How to obtain an InputStream of a public webconten

问题:

I have a collection of images packaged in my WAR and I depict them in a <p:dataGrid> using <p:graphicImage>. The images are located in the /resources/icons folder. I want to be able to select an image and save a copy of this image to disk on submit.

How can this be done? How can I get a reference (InputStream or whatever) to this image?

回答1:

Given this folder structure,

YourProject
 |-- src
 |    `-- com
 |         `-- example
 |              `-- BackingBean.java
 |-- WebContent
 |    |-- META-INF
 |    |-- WEB-INF
 |    |-- resources
 |    |    `-- icons
 |    |         `-- foo.png
 |    `-- foo.xhtml
 :

You can get it by either ExternalContext#getResourceAsStream() which takes webcontent-relative path:

ExternalContext externalContext = FacesContext.getCurrentInstance().getExternalContext();
InputStream input = externalContext.getResourceAsStream("/resources/icons/foo.png");
// ...

Or by Resource#getInputStream() wherein Resource is obtained from ResourceHandler#createResource() which takes a /resources-relative path:

ResourceHandler resourceHandler = FacesContext.getCurrentInstance().getApplication().getResourceHandler();
InputStream input = resourceHandler.createResource("icons/foo.png").getInputStream();
// ...

As to selecting the image and passing its path around, just do something like as follows:

<h:graphicImage name="icons/foo.png">
    <f:ajax event="click" listener="#{bean.setImage(component.name)}" />
</h:graphicImage>
<h:graphicImage name="icons/bar.png">
    <f:ajax event="click" listener="#{bean.setImage(component.name)}" />
</h:graphicImage>
<h:commandButton value="submit" action="#{bean.saveImage}" />

See also:

• getResourceAsStream() vs FileInputStream
• Where to place and how to read configuration resource files in servlet based application?
• Maven and JSF webapp structure, where exactly to put JSF resources