2014-07-17 Java Web的学习(14)-----struts2(0)----简单入门
一、什么是strut2?
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主要的功能:传统Servlet中功能(控制转发),校验框架,封装数据.
MVC框架如下图所示:
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二、Filter VS Servlet(Struts2 入口程序之争)
三、struts2的解决问题
四、搭建strut2的开发环境(自带应用模仿)图示
1.将所需架包放入构建路径中
2.web.xml文件配置过滤器
3.在应用的构建路径的顶端(WEB-INF/classes),建立配置文件struts.xml
4.部署到Tomcat中.
注意:Struts2框架默认处理的URL的扩展名:以.action结尾,或者什么都没有.hello.action或者hello
五、struts2简单工作原理(图示)
六、struts2的常用配置.
各种的配置文件按顺序加载.
七、struts2中Action的配置
八、动作类的编写
定义有三种方式:
推荐:extends ActionSupport
九、动作类的生命周期
动作类每次访问都会重新被实例化,是线程安全的。为什么线程安全.
十、动作方法的定义.
1.Struts2的核心入口程序
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如何进入Struts框架内部,从功能上讲必须能够处理客户端的Http请求.真实表示层框架的基本的要求.而SUN公司规定Servlet标准.有两种方式可以进行Http请求的处理.实现标准的Servlet接口和Filter接口.而Struts2为什么选择Filter??而Filter相对于Servlet接口的优势在哪?
从Servlet API中可以发现Servlet和Filter的区别:
a.实例何时被WEB服务器创建?
默认情况下第一次访问Servlet时,容器创建实例,初始化该对象.应用启动时,Filter对象被容器创建,执行init方法.Struts2容器需要初始化相关Bean.
b.Filter如果配置信息错误,服务器启动就会出错.抛出异常,可以较早发现程序错误.
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接下来程序分为两部分:
初始化的特点(init方法):
![QQ拼音截图未命名 [1]](http://img.e-com-net.com/image/info2/6e54dee6642f4067938497c10d6a3489.jpg "QQ拼音截图未命名 [1]")
初始化的主要内容(init方法):
![QQ拼音截图未命名 [2]](http://img.e-com-net.com/image/info2/544b350e2a834b50af8d630bd64f6ddc.jpg "QQ拼音截图未命名 [2]")
处理Http请求的内容(doFilter方法):
![QQ拼音截图未命名 [3]](http://img.e-com-net.com/image/info2/a48d6fb285334eed926263320b05ae82.jpg "QQ拼音截图未命名 [3]")
![QQ拼音截图未命名 [4]](http://img.e-com-net.com/image/info2/a61b5b1ffff2430895f808944e11ce80.jpg "QQ拼音截图未命名 [4]")
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StrutsPrepareAndExecuteFilter源码可知.所以从严格意义上的Struts2,实际上有两个不同的框架组成.传统Struts2的工作处理Http请求,然后委托XWork完成真正的逻辑处理.做到与Servlet API(即Web容器)分离.
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2.Struts2的初始化.
初始化什么?
内置对象+事件响应模型
怎么知道初始化哪些内置对象和事件响应模型?
XML配置文件:default.properties......
3.Http请求预处理和XWork执行业务逻辑(重点).
![QQ拼音截图未命名 [5]](http://img.e-com-net.com/image/info2/62ef410704424e70815e4c1f153d4926.jpg "QQ拼音截图未命名 [5]")
4.Struts2如何初始化加载配置文件(default.properties,struts-default.xml,struts-plugin.xml,struts.xml)
![无标题 [1]](http://img.e-com-net.com/image/info2/8979b14277ac4b65a3491996861af2f3.jpg "无标题 [1]")
5.通过配置文件中的<bean>节点,熟悉Struts2容器的静态注入.
5.1 default-struts.xml.
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<
bean
type
=
"com.opensymphony.xwork2.ObjectFactory"
name
=
"struts"
class
=
"org.apache.struts2.impl.StrutsObjectFactory"
/>
当Web容器启动时,就会加载配置文件,然后实例化该Bean.
