in preliminary form. They are working toward releasing a version 1.0, but as with any 1.0 version, it does not provide all the bells and whistles. • Change The framework is undergoing a rapid amount of change. A great deal of change has occurred between Struts 0.5 and 1.0. You may want to download the most current Struts nightly distributions, to avoid deprecated methods. In the last 6 months, I have seen the Struts library grow from 90K to over 270K. I had to modify my examples several times because of changes in Struts, and I am not going to guarantee my examples will work with the version of Struts you download. • Correct level of abstraction Does Struts provide the correct level of abstraction? What is the proper level of abstraction for the page designer? That is the $64K question. Should we allow a page designer access to Java code in page development? Some frameworks like Velocity say no, and provide yet another language to learn for Web development. There is some validity to limiting Java code access in UI development. Most importantly, give a page designer a little bit of Java, and he will use a lot of Java. I saw this happen all the time in Microsoft ASP development. In ASP development, you were supposed to create COM objects and then write a little ASP script to glue it all together. Instead, the ASP developers would go crazy with ASP script. I would hear "Why wait for a COM developer to create it when I can program it directly with VBScript?" Struts helps limit the amount of Java code required in a JSP file via tag libraries. One such library is the Logic Tag, which manages conditional generation of output, but this does not prevent the UI developer from going nuts with Java code. Whatever type of framework you decide to use, you should understand the environment in which you are deploying and maintaining the framework. Of course, this task is easier said than done. • Limited scope Struts is a Web-based MVC solution that is meant be implemented with HTML, JSP files, and servlets. • J2EE application support Struts requires a servlet container that supports JSP 1.1 and Servlet 2.2 specifications. This alone will not solve all your install issues, unless you are using Tomcat 3.2. I have had a great deal of problems installing the library with Netscape iPlanet 6.0, which is supposedly the first J2EE-compliant application server. I recommend visiting the Struts User Mailing List archive (see Resources) when you run into problems. • Complexity Separating the problem into parts introduces complexity. There is no