引言:最近在看一個(gè)開源的聊天室AjaxChat 時(shí)看到一個(gè)被引用的包:javawebparts,處于好奇去看了一下，突然發(fā)現(xiàn)這么好的一個(gè)常用web組件不去用實(shí)在是太可惜了，下面逐一介紹，詳細(xì)文檔大家可以去官方文檔看看，最好看它的Demo,很直觀。
javawebparts的口號(hào)是:不用重新發(fā)明輪子 !
對(duì)這點(diǎn)我是嚴(yán)重支持啊，在我的身邊看到N多所謂的牛人來到項(xiàng)目組作的第一件事就是把以前的項(xiàng)目推倒，重新實(shí)現(xiàn)自己的所謂一套先進(jìn)的東西，靠，你有多先進(jìn)啊，你的自己"方言"一邊自我欣賞，一邊還讓別人接受，再來一個(gè)人又把這個(gè)推倒，循環(huán)。。。。無語.
所以,用開源吧 ,是不是繞的太遠(yuǎn)了? :) 讓我們言歸正傳吧.
一。管理你的web配置文件信息
web的配置文件是我們經(jīng)常要用到的，配置信息我們可以分為兩大類，一類是最簡(jiǎn)單的"平板"型的,比如:
For an XML config file like this:
<
config
>
<
firstName
>
Frank
</
firstName
>
</
config
>
The following bean could be used:
public
?
class
?MyConfigBean?{
private
?
static
?String?firstName;
public
?
void
?setFirstName(String?inFirstName)?{
firstName?
=
?inFirstName;
}
public
?String?getFirstName()?{
return
?firstName;
}
}
在應(yīng)用中你不用去自己解析xml了，javawebparts已經(jīng)幫你做好了，你只要getFirstName()就可以了，是不是很方便?
你所要做的工作就是在web.xml中引用一個(gè)listener,配置如下:
<context-param>
<param-name>configFile</param-name>
<param-value>/WEB-INF/app_config.xml<?/param-value></context-param>
<context-param>
<param-name>rootElement</param-name>
<param-value>config</param-value>?</context-param>
<context-param>
<param-name>configClass</param-name>
<param-value>javawebparts.sampleapp.?SampleAppConfigBean</param-value>
</context-param>
<context-param>
<param-name>AjaxPartsTaglibConfig</param-name>
<param-value>/WEB-INF/ajax_config.xml</param-value>
</context-param>
<listener>
<listener-class>javawebparts.listener.?AppConfigContextListener</listener-class>
</listener>
這種平板型結(jié)構(gòu)的數(shù)據(jù)這樣就已經(jīng)OK了，還有一種是復(fù)雜一點(diǎn)的，有層次結(jié)構(gòu)，比如在Bean中可能還有collection,需要自己實(shí)現(xiàn)一下，也不復(fù)雜直接調(diào)用apache的Digester就可以了（實(shí)際上在javawebparts到處都有Digester的影子）,需要了解的請(qǐng)參看 用Digester解析xml到bean
二。緩存頁面
比如，我想緩存所有的gif圖片，但是jpg的不緩存，web.xml中配置如下:
<filter>
<filter-name>CacheControlFilter</filter-name>
<filter-class>javawebparts.filter.?CacheControlFilter</filter-class>
<init-param>
<param-name>pathSpec</param-name>
<param-value>include</param-value>
</init-param>
<init-param>
<param-name>pathList</param-name>
<param-value>*/header1.gif,?*.jpg</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>CacheControlFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
它的后臺(tái)實(shí)現(xiàn)機(jī)制很簡(jiǎn)單，內(nèi)部部分代碼如下:
((HttpServletResponse)response).setHeader("Pragma",?"No-cache");
((HttpServletResponse)response).setHeader("Cache-Control",
"no-cache,no-store,max-age=0");
((HttpServletResponse)response).setDateHeader("Expires",?1);
三。圖片壓縮
是不是對(duì)gzip壓縮很親切？ 對(duì)的，就是傳說中可以壓縮圖片減少網(wǎng)絡(luò)傳輸體積的玩意，現(xiàn)在你只要在web.xml中增加以下內(nèi)容就可以輕松實(shí)現(xiàn)了:
<filter>
<filter-name>CompressionFilter</filter-name>
<filter-class>javawebparts.filter.?CompressionFilter</filter-class>
<init-param>
<param-name>pathSpec</param-name>
<param-value>include</param-value>
</init-param>
<init-param>
