是否有关于获取URL的新闻 ？

问题描述 投票：0回答：1

基本上我的问题与this one五年前回答的问题相同：我想从<p:graphicImage>输出服务器提供的图像的URL，但只输出URL而不是<img>标记。我正在寻找的是这样的解决方案：

（这不是工作代码，只是为了说明:)

<p:graphicImage var="url" value="#{MyForm.image}"/>
<span id="imageData" data-image="#{url}/>

哪个应该像这样输出到HTML：

<span id="imageData" data-image="http://localhost:8080/contextPath/javax.faces.resource/dy...

我目前正在使用JavaScript work-around，但这个要求对我来说似乎很常见，我希望新的开发已经针对它并且有一个内置的解决方案。自过去五年以来，该主题是否有新闻？

jsf primefaces graphicimage
1个回答
2
投票

只是看看GraphicImageRenderer想要弄清楚他们是如何产生动态URL的。他们在DynamicContentSrcBuilder上使用静态方法：

protected String getImageSrc(FacesContext context, GraphicImage image) throws Exception {
    String name = image.getName();

    if (name != null) {
        // ...
    } else {
      return DynamicContentSrcBuilder.build(context, image.getValue(), image, image.isCache(), DynamicContentType.STREAMED_CONTENT, image.isStream());
    }
}

那么为什么不在p:graphicImage组件上重现这个调用呢？我首先将bind转换为RequestScoped bean的属性，然后从该bean获取URI，该URI再现上面显示的渲染器的行为：

XHTML代码：

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
    xmlns:h="http://xmlns.jcp.org/jsf/html"
    xmlns:p="http://primefaces.org/ui"
    xmlns:pt="http://xmlns.jcp.org/jsf/passthrough">
<h:head/>
<body>
    <p:graphicImage binding="#{myBean.imgComponent}"
        value="#{myBean.img}" />
    <h:outputText id="imageData" pt:data-image="#{myBean.getImgUri()}" />
</body>
</html>

而我的豆又名myBean：

package test;

import java.io.IOException;
import java.io.UnsupportedEncodingException;

import javax.enterprise.context.RequestScoped;
import javax.faces.context.FacesContext;
import javax.inject.Named;

import org.primefaces.application.resource.DynamicContentType;
import org.primefaces.component.graphicimage.GraphicImage;
import org.primefaces.model.StreamedContent;
import org.primefaces.util.DynamicContentSrcBuilder;

@Named
@RequestScoped
public class MyBean {

    private GraphicImage imgComponent;

    private String imgUri;

    public StreamedContent getImg() throws IOException {
        // ...
    }

    public GraphicImage getImgComponent() {
        return imgComponent;
    }

    public void setImgComponent(GraphicImage imgComponent) {
        this.imgComponent = imgComponent;
    }

    public String getImgUri() throws UnsupportedEncodingException {
        assert null != imgComponent;
        if (null == imgUri) {
            // here we reproduce the GraphicImageRenderer behavior:
            imgUri = DynamicContentSrcBuilder.build(FacesContext.getCurrentInstance(), imgComponent.getValue(),
                    imgComponent, imgComponent.isCache(), DynamicContentType.STREAMED_CONTENT, imgComponent.isStream());
        }
        return imgUri;
    }

}

或者我们可以使用GraphicImageRenderer并发布protected方法getImageSrc：

public class MyBean {
  // ...
  public String getImgUri() throws Exception {
    assert null != imgComponent;
    if (null == imgUri) {
        imgUri = new GraphicImageRendererXtension().getPublicImageSrc(FacesContext.getCurrentInstance(),
                imgComponent);
    }
    return imgUri;
  }
}

public class GraphicImageRendererXtension extends GraphicImageRenderer {
    // publish the protected GraphicImageRenderer#getImageSrc method:
    public String getPublicImageSrc(FacesContext context, GraphicImage image) throws Exception {
        return getImageSrc(context, image);
    }
}

但为什么我写#{myBean.getImgUri()}而不是#{myBean.imgUri}？我仍然不确定，但使用后者会产生一个PropertyNotFoundException：

javax.el.PropertyNotFoundException: /myView.xhtml @20,46 value="#{myBean.imgUri}": ELResolver did not handle type: [null] with property of [imgUri]
    at com.sun.faces.facelets.el.TagValueExpression.getValue(TagValueExpression.java:117)
    at javax.faces.component.ComponentStateHelper.eval(ComponentStateHelper.java:200)
    at javax.faces.component.ComponentStateHelper.eval(ComponentStateHelper.java:187)
    at javax.faces.component.UIOutput.getValue(UIOutput.java:179)
    at com.sun.faces.renderkit.html_basic.HtmlBasicInputRenderer.getValue(HtmlBasicInputRenderer.java:205)
    at com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.getCurrentValue(HtmlBasicRenderer.java:360)
    at com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.encodeEnd(HtmlBasicRenderer.java:171)
    at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:949)
    at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1912)
    at javax.faces.render.Renderer.encodeChildren(Renderer.java:176)
    at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:918)
    at com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.encodeRecursive(HtmlBasicRenderer.java:309)
    at com.sun.faces.renderkit.html_basic.GroupRenderer.encodeChildren(GroupRenderer.java:114)
    at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:918)
    at org.primefaces.renderkit.CoreRenderer.renderChild(CoreRenderer.java:86)
    at org.primefaces.renderkit.CoreRenderer.renderChildren(CoreRenderer.java:73)
    at org.primefaces.component.layout.LayoutUnitRenderer.encodeEnd(LayoutUnitRenderer.java:49)
    at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:949)
    at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1912)
    at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1908)
    at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1908)
    at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1908)
    at com.sun.faces.application.view.FaceletViewHandlingStrategy.renderView(FaceletViewHandlingStrategy.java:491)
    at javax.faces.view.ViewDeclarationLanguageWrapper.renderView(ViewDeclarationLanguageWrapper.java:126)
...
Caused by: javax.el.PropertyNotFoundException: ELResolver did not handle type: [null] with property of [imgUri]
    at org.apache.el.parser.AstValue.getValue(AstValue.java:174)
    at org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:190)
    at org.apache.webbeans.el22.WrappedValueExpression.getValue(WrappedValueExpression.java:68)
    at com.sun.faces.facelets.el.TagValueExpression.getValue(TagValueExpression.java:115)
    ... 122 more

可能调用DynamicContentSrcBuilder.build()方法不知何故弄乱了值表达式#{myBean.imgUri}的持续解析，而#{myBean.getImgUri()}不受影响。

回到你的问题：没有新闻。构建动态URI并在呈现时直接发送到浏览器。 GraphicImage组件不为此提供任何吸气剂。我在这里介绍的是一个解决方案的服务器端变体，无需创建新的servlet。

编辑：

当然你也可以参数化getImageUri方法并将你的Image组件绑定到一些任意变量，这将使你更接近你的演示var="..."示例：

public class MyBean {
  // ...
  public String getImgUri(GraphicImage imgComponent) throws Exception {
    assert null != imgComponent;
    String imgUri = new GraphicImageRendererXtension().getPublicImageSrc(FacesContext.getCurrentInstance(),
                imgComponent);
    return imgUri;
  }
}

然后使用此方法：

<p:graphicImage binding="#{myImage}" value="#{myBean.img}" />
<h:outputText id="imageData" pt:data-image="#{myBean.getImgUri(myImage)}" />

这样就不需要为每个图像创建一个bean或方法。

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