question that some education will have to go on to understand Struts. With the constant changes occurring, this can be frustrating at times. Welcome to the Web. • Where is... I could point out other issues, for instance, where are the client side validations, adaptable workflow, and dynamic strategy pattern for the controller? However, at this point, it is too easy to be a critic, and some of the issues are insignificant, or are reasonable for a 1.0 release. The way the Struts team goes at it, Struts might have these features by the time you read this article, or soon after. Future of Struts Things change rapidly in this new age of software development. In less than 5 years, I have seen things go from cgi/perl, to ISAPI/NSAPI, to ASP with VB, and now Java and J2EE. Sun is working hard to adapt changes to the JSP/servlet architecture, just as they have in the past with the Java language and API. You can obtain drafts of the new JSP 1.2 and Servlet 2.3 specifications from the Sun Web site. Additionally, a standard tag library for JSP files is appearing. 2:外文资料翻译译文 Struts——MVC 的一种开放源码实现 本文介绍 Struts,它是使用 servlet 和 JavaServer Pages 技术的一种 Model-View-Controller 实现。Struts 可帮助您控制 Web 项目中的变化并提高专业化水平。尽管您可能永远不会用 Struts 实现一个系统,但您可以将其中的一些思想用于您以后的 servlet 和 JSP 网页的实现中。 简介 小学生也可以在因特网上发布 HTML 网页。但是,小学生的网页和专业开发的网站有质的区别。网页设计人员(或者 HTML 开发人员)必须理解颜色、用户、生产流程、网页布局、浏览器兼容性、图像创建和 JavaScript 等等。设计漂亮的网站需要做大量的工作,大多数 Java 开发人员更注重创建优美的对象接口,而不是用户界面。JavaServer Pages (JSP) 技术为网页设计人员和 Java 开发人员提供了一种联系钮带。 如果您开发过大型 Web 应用程序,您就理解 变化 这个词的含义。“模型-视图-控制器”(MVC) 就是用来帮助您控制变化的一种设计模式。MVC 减弱了业务逻辑接口和数据接口之间的耦合。Struts 是一种 MVC 实现,它将 Servlet 2.2 和 JSP 1.1 标记(属于 J2EE 规范)用作实现的一部分。尽管您可能永远不会用 Struts 实现一个系统,但了解一下 Struts 或许使您能将其中的一些思想用于您以后的 Servlet 的 JSP 实现中。 模型-视图-控制器 (MVC) JSP 标记只解决了部分问题。我们还得处理验证、流程控制和更新应用程序的状态等问题。这正是 MVC 发挥作用的地方。MVC 通过将问题分为三个类别来帮助解决单一模块方法所遇到的某些问题: • Model(模型) 模型包含应用程序的核心功能。模型封装了应用程序的状态。有时它包含的唯一功能就是状态。它对视图或控制器一无所知。 • View(视图) 视图提供模型的表示。它是应用程序的 外观。视图可以访问模型的读方法,但不能访问写方法。此外,它对控制器一无所知。当更改模型时,视图应得到通知。 • Controller(控制器) 控制器对用户的输入作出反应。它创建并设置模型。 MVC Model 2 Web 向软件开发人员提出了一些特有的挑战,最明显的就是客户机和服务器的无状态连接。这种无状态行为使得模型很难将更改通知视图。在 Web 上,为了发现对应用程序状态的修改,浏览器必须重新查询服务器。 另一个重大变化是实现视图所用的技术与实现模型或控制器的技术不同。当然,我们可以使用 Java(或者 PERL、C/C++ 或别的语言)代码生成 HTML。这种方法有几个缺点: • Java 程序员应该开发服务,而不是 HTML。 • 更改布局时需要更改代码。 • 服务的用户应该能够创建网页来满足它们的特定需要。 • 网页设计人员不能直接参与网页开发。 • 嵌在代码中的 HTML 很难看。 对于 Web,需要修改标准的 MVC 形式。图 4 显示了 MVC 的 Web 改写版,通常也称为 MVC Model 2 或 MVC 2。 Struts,MVC 2 的一种实现 Struts 是一组相互协作的类、servlet 和 JSP 标记,它们组成一个可重用的 MVC 2 设计。这个定义表示 Struts 是一个框架,而不是一个库,但 Struts 也包含了丰富的标记库和独立于该框架工作的实用程序类。图 5 显示了 Struts 的一个概览。 