原創(chuàng)文章，轉(zhuǎn)載請(qǐng)注明作者：Nomad，出處：
www.jialing.net
??? 在網(wǎng)上找了一圈Ajax的Java框架，感覺(jué)不錯(cuò)的只有兩個(gè)，一個(gè)是被提到比較多的DWR（Direct Web Remoting)，另一個(gè)是剛剛1.0的Ajax4JSF。本文先用代碼說(shuō)話，各用兩個(gè)框架開(kāi)發(fā)同樣功能的Ajax輸入驗(yàn)證的小程序。在最后表達(dá)一下鄙人對(duì)這兩個(gè)框架的淺見(jiàn)。
·程序功能??? 頁(yè)面上有兩個(gè)輸入框，一個(gè)填用戶名，一個(gè)填密碼。兩個(gè)框空著時(shí)提示“請(qǐng)?zhí)顚?xiě)”；用戶名字符長(zhǎng)度小于3時(shí)提示“長(zhǎng)度應(yīng)大于3”；當(dāng)用戶名是“root”，密碼是“123”時(shí)提示密碼正確，否則提示密碼錯(cuò)誤。
·DWR的實(shí)現(xiàn)??? Java邏輯： 這是提供給頁(yè)面異步調(diào)用的Java代碼
?1?package?net.jialing;
?2?
?3?public?class?ValidateBean?{
?4?
?5?????public?String?checkName(String?name)?{
?6?????????if(name?==?null?||?name.equals(""))?return?"請(qǐng)?zhí)钊胗脩裘?/span>";
?7?????????
?8?????????if(name.length()<3)?return?"用戶名長(zhǎng)度須大于3";
?9?????????
10?????????return?"";
11?????}
12?
13?????public?String?checkPwd(String?name,String?password)?{
14?????????if(password?==?null?||?password.equals(""))?return?"請(qǐng)?zhí)钊朊艽a";
15?????????
16?????????if(name?!=?null?&&?password?!=?null)?{
17?????????????if(name.equals("root")?&&?password.equals("123"))
18?????????????????return?"密碼正確！";
19?????????????else
20?????????????????return?"密碼不正確！";
21?????????}
22?????????
23?????????return?"";
24?????}
25?
26?}
??? DWR的配置：
<dwr>
??<allow>
????<create?creator="new"?javascript="JValidate">
????????<param?name="class"?value="net.jialing.ValidateBean"/>
????</create>
??</allow>
</dwr>
??? JSP頁(yè)面：在頁(yè)面中寫(xiě)了四個(gè)函數(shù)來(lái)調(diào)用各自的Java驗(yàn)證代碼。
<%@?page?contentType="text/html;?charset=gb2312"?language="java"?errorPage=""?%>
<!DOCTYPE?HTML?PUBLIC?"-//W3C//DTD?HTML?4.01?Transitional//EN"?"http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta?http-equiv="Content-Type"?content="text/html;?charset=gb2312">
<title>Struts?+?DWR?AJAX?Validation</title>
<script?type='text/javascript'?src='dwr/engine.js'></script>
<script?type='text/javascript'?src='dwr/util.js'></script>
<script?type='text/javascript'?src='dwr/interface/JValidate.js'></script>
<script>
function?changeName()?{
????var?name?=?document.getElementById("name").value;
????JValidate.checkName(name,validateName);
}
function?validateName(data)?{
????document.getElementById("name_message").innerHTML?=?data;
}
function?changePwd()?{
????var?name?=?document.getElementById("name").value;
????var?pwd?=?document.getElementById("password").value;
????JValidate.checkPwd(name,pwd,validatePwd);
}
function?validatePwd(data)?{
????document.getElementById("password_message").innerHTML?=?data;
}
</script>
</head>
<body>
Struts?+?DWR?AJAX?Validation:?<br>
Name:<input?name="name"?type="text"?id="name"?onkeyup="changeName()">?<label?id="name_message"></label><br>
Password:<input?name="password"?type="password"?id="password"?onkeyup="changePwd()">?<label?id=?password_message"></label>
</body>
</html>
?? ?
·A4J的實(shí)現(xiàn)??? Java邏輯：這是JSF控制下的JavaBean
package?net.jialing;
public?class?ValidateBean?{
????private?String?name;
????private?String?password;
????private?String?name_message;
????private?String?password_message;
????public?String?getName()?{
????????return?name;
????}
????public?void?setName(String?name)?{
????????this.name?=?name;
????}
????public?String?getName_message()?{
????????if(name?==?null?||?name.equals(""))?return?"請(qǐng)?zhí)钊胗脩裘?/span>";
????????
????????if(name.length()<3)?return?"用戶名長(zhǎng)度須大于3";
????????
????????return?"";
????}
????public?void?setName_message(String?name_message)?{
????????this.name_message?=?name_message;
????}
????public?String?getPassword()?{
????????return?password;
????}
????public?void?setPassword(String?password)?{
????????this.password?=?password;
????}
????public?String?getPassword_message()?{
????????if(password?==?null?||?password.equals(""))?return?"請(qǐng)?zhí)钊朊艽a";
????????
????????if(name?!=?null?&&?password?!=?null)?{
????????????if(name.equals("root")?&&?password.equals("123"))
????????????????return?"密碼正確！";
????????????else
????????????????return?"密碼不正確！";
????????}
????????
