---------- Forwarded message ----------
From: Howard Lewis Ship <[EMAIL PROTECTED]>
Date: Jun 7, 2007 10:10 PM
Subject: Re: How to load a image dynamically in tapestry5.0.4
To: "[EMAIL PROTECTED]" <[EMAIL PROTECTED]>
Let me use 5.0.5 syntax since its a little cleared and will be totally
relevant pretty soon.
Let's say you have a page named Catalog on which you want to display images:
Catalog.html:
<t:loop source="products" value="product">
<img src="${productImageURL}"/>
</t:loop>
Ok, now Catalog.java (i'll omit the ordinary getters/setters):
public class Catalog {
private Product _product;
@Inject
private ComponentResources _resources;
public Link getProductImageURL() {
return _resources.createActionLink("image", false, _product.getId());
}
public Object onImage(long productId) {
final InputStream is = // ... get InputStream from productId
return new StreamResponse() {
public String getContentType() { return "img/jpeg"; }
public InputStream getStream() throws IOException { return is; }
};
}
... so what do we have?
We have an <img> element that gets its URL from the code.
getProductImageURL() generates a URL that triggers inside the Catalog
page (not a component within the page), with an event type of "image"
and places the product's id property as path info. It will look like:
http://localhost:8080/catalog:image/12345
Now, when the page renders, the <img> element in the browser will use
that URL. Thus a new request comes up, which fires the "image" event
on the Catalog page. We provide an event hander as "onImage"
(whereas normally we use "onAction").
The return value is an instance of StreamResponse (that's an
interface). In the current code, a StreamResponse provides a content
type and an InputStream.
Tapestry will use this to "pump down" the bytes in the stream.
The only thing new in 5.0.5 is the way we were able to put an
expansion into the src attribute of the <img> element. In 5.0.4 you'd
have to use a Img component.
That's it ... I like this because it was hard to do (properly) in T4
and is cake in T5.
On 6/7/07, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote:
Hi Howard,
In your reply below you mentioned that
> There's another approach used when the data is inside the database, but we
> can dive into that if the above solution is insufficient.
Can you please provide some more information as to what this approach is?
Knowing how busy you are I don't expect a complete solution but I would
appreciate it if you could point me to the right direction.
I am thinking of an approach similar to JSP where you write the byte[]
retrieved from the database directly into the OutputStream but I don't know if
this is the best way to do this with T5 or if it's even possible.
Thanks
Petros
Howard Lewis Ship wrote:
>
> In order to answer this question, some background is needed.
>
> If you know the product's id (whatever you use, where it's SKU number or
> a
> surrogate key) ... what is the exact process from going from that to a URL
> suitable for an tag?
>
> That is ... are the images stored in the database? Or are they on the
> file
> system somewhere? If they are files on the file system, are those files
> mapped to a client-visible URL?
>
> In the latter case, you can do something like:
>
> prop:productImageURL
>
> public String getProductImageURL() {
> return "http://static.myco.com/product-images/"; + _productId + ".gif";
> }
>
>
>
> Assigning a t:id to a tag without specifying a component type creates an
> Any
> component, a component that just renders whatever tag and informal
> parameters you provide it. Here wer'e linking that to some Java code in
> the
> corresponding page or component that computes the URL of the product based
> on an instance variable. Probably your example is more complicated, but
> you
> get the idea.
>
> There's another approach used when the data is inside the database, but we
> can dive into that if the above solution is insufficient.
>
> Assets are useful for accessing resources inside the web application
> context, or on the classpath, and includes logic related to localization
> ...
> but it is not always appropriate when accessing resources that are well
> outside the web application itself.
>
> On 5/19/07, Allen Guo <[EMAIL PROTECTED]> wrote:
>>
>> Hi All,
>>
>> I want to show the ProductDetail page with product image. It looks like
>> p_001.jpg .
>> You know, every product has different image name,so I need to pass the
>> string 'p_001.jpg' to the corresponding page.
>> As result the img tag should look like ${product.image} or
>> I can use Asset to do it.
>>
>> But I tried to do it using the first approach, exception occured.
>> And I don't know how to the second approach.
>> Can anyone give me an idea?
>>
>> Thank in advance
>> Allen Guo
>>
>>
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>>
>
>
> --
> Howard M. Lewis Ship
> TWD Consulting, Inc.
> Independent J2EE / Open-Source Java Consultant
> Creator and PMC Chair, Apache Tapestry
> Creator, Apache HiveMind
>
> Professional Tapestry training, mentoring, support
> and project work. http://howardlewisship.com
>
>
Quoted from:
http://www.nabble.com/How-to-load-a-image-dynamiclly-in-tapestry5.0.4-tf3784430.html#a10707188
--
Howard M. Lewis Ship
TWD Consulting, Inc.
Independent J2EE / Open-Source Java Consultant
Creator and PMC Chair, Apache Tapestry
Creator, Apache HiveMind
Professional Tapestry training, mentoring, support
and project work. http://howardlewisship.com
--
Howard M. Lewis Ship
TWD Consulting, Inc.
Independent J2EE / Open-Source Java Consultant
Creator and PMC Chair, Apache Tapestry
Creator, Apache HiveMind
Professional Tapestry training, mentoring, support
and project work. http://howardlewisship.com
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