AdvancED Flex 4

INTEGRATING VIA DATA SERVICES

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The HTTP proxy adapter in BlazeDS uses the Apache HttpClient as the user agent. The configuration

max-total-connections translates to the use of a multithreaded concurrent connections manager for

HttpClient. max-connections-per-host sets the default number of connections if the host supports

hardware clustering. The allow-lax-ssl true value means self-signed certificates will work. If the

connection to the host is made through an external proxy, the external proxy can be specified in the

configuration file as well. Authentication credentials like the password can be passed to the external proxy.

Additional Useful Data Services Tips

Data services are useful and extensible pieces of software. You have seen how they can be extended to

support additional features with the help of custom factories and custom service adapters. What I discuss

next are the interesting features around run-time configuration and application security that data services

offer.

Configuring at Run Time

So far, almost all the configurations I have spoken about have related to compile-time configuration, where

the entries are made in the configuration files. However, it’s also possible to make many of these

configurations and settings at run time. Run-time configuration makes systems more flexible and

amenable to tweaking at the time of use. At run time, you can define channels, create consumers, set up

subscriptions, and affect destination configurations. However, I only show you one of these possibilities

here: channel definitions.

Defining channels at run time At run time, channels can be created on the client with the help of a

ChannelSet object, which may contain one or more Channel objects. Essentially, the process is first to

create a ChannelSet object and then dynamically create channels and add channels to it. After this, the

channel set is associated with the channelSet property of the RemoteObject. This is what a sample

piece of code may look like:

var cs:ChannelSet = new ChannelSet();

var newChannel:Channel = new AMFChannel("my-amf", endpointUrl);

cs.addChannel(newChannel);

remoteObject.channelSet = cs;

The endpoint URL can be defined dynamically at run time. ChannelSet has the ability to search among

the set of configured channels. Each channel can define a failover URL.

Application Security

In many cases, especially in enterprise scenarios, you may need to restrict access to server-side

destinations. It’s possible to define a secure destination without much trouble. Data service configurations

allow definitions for both authentication and authorization. Authentication means confirming one’s identity,

and authorization relates to the server-side resources that an authenticated user can access.

Security is configured using security constraints. These constraints can be defined at multiple levels,

namely the following:

• Global: One set of definitions for all destinations. Usually such configuration would reside in

the common configuration area: within services-config.xml itself.

• Destination specific: Security constraints for a destination. You can define such constraints

inline within the destination configuration tags.