Struts2核心技術簡介，struts2核心技術
Struts2核心技術簡介
使用Struts2框架，只要注重以下三大元素：配置文件、映射文件和Action：
全局屬性文件struts.properties：保存系統運行的一些參數變量，整個系統只有一個屬性文件；
映射文件struts.xml：用於配置請求映射的Action和攔截器，可以有多個映射文件；
業務控制器Action：可以使用POJO（類似JavaBean）類，也可以集成ActionSupport，在該類中不僅可以取得表單數據，還可以取得上下文變量。以下是詳細說明：
1、全局屬性文件struts.properties
struts.properties文件主要定義系統的屬性，請看以下示例代碼：
![]()
### Struts default properties
###(can be overridden by a struts.properties file in the root of the classpath)
###
###指定Struts2的配置類，默認為下面的配置，也可以通過繼承
### Specifies the Configuration used to configure Struts
### one could extend org.apache.struts2.config.Configuration
### to build one's customize way of getting the configurations parameters into Struts
# struts.configuration=org.apache.struts2.config.DefaultConfiguration
###設置默認的國際化地區信息和國際化信息內碼
### This can be used to set your default locale and encoding scheme
# struts.locale=en_US
struts.i18n.encoding=UTF-8
###指定對象工廠類，也可以實現自己的工廠類
### 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
###當使用Spring的工廠類時，指定自動植入autoWrite的機制
### specifies the autoWiring logic when using the SpringObjectFactory.
### valid values are: name, type, auto, and constructor (name is the default)
struts.objectFactory.spring.autoWire = name
###使用Spring集成時，是否使用類緩存，可選值有：true和false
### indicates to the struts-spring integration if Class instances should be cached
### this should, until a future Spring release makes it possible, be left as true
### unless you know exactly what you are doing!
### valid values are: true, false (true is the default)
struts.objectFactory.spring.useClassCache = true
###指定對象類型檢查器，可用值有“tiger”和“notiger”，也可以使用自己的類
### if specified, the default object type determiner can be overridden here
### Note: short-hand notation is supported in some cases, such as "tiger" or "notiger"
### Alternatively, you can provide a com.opensymphony.xwork2.util.ObjectTypeDeterminer
implementation name here
### Note: By default, com.opensymphony.xwork2.util.DefaultObjectTypeDeterminer is used which
handles type detection
### using generics. com.opensymphony.xwork2.util.GenericsObjectTypeDeterminer was deprecated
since XWork 2, it's
### functions are integrated in DefaultObjectTypeDeterminer now.
### To disable tiger support use the "notiger" property value here.
#struts.objectTypeDeterminer = tiger
#struts.objectTypeDeterminer = notiger
###指定使用MIME-type multipart/form-data時的解析器
### Parser to handle HTTP POST requests, encoded using the MIME-type multipart/form-data
# struts.multipart.parser=cos
# struts.multipart.parser=pell
struts.multipart.parser=jakarta
# uses javax.servlet.context.tempdir by default
struts.multipart.saveDir=
struts.multipart.maxSize=2097152
###指定自定義的屬性文件
### Load custom property files (does not override struts.properties!)
# struts.custom.properties=application,org/apache/struts2/extension/custom
###URL與Action映射處理器
### How request URLs are mapped to and from actions
#struts.mapper.class=org.apache.struts2.dispatcher.mapper.DefaultActionMapper
###指定URL的擴展名，可以指定多個擴展名，用逗號分隔，例如action、jnlp、do
### Used by the DefaultActionMapper
### You may provide a comma separated list, e.g. struts.action.extension=action,jnlp,do
struts.action.extension=do
###被FilterDispatcher所使用，true表示Struts serves static content來自於內部jar
### Used by FilterDispatcher
### If true then Struts serves static content from inside its jar.
### If false then the static content must be available at <context_path>/struts
struts.serve.static=true
###是否Struts過濾器中提供的靜態內容應該被浏覽器緩存到頭部屬性中
### Used by FilterDispatcher
### This is good for development where one wants changes to the static content be
### fetch on each request.
### NOTE: This will only have effect if struts.serve.static=true
### If true -> Struts will write out header for static contents such that they will
### be cached by web browsers (using Date, Cache-Content, Pragma, Expires)
### headers).
### If false -> Struts will write out header for static contents such that they are
### NOT to be cached by web browser (using Cache-Content, Pragma, Expires
### headers)
struts.serve.static.browserCache=true
###是否允許動態方法調用，如果為true，則可以配置如下的<action>參數映射
### mappings, such as <action name="*/*" method="{2}" class="actions.{1}">
### Set this to false if you wish to disable implicit dynamic method invocation
### via the URL request. This includes URLs like foo!bar.action, as well as params
### like method:bar (but not action:foo).
### An alternative to implicit dynamic method invocation is to use wildcard
### mappings, such as <action name="*/*" method="{2}" class="actions.{1}">
struts.enable.DynamicMethodInvocation = true
###是否在action名稱中允許“/”
