What's new in DWR version 3

What’s new in DWR v3

Joe Walker
DWR Lead Developer
SitePen UK

Recap
Since we last talked ...
Named Parameters
Binary Files
JavaScript Extending Java
Better Reverse Ajax
Data Sync: Dojo Data Store
JSON / JSONP / JSON-RPC
Varargs and Overloaded Methods
What’s Next

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Recap


Marshalling Types

Primitive types, and their Object counterparts
int, boolean, long, ﬂoat, double, etc
Obvious classes
String, Date, BigDecimal, BigInteger, Enum, etc
Arrays and Collections
Map, List, Set, Iterator, ...
JavaBeans and Objects
XML objects
DOM, XOM, JDom, Dom4J


Since we last talked ...

TIBCO General Interface
SitePen
http://svn.directwebremoting.org


Named Parameters


Named Parameters

DWR will create client-side classes to look like
server-side classes to make passing parameters
easy


Named Parameters

Java:

public interface Person { ... }
public class Employee implements Person { ... }
public class Manager extends Employee { ... }

public HumanResources {
public void addPerson(Person p) { ... }
}

JavaScript:

Manager m = new Manager();
HumanResources.addPerson(m);


Named Parameters

Why?
• Inheritance is useful in places
• It saves creating addEmployee() and addManager()
methods


Lightweight Named
Parameters


Lightweight Named Parameters

DWR also allows a lighter-weight method of
declaring types



Java:

public interface Person { ... }
public class Employee implements Person { ... }
public class Manager extends Employee { ... }

public HumanResources {
public void addPerson(Person p) { ... }
}

JavaScript:

var m = { $dwrClassName:'Manager', firstname:'Joe', ...};
HumanResources.addPerson(m);



Why?
• Everything as for Named Parameters
• But sometimes you get an object from somewhere
else


Binary Files: File Upload



DWR has always had a long list of things that it will
marshall including Dates, DOM trees, etc

In addition, DWR will now marshall binary ﬁles just
as if they were the text resources it handles now



Java:

public Remoted {
public void receiveBinaryFile(byte[] uploaded) { ... }
}

HTML:

<input id='fileId' type='file'/>

JavaScript:

var binary = dwr.util.getValue('fileId');
Remoted.receiveBinaryFile(binary);



Will marshall to:
• byte[]
• java.awt.BufferedImage
• java.io.InputStream
• org.directwebremoting.io.FileTransfer
(gives access to ﬁlename and mime-type in
addition to the contents)



Why?
• This is a lot easier than using commons-ﬁleupload
or similar
• We can provide integration with progress bar
widgets


Binary Files: Download



Binary ﬁle handling is 2 way. It’s good for:
• Images
• PDF ﬁles
• Word, Excel documents
• etc.



Java:
public Remoted {
public void getPDF(String contents) {
ByteArrayOutputStream buf = new ByteArrayOutputStream();
Document doc = new Document();
PdfWriter.getInstance(doc, buf);
doc.open();
doc.add(new Paragraph(contents));
doc.close();
return new FileTransfer(quot;ex.pdfquot;, quot;application/pdfquot;, buf.toByteArray());
}

JavaScript:
Remoted.getPDF('Joe', function(data) {
dwr.engine.openInDownload(data);
});



Why?
• This is a lot easier than creating a special PDF/
image/etc serving servlet


Javascript extending Java



DWR will allow you to implement Java interfaces
using JavaScript


Java:
public interface BazListener {
void somethingChanged(String msg);
}
public class Remote {
public void addBazListener(BazListener bl) { ... }

public void calledLater() {
for (BazListener bl : listeners)
bl.somethingChanged(quot;JS objects can implement Java interfacesquot;);
}
...
}

JavaScript:
function BazListener() {this.$dwrByRef;}
BazListener.prototype.somethingChanged = function(msg){alert(msg);};

var bl = new BazListener();
Remote.addBazListener(bl);



Why?
• Intuitive way to interact
• Easy Pub-sub
• Allows interaction with existing APIs


Scalable Reverse Ajax



Previously there were some scalability limitations
with the 2.0 reverse ajax API.
3.0 deprecates the problem areas.



Reverse Ajax proxies no longer take a list of
ScriptSessions in the constructor, they just write to
the current ‘destination’

The Browser API allows you to change the current
‘destination’



// The default destination is the browser
// that caused the current action to happen.
Window.alert(quot;Helloquot;);

// Non DWR thread have no default destination
Thread t = new Thread(new Runnable()) {
public void run() {
// Error
}
});



// Set the destination to be all browsers that
// are looking at the current page
Browser.withCurrentPage(new Runnable()) {
public void run() {
}
});

// Set the destination to be all browsers that
// are looking at the current page
Browser.withCurrentPage(quot;index.htmlquot;, new Runnable()) {
public void run() {
}
});



// Broadcast to everyone
Browser.withAllSessions(...);

// Broadcast to subsets
Browser.with*Filtered(scriptSesssionFilter, ...);

// To a known individual
Browser.withSession(sessionId, ...);



Why?
• It’s generally easier to use
• It decouples generation from routing
• It scales


Reverse Ajax APIs


Reverse Ajax APIs

Reverse Ajax != Comet

Reverse Ajax == Comet + Polling + Piggyback


Reverse Ajax APIs: JS Level

// Low level: Use server-side W3C DOM methods
Element ele = doc.createElement(quot;pquot;);