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5.2 ObjectFactory API
5.3 Struts2默认是由ObjectFactory管理所有相关的Bean,现在通过改变管理Bean的工厂,来改变Action的产生方式.根据配置文件加载顺序和复写规则,重新指定新的工厂.
![Image [1]](http://img.e-com-net.com/image/info2/b6d7d1e17fe44a6bb68c419cc46f199e.jpg "Image [1]"){kind=small} PS:有关struts.objectFactory的介绍,### if specified, the default object factory can be overridden here
### Note: short-hand notation is supported in some cases, such as "spring"
### Alternatively, you can provide a com.opensymphony.xwork2.ObjectFactory subclass name here
# struts.objectFactory = spring
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6.Struts2拦截器机制
6.1 Struts2为什么采用拦截器？
有人这样描述Interceptor和Action之间的关系:这时一个策应部队和主力部队之间的关系.这就如同作任何事
都要分清主次,当我们将事件处理的主要职责(进行核心业务逻辑处理)交给Action对象,而将一些次要的职责(如何设置Action的运行参数,校验表单数据)交付给Interceptor对象.这样的话,就将不同职责分而治之.并且分派到不同的对象上去执行。分而治之,各司其职。所以拦截器的作用:"干杂活"---(重复性和开发常用的功能).
情
6.2 Interceptor的基本概念
拦截器是原本属于AOP中的概念,其本质是一个代码段,可以通过定义织入点.来指定Interceptor的代码逻辑在织入点元素的之前或者之后执行。从而起到拦截的作用.Xwork是用AOP来实现Ioc(通过拦截器封装Action对象中属性,实现注入).而Spring是用Ioc实现AOP(同注入属性赋值,然后类与类之间的关联关系依赖实例化).
在Struts2中还存在拦截器链（Interceptor Chain,在struts2中称为拦截器栈Interceptor Stack）.拦截器栈就是将拦截器按一定的顺序联结成一条链.在访问被拦截的Action时,拦截器链中的拦截器就会按其之前定义的顺序被调用.
![Image [2]](http://img.e-com-net.com/image/info2/17b0281fed75432783f4b0b4630d5166.jpg "Image [2]")
6.3 Interceptor实现原理
Struts 2的拦截器实现相对简单.当请求到达Struts 2的ServletDispatcher时,Struts2会查找配置文件,并根据其配置实例化相对的拦截器对象，然后串成一个列表(list),最后一个一个地调用列表中的拦截器. ![Image [3]](http://img.e-com-net.com/image/info2/e951d914958141fa852d88ef5a04f5f0.jpg "Image [3]") |
6.4 struts2内置的拦截器和默认使用的拦截器栈(
struts-default.xml
).
| <interceptors>
<
interceptor
name
=
"alias"
class
=
"com.opensymphony.xwork2.interceptor.AliasInterceptor"
/>
<
interceptor
name
=
"autowiring"
class
=
"com.opensymphony.xwork2.spring.interceptor.ActionAutowiringInterceptor"
/>
<
interceptor
name
=
"chain"
class
=
"com.opensymphony.xwork2.interceptor.ChainingInterceptor"
/>
<
interceptor
name
=
"conversionError"
class
=
"org.apache.struts2.interceptor.StrutsConversionErrorInterceptor"
/>
<
interceptor
name
=
"cookie"
class
=
"org.apache.struts2.interceptor.CookieInterceptor"
/>
<
interceptor
name
=
"cookieProvider"
class
=
"org.apache.struts2.interceptor.CookieProviderInterceptor"
/>
<
interceptor
name
=
"clearSession"
class
=
"org.apache.struts2.interceptor.ClearSessionInterceptor"
/>
<
interceptor
name
=
"createSession"
class
=
"org.apache.struts2.interceptor.CreateSessionInterceptor"
/>
<
interceptor
name
=
"debugging"
class
=
"org.apache.struts2.interceptor.debugging.DebuggingInterceptor"
/>
<
interceptor
name
=
"execAndWait"
class
=
"org.apache.struts2.interceptor.ExecuteAndWaitInterceptor"
/>
<
interceptor
name
=
"exception"
class
=
"com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor"
/>
<
interceptor
name
=
"fileUpload"
class
=
"org.apache.struts2.interceptor.FileUploadInterceptor"
/>
<
interceptor
name
=
"i18n"
class
=
"com.opensymphony.xwork2.interceptor.I18nInterceptor"
/>
<
interceptor
name
=
"logger"
class
=
"com.opensymphony.xwork2.interceptor.LoggingInterceptor"
/>
<
interceptor
name
=
"modelDriven"
class
=
"com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor"
/>
<
interceptor
name
=
"scopedModelDriven"
class
=
"com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor"