### Set this to true if you wish to allow slashes in your action names. If false,
### Actions names cannot have slashes, and will be accessible via any directory
### prefix. This is the traditional behavior expected of WebWork applications.
### Setting to true is useful when you want to use wildcards and store values
### in the URL, to be extracted by wildcard patterns, such as
### <action name="*/*" method="{2}" class="actions.{1}"> to match "/foo/edit" or
### "/foo/save".
struts.enable.SlashesInActionNames = false
###是否可以用替代的語法%{}代替tags
### use alternative syntax that requires %{} in most places
### to evaluate expressions for String attributes for tags
struts.tag.altSyntax=true
###是否為Struts開發模式
### when set to true, Struts will act much more friendly for developers. This
### includes:
### - struts.i18n.reload = true
### - struts.configuration.xml.reload = true
### - raising various debug or ignorable problems to errors
### For example: normally a request to foo.action?someUnknownField=true should
### be ignored (given that any value can come from the web and it
### should not be trusted). However, during development, it may be
### useful to know when these errors are happening and be told of
### them right away.
struts.devMode = false
###是否國際化信息自動加載
### when set to true, resource bundles will be reloaded on _every_ request.
### this is good during development, but should never be used in production
struts.i18n.reload=false
### Standard UI theme
### Change this to reflect which path should be used for JSP control tag templates by default
struts.ui.theme=xhtml
struts.ui.templateDir=template
#sets the default template type. Either ftl, vm, or jsp
struts.ui.templateSuffix=ftl
###在struts.xml 文件更改時，是否允許重載
### Configuration reloading
### This will cause the configuration to reload struts.xml when it is changed
struts.configuration.xml.reload=false
###velocity配置文件路徑，默認為velocity.properties
### Location of velocity.properties file. defaults to velocity.properties
struts.velocity.configfile = velocity.properties
###Cvelocity的context列表
### Comma separated list of VelocityContext classnames to chain to the StrutsVelocityContext
struts.velocity.contexts =
###velocity工具盒的位置
### Location of the velocity toolbox
struts.velocity.toolboxlocation=
### used to build URLs, such as the UrlTag
struts.url.http.port = 80
struts.url.https.port = 443
### possible values are: none, get or all
struts.url.includeParams = get
###加載附加的國際化屬性文件（不包含.properties）
### Load custom default resource bundles
struts.custom.i18n.resources=com.demo.struts2.resources.ApplicationResources
### workaround for some app servers that don't handle HttpServletRequest.getParameterMap()
### often used for WebLogic, Orion, and OC4J
struts.dispatcher.parametersWorkaround = false
### configure the Freemarker Manager class to be used
### Allows user to plug-in customised Freemarker Manager if necessary
### MUST extends off org.apache.struts2.views.freemarker.FreemarkerManager
#struts.freemarker.manager.classname=org.apache.struts2.views.freemarker.FreemarkerManager
### Enables caching of FreeMarker templates
### Has the same effect as copying the templates under WEB_APP/templates
struts.freemarker.templatesCache=false
### Enables caching of models on the BeanWrapper
struts.freemarker.beanwrapperCache=false
### See the StrutsBeanWrapper javadocs for more information
struts.freemarker.wrapper.altMap=true
### configure the XSLTResult class to use stylesheet caching.
### Set to true for developers and false for production.
struts.xslt.nocache=false
###struts自動加載的配置文件列表
### A list of configuration files automatically loaded by Struts
struts.configuration.files=struts-default.xml,struts-plugin.xml,struts.xml
### Whether to always select the namespace to be everything before the last slash or not
struts.mapper.alwaysSelectFullNamespace=false
View Code
2、映射文件struts.xml
Struts2框架的核心配置文件時Struts.xml，該文件主要負責管理Struts框架的業務控制器Action。該文件包含唯一的根元素<struts>，可以在該元素中添加子標簽來實現自己的配置。一般開發主要用到如下的七個配置功能：
（1）屬性定義元素<constant>
可以使用<constant>標簽來定義一個屬性，該屬性與struts.properties中屬性重名，並覆蓋struts.properties中該屬性的值。這樣做的好處是，如果使用了多個映射文件時，允許每一個文件都使用不同的屬性。
（2）導入子文件元素<include>
使用<include>標簽來導入一個子文件，子文件與struts.xml有同樣的結構，使用相同的配置語法。通過這種方式提供了一種模塊化的方式來管理struts.xml文件。
（3）包定義元素<package>
<package>定義了一組<action>和攔截器元素，可以定義多個<action>元素，name表示包的名字，extends屬性表示繼承自struts-default.xml中所定義的包的名字。
（4）Action映射配置元素<action>
Action mapping是框架中的基本工作單元，框架通過對請求路徑進行映射來決定由哪個Action來處理請求。
（5）Result配置元素<result>
Action類處理完一個請求後會返回一個字符串，這個字符串將被用來選擇一個<result>元素。通常一個action mapping會有多個<result>，代表各個可能不同的結果。
（6）配置全局映射元素<global-results>
定義在<action>元素裡面的<result>我們可以稱之為局部<result>，除此之外我們還可以定義全局的<result>，這些全局的<result>會悲哀多個<action>所共享。框架會首先尋找嵌套在<action>元素中的<result>，如果沒有匹配的就去全局<result>中去尋找。
（7）配置攔截器<interceptors>
通過使用攔截器，我們可以在Action中的方法執行之前先執行一些我們事先定義好的方法，也可以在Action中的方法執行之後立即執行一些我們事先定義好的方法。
下面請看一個struts.xml文件代碼示例：
![]()
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC
"-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
"http://struts.apache.org/dtds/struts-2.0.dtd">
<struts>
<constant name="struts.enable.DynamicMethodInvocation" value="false" />
<constant name="struts.devMode" value="false" />
<include file="example.xml"/>
<!-- Add packages here -->
<package name="main" extends="struts-default">
<action name="test" class="com.demo.struts2.actions.TestAction">
<result name="success">success.jsp</result>
<result name="input">input.jsp</result>
</action>
</package>
</struts>
View Code
3、業務控制器Action
使用Struts2框架，不需要開發ActionForm類，主要注意一下三點：
Action可以是任意的POJO（類似JavaBean）類
一般繼承ActionSupport類
可以在Action中訪問上下文變量
