首页 > 代码库 > Struts2 - Conversion Plugin
Struts2 - Conversion Plugin
转载：http://www.cnblogs.com/ikuman/archive/2013/11/04/3403073.html
1、struts2自2.1以后推荐使用Convention Plugin支持struts零配置支持(引入jar：struts2-convention-plugin-2.x.x.jar)
①convention默认扫描所有实现com.opensymphony.xwork2.Action的类和指定包路径下以Action结尾的类名
②struts.convention.package.locators指定默认的根packages，struts.convention.action.packages指定搜索的packages下的action，
struts.convention.exclude.packages指定忽略的packages
③默认视图路径：WEB-INF/content(可通过struts.convention.result.path修改)
2、results和resultcodes
①容器启动后，convention会自动加载所有action和jsp
②可以指定不同的结果页面，action-resultcode.jsp
③可以认为默认匹配顺序为actionName+resultcode+suffix>actionName+suffix
URL | Result | File that could match | Result Type |
/hello | success | /WEB-INF/content/hello.jsp | Dispatcher |
/hello | success | /WEB-INF/content/hello-success.htm | Dispatcher |
/hello | success | /WEB-INF/content/hello.ftl | FreeMarker |
/hello-world | input | /WEB-INF/content/hello-world-input.vm | Velocity |
/test1/test2/hello | error | /WEB-INF/content/test/test2/hello-error.html | Dispatcher |
3、chain链
①一个action调用同一个包中的另一个action
②若一个action未定义相对应的resultcode的result，且同一个包中有形如action-resultcode的action，如：
package com.example.actions;import com.opensymphony.xwork2.Action;import com.opensymphony.xwork2.ActionSupport; public class HelloAction extends ActionSupport { @Action("foo") public String foo() { return "bar"; } @Action("foo-bar") public String bar() { return SUCCESS; }}此时，若未定义"foo-bar"的result，则convention尝试在同一个包下寻找action名为”foo-bar”的action。如果找到这样的action，
convention将会调用并返回相关联的result。
4、XWork packages
①为了避免冲突，可将action放在一个自定义XWORK的package下
②package命名由action所在的Java包,action对应的URL中namespace部分以及action的parent XWork package三个部分组成，即：
<java-package>#<namespace>#<parent-package>③parent XWork package 值在属性 struts.convention.default.parent.package 中指定（默认为convention-default）
<constant name="struts.convention.default.parent.package" value="http://www.mamicode.com/convention-default"/>
5、Annotation reference
Convention使用很多注解来重写默认插件的action到url的映射和result路径。同时，也可以通过修改parent XWork package
通过使用@Action注解，Convention plugin可以改变action映射的url，同时也可以使一个action对应多个url地址，例如：
package com.example.actions;import com.opensymphony.xwork2.ActionSupport; import org.apache.struts2.convention.annotation.Action;public class HelloWorld extends ActionSupport { @Action("/different/url") public String execute() { return SUCCESS; }}这时，action映射的url地址将是/different/url，如果没有定义@Result，则该namespace下的action路径将被当作result path，即WEB-
INF/content/different/url.jsp
通过@Actions注解，一个方法可以对应多个url路径，如：
package com.example.actions;import com.opensymphony.xwork2.ActionSupport; import org.apache.struts2.convention.annotation.Action;import org.apache.struts2.convention.annotation.Actions;public class HelloWorld extends ActionSupport { @Actions({ @Action("/different/url"), @Action("/another/url") }) public String execute() { return SUCCESS; }}另外一种使用@Action和@Actions的例子是在一个Action类中定义多个方法，使用不同的注解，对应不同的url，如：
package com.example.actions;import com.opensymphony.xwork2.ActionSupport; import org.apache.struts2.convention.annotation.Action;import org.apache.struts2.convention.annotation.Actions;public class HelloWorld extends ActionSupport { @Action("/different/url") public String execute() { return SUCCESS; } @Action("url") public String doSomething() { return SUCCESS; }}第二个方法中的相对路径注解不推荐使用，它的路径将取决与package对应的namespace而不是由Action注解决定
Interceptor和interceptor stacks同样可以使用注解，下面的例子使用了validation interceptor和defaultStack interceptor stack：
package com.example.actions;import com.opensymphony.xwork2.ActionSupport; import org.apache.struts2.convention.annotation.Action;import org.apache.struts2.convention.annotation.Actions;public class HelloWorld extends ActionSupport { @Action(interceptorRefs={@InterceptorRef("validation"), @InterceptorRef("defaultStack")}) public String execute() { return SUCCESS; } @Action("url") public String doSomething() { return SUCCESS; }}InterceptorRefs可用于方法或Action类，若用于类上，则对所有方法有效
package com.example.actions;import com.opensymphony.xwork2.ActionSupport; import org.apache.struts2.convention.annotation.Action;import org.apache.struts2.convention.annotation.Actions;@InterceptorRefs({ @InterceptorRef("interceptor-1"), @InterceptorRef("defaultStack")})public class HelloWorld extends ActionSupport { @Action(value="http://www.mamicode.com/action1", interceptorRefs=@InterceptorRef("validation")) public String execute() { return SUCCESS; } @Action(value="http://www.mamicode.com/action2") public String doSomething() { return SUCCESS; }}注意：如果遇到"Unable to find interceptor class referenced by ref-name XYZ",则说明在convention扫描Action类时，没有Interceptor指定的拦截器。处理方式为：1使用@ParentPackage注解(或者指定struts.convention.default.parent.package)指定定义了该Interceptor的package;2创建一个package并继承定义了该Interceptor的package，同时使用@ParentPackage(或者 struts.convention.default.parent.package)指定该package同时也可以指定params参数，使用 {"key0", "value0, "key1", "value1" ... "keyN", "valueN"}形式
