| Making Pro/ENGINEER data accessible via the
Web: Using J-Link and Pro/Web.Link as a component of Web
applications
Scott Conover Pro/ENGINEER models represent a
rich storehouse of information such as design intent, annotations,
and manufacturing details that could be valuable to your business if
you could make it available to employees outside the design team
that created the data. There may also be situations where automating
frequent or tedious, error-prone tasks for Pro/ENGINEER designers
could improve their productivity and your company's bottom line.
Both of these problems can be addressed using a customized Java web
application, applied using one or both of Pro/ENGINEER's free
customization tools: J-Link and Pro/Web.Link. These tools allow
deployment of customized Web applications accessing Pro/ENGINEER and
Pro/ENGINEER data either from within Pro/ENGINEER or via
light-weight, Pro/ENGINEER-independent web clients.
Java Web
Applications
Java web applications are structured to
perform an operation on a server but interact with one or more
clients. Typically Java web applications fall under two categories:
Servlet and Java Server Pages (JSP).
Servlets are
Java classes constructed specifically to handle client requests and
serve responses. These are the most flexible type of Web
application, capable of generating virtually any type of output. A
Servlet class extends a standard supported Java interface:
javax.servlet.Servlet. The servlet Java code executes in the context
of a “servlet engine” on the server. Typically, servlets are
deployed on a Web Server supporting HTTP (Hyper-Text Transfer
Protocol). A HTTP servlet extends the basic servlet class but
provides a separate class for users to inherit from:
javax.servlet.http.HTTPServlet. Users can provide the following
methods :
• doGet() – executes an HTTP GET request
• doPost()
– executes an HTTP POST request
Other HTTP request types have
their own standard implementation but can be
overridden
also.
Web clients viewing HTTP servlets support all standard
forms and widgets used in Web pages like input panels, check
buttons, radio buttons, text areas, menus and image maps. Client
input is passed to the servlet code as “parameters” to the GET or
POST request from the data in the forms. Hidden form elements allow
nonuser visible data to be passed. The Webmaster can also configure
initial parameters (names of databases, resources) so that the same
application can be used even when those resources change.
The
servlet response is typically a web page that is returned to the
client. Pages can be created entirely from Java code. Other formats
that can be returned include Excel (csv), Bitmaps/Images, PDF,
Binary formats (zip files, Pro/ENGINEER models,...).
Java Server Pages (JSP) are a specialized form of
servlet. A JSP application is constructed as a standard HTML
(Hyper-Text Markup Language) with embedded JSP code capable of
customizing the output. This allows Web developers to maintain and
enhance pages by working with HTML while still inserting dynamic
server contents into the pages sent to the client. Like servlets,
JSP also have access to the same properties like request parameters,
context level attributes, and response data.
J-Link
J-Link is a platform
independent, object oriented, Java-based programming interface to
Pro/ENGINEER. It allows for customization of the Pro/ENGINEER user
interface and access to data stored in models and drawings. J-Link
is provided free of charge with any Pro/ENGINEER Wildfire
installation. J-Link has a wide range of capabilities in the form of
API's (Application Programming Interfaces) covering topics such as
solid models, assemblies, drawings, data exchange, features, family
tables, dimensions, parameters, graphics and interoperability. To
get started using J-Link, consult the documentation and examples
under the Pro/ENGINEER CD image. These files will be installed under
the directory “jlink” and include an interactive browser for viewing
details on all of the API’s covered in this project.
Because
J-Link features a Java API, it can naturally be implanted in a Java
servlet application running on the Web server. This “J-Link servlet”
would start Pro/ENGINEER on the server and use the servlet
parameters to modify models or generate needed output. The client
would require only an Internet connection and a Web browser
(Pro/ENGINEER is not required on the client machine). A J-Link
servlet could automate various tasks, generate output deliverables,
perform basic configuration options, and automate designs based on
user input.
One of the possible objectives for deploying a
J-Link servlet is to gather information from a Pro/ENGINEER model
and display it in a web page to a client who does not have direct
access to Pro/ENGINEER. In the following image, a J-Link servlet
presents the feature names, ids, and types from the model next to a
dynamically generated JPEG image of the model:
Fig.1. A web server runs a J-Link servlet to generate
custom web pages featuring model images, parameters and other
data
There are some important details that need
to be considered in order to setup the J-Link servlet. First, a
J-Link servlet must be configured to only load the native library
once. This is discussed in a PTC
Technical Support Solution document. To access this document,
you must be a PTC Support customer. Also, J-Link access is limited
to a single thread of the Java process. Because servlets are
inherently multi-threaded, the J-Link servlet must perform
synchronization to ensure that two clients do not attempt to
simultaneously execute J-Link commands.