/>
<
interceptor
name
=
"params"
class
=
"com.opensymphony.xwork2.interceptor.ParametersInterceptor"
/>
<
interceptor
name
=
"actionMappingParams"
class
=
"org.apache.struts2.interceptor.ActionMappingParametersInteceptor"
/>
<
interceptor
name
=
"prepare"
class
=
"com.opensymphony.xwork2.interceptor.PrepareInterceptor"
/>
<
interceptor
name
=
"staticParams"
class
=
"com.opensymphony.xwork2.interceptor.StaticParametersInterceptor"
/>
<
interceptor
name
=
"scope"
class
=
"org.apache.struts2.interceptor.ScopeInterceptor"
/>
<
interceptor
name
=
"servletConfig"
class
=
"org.apache.struts2.interceptor.ServletConfigInterceptor"
/>
<
interceptor
name
=
"timer"
class
=
"com.opensymphony.xwork2.interceptor.TimerInterceptor"
/>
<
interceptor
name
=
"token"
class
=
"org.apache.struts2.interceptor.TokenInterceptor"
/>
<
interceptor
name
=
"tokenSession"
class
=
"org.apache.struts2.interceptor.TokenSessionStoreInterceptor"
/>
<
interceptor
name
=
"validation"
class
=
"org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor"
/>
<
interceptor
name
=
"workflow"
class
=
"com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor"
/>
<
interceptor
name
=
"store"
class
=
"org.apache.struts2.interceptor.MessageStoreInterceptor"
/>
<
interceptor
name
=
"checkbox"
class
=
"org.apache.struts2.interceptor.CheckboxInterceptor"
/>
<
interceptor
name
=
"profiling"
class
=
"org.apache.struts2.interceptor.ProfilingActivationInterceptor"
/>
<
interceptor
name
=
"roles"
class
=
"org.apache.struts2.interceptor.RolesInterceptor"
/>
<
interceptor
name
=
"annotationWorkflow"
class
=
"com.opensymphony.xwork2.interceptor.annotations.AnnotationWorkflowInterceptor"
/>
<
interceptor
name
=
"multiselect"
class
=
"org.apache.struts2.interceptor.MultiselectInterceptor"
/>
<
interceptor-stack
name
=
"defaultStack"
>
<
interceptor-ref
name
=
"exception"
/>
<
interceptor-ref
name
=
"alias"
/>
<
interceptor-ref
name
=
"servletConfig"
/>
<
interceptor-ref
name
=
"i18n"
/>
<
interceptor-ref
name
=
"prepare"
/>
<
interceptor-ref
name
=
"chain"
/>
<
interceptor-ref
name
=
"scopedModelDriven"
/>
<
interceptor-ref
name
=
"modelDriven"
/>
<
interceptor-ref
name
=
"fileUpload"
/>
<
interceptor-ref
name
=
"checkbox"
/>
<
interceptor-ref
name
=
"multiselect"
/>
<
interceptor-ref
name
=
"staticParams"
/>
<
interceptor-ref
name
=
"actionMappingParams"
/>
<
interceptor-ref
name
=
"params"
>
<
param
name
=
"excludeParams"
>
dojo\..*,^struts\..*,^session\..*,^request\..*,^application\..*,^servlet(Request|Response)\..*,parameters\...*
</
param
>
</
interceptor-ref
>
<
interceptor-ref
name
=
"conversionError"
/>
<
interceptor-ref
name
=
"validation"
>
<
param
name
=
"excludeMethods"
>
input,back,cancel,browse
</
param
>
</
interceptor-ref
>
<
interceptor-ref
name
=
"workflow"
>
<
param
name
=
"excludeMethods"
>
input,back,cancel,browse
</
param
>
</
interceptor-ref
>
<
interceptor-ref
name
=
"debugging"
/>
</
interceptor-stack
>
</
interceptors
>
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6.5 自定义拦截器及其XML的配置
![Image [4]](http://img.e-com-net.com/image/info2/a2620fadfb704b41b6c7e14394899ffd.jpg "Image [4]") ![Image [5]](http://img.e-com-net.com/image/info2/e3aefcd7020d436fa0a4aa2108f24ece.jpg "Image [5]") |
6.6 通过源码熟悉模型驱动和属性驱动的拦截器(AOP编程实现Action属性的注入)
struts-default.xml中defaultStack栈.