Struts 概览 • Client browser(客户浏览器) 来自客户浏览器的每个 HTTP 请求创建一个事件。Web 容器将用一个 HTTP 响应作出响应。 • Controller(控制器) 控制器接收来自浏览器的请求,并决定将这个请求发往何处。就 Struts 而言,控制器是以 servlet 实现的一个命令设计模式。 struts-config.xml 文件配置控制器。 • 业务逻辑 业务逻辑更新模型的状态,并帮助控制应用程序的流程。就 Struts 而言,这是通过作为实际业务逻辑“瘦”包装的 Action 类完成的。 • Model(模型)的状态 模型表示应用程序的状态。业务对象更新应用程序的状态。ActionForm bean 在会话级或请求级表示模型的状态,而不是在持久级。JSP 文件使用 JSP 标记读取来自 ActionForm bean 的信息。 • View(视图) 视图就是一个 JSP 文件。其中没有流程逻辑,没有业务逻辑,也没有模型信息 -- 只有标记。标记是使 Struts 有别于其他框架(如 Velocity)的因素之一。 详细分析 Struts 图 6 显示的是 org.apache.struts.action 包的一个最简 UML 图。图 6 显示了 ActionServlet (Controller)、 ActionForm (Form State) 和 Action (Model Wrapper) 之间的最简关系。 ActionServlet 类 您还记得函数映射的日子吗?在那时,您会将某些输入事件映射到一个函数指针上。如果您对此比较熟悉,您会将配置信息放入一个文件,并在运行时加载这个文件。函数指针数组曾经是用 C 语言进行结构化编程的很好方法。 现在好多了,我们有了 Java 技术、XML、J2EE,等等。Struts 的控制器是将事件(事件通常是 HTTP post)映射到类的一个 servlet。正如您所料 -- 控制器使用配置文件以使您不必对这些值进行硬编码。时代变了,但方法依旧。 ActionServlet 是该 MVC 实现的 Command 部分,它是这一框架的核心。 ActionServlet (Command) 创建并使用 Action 、 ActionForm 和 ActionForward 。如前所述, struts-config.xml 文件配置该 Command。在创建 Web 项目时,您将扩展 Action 和 ActionForm 来解决特定的问题。文件 struts-config.xml 指示 ActionServlet 如何使用这些扩展的类。这种方法有几个优点: • 应用程序的整个逻辑流程都存储在一个分层的文本文件中。这使得人们更容易查看和理解它,尤其是对于大型应用程序而言。 • 网页设计人员不必费力地阅读 Java 代码来理解应用程序的流程。 • Java 开发人员也不必在更改流程以后重新编译代码。 可以通过扩展 ActionServlet 来添加 Command 功能。 ActionForm 类 ActionForm 维护 Web 应用程序的会话状态。 ActionForm 是一个抽象类,必须为每个输入表单模型创建该类的子类。当我说 输入表单模型 时,是指 ActionForm 表示的是由 HTML 表单设置或更新的一般意义上的数据。例如,您可能有一个由 HTML 表单设置的 UserActionForm 。Struts 框架将执行以下操作: • 检查 UserActionForm 是否存在;如果不存在,它将创建该类的一个实例。 • Struts 将使用 HttpServletRequest 中相应的域设置 UserActionForm 的状态。没有太多讨厌的 request.getParameter() 调用。例如,Struts 框架将从请求流中提取 fname ,并调用 UserActionForm.setFname() 。 • Struts 框架在将 UserActionForm 传递给业务包装 UserAction 之前将更新它的状态。 • 在将它传递给 Action 类之前,Struts 还会对 UserActionForm 调用 validation() 方法进行表单状态验证。 注: 这并不总是明智之举。别的网页或业务可能使用 UserActionForm ,在这些地方,验证可能有所不同。在 UserAction 类中进行状态验证可能更好。 • 可在会话级维护 UserActionForm 。 注: • struts-config.xml 文件控制 HTML 表单请求与 ActionForm 之间的映射关系。 • 可将多个请求映射到 UserActionForm 。 • UserActionForm 可跨多页进行映射,以执行诸如向导之类的操作。 Action 类 Action 类是业务逻辑的一个包装。 Action 类的用途是将 HttpServletRequest 转换为业务逻辑。要使用 Action ,请创建它的子类并覆盖 process() 方法。 ActionServlet (Command) 使用 perform() 方法将参数化的类传递给 ActionForm 。仍然没有太多讨厌的 request.getParameter() 调用。当事件进展到这一步时,输入表单数据(或 HTML 表单数据)已被从请求流中提取出来并转移到 ActionForm 类中。 注:扩展 Action 类时请注意简洁。 Action 类应该控制应用程序的流程,而不应该控制应用程序的逻辑。通过将业务逻辑放在单独的包或 EJB 中,我们就可以提供更大的灵活性和可重用性。 考虑 Action 类的另一种方式是 Adapter 设计模式。 Action 的用途是“将类的接口转换为客户机所需的另一个接口。Adapter 使类能够协同工作,如果没有 Adapter,则这些类会因为不兼容的接口而无法协同工作。”