????????return?"";
????}
????public?void?setPassword_message(String?password_message)?{
????????this.password_message?=?password_message;
????}
}
??? JSF的配置：
<faces-config>
<managed-bean>
????????<managed-bean-name>validate</managed-bean-name>
????????<managed-bean-class>
????????????net.jialing.ValidateBean
????????</managed-bean-class>
????????<managed-bean-scope>request</managed-bean-scope>
????????<managed-property>
????????????<property-name>name</property-name>
????????????<null-value/>
????????</managed-property>
????????<managed-property>
????????????<property-name>password</property-name>
????????????<null-value/>
????????</managed-property>
????????<managed-property>
????????????<property-name>name_message</property-name>
????????????<null-value/>
????????</managed-property>
????????<managed-property>
????????????<property-name>password_message</property-name>
????????????<null-value/>
????????</managed-property>
</managed-bean>
</faces-config>
??? JSP頁(yè)面：
<%@?page?language="java"?pageEncoding="ISO-8859-1"%>
<%@?taglib?uri="https://ajax4jsf.dev.java.net/ajax"?prefix="a4j"%>
<%@?taglib?uri="http://java.sun.com/jsf/html"?prefix="h"?%>
<%@?taglib?uri="http://java.sun.com/jsf/core"?prefix="f"?%>
<!DOCTYPE?HTML?PUBLIC?"-//W3C//DTD?HTML?4.01?Transitional//EN">
<html>
<head>
????<title>Ajax4JSF?Validate?Page</title>
</head>
<body>
????<f:view>
????????This?is?my?Ajax4JSF?Validate?page.?<br>
????????<h:form>
????????????Name:<h:inputText?id="name"?value="#{validate.name}"?>
????????<a4j:support?event="onkeyup"?reRender="rename"?/>
????????</h:inputText>?<h:outputText?id="rename"?value="#{validate.name_message}"?/><br>
????????
????????????Password:<h:inputSecret?id="password"?value="#{validate.password}"?>
????????<a4j:support?event="onkeyup"?reRender="repwd"?/>
??????????</h:inputSecret>?<h:outputText?id="repwd"?value="#{validate.password_message}"?/>
????????</h:form>
????</f:view>
</body>
</html>
·對(duì)比1.代碼量
??? 這是程序員最關(guān)心問(wèn)題，哪個(gè)框架能減輕我們更多的負(fù)擔(dān)呢。首先看Java代碼，DWR似乎比A4J少一點(diǎn)，其實(shí)不然，因?yàn)锳4J是基于JSF的Managed Bean上開(kāi)發(fā)的，所以Bean里的其它代碼都可以用到JSF其它的地方，所以Java的開(kāi)發(fā)量是相同的。其次看配置量，A4J稍有一些優(yōu)勢(shì)，只要在JSF中配置了就不用在配置，而DWR還需要再配置一個(gè)XML文件。最后看頁(yè)面的代碼量，這一點(diǎn)A4J的優(yōu)勢(shì)更加明顯，程序員完全不用寫(xiě)JavaScript代碼，只需將要異步刷新的地方加入a4j的標(biāo)簽即可。
??? 總的來(lái)說(shuō)，在節(jié)省代碼量這個(gè)方面A4J是勝利的。
2.靈活性
??? 這一點(diǎn)DWR是明顯的贏家，DWR適合各種框架，在設(shè)計(jì)時(shí)都考慮到了如Spring、JSF、Struts等的集成。而A4J僅適合JSF框架，對(duì)應(yīng)用范圍做了很大的限制。在集成方面不僅僅是Java框架，還有現(xiàn)在越來(lái)越流行的JavaScript框架（如Dojo、Qooxdoo等），因?yàn)锳4J封裝了JavaScript代碼，開(kāi)發(fā)者無(wú)法像DWR一樣可以自由的使用JavaScript。當(dāng)開(kāi)發(fā)者習(xí)慣于將一些邏輯寫(xiě)在JavaScipt中時(shí)，使用A4J可能會(huì)造成很多的不便。
3.風(fēng)險(xiǎn)性
??? A4J以標(biāo)簽為開(kāi)發(fā)手段，減去了應(yīng)用程序開(kāi)發(fā)者在JavaScript和DHTML等方面開(kāi)發(fā)的時(shí)間，但同時(shí)也可能埋下風(fēng)險(xiǎn)的隱患。在開(kāi)發(fā)一個(gè)Web應(yīng)用的時(shí)候，開(kāi)發(fā)者需要全面的評(píng)估應(yīng)用中會(huì)使用到的技術(shù)功能，確定利用A4J可以實(shí)現(xiàn)，畢竟這是一個(gè)新成長(zhǎng)起來(lái)的框架，需要更加留意。另外在安全方面，兩個(gè)框架都還無(wú)從考證。
4.前景
??? DWR在2.0里實(shí)現(xiàn)了Ajax的反轉(zhuǎn)，即在Java中執(zhí)行JavaScript代碼，似乎標(biāo)志著一種新的開(kāi)發(fā)方式。A4J則搭上了JSF這趟快車，各個(gè)大公司都在謀劃著將應(yīng)用開(kāi)發(fā)進(jìn)一步的分工，上游廠商制定組件，下游的公司使用組件為企業(yè)提供服務(wù)，JSF是它們賺錢的一個(gè)好工具，一定會(huì)繼續(xù)推而廣之，而A4J也會(huì)隨著JSF的成長(zhǎng)而成長(zhǎng)。
·總結(jié)??? 也許還不到總結(jié)的時(shí)候。我想用DWR還是A4J，可以參考究竟使用Struts還是JSF，DWR的靈活性和Struts是對(duì)應(yīng)的，兩者結(jié)合可以開(kāi)發(fā)出靈活性很高的程序。A4J則肯定和JSF搭配，JSF的組件樹(shù)也可以讓開(kāi)發(fā)的速度加快。
·參考DWR：http://getahead.ltd.uk/dwr
Ajax4jsf: https://ajax4jsf.dev.java.net/
·示例下載基于DWR的示例：http://www.jialing.net/download/ajax/Struts_DWR_Validate.rar
基于A4J的示例：http://www.jialing.net/download/ajax/A4J_Validate.rar