<param-name>pathList</param-name>
<param-value>*/bigimage2.gif</?param-value>
</init-param>
<init-param>
<param-name>compressType</param-name>
<param-value>gzip_first</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>CompressionFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
上面的配置表示只對(duì)bigimage2.gif的文件進(jìn)行壓縮，其他不用,pathSpec的屬性有兩種include,exclude,意思已經(jīng)很明確了，相反地意思,而pathList得內(nèi)部實(shí)現(xiàn)也是用正則表達(dá)式實(shí)現(xiàn)的，支持*等用法.這些內(nèi)部實(shí)現(xiàn)你覺得復(fù)雜的話就不用管它了，反正人家已經(jīng)給你實(shí)現(xiàn)好了，你只要說"給我壓縮'美女與野獸.JPG'"就可以了
四.控制只在設(shè)定的時(shí)間范圍內(nèi)訪問應(yīng)用
比如說只允許在工作時(shí)間內(nèi)可以訪問應(yīng)用，其他時(shí)間禁止訪問，雖然不是很普遍不過這種需求還是有的,如果自己實(shí)現(xiàn)還是比較麻煩的，我們用現(xiàn)成的，配置如下：(怎么都是配置阿？對(duì)，全部是配置就可以了，難道不好嗎?太爽了啊，乖乖龍地動(dòng))
<filter>
<filter-name>AppAvailabilityFilter</filter-name>
<filter-class>javawebparts.filter.?AppAvailabilityFilter</filter-class>
<init-param>
<param-name>pathSpec</param-name>
<param-value>include</param-value>
</init-param>
<init-param>
<param-name>pathList</param-name>
<param-value>*/AAFTestTarget.jsp?</param-value>
</init-param>
<init-param>
<param-name>monday</param-name>
<param-value>0600-2359</param-value>
</init-param>
<init-param>
<param-name>tuesday</param-name>
<param-value>0600-2359</param-value>
</init-param>
<init-param>
<param-name>wednesday</param-name>
<param-value>0600-2359</param-value>
</init-param>
<init-param>
<param-name>thursday</param-name>
<param-value>0600-2359</param-value>
</init-param>
<init-param>
<param-name>friday</param-name>
<param-value>0600-2359</param-value>
</init-param>
<init-param>
<param-name>saturday</param-name>
<param-value>0600-2359</param-value>
</init-param>
<init-param>
<param-name>sunday</param-name>
<param-value>0600-2359</param-value>
</init-param>
<init-param>
<param-name>redirectTo</param-name>
<param-value>AAFReject.jsp<?/param-value>
</init-param>
<init-param>
<param-name>bypassCheckClass<?/param-name>
<param-value>javawebparts.sampleapp.?AAFBypassCheck</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>AppAvailabilityFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
上面的配置很明確了吧，表示在訪問AAFTestTarget.jsp 文件的時(shí)候必須在設(shè)定的時(shí)間內(nèi)，其他則無限制，很清楚了哦.
五。統(tǒng)一重定向
redirect或者forward大家都再熟悉不過了，不過這個(gè)是基于配置的，不用你寫代碼，比如，你希望在訪問某個(gè)目錄的時(shí)候自動(dòng)重訂向到其他文件，或者直接轉(zhuǎn)到其他網(wǎng)站比如google.com,配置如下:
<filter>
<filter-name>URLRedirectFilter</filter-name>
<filter-class>javawebparts.filter.URLRedirectFilter</?filter-class>
<init-param>
<param-name>configFile</param-name>
<param-value>/WEB-INF/redirect_config.xml?</param-value>
</filter>
<filter-mapping>
<filter-name>URLRedirectFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
其中redirect_config.xml配置如下:
<config>
<redirect?from="*/app/redirect_test/*"?to="http://www.google.com"?/>
<forward?from="*/app/forward/test.htm"?to="/index.jsp"?/>
</config>
很直觀吧?凡是訪問/app/redirect_test下的所有應(yīng)用都重訂向到google,太簡(jiǎn)單了,我就不多說了.