Source code for this
J-Link servlet example is available on the Pro/ENGINEER Wildfire 3.0
CD image and is also available to PTC Support customers from a solution
document on PTC Customer Support.
Users should consider
a J-Link servlet application like this one when they have needs that
are not covered by standard viewer products like ProductView
Express. J-Link, as a customization API, gives the user a chance to
completely control the type of information extracted, its
formatting, and lets the application present options which are not
normally presented from a standard viewer product. The servlet page
could even be deployed in conjunction with a standard viewer like
ProductView Express to give the client even more viewing options for
the Pro/ENGINEER model and model data.
Pro/Web.Link
Pro/Web.Link is a
JavaScript based programming library with a comprehensive interface
to Pro/ENGINEER data and models. Applications are stored in HTML
pages and loaded into the embedded browser in Pro/ENGINEER Wildfire.
Pro/Web.Link running in the embedded browser of Pro/ENGINEER is
provided free of charge with every installation of Pro/ENGINEER
Wildfire. Pages using Pro/WebLink code can be served from an
internal or external webserver. The type of data accessible via
Pro/Web.Link exactly matches the data accessible from J-Link: solid
models, assemblies, drawings, data exchange, features, family
tables, dimensions, parameters, graphics and interoperability. Users
can review the examples and documentation for Web.Link by viewing
the contents of the weblink directory under the Pro/ENGINEER
installation directory.
Because Web.Link must operate within
the Pro/ENGINEER embedded browser on the client side, the deployment
scenarios for Pro/Web.Link web applications are quite different from
those of J-Link servlets. The client for a Pro/Web.Link application
must be running Pro/ENGINEER in order to use the customization.
However, the data used by the Web.Link application does not
necessarily need to be input by the client; the data can be taken
from a database or other server-based resource and embedded into the
page sent to the client. This makes Web.Link fit well with JSP
pages, where JSP Web applications incorporate Pro/Web.Link code.
Typically JSP is used for this purpose because the majority of the
code could be written and edited normally but the Web server would
embed special parameters to configure the code sent to the
client.
This application design allows for a
manually-reviewed configuration activity: data available on the
server would be applied to the model, and the engineer could review
it and try it out in design scenarios. In the image below, a
Pro/Web.Link JSP page automatically adds a new family table instance
to the model and regenerates it. The engineer is given controls
allowing him to accept the new configuration or reject it based upon
the model he is analyzing in Pro/ENGINEER.
Fig. 2. Web.Link code from the internal web server
injects design data into the cart model
Conclusions
This article discusses two tools
offered by Pro/ENGINEER Wildfire that allow deployment of customized
Web applications accessing Pro/ENGINEER and Pro/ENGINEER data. These
tools are J-Link and Pro/Web.Link. Both of these
tools offer a comprehensive interface to solid model and drawing
data. As a Java API, J-Link can naturally be installed in a Java
servlet application running on the Web server. It allows clients
without Pro/ENGINEER to view or modify Pro/ENGINEER data.
Pro/Web.Link runs within JavaScript code loaded into the
embedded browser in Pro/ENGINEER. Thus the client must have
Pro/ENGINEER installed to use this tool, but the data used to drive
the models can be obtained from a Web application running on the
server.
Note:
For further details on Web
applications, the following reading is recommended:
Servlet
& web application references:
• http://java.sun.com/j2ee/index.jsp
• http://java.sun.com/products/servlet/index.jsp
•
http://java.sun.com/products/jsp/index.jsp
• http://java.sun.com/j2ee/javaserverfaces/index.jsp
•
Your local or online bookstore has many Java, servlet, and JSP
reference books
Tomcat
• http://jakarta.apache.org/tomcat/
For
further details on J-Link and Pro/Web.Link, consult the Pro/ENGINEER
loadpoint for documentation and examples:
• [Pro/ENGINEER
Loadpoint]/jlink/jlinkdoc/index.html
• [Pro/ENGINEER
Loadpoint]/weblink/weblinkdoc/index.html
Scott Conover is the Manager for MCAD
Customization at PTC. Scott has been with PTC for seven years, and
is responsible for project planning, development and quality for
Pro/E customization products: Pro/TOOLKIT, J-Link and Pro/Web.Link.
Published 11/08/2005 00:00:00 | Print
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