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Struts2 Convention Plugin ( struts2 零配置 )

發布時間：2025/3/15 编程问答 39 豆豆

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convention-plugin 可以用來實現 struts2 的零配置。
零配置的意思并不是說沒有配置，而是通過約定大于配置的方式，大量通過約定來調度頁面的跳轉而使得配置大大減少。
考慮到某種因素，這里采用 myeclipse 作為示例 IDE，環境 :

JDK?1.6 myeclipse?8.6.1 struts?2.1.8

web.xml

? <filter> ??????<filter-name>struts2</filter-name> ??????<filter-class>org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter</filter-class> ??</filter> ??<filter-mapping> ??????<filter-name>struts2</filter-name> ??????<url-pattern>/*</url-pattern> ??</filter-mapping>

struts.xml

convention?幾項重要配置 :

Action 類后綴名 :?<constant?name="struts.convention.action.suffix"?value="Action"?/>
繼承了 struts2 的 ActionSupport 類的類不是一個普通的類，它具有能夠處理請求和對請求作出響應的能力，
通常，開發者常常為這種特殊的類起一個后綴名，以區分一般普通的類。例如，xxAction，xxController，
這里的類名的后綴 Action，Controller 就是對應上面配置中的 value 的值，這個值會在發起 URL 請求的時候被截去。例如 : TestAction ---> test

Action類擴展名 [多項以逗號隔開]??:???<constant?name="struts.action.extension"?value="action,do,html,htm,php,aspx"?/> 與文件的擴展名相似的，例如 : TestAction ---> test.action 或 test.do 或 test.html 或 test.php 或 test.aspx 或 ...
注意 :?若該項被配置，則，訪問所有的 Action 都需帶上 Action 的擴展名，否則客戶端將拋出 404 ERROR

Action類名分隔符 :?<constant?name="struts.convention.action.name.separator"?value="_"?/>
若 Action 類名中出現駝峰標識的串，則用分隔符來切割串，如 HelloWorldAction ---> hello_world

搜索 Action 資源的包路徑 [多項以逗號隔開] :?<constant?name="struts.convention.package.locators"?value="action,actions"?/> 只有當包名含有以上配置中 value 值中至少一項時，convention plugin 才能搜索找得到該 Action，
否則就算訪問的 Action 是存在的，convention plugin 也無法找得到該 Action
注意 :?若包名不是以上列出現過的串結束，則后面的串相當于該包下所有 Action 訪問的命名空間 (?以下面的 LoginAction?作為示例?)。

搜索視圖資源(JSP,freemarker,等)的路徑 :?<constant?name="struts.convention.result.path"?value="/view/"?/>
所有的視圖資源都需放在配置指定的文件夾路徑下，否則，就算結果視圖是真實存在的，convention plugin 也無法找得到該視圖。默認值是 /WEB-INF/content/

demo 結構圖 :

convention?約定 :
1. [?Action 不存在的情況?] 若 convention plugin 在包搜索路徑中搜索不到與請求的 URL 相匹配的 Action，則會到視圖的搜索路徑下搜索
與請求的 URL 相匹配的視圖資源，若還搜索不到，則拋出 no Action mapped Exception?
示例 :?
view/hello_world.jsp [?沒有與之匹配的 Action 類?]

<html> ?<body> ??<h2>Hello?World!!</h2> ?</body> </html>

2. [?Action 的 execute 方法或動態方法調用的情況?] 如請求 name!method.action，若 NameAction 存在，且 NameAction 中存在 method 這樣一個方法，
則根據 method 方法返回的字符串，結果的視圖資源名稱規則 (?視圖以 JSP 文件為例?) :
① success? ----->? name.jsp 或 name_success.jsp ; 若這兩個視圖同時存在，則 convention plugin 會選擇 name_success.jsp 作為視圖來展示
② 非 success 的任意串 string? ----->? name_string.jsp
示例 :?

package?net.yeah.fancydeepin.action;
import?com.opensymphony.xwork2.ActionSupport; /** ?*?----------------------------------------- ?*?@描述??TODO ?*?@作者??fancy ?*?@郵箱??fancydeepin@yeah.net ?*?@日期??2012-10-26?<BR> ?*?----------------------------------------- ?*/ public?class?SayHelloAction?extends?ActionSupport{
????private?static?final?long?serialVersionUID?=?1L;
????private?String?message; ???? ????public?String?execute(){ ???????? ????????message?=?"Hello?struts2?convention?plugin!"; ????????return?SUCCESS; ????} ???? ????public?String?say(){ ???????? ????????message?=?"SayHelloAction,?say"; ????????return?"world"; ????} ???? ????public?String?sayHello(){ ???????? ????????message?=?"SayHelloAction,?sayHello"; ????????return?"conventionPlugin"; ????}
????public?String?getMessage()?{ ????????return?message; ????} ???? }

view/say_hello.jsp

<html> ?<body> ??<h2>say_hello.jsp?→?Message?:?${message}</h2> ?</body> </html>

view/say_hello_world.jsp

<html> ?<body> ??<h2>say_hello_world.jsp?→?Message?:?${message}</h2> ?</body> </html>

view/say_hello_conventionPlugin.jsp

<html> ?<body> ??<h2>say_hello_conventionPlugin.jsp?→?Message?:?${message}</h2> ?</body> </html>

convention?注解 :
@ParentPackage?: 對應于 struts.xml 常量配置項的?<constant?name="struts.convention.default.parent.package"?value="xx"/>?默認值是 convention-default
@ResultPath?: 對應于 struts.xml 常量配置項的?<constant?name="struts.convention.result.path"?value="xx"?/>?默認值是 /WEB-INF/content/
@Namespace?: Action 訪問的命名空間，該注解一旦聲明，結果的視圖資源需放在 : 視圖搜索目錄/命名空間 (?如 : view/simple/demo.jsp?)