六.估算每個(gè)請(qǐng)求所花費(fèi)的時(shí)間
這個(gè)對(duì)性能調(diào)整是很有好處的,性能的調(diào)整的前提是你了解你的系統(tǒng)的瓶頸在什么地方,更具體的說是你的應(yīng)用哪些地方花費(fèi)的資源較多,一個(gè)是監(jiān)控sql的執(zhí)行情況,這里推薦jdbmonitor,大家可以去看看,另一種就是本文所說的查看每個(gè)請(qǐng)求的執(zhí)行時(shí)間,他會(huì)告訴你本請(qǐng)求花費(fèi)了多少秒,很直觀了.
配置如下:
<filter>
<filter-name>ElapsedTimeFilter</filter-name>
<filter-class>javawebparts.filter.ElapsedTimeFilter</?filter-class>
<init-param>
<param-name>pathSpec</param-name>
<param-value>include</param-value>
</init-param>
<init-param>
<param-name>pathList</param-name>
<param-value>*</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>ElapsedTimeFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
上面的一個(gè)include ,一個(gè)pathList的*就代表了所有的應(yīng)用都過濾,反之,你想暫時(shí)取消這個(gè)功能就直接把include換成exclude就行了
應(yīng)用在啟動(dòng)后你直接觀察后臺(tái)日志就可以了,就這么就OK了,還要你做什么呢? 沒有.
七.監(jiān)控session的會(huì)話
經(jīng)常碰到這樣的一個(gè)情況,用戶在登陸系統(tǒng)一段時(shí)間后session實(shí)效,但是他接著點(diǎn)擊里面的連接,結(jié)果報(bào)異常,因?yàn)閟ession里已經(jīng)取不到數(shù)據(jù)了,常常是空指針錯(cuò)誤,在每一個(gè)頁面里都進(jìn)行這種低級(jí)問題的判斷是很煩人的,現(xiàn)在我們有新的方式可以一次性解決所有的問題,還是一段簡(jiǎn)單的配置:
<filter>
<filter-name>SessionInactivityFilter<?/filter-name>
<filter-class>javawebparts.filter.?SessionInactivityFilter</filter-class>
<init-param>
<param-name>forwardTo</param-name>
<param-value>/login.jsp<?/param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>SessionInactivityFilter<?/filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
表示會(huì)話失效后直接重定向到登陸界面,讓用戶重新登陸.
