AJAX，或者说是异步JavaScript和XML，
描述了一种使用混合了HTML(或XHTML)和层叠样式表作为表达信息,
来创建交互式的Web应用的开发技术;文档对象模型（DOM），
JavaScript,动态地显示和与表达信息进行交互;并且XMLHttpRequest对象与Web服务器异步地交换和处理数据。
DWR(直接Web远程控制)项目是在Apache许可下的一个开源的解决方案，
它供给那些想要以一种简单的方式使用AJAX和 XMLHttpRequest的开发者。
它具有一套Javascript功能集，它们把从HTML页面调用应用服务器上的Java对象的方法简化了。
它操控不同类型的参数，并同时保持了HTML代码的可读性，它可以与spring结合在一起。
举个非常实用的小例子，检测是否有重复的用户名
1。web。xml的配置（包括spring和dwr）
<?
xmlversion="1.0"encoding="ISO-8859-1"
?>
<!
DOCTYPEweb-app
PUBLIC"-//SunMicrosystems,Inc.//DTDWebApplication2.3//EN"
"http://java.sun.com/j2ee/dtds/web-app_2_3.dtd"
>
<
web-app
>
<
context-param
>
<
param-name
>
log4jConfigLocation
</
param-name
>
<
param-value
>
/WEB-INF/log4j.properties
</
param-value
>
</
context-param
>
<
context-param
>
<
param-name
>
contextConfigLocation
</
param-name
>
<
param-value
>
/WEB-INF/applicationContext.xml,/WEB-INF/main-servlet.xml
</
param-value
>
</
context-param
>
<
listener
>
<
listener-class
>
org.springframework.web.util.Log4jConfigListener
</
listener-class
>
</
listener
>
<
servlet
>
<
servlet-name
>
context
</
servlet-name
>
<
servlet-class
>
org.springframework.web.context.ContextLoaderServlet
</
servlet-class
>
<
load-on-startup
>
1
</
load-on-startup
>
</
servlet
>
<
servlet
>
<
servlet-name
>
dwr
</
servlet-name
>
<
display-name
>
DWRServlet
</
display-name
>
<
description
>
DirectWebRemoterServlet
</
description
>
<
servlet-class
>
uk.ltd.getahead.dwr.DWRServlet
</
servlet-class
>
<
init-param
>
<
param-name
>
debug
</
param-name
>
<
param-value
>
true
</
param-value
>
</
init-param
>
</
servlet
>
<
servlet-mapping
>
<
servlet-name
>
dwr
</
servlet-name
>
<
url-pattern
>
/dwr/*
</
url-pattern
>
</
servlet-mapping
>
</
web-app
>
<?
xmlversion="1.0"encoding="UTF-8"
?>
<!
DOCTYPEbeansPUBLIC"-//SPRING//DTDBEAN//EN""http://www.springframework.org/dtd/spring-beans.dtd"
>
<
beans
>
<
bean
id
="propertyConfigurer"
class
="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer"
>
<
property
name
="location"
>
<
value
>
/WEB-INF/jdbc.properties
</
value
>
</
property
>
</
bean
>
<!--
LocalDataSourcethatworksinanyenvironment
-->
<
bean
id
="dataSource"
class
="org.springframework.jdbc.datasource.DriverManagerDataSource"
>
<
property
name
="driverClassName"
>
<
value
>
${jdbc.driverClassName}
</
value
>
</
property
>
<
property
name
="url"
>
<
value
>
${jdbc.url}
</
value
>
</
property
>
<
property
name
="username"
>
<
value
>
${jdbc.username}
</
value
>
</
property
>
<
property
name
="password"
>
<
value
>
${jdbc.password}
</
value
>
</
property
>
</
bean
>
<!--
OrderManager
-->
<
bean
id
="UserManager"
class
="dwr.manager.UserManager"
>
<
property
name
="dataSource"
>
<
ref
local
="dataSource"
/>
</
property
>
</
bean
>
</
beans
>
package
dwr.manager;
import
org.springframework.jdbc.core.support.JdbcDaoSupport;
import
org.apache.commons.logging.Log;
import
org.apache.commons.logging.LogFactory;
public
class
UserManager
extends
JdbcDaoSupport
{
private
final
Loglog
=
LogFactory.getLog(getClass().getName());
public
boolean
getUser(Stringusername)
{
Stringsql
=
"
selectcount(*)fromuserwhereuserName=?
