How to use a4j:mediaOutput correctly for displaying images?

问题

Using the code below I can't get the image in the web page. I'm not sure if I understand the documentation in the right way and I'm not able to find any problem with this code.

BEAN

@ManagedBean(name = "imageBean")
@RequestScoped
public class ImageBean {
    public void paint(OutputStream os, Object data) throws IOException {
        BinaryContent content = (BinaryContent) data;
        BufferedImage image = ImageIO.read(new ByteArrayInputStream(content.getContent()));
        ImageIO.write(image, "jpg", os);
    }
}

PAGE

<rich:dataTable value="#{dataProviderBean.aoRequests}" var="item">
    <f:facet name="noData">No messages are available.</f:facet>
    ...
    <rich:column>
        <f:facet name="header">Image data</f:facet>
        <rich:list value="#{item.imageContents}" var="content">
            <a4j:mediaOutput element="img" cacheable="false" session="false"
                createContent="#{imageBean.paint}" value="#{content}" />
        </rich:list>
    </rich:column>
</rich:dataTable>

回答1:

If someone will have the same problem in the future, here is the solution:

The content I put into value attribute is an object which holds binary data of a image. Because it is serialized in URL, the length is too big and it does not work. You have to pass some id and fetch the object in the paint method.

Example

<rich:dataTable value="#{dataProviderBean.aoRequests}" var="item">
    <f:facet name="noData">No messages are available.</f:facet>
    ...
    <rich:column>
        <f:facet name="header">Image data</f:facet>
        <rich:list value="#{item.imageContents}" var="content">
            <a4j:mediaOutput element="img" cacheable="false" session="false"
                createContent="#{imageBean.paint}" value="#{content.id}" />
        </rich:list>
    </rich:column>
</rich:dataTable>

BEAN

public void paint(OutputStream os, Object data) throws IOException {
    String id = (String) data;
    BinaryContent content = (BinaryContent) getContentById(id);
    os.write(content.getContent());
}

回答2:

ImageBean use @SessionScoped or @ApplicationScope https://community.jboss.org/thread/168523

来源：https://stackoverflow.com/questions/7677207/how-to-use-a4jmediaoutput-correctly-for-displaying-images

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java

jsf

richfaces