八.控制訪問應(yīng)用的IP
出于安全考慮,過濾某些IP能或不能訪問,配置如下:
<filter>
<filter-name>IPAccessControlFilter</filter-name>
<filter-class>javawebparts.filter.?IPAccessControlFilter</filter-class>
<init-param>
<param-name>pathSpec</param-name>
<param-value>include</param-value>
</init-param>
<init-param>
<param-name>pathList</param-name>
<param-value>*/IACTestTarget.jsp</?param-value>
</init-param>
<init-param>
<param-name>addressSpec</param-name>
<param-value>include</param-value>
</init-param>
<init-param>
<param-name>addressList</param-name>
<param-value>localhost</param-value>
</init-param>
<init-param>
<param-name>forwardTo</param-name>
<param-value>/IACReject.jsp</param-value>?</init-param>
</filter>
<filter-mapping>
<filter-name>IPAccessControlFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
以上的配置效果就是只允許是從服務(wù)器上訪問應(yīng)用的來源(太苛刻了吧? :))
九.隨機(jī)顯示文字
比如每日一語,隨機(jī)廣告,很實(shí)用的,配置如下:
<servlet>
<servlet-name>TextReturnerServlet</servlet-name>
<servlet-class>javawebparts.servlet.?TextReturnerServlet</servlet-class>
<init-param>
<param-name>order</param-name>
<param-value>random</param-value>
</init-param>
<init-param>
<param-name>itemsFile</param-name>
<param-value>/WEB-INF/text_returner_items.xml?</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>TextReturnerServlet</servlet-name>
<url-pattern>/textReturner</url-pattern>
</servlet-mapping>
上面的配置表示隨機(jī)顯示text_returner_items.xml 中的文字,text_returner_items.xml 內(nèi)容如下:
<TextReturnerServletItems>
<item>0?-?It's?always?darkest?before?the?dawn</item>
<item>1?-?A?journey?of?a?thousand?miles?begins?with?a?single?step</item>
<item>2?-?The?universe?is?like?stupidity:?both?are?infinite
?and?actually,?I'm?not?sure?about?the?universe</item>
<item>3?-?I?believe?there?is?intelligent?life?in?the?universe,?except?for?some?parts?of?New?Jersey</item>
<item>4?-?If?your?falling?of?a?cliff,?you?might?as?well?try?and?fly</item>
<item>5?-?The?cost?of?life?is?to?chance?the?consequence</item>
</TextReturnerServletItems> 十.隨機(jī)顯示圖片
和上面有點(diǎn)類似,只是顯示的內(nèi)容可以是圖片
<servlet>
<servlet-name>RedirectReturnerServlet</servlet-name>
<servlet-class>javawebparts.servlet.?RedirectReturnerServlet</servlet-class>
<init-param>
<param-name>order</param-name>
<param-value>random</param-value>
</init-param>
<init-param>
<param-name>itemsFile</param-name>
<param-value>?/WEB-INF/redirect_returner_items.xml</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>RedirectReturnerServlet</servlet-name>
<url-pattern>/redirectReturner</url-pattern>
</servlet-mapping>
redirect_returner_items.xml的內(nèi)容如下:
<RedirectReturnerServletItems>
<item>http://www.google.com/intl/en/images/logo.gif</item>
<item>/img/header1.gif</item>
<item>/img/mouse.gif</item>
<item>http://javawebparts.sourceforge.net/logo.jpg</item>
</RedirectReturnerServletItems>
我就不用解釋了吧
十一.生成文字圖片
你提供文字,系統(tǒng)幫你生成對(duì)應(yīng)的圖片,是不是很有用? 比如驗(yàn)證碼里經(jīng)常需要用到,生成的效果如下:
配置如下:
<servlet>
<servlet-name>TextRendererServlet</servlet-name>
<servlet-class>javawebparts.servlet.?TextRendererServlet</servlet-class>
<init-param>
<param-name>fontName</param-name>
<param-value>arial</param-value>
</init-param>
<init-param>
<param-name>fontPoint</param-name>
<param-value>24</param-value>
</init-param>
<init-param>
<param-name>color</param-name>
<param-value>255,0,0?</param-value>
</init-param>
<init-param>
<param-name>backColor</param-name>
<param-value>255,255,0?</param-value>
</init-param>
<init-param>
<param-name>stylePlain</param-name>
<param-value>false</param-value>
</init-param>
<init-param>
<param-name>styleBold</param-name>
<param-value>true</param-value>
</init-param>
<init-param>
<param-name>styleItalic</param-name>
<param-value>true</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>TextRendererServlet</servlet-name>
<url-pattern>/textRenderer</url-pattern>
</servlet-mapping>
好了，基本介紹到這里，基本感覺web常碰到的東西都有所涉及，另外還有Ajax的封裝，但我個(gè)人感覺沒什么大用，如果需要可以考慮別的開源產(chǎn)品，比如prototype或者DWR等，感覺更方便.
好東西不敢獨(dú)享,如果你覺得有點(diǎn)用我就很開心了 :)