package com.example.actions;import com.opensymphony.xwork2.ActionSupport; import org.apache.struts2.convention.annotation.Action;import org.apache.struts2.convention.annotation.Actions;public class HelloWorld extends ActionSupport { @Action(interceptorRefs=@InterceptorRef(value="http://www.mamicode.com/validation",params={"programmatic", "false", "declarative", "true})) public String execute() { return SUCCESS; } @Action("url") public String doSomething() { return SUCCESS; }}若未指定interceptors，则使用default stack
如果将@Action，@Actions用于Action类，若该类中定义了execute，则该方法将用于action映射，否则应用的方法取决于请求
对于结果注解@Results可分为全局和局部，全局@Results定义在Action类，对所有方法有效，局部@Results定义在方法上，只对该方法有效
package com.example.actions;import com.opensymphony.xwork2.ActionSupport; import org.apache.struts2.convention.annotation.Action;import org.apache.struts2.convention.annotation.Actions;import org.apache.struts2.convention.annotation.Result;import org.apache.struts2.convention.annotation.Results;@Results({ @Result(name="failure", location="fail.jsp")})public class HelloWorld extends ActionSupport { @Action(value="http://www.mamicode.com/different/url", results={@Result(name="success", location="http://struts.apache.org", type="redirect")} ) public String execute() { return SUCCESS; } @Action("/another/url") public String doSomething() { return SUCCESS; }}在@Results注解中可以使用@params, {"key0", "value0, "key1", "value1" ... "keyN", "valueN"}
package com.example.actions;import com.opensymphony.xwork2.ActionSupport; import org.apache.struts2.convention.annotation.Action;import org.apache.struts2.convention.annotation.Actions;import org.apache.struts2.convention.annotation.Result;import org.apache.struts2.convention.annotation.Results;public class HelloWorld extends ActionSupport { @Action(value="http://www.mamicode.com/different/url", results={@Result(name="success", type="httpheader", params={"status", "500", "errorMessage", "Internal Error"})} ) public String execute() { return SUCCESS; } @Action("/another/url") public String doSomething() { return SUCCESS; }}从2.1.7版本后,@Results可以被子类继承
对于@Namespace注解可应用于Action类和packages中，在类上使用时为非完全限定
package com.example.actions;import com.opensymphony.xwork2.ActionSupport; import org.apache.struts2.convention.annotation.Action;import org.apache.struts2.convention.annotation.Namespace;@Namespace("/custom")public class HelloWorld extends ActionSupport { @Action("/different/url") public String execute() { return SUCCESS; } @Action("url") public String doSomething() { return SUCCESS; }}该Action类对应两个url： /different/url和/custom/url
@org.apache.struts2.convention.annotation.Namespace("/custom")package com.example.actions;应用于package时，子包不继承该namespace
对于@ResultPath允许改变默认的结果存放地址，该注解可用于Action类和package
package com.example.actions;import com.opensymphony.xwork2.ActionSupport; import org.apache.struts2.convention.annotation.Action;import org.apache.struts2.convention.annotation.ResultPath;@ResultPath("/WEB-INF/jsps")public class HelloWorld extends ActionSupport { public String execute() { return SUCCESS; }}经过注解，该Action类对应的result地址为/WEB-INF/jsps,而不是默认的/WEB-INF/content
对于@ParentPackage允许应用为Action类或java package定义不同的parent Struts package，也可以通过struts.convention.default.parent.package指定
package com.example.actions;import com.opensymphony.xwork2.ActionSupport; import org.apache.struts2.convention.annotation.Action;import org.apache.struts2.convention.annotation.ParentPackage;@ParentPackage("customXWorkPackage")public class HelloWorld extends ActionSupport { public String execute() { return SUCCESS; }}对于@ExceptionMappings可以指定Action类或方法的异常映射
@ExceptionMappings({ @ExceptionMapping(exception = "java.lang.NullPointerException", result = "success", params = {"param1", "val1"})})public class ExceptionsActionLevelAction { public String execute() throws Exception { return null; }}public class ExceptionsMethodLevelAction { @Action(value = "http://www.mamicode.com/exception1", exceptionMappings = { @ExceptionMapping(exception = "java.lang.NullPointerException", result = "success", params = {"param1", "val1"}) }) public String run1() throws Exception { return null; }}对于jar包，Convention plugin默认不会扫描其中的Action，若希望扫描，则需要配置struts.convention.action.includeJars
<constant name="struts.convention.action.includeJars" value="http://www.mamicode.com/.*?/myjar1.*?jar(!/)?,.*?/myjar2*?jar(!/)?">
注意，此处正则表达式匹配的是jar的路径而不是文件名，该路径下应包含jar并以"!/"结尾
Convention plugin可以自动重载配置的修改，扫描Action的改动，若要启用该功能，需要配置
<constant name="struts.devMode" value="http://www.mamicode.com/true"/><constant name="struts.convention.classes.reload" value="http://www.mamicode.com/true" />
生产环境下，强烈建议不使用该功能