ScriptSessions.addFunctionCall(
quot;document.body.appendChildquot;,
ele);


Reverse Ajax APIs: JS Level

// Low level: Any arbitrary JavaScript
String s = quot;if (document.all) window.alert('IE');quot;;

ScriptSessions.addScript(s);


Reverse Ajax APIs: DOM Level

// Some methods from Window and Document
import javax.servlet.http.Cookie;
import org.directwebremoting.ui.browser.Document;

Cookie c = new Cookie(quot;namequot;, quot;valuequot;);
Document.setCookie(c);


Reverse Ajax APIs: dwr.util

// dwr.util in Java
import org.directwebremoting.ui.dwr.Util;

String[] opts = new String[] {quot;onequot;,quot;twoquot;,...};
Util.addOptions(quot;liquot;, opts);


Reverse Ajax APIs: Scriptaculous

// Scriptaculous Effects in Java
import org.directwebremoting.ui.scriptaculous.Effect;

Effect.fade(quot;someIdquot;);


Reverse Ajax APIs: TIBCO GI

// TIBCO General Interface in Java
import jsx3.GI;
import jsx3.app.*;
import jsx3.gui.*;

Server server = GI.getServer(quot;servernamequot;);
TextBox phoneNum = server.getJSXByName(quot;phoneNumquot;,
TextBox.class);

phoneNum.setValue(quot;servernamequot;);


Reverse Ajax APIs: Dojo

// Dojo in Java
import org.dojotoolkit.dijit.Dijit;
import org.dojotoolkit.dijit.Editor;

Editor e = Dijit.byId(quot;pricequot;, Editor.class);
e.setValue(42);



Why?
• A full range of APIs for dynamically updating client
data
• DWR doesn’t do widgets, but it does talk to the
people that do

Drapgen can be used to create and maintain large
APIs


Dojo Data Store


Dojo Data Store

DWR now implements all 4 interfaces to allow Dojo
to sync data with Java code on the server


Dojo Data Store

Java:

// Load the data somehow
Map<String, Person> ppl = ...;

// Create an implementation of StoreProvider to hold the data
MapStoreProvider provider = new MapStoreProvider(ppl, Person.class);

// Tell DWR to expose the data to the internet
Directory.register(quot;testServerDataquot;, provider);


Dojo Data Store

HTML:
<table id=quot;gridquot; dojoType=quot;dojox.grid.DataGridquot; ><tr>
<th field=quot;namequot; width=quot;120pxquot; editable=quot;truequot;>Name</th>
...
</tr></table>

JavaScript:
dojo.registerModulePath(quot;dwrquot;, quot;path/from/dojo/to/dwrquot;);
dojo.require(quot;dwr.data.Storequot;);

dwrStore = new dwr.data.Store(quot;testServerDataquot;, { subscribe:true });
dijit.byId(quot;gridquot;).setStore(dwrStore);


Dojo Data Store

Java:

// The StoreProvider from earlier
MapStoreProvider provider = ...

// Get a representation of the internal data
Map<String, Person> data = provider.asMap();

// Mutate it
data.addPerson(new Person(...));

// The browsers viewing the data automagically update


Dojo Data Store

Why?
• Data-Sync APIs are hard to get right, but are really
simple to use
• There is lots of potential for network level
optimization


Dojo Data Store

DWR now supports:
• plain JSON
• JSONP
• JSON-RPC


JSONP

Java:

public class Demo {
public sayHello(String name) {
return quot;Hello, quot; + name;
}
}

Shell:

$ wget http://example.com/app/dwr/jsonp/Demo/sayHello? ↩
callback=callback&param0=quot;Joequot;

-> callback(quot;Hello, Joequot;);


JSONP
Dojo:

dojo.io.script.get({
url:'http://example.com/app/dwr/jsonp/Demo/sayHello',
content:{param:'Joe'}
}).addCallback(function() { ... });

JQuery:

$.ajax({
dataType:'jsonp',
data:'param=Joe',
url:'http://example.com/app/dwr/jsonp/Demo/sayHello',
success:function () { ... },
});



Why?
• To allow DWR to remote functions to things other
than a DWR client
• ‘DWRP’ is designed to be something we can change
without a long deprecation process


Varargs


Varargs

You can now call methods with a vararg parameter


Varargs

Java:

public Remoted {
public void method(String... arg) { ... }
}

JavaScript:

Remoted.method(quot;Onequot;, quot;Twoquot;, quot;Threequot;);


Varargs

Why?
• It saves the hassle of wrapping options in an array
or collection before a method is called

Alert:
• It could break some corner cases when mixing
servlet parameters with normal parameters


Overloaded Methods


Overloaded Methods

Previously DWR prevented you from reliably calling
overloaded methods


Overloaded Methods

Java:
public Remoted {
public void method(int num) {
log.debug(quot;int method called with quot; + num);
}
public void method(String str) {
log.debug(quot;String method called with quot; + str);
}
}

JavaScript:
Remoted.method(quot;String Paramquot;);
Remoted.method(42);


Overloaded Methods

Why?
• It saves you from creating multiple proxy methods
to existing APIs


What’s Next


Top Directions for DWR 3.1

Shorter release cycle
Gears
SMD
Dojo:
• Reverse Ajax API support
• Auto-build
Rest


Any Questions?

• http://directwebremoting.org
• http://sitepen.com


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