(摘自 Gof 所著的 Design Patterns - Elements of Reusable OO Software )。本例中的客户机是 ActionServlet ,它对我们的具体业务类接口一无所知。因此,Struts 提供了它能够理解的一个业务接口,即 Action 。通过扩展 Action ,我们使得我们的业务接口与 Struts 业务接口保持兼容。(一个有趣的发现是, Action 是类而不是接口)。 Action 开始为一个接口,后来却变成了一个类。真是金无足赤。) ActionMapping 类 输入事件通常是在 HTTP 请求表单中发生的,servlet 容器将 HTTP 请求转换为 HttpServletRequest 。控制器查看输入事件并将请求分派给某个 Action 类。 struts-config.xml 确定 Controller 调用哪个 Action 类。 struts-config.xml 配置信息被转换为一组 ActionMapping ,而后者又被放入 ActionMappings 容器中。(您可能尚未注意到这一点,以 s结尾的类就是容器) ActionMapping 包含有关特定事件如何映射到特定 Action 的信息。 ActionServlet (Command) 通过 perform() 方法将 ActionMapping 传递给 Action 类。这样就使 Action 可访问用于控制流程的信息。 ActionMappings ActionMappings 是 ActionMapping 对象的一个集合。 Struts 的优点 • JSP 标记机制的使用 标记特性从 JSP 文件获得可重用代码和抽象 Java 代码。这个特性能很好地集成到基于 JSP 的开发工具中,这些工具允许用标记编写代码。 • 标记库 为什么要另发明一种轮子,或标记库呢?如果您在库中找不到您所要的标记,那就自己定义吧。此外,如果您正在学习 JSP 标记技术,则 Struts 为您提供了一个起点。 • 开放源码 您可以获得开放源码的全部优点,比如可以查看代码并让使用库的每个人检查代码。许多人都可以进行很好的代码检查。 • MVC 实现样例 如果您希望创建您自己的 MVC 实现,则 Struts 可增加您的见识。 • 管理问题空间 分治是解决问题并使问题可管理的极好方法。当然,这是一把双刃剑。问题越来越复杂,并且需要越来越多的管理。 Struts 的缺点 • 仍处于发展初期 Struts 开发仍处于初级阶段。他们正在向着发行版本 1.0 而努力,但与任何 1.0 版本一样,它不可能尽善尽美。 • 仍在变化中 这个框架仍在快速变化。Struts 1.0 与 Struts 0.5 相比变化极大。为了避免使用不赞成使用的方法,您可能隔一天就需要下载最新的 Struts。在过去的 6 个月中,我目睹 Struts 库从 90K 增大到 270K 以上。由于 Struts 中的变化,我不得不数次修改我的示例,但我不保证我的示例能与您下载的 Struts 协同工作。 • 正确的抽象级别 Struts 是否提供了正确的抽象级别?对于网页设计人员而言,什么是正确的抽象级别呢?这是一个用 $64K 的文字才能解释清楚的问题。在开发网页的过程中,我们是否应该让网页设计人员访问 Java 代码?某些框架(如 Velocity)说不应该,但它提供了另一种 Web 开发语言让我们学习。在 UI 开发中限制访问 Java 有一定的合理性。最重要的是,如果让网页设计人员使用一点 Java,他将使用大量的 Java。在 Microsoft ASP 的开发中,我总是看到这样的情况。在 ASP 开发中,您应该创建 COM 对象,然后编写少量的 ASP 脚本将这些 COM 对象联系起来。但是,ASP 开发人员会疯狂地使用 ASP 脚本。我会听到这样的话,“既然我可以用 VBScript 直接编写 COM 对象,为什么还要等 COM 开发人员来创建它呢?”通过使用标记库,Struts 有助于限制 JSP 文件中所需的 Java 代码的数量。Logic Tag 就是这样的一种库,它对有条件地生成输出进行管理,但这并不能阻止 UI 开发人员对 Java 代码的狂热。无论您决定使用哪种类型的框架,您都应该了解您要在其中部署和维护该框架的环境。当然,这项任务真是说起来容易做起来难。 • 有限的适用范围 Struts 是一种基于 Web 的 MVC 解决方案,所以必须用 HTML、JSP 文件和 servlet 来实现它。 • J2EE 应用程序支持 Struts 需要支持 JSP 1.1 和 Servlet 2.2 规范的 servlet 容器。仅凭这一点远不能解决您的全部安装问题,除非使用 Tomcat 3.2。我用 Netscape iPlanet 6.0 安装这个库时遇到一大堆问题,按理说它是第一种符合 J2EE 的应用程序服务器。我建议您在遇到问题时访问 Struts 用户邮件列表的归档资料。 • 复杂性 在将问题分为几个部分的同时也引入了复杂性。毫无疑问,要理解 Struts 必须接受一定的培训。随着变化的不断加入,这有时会令人很沮丧。欢迎访问本网站。 Struts 的前景 在这个软件开发的新时代,一切都变得很快。在不到 5 年的时间内,我已经目睹了从 cgi/perl 到 ISAPI/NSAPI、再到使用 VB 的 ASP、一直到现在的 Java 和 J2EE 的变迁。Sun 正在尽力将新的变化反映到 JSP/servlet 体系结构中,正如他们对 Java 语言和 API 所作的更改一样。您可以从 Sun 的网站获得新的 JSP 1.2 和 Servlet 2.3 规范的草案。此外,一个标准 JSP 标记库即将出现。 3:外文出处 [1]Malcolm Davis. Struts——an open-source MVC implementation [2]IBM System Journal,2006

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