6、Tips
①确保action的namespace与locators中的一个匹配，在locators后面的包路径后面，将作为action的namespace，同时将用于定位results。例如对于位
于"my.example.actions.orders"路径下的ViewAction将对应映射‘/orders/view.action‘,并且结果必将位于/WEB-INF/content/orders,类似/WEB-
INF/content/orders/view-success.jsp
②使用Configuration Browser查看action映射
③打开跟踪或调试，如log4j中增加：log4j.logger.org.apache.struts2.convention=DEBUG
常见问题
①‘There is no Action mapped for namespace /orders and action name view.‘这意味着URL /orders/view.action为对应任何一个action类，检查namespace和该
名称的action
②‘No result defined for action my.example.actions.orders.ViewAction and result success‘这意味者action已成功映射到Url，但是Convention插件没有找到
success result，检查视图文件是否存在，类似/WEB-INF/content/orders/view-success.jsp
③‘java.lang.Exception: Could not load org/apache/velocity/runtime/resource/loader/ClasspathResourceLoader.class‘这发生在
struts.convention.action.includeJars匹配外部jar包时
④当使用自定义interceptor stack时，发生‘Unable to find interceptor class referenced by ref-name XYZ‘这意味着convention插件在解析actions时，没有继
承该Interceptor定义的那个package，解决方式有两种1)使用 @ParentPackage(或struts.convention.default.parent.package)指定定义了该拦截器的package;2)自
定义package并继承定义了该Interceptor的package，并使用@ParentPackage(或struts.convention.default.parent.package)指定
7、重写convention实现rent.package)指定
<bean type="org.apache.struts2.convention.ActionNameBuilder" name="MyActionNameBuilder" class="example.SultansOfSwingNameBuilder"/><constant name="struts.convention.actionNameBuilder" value="http://www.mamicode.com/MyActionNameBuilder"/>8、convention插件配置：
| Name | Default Value | Description |
|---|---|---|
| struts.convention.action.alwaysMapExecute | true | Set to false, to prevent Convention from creating a default mapping to "execute" when there are other methods annotated as actions in the class |
| struts.convention.action.includeJars | Comma separated list of regular expressions of jar URLs to be scanned. eg. ".*myJar-0\.2.*,.*thirdparty-0\.1.*" | |
| struts.convention.action.packages | An optional list of action packages that this should create configuration for (they don‘t need to match a locator pattern) | |
| struts.convention.result.path | /WEB-INF/content/ | Directory where templates are located |
| struts.convention.result.flatLayout | true | If set to false, the result can be put in its own directory: resultsRoot/namespace/actionName/result.extension |
| struts.convention.action.suffix | Action | Suffix used to find actions based on class names |
| struts.convention.action.disableScanning | false | Scan packages for actions |
| struts.convention.action.mapAllMatches | false | Create action mappings, even if no @Action is found |
| struts.convention.action.checkImplementsAction | true | Check if an action implements com.opensymphony.xwork2.Action to create an action mapping |
| struts.convention.default.parent.package | convention-default | Default parent package for action mappins |
| struts.convention.action.name.lowercase | true | Convert action name to lowercase |
| struts.convention.action.name.separator | - | Separator used to build the action name, MyAction -> my-action. This character is also used as the separator between the action name and the result in templates, like action-result.jsp |
| struts.convention.package.locators | action,actions,struts,struts2 | Packages whose name end with one of these strings will be scanned for actions |
| struts.convention.package.locators.disable | false | Disable the scanning of packages based on package locators |
| struts.convention.exclude.packages | org.apache.struts.*, org.apache.struts2.*, org.springframework.web.struts.*, org.springframework.web.struts2.*, org.hibernate.* | Packages excluded from the action scanning |
| struts.convention.package.locators.basePackage | If set, only packages that start with its value will be scanned for actions | |
| struts.convention.relative.result.types | dispatcher,velocity,freemarker | The list of result types that can have locations that are relative and the result location (which is the resultPath plus the namespace) prepended to them |
| struts.convention.redirect.to.slash | true | A boolean parameter that controls whether or not this will handle unknown actions in the same manner as Apache, Tomcat and other web servers. This handling will send back a redirect for URLs such as /foo to /foo/ if there doesn‘t exist an action that responds to /foo |
| struts.convention.classLoader.excludeParent | true | Exclude URLs found by the parent class loader from the list of URLs scanned to find actions (needs to be set to false for JBoss 5) |
| struts.convention.action.eagerLoading | false | If set, found action classes will be instantiated by the ObjectFactory to accelerate future use, setting it up can clash with Spring managed beans |
Struts2 - Conversion Plugin