What's new in DWR version 3

What’s new in DWR v3

Joe WalkerDWR Lead DeveloperSitePen UK

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RecapSince we last talked ...

Named ParametersBinary Files

JavaScript Extending JavaBetter Reverse Ajax

Data Sync: Dojo Data StoreJSON / JSONP / JSON-RPC

Varargs and Overloaded MethodsWhat’s Next


Recap



Marshalling Types

Primitive types, and their Object counterpartsint, boolean, long, float, double, etc

Obvious classesString, Date, BigDecimal, BigInteger, Enum, etc

Arrays and CollectionsMap, List, Set, Iterator, ...

JavaBeans and ObjectsXML objects

DOM, XOM, JDom, Dom4J



Since we last talked ...

TIBCO General InterfaceSitePenhttp://svn.directwebremoting.org


Named Parameters


Named Parameters

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


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


Named Parameters

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

methods


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("ex.pdf", "application/pdf", 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("JS objects can implement Java interfaces"); } ...}

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("Hello");

// Non DWR thread have no default destinationThread t = new Thread(new Runnable()) { public void run() { // Error Window.alert("Hello"); }});



// Set the destination to be all browsers that// are looking at the current pageBrowser.withCurrentPage(new Runnable()) { public void run() { Window.alert("Hello"); }});

// Set the destination to be all browsers that// are looking at the current pageBrowser.withCurrentPage("index.html", new Runnable()) { public void run() { Window.alert("Hello"); }});



// Broadcast to everyoneBrowser.withAllSessions(...);

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

// To a known individualBrowser.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


// Low level: Use server-side W3C DOM methodsElement ele = doc.createElement("p");

ScriptSessions.addFunctionCall("document.body.appendChild",ele);

Reverse Ajax APIs: JS Level


// Low level: Any arbitrary JavaScriptString s = "if (document.all) window.alert('IE');";

ScriptSessions.addScript(s);

Reverse Ajax APIs: JS Level


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

Cookie c = new Cookie("name", "value");Document.setCookie(c);

Reverse Ajax APIs: DOM Level


// dwr.util in Javaimport org.directwebremoting.ui.dwr.Util;

String[] opts = new String[] {"one","two",...};Util.addOptions("li", opts);

Reverse Ajax APIs: dwr.util


// Scriptaculous Effects in Javaimport org.directwebremoting.ui.scriptaculous.Effect;

Effect.fade("someId");

Reverse Ajax APIs: Scriptaculous


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

Server server = GI.getServer("servername");TextBox phoneNum = server.getJSXByName("phoneNum", TextBox.class);

phoneNum.setValue("servername");

Reverse Ajax APIs: TIBCO GI


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

Editor e = Dijit.byId("price", Editor.class);e.setValue(42);

Reverse Ajax APIs: Dojo



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


Java:

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

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

// Tell DWR to expose the data to the internetDirectory.register("testServerData", provider);

Dojo Data Store


HTML:

<table id="grid" dojoType="dojox.grid.DataGrid" ><tr> <th field="name" width="120px" editable="true">Name</th> ...</tr></table>

JavaScript:

dojo.registerModulePath("dwr", "path/from/dojo/to/dwr");dojo.require("dwr.data.Store");

dwrStore = new dwr.data.Store("testServerData", { subscribe:true });dijit.byId("grid").setStore(dwrStore);

Dojo Data Store


Java:

// The StoreProvider from earlierMapStoreProvider provider = ...

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

// Mutate itdata.addPerson(new Person(...));

// The browsers viewing the data automagically update

Dojo Data Store


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


JSON / JSONP / JSON-RPC


Dojo Data Store

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


Java:

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

Shell:

$ wget http://example.com/app/dwr/jsonp/Demo/sayHello? ↩ callback=callback&param0="Joe"

-> callback("Hello, Joe");

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 () { ... },});

JSONP


JSON / JSONP / JSON-RPC

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


Java:

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

JavaScript:

Remoted.method("One", "Two", "Three");

Varargs


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


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

JavaScript:Remoted.method("String Param");Remoted.method(42);

Overloaded Methods


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 cycleGearsSMDDojo:

• Reverse Ajax API support• Auto-build

Rest


Any Questions?

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

Technology

What's new in DWR version 3