"
;
int
i
=
getJdbcTemplate().queryForInt(sql,
new
Object[]
{username}
);
if
(i
>
0
)
return
true
;
else
return
false
;
}
}
<%
@pagecontentType
=
"
text/html;charset=GBK
"
language
=
"
java
"
%>
<
html
>
<
head
><
title
>
Simplejsppage
</
title
></
head
>
<
script
type
='text/javascript'
src
='<%=request.getContextPath()%
>
/
dwr
/
interface
/
UserManager.js
'
>
</script>
<scripttype=
'
text
/
javascript
'
src=
'
<%=
request.getContextPath()
%>/
dwr
/
engine.js
'
>
</script>
<scripttype=
'
text
/
javascript
'
src=
'
<%=
request.getContextPath()
%>/
dwr
/
util.js
'
></script>
<scripttype="text/javascript">
functionshowResult(b){
if(b){
alert("已经有重复的登录名了！");
}else{
alert("登录名尚未注册过！");
}
}functioncheckRepeat(s){
varo=getElement(s);
if(o){
UserManager.getUser(o.value,showResult);
}
}
functiongetElement(name){
varresult=null;
varobjs=document.getElementsByName(name);
if(objs){
varo=objs[0];
result=o;
}
returnresult;
}
</script>
<body>
<inputtype="text"name="user">
<inputtype="button"onclick="checkRepeat(
'
user
'
)"value="检查是否重复">
</body>
</html>
6 classpath加入dwr和spring的jar文件，注意必须有hibernate3.jar和bsf.jar，在IE和FireFox下，就可以用了。
其中参考了magicgod's blog（ http://www.matrix.org.cn/blog/magicgod/archives/week_2005_09_04.html#001419 ）
描述了一种使用混合了HTML(或XHTML)和层叠样式表作为表达信息,
来创建交互式的Web应用的开发技术;文档对象模型（DOM），
JavaScript,动态地显示和与表达信息进行交互;并且XMLHttpRequest对象与Web服务器异步地交换和处理数据。
DWR(直接Web远程控制)项目是在Apache许可下的一个开源的解决方案，
它供给那些想要以一种简单的方式使用AJAX和 XMLHttpRequest的开发者。
它具有一套Javascript功能集，它们把从HTML页面调用应用服务器上的Java对象的方法简化了。
它操控不同类型的参数，并同时保持了HTML代码的可读性，它可以与spring结合在一起。
举个非常实用的小例子，检测是否有重复的用户名
1。web。xml的配置（包括spring和dwr）
<?
xmlversion="1.0"encoding="ISO-8859-1"
?>
<!
DOCTYPEweb-app
PUBLIC"-//SunMicrosystems,Inc.//DTDWebApplication2.3//EN"
"http://java.sun.com/j2ee/dtds/web-app_2_3.dtd"
>
<
web-app
>
<
context-param
>
<
param-name
>
log4jConfigLocation
</
param-name
>
<
param-value
>
/WEB-INF/log4j.properties
</
param-value
>
</
context-param
>
<
context-param
>
<
param-name
>
contextConfigLocation
</
param-name
>
<
param-value
>
/WEB-INF/applicationContext.xml,/WEB-INF/main-servlet.xml
</
param-value
>
</
context-param
>
<
listener
>
<
listener-class
>
org.springframework.web.util.Log4jConfigListener
</
listener-class
>
</
listener
>
<
servlet
>
<
servlet-name
>
context
</
servlet-name
>
<
servlet-class
>
org.springframework.web.context.ContextLoaderServlet
</
servlet-class
>
<
load-on-startup
>
1
</
load-on-startup
>
</
servlet
>
<
servlet
>
<
servlet-name
>
dwr
</
servlet-name
>
<
display-name
>
DWRServlet
</
display-name
>
<
description
>
DirectWebRemoterServlet
</
description
>
<
servlet-class
>
uk.ltd.getahead.dwr.DWRServlet
</
servlet-class
>
<
init-param
>
<
param-name
>
debug
</
param-name
>
<
param-value
>
true
</
param-value
>
</
init-param
>
</
servlet
>
<
servlet-mapping
>
<
servlet-name
>
dwr
</
servlet-name
>
<
url-pattern
>
/dwr/*
</
url-pattern
>
</
servlet-mapping
>
</
web-app
>
2。dwr。xml的配置
<?
