It is a technique by which interaction between
client and server takes place by marshalling objects to and fro (Java script object to Java object and vice versa).
The actual remote calls takes place using Ajax with out even user know about it.
It can call any java objects directly from Java script without having own servlet class, its inbuilt DWRServlet do your work. It has inbuilt Ajax,Object Serialization etc., and it also provides
utility scripts to format display data in the web page.
The learning curve of DWR is steep. User just have to know about using config file and using utility classes provided by DWR.
Here is one of the simple way to implment DWR.
Have these java classes in the classpath
DataManager.Java
public List getCustomers(){
List list = new ArrayList();
list.add(new Customer(1, "Bill", "Los Angeles", "000000001"));
list.add(new Customer(2, "Kumar", "Chennai", 00000000020"));
list.add(new Customer(3, "Tom", "Chicago", "000000003"));
list.add(new Customer(4, "Chian", "Kualalumpur", 000000004"));
list.add(new Customer(5, "Hong", "Singapore", "000000005"));
list.add(new Customer(6, "Jade", "Holborn", "0000000006"));
return list;
}
Customer.java
private int id; private String name; private String city; private String phone;
//have getter/setter methods for above.
DWR Configuration
Have this in claspath, preferably under WEB-INF
<!DOCTYPE dwr PUBLIC
"-//GetAhead Limited//DTD Direct Web Remoting 2.0//EN"
"http://getahead.org/dwr/dwr20.dtd">
<dwr>
<allow>
<create creator="new" javascript="JDate">
<param name="class" value="java.util.Date"/>
</create>
<create creator="new" javascript="DataManager" scope="session">
<param name="class" value="com.dwrtest.data.DataManager" />
</create>
<convert converter="bean" match="com.dwrtest.data.Customer"/>
</allow>
</dwr>
Add DWRServlet to web.xml
<servlet>
<servlet-name>dwr-invoker</servlet-name>
<display-name>DWR Servlet</display-name>
<description>DWR Servlet</description>
<servlet-lass>
org.directwebremoting.servlet.DwrServlet
</servlet-class>
<init-param></servlet-class>
<param-name>debug</param-name>
<param-value>true</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>dwr-invoker</servlet-name>
<url-pattern>/dwr/*</url-pattern>
</servlet-mapping>
Testing
http://localhost:<port>/<your-webapp-context>/dwr/index.html
you should be able to see
DataManager
JDate
which is defined in dwr.xml
Clicking on DataManager will show methods defined in that. You can test methods by passing required parameters if any by clicking 'Execute' buttons.
If that works you can go to next step creating your jsp.
test.jsp
Have the below given scripts
<script type='text/javascript' src='/dwrtest/dwr/engine.js'></script>
<script type='text/javascript' src='/dwrtest/dwr/util.js'></script>
<script type='text/javascript' src='/dwrtest/dwr/interface/DataManager.js'></script>
//DataManager.jsp corresponds to the name defined in dwr.xml
function handleData(dat) {
dwr.util.addRows( "mytable",dat,[function(dat){{return dat.name}},function(dat){{return dat.city}},function(dat){{return dat.phone}}]);
dwr.util.addOptions("myselect",dat,"name","name");
}
function loadData(){
DataManager.getCustomers(handleData);
}
<table id='mytable' border="1">
</table>
Optons:<br/>
<select id='myselect'>
</select>
Output
Table :
| Bill | Los Angeles | 000000001 |
| Kumar | Chennai | 00000000020 |
| Tom | Chicago | 000000003 |
| Chian | Kualalumpur | 0000000004 |
| Hong | Singapore | 000000005 |
| Jade | Holborn | 0000000006 |
Options
Download : DWR
Reference : Documentation