package?net.yeah.fancydeepin.action;
import?org.apache.struts2.convention.annotation.Namespace; import?org.apache.struts2.convention.annotation.ParentPackage; import?org.apache.struts2.convention.annotation.ResultPath; import?com.opensymphony.xwork2.ActionSupport; /** ?*?----------------------------------------- ?*?@描述??TODO ?*?@作者??fancy ?*?@郵箱??fancydeepin@yeah.net ?*?@日期??2012-10-26?<BR> ?*?----------------------------------------- ?*/ @ParentPackage("convention-default") @Namespace("/simple") @ResultPath("/view/") public?class?DemoAction?extends?ActionSupport{
????private?static?final?long?serialVersionUID?=?1L; ????private?String?message; ???? ????public?String?execute(){ ???????? ????????message?=?"DemoAction"; ????????return?SUCCESS; ????}
????public?String?getMessage()?{ ????????return?message; ????} }

view/simple/demo.jsp

<html> ?<body> ??<h2>demo.jsp?→?Hello?World?${message}!</h2> ?</body> </html>

@Action

package?net.yeah.fancydeepin.action;
import?org.apache.struts2.convention.annotation.Action; import?com.opensymphony.xwork2.ActionSupport; /** ?*?----------------------------------------- ?*?@描述??TODO ?*?@作者??fancy ?*?@郵箱??fancydeepin@yeah.net ?*?@日期??2012-10-26?<BR> ?*?----------------------------------------- ?*/ public?class?ActionannotationAction?extends?ActionSupport{
????private?static?final?long?serialVersionUID?=?1L; ????private?String?message; ???? ????@Action("invoke") ????public?String?invokeMethod(){ ???????? ????????message?=?"ActionannotationAction,?invokeMethod"; ????????return?SUCCESS; ????}
????public?String?getMessage()?{ ????????return?message; ????} }

view/invoke.jsp

<html> ?<body> ??<h2>invoke.jsp?→?Message?:?${message}</h2> ?</body> </html>

@Result，@Results

package?net.yeah.fancydeepin.action;
import?java.util.Random; import?org.apache.struts2.convention.annotation.Action; import?org.apache.struts2.convention.annotation.Result; import?org.apache.struts2.convention.annotation.Results; import?com.opensymphony.xwork2.ActionSupport; /** ?*?----------------------------------------- ?*?@描述??TODO ?*?@作者??fancy ?*?@郵箱??fancydeepin@yeah.net ?*?@日期??2012-10-26?<BR> ?*?----------------------------------------- ?*/ @Results({@Result(name?=?"success",?location?=?"result.jsp")}) public?class?ResultAction?extends?ActionSupport{
????private?static?final?long?serialVersionUID?=?1L; ????private?String?message; ???? ????public?String?execute(){ ???????? ????????message?=?"ResultAction,?execute"; ????????return?SUCCESS; ????} ???? ????@Action(value?=?"doIt",? ????????results?=?{ ????????????@Result(name?=?"isTrue",?location?=?"result_true.jsp"), ????????????@Result(name?=?"isFalse",?location?=?"result_false.jsp") ????????} ????) ????public?String?doExecute(){
????????message?=?"doExecute?isFalse."; ????????if(new?Random().nextBoolean()){ ????????????message?=?"doExecute?isTrue."; ????????????return?"isTrue"; ????????} ????????return?"isFalse"; ????}
????public?String?getMessage()?{ ????????return?message; ????} }

view/result.jsp

<html> ?<body> ??<h2>result.jsp?→?Message?:?${message}</h2> ?</body> </html>

view/result_true.jsp

<html> ?<body> ??<h2>result_true.jsp?→?Message?:?${message}</h2> ?</body> </html>

view/result_false.jsp

<html> ?<body> ??<h2>result_false.jsp?→?Message?:?${message}</h2> ?</body> </html>

The last example

package?net.yeah.fancydeepin.action.admin;
import?com.opensymphony.xwork2.ActionSupport; /** ?*?----------------------------------------- ?*?@描述??TODO ?*?@作者??fancy ?*?@郵箱??fancydeepin@yeah.net ?*?@日期??2012-10-26?<BR> ?*?----------------------------------------- ?*/ public?class?LoginAction?extends?ActionSupport{
????private?static?final?long?serialVersionUID?=?1L; ????private?String?username; ????private?String?password;
????public?String?log(){ ???????? ????????username?=?username.intern(); ????????password?=?password.intern(); ????????if(username?==?"admin"?&&?password?==?"fancy"){ ????????????return?SUCCESS; ????????} ????????return?ERROR; ????}
????public?void?setUsername(String?username)?{ ????????this.username?=?username; ????}
????public?void?setPassword(String?password)?{ ????????this.password?=?password; ????} }

view/admin/login_success.jsp

<html> ?<body> ??<h2>Welcome!!</h2> ?</body> </html>

view/admin/login_error.jsp

<html> ?<body> ??<h2>Login?Failed!!</h2> ?</body> </html>

文章轉自：http://www.blogjava.net/fancydeepin/archive/2012/10/26/struts2_convention_plugin.html

轉載于:https://www.cnblogs.com/Neil223/p/5587535.html

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