xmlversion="1.0"encoding="UTF-8"
?>
<! DOCTYPEdwrPUBLIC"-//GetAheadLimited//DTDDirectWebRemoting1.0//EN""http://www.getahead.ltd.uk/dwr/dwr10.dtd" >
< dwr >
< allow >
< create
creator ="spring"
javascript ="UserManager" >
< param name ="beanName" value ="UserManager" />
</ create >
</ allow >
</ dwr >
<! DOCTYPEdwrPUBLIC"-//GetAheadLimited//DTDDirectWebRemoting1.0//EN""http://www.getahead.ltd.uk/dwr/dwr10.dtd" >
< dwr >
< allow >
< create
creator ="spring"
javascript ="UserManager" >
< param name ="beanName" value ="UserManager" />
</ create >
</ allow >
</ dwr >
3。applicationContext.xml文件
<?
xmlversion="1.0"encoding="UTF-8"
?>
<!
DOCTYPEbeansPUBLIC"-//SPRING//DTDBEAN//EN""http://www.springframework.org/dtd/spring-beans.dtd"
>
<
beans
>
<
bean
id
="propertyConfigurer"
class
="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer"
>
<
property
name
="location"
>
<
value
>
/WEB-INF/jdbc.properties
</
value
>
</
property
>
</
bean
>
<!--
LocalDataSourcethatworksinanyenvironment
-->
<
bean
id
="dataSource"
class
="org.springframework.jdbc.datasource.DriverManagerDataSource"
>
<
property
name
="driverClassName"
>
<
value
>
${jdbc.driverClassName}
</
value
>
</
property
>
<
property
name
="url"
>
<
value
>
${jdbc.url}
</
value
>
</
property
>
<
property
name
="username"
>
<
value
>
${jdbc.username}
</
value
>
</
property
>
<
property
name
="password"
>
<
value
>
${jdbc.password}
</
value
>
</
property
>
</
bean
>
<!--
OrderManager
-->
<
bean
id
="UserManager"
class
="dwr.manager.UserManager"
>
<
property
name
="dataSource"
>
<
ref
local
="dataSource"
/>
</
property
>
</
bean
>
</
beans
>
4。。spring的bean
package
dwr.manager;
import
org.springframework.jdbc.core.support.JdbcDaoSupport;
import
org.apache.commons.logging.Log;
import
org.apache.commons.logging.LogFactory;
public
class
UserManager
extends
JdbcDaoSupport
{
private
final
Loglog
=
LogFactory.getLog(getClass().getName());
public
boolean
getUser(Stringusername)
{
Stringsql
=
"
selectcount(*)fromuserwhereuserName=?
"
;
int
i
=
getJdbcTemplate().queryForInt(sql,
new
Object[]
{username}
);
if
(i
>
0
)
return
true
;
else
return
false
;
}
}
5。jsp的代码
<%
@pagecontentType
=
"
text/html;charset=GBK
"
language
=
"
java
"
%>
<
html
>
<
head
><
title
>
Simplejsppage
</
title
></
head
>
<
script
type
='text/javascript'
src
='<%=request.getContextPath()%
>
/
dwr
/
interface
/
UserManager.js
'
>
</script>
<scripttype=
'
text
/
javascript
'
src=
'
<%=
request.getContextPath()
%>/
dwr
/
engine.js
'
>
</script>
<scripttype=
'
text
/
javascript
'
src=
'
<%=
request.getContextPath()
%>/
dwr
/
util.js
'
></script>
<scripttype="text/javascript">
functionshowResult(b){
if(b){
alert("已经有重复的登录名了！");
}else{
alert("登录名尚未注册过！");
}
}functioncheckRepeat(s){
varo=getElement(s);
if(o){
UserManager.getUser(o.value,showResult);
}
}
functiongetElement(name){
varresult=null;
varobjs=document.getElementsByName(name);
if(objs){
varo=objs[0];
result=o;
}
returnresult;
}
</script>
<body>
<inputtype="text"name="user">
<inputtype="button"onclick="checkRepeat(
'
user
'
)"value="检查是否重复">
</body>
</html>
6 classpath加入dwr和spring的jar文件，注意必须有hibernate3.jar和bsf.jar，在IE和FireFox下，就可以用了。
其中参考了magicgod's blog（ http://www.matrix.org.cn/blog/magicgod/archives/week_2005_09_04.html#001419 ）