![Image [6]](http://img.e-com-net.com/image/info2/a26b008f0a2e49a88b592cb64f51f69f.jpg "Image [6]"){kind=small} a.模型驱动拦截器源代码(ModelDrviernInterceptor拦截器负责生成对象,在后面扥拦截器是ParametersInterceptor拦截器赋值) ![Image [7]](http://img.e-com-net.com/image/info2/3b8aa06d3b1845a49f3a1a80edc8d6b1.jpg "Image [7]"){kind=small} 使用模型驱动的话,必须实现ModelDriven接口. ![Image [8]](http://img.e-com-net.com/image/info2/b4890523dcb14636b2d365fc0e1442de.jpg "Image [8]") b.属性驱动的源代码 ![Image [9]](http://img.e-com-net.com/image/info2/395db5b34606429fb58e7f8736b00e03.jpg "Image [9]"){kind=small} ![Image [10]](http://img.e-com-net.com/image/info2/c04c2ee552df4c8da05935230bd7311d.jpg "Image [10]"){kind=small} //封装REQUEST请求参数到Map集合中 ![Image [11]](http://img.e-com-net.com/image/info2/d1747c6217d249bd9b914b3a3393106a.jpg "Image [11]"){kind=small} //调用方法,注意参数 ![Image [12]](http://img.e-com-net.com/image/info2/9eeab53ecd4941b38c0f546812cbf82a.jpg "Image [12]"){kind=small} //由于Action对象已经在对象栈中,然后将Action对象属性赋值(请求参数中的值). |
6.7 通过源码熟悉Struts2验证机制(主要是两个拦截器实现)
a.准备一个Action类继承ActionSupport,重写validate方法.(采用手工验证方式) ![Image [13]](http://img.e-com-net.com/image/info2/b48ddac0c66b4ad3a9b7ff73b81b319e.jpg "Image [13]") b.查看AnnotationValidationInterceptor拦截器的源代码: ![Image [14]](http://img.e-com-net.com/image/info2/2e1183ec458c4b8984fa97896774b6f7.jpg "Image [14]"){kind=small} ![Image [15]](http://img.e-com-net.com/image/info2/fbba8af441114e85b3dbc5f89b8f1d1a.jpg "Image [15]"){kind=small} ![Image [16]](http://img.e-com-net.com/image/info2/186f4035ee654813bd12101c82af0a68.jpg "Image [16]"){kind=small} //调用父类的doIntercept方法 ![Image [17]](http://img.e-com-net.com/image/info2/71df4956242c4d7dbd675a8b662c7b28.jpg "Image [17]"){kind=small} //父类 ![Image [18]](http://img.e-com-net.com/image/info2/d0be612eff6847b687d3c61862a51e9d.jpg "Image [18]"){kind=small} ![Image [19]](http://img.e-com-net.com/image/info2/0ec4cd2692e74305828a4ee0271f20a6.jpg "Image [19]"){kind=small} 由于自定义UserAction继承ActionSupport,从而间接实现Validateable接口 ![Image [20]](http://img.e-com-net.com/image/info2/43004a22a30d45b490d6ca637978c8a9.jpg "Image [20]"){kind=small} ![Image [21]](http://img.e-com-net.com/image/info2/ee0db96a4dab4d4f820844186a92956f.jpg "Image [21]"){kind=small} ------>完成校验的前期工作.但是最后如何返回视图(Result)呢?接下来就是workflow拦截器的事. c.查看DefaultWorkflowInterceptor拦截器的源代码 ![Image [22]](http://img.e-com-net.com/image/info2/40830eba619147aeb1a01be639d77e3d.jpg "Image [22]"){kind=small} ![Image [23]](http://img.e-com-net.com/image/info2/f70a87c2b01642e581530590e452f935.jpg "Image [23]"){kind=small} ![Image [24]](http://img.e-com-net.com/image/info2/4b00c74c2406465bab90a6402cedf5b0.jpg "Image [24]"){kind=small} //判断有没有错误信息、确定该返回什么视图. ![Image [25]](http://img.e-com-net.com/image/info2/db5da316c0ad47b29f5ea3120af23c0d.jpg "Image [25]") //常量:"input" |
7.struts2插件机制
从源代码看来,struts2在服务器启动时,会加载四种配置文件
![Image [26]](http://img.e-com-net.com/image/info2/935b1dd7285245b599055f297ac89db1.jpg "Image [26]")
其中的struts-plugin.xml就是插件配置文件.struts2容器会去web工程的lib下查找所有的.jar文件,查看jar文件的根目录下面是否有struts.plugin.xml文件.该文件的内容信息同时也会加载struts容器中。有可能会覆盖配置信息.如struts2-spring-plugin-2.3.15.3.jar根目录下struts-plugin.xml配置:
其中的struts-plugin.xml就是插件配置文件.struts2容器会去web工程的lib下查找所有的.jar文件,查看jar文件的根目录下面是否有struts.plugin.xml文件.该文件的内容信息同时也会加载struts容器中。有可能会覆盖配置信息.如struts2-spring-plugin-2.3.15.3.jar根目录下struts-plugin.xml配置:
![Image [27]](http://img.e-com-net.com/image/info2/300c642589f54f67a3a506c96e1bd6bc.jpg "Image [27]")