包含包含来自流的 JSF 标签/组件的动态内容

Question

我正在开发一个应用程序，我想在其中包含来自流的动态 XHTML 内容。为了处理这个问题，我编写了一个标记处理程序扩展，它将动态 XHTML 内容转储到输出组件，如下所示：

UIOutput htmlChild = (UIOutput) ctx.getFacesContext().getApplication().createComponent(UIOutput.COMPONENT_TYPE);
htmlChild.setValue(new String(outputStream.toByteArray(), "utf-8"));

这对于没有 JSF 标签的 XHTML 内容效果很好。如果我的动态 XHTML 内容中有 JSF 标记（如

<h:inputText value="#{bean.item}"/>

），那么它们会以纯文本形式打印。我希望它们呈现为输入字段。我怎样才能实现这个目标？ 

Answer 1

本质上，您应该将

<ui:include>

 与自定义 

ResourceHandler 结合使用，它能够以 URL

 的方式返回资源。因此，当有 

OutputStream

 时，您确实应该将其写入（临时）文件，以便可以从中获取 

URL

。

例如

<ui:include src="/dynamic.xhtml" /> 与

public class DynamicResourceHandler extends ResourceHandlerWrapper {

    private ResourceHandler wrapped;

    public DynamicResourceHandler(ResourceHandler wrapped) {
        this.wrapped = wrapped;
    }

    @Override
    public ViewResource createViewResource(FacesContext context, String resourceName) {
        if (resourceName.equals("/dynamic.xhtml")) {
            try {
                File file = File.createTempFile("dynamic-", ".xhtml");

                try (Writer writer = new FileWriter(file)) {
                    writer
                        .append("<ui:composition")
                        .append(" xmlns:ui='http://java.sun.com/jsf/facelets'")
                        .append(" xmlns:h='http://java.sun.com/jsf/html'")
                        .append(">")
                        .append("<p>Hello from a dynamic include!</p>")
                        .append("<p>The below should render as a real input field:</p>")
                        .append("<p><h:inputText /></p>")
                        .append("</ui:composition>");
                }

                final URL url = file.toURI().toURL();
                return new ViewResource(){
                    @Override
                    public URL getURL() {
                        return url;
                    }
                };
            }
            catch (IOException e) {
                throw new FacesException(e);
            }
        }

        return super.createViewResource(context, resourceName);
    }

    @Override
    public ResourceHandler getWrapped() {
        return wrapped;
    }

}

（警告：基本启动示例！这会在每个请求上创建一个新的临时文件，您应该自己发明一个重用/缓存系统）

在

faces-config.xml

中注册如下

<application>
    <resource-handler>com.example.DynamicResourceHandler</resource-handler>
</application>

---

注意：以上所有内容都是针对 JSF 2.2 的。对于偶然发现此答案的 JSF 2.0/2.1 用户，您应该使用

ResourceResolver

 来代替，此答案中提供了一个示例：

从外部文件系统或数据库获取 Facelets 模板/文件。重要提示：JSF 2.2 中ResourceResolver

已被

弃用，取而代之的是ResourceHandler#createViewResource()

。

Answer 2

我的 JSF 2.2 和自定义 URLStream 处理程序的解决方案

public class DatabaseResourceHandlerWrapper extends ResourceHandlerWrapper {

    private ResourceHandler wrapped;

    @Inject
    UserSessionBean userBeean;

    public DatabaseResourceHandlerWrapper(ResourceHandler wrapped) {
        this.wrapped = wrapped;
    }

    @Override
    public Resource createResource(String resourceName, String libraryName) {
        return super.createResource(resourceName, libraryName); //To change body of generated methods, choose Tools | Templates.
    }

    @Override
    public ViewResource createViewResource(FacesContext context, String resourceName) {
        if (resourceName.startsWith("/dynamic.xhtml?")) {
            try {
                String query = resourceName.substring("/dynamic.xhtml?".length());
                Map<String, String> params = splitQuery(query);
                //do some query to get content
                String content = "<ui:composition"
                        + " xmlns='http://www.w3.org/1999/xhtml' xmlns:ui='http://java.sun.com/jsf/facelets'"
                        + " xmlns:h='http://java.sun.com/jsf/html'> MY CONTENT"
                        + "</ui:composition>";

                final URL url = new URL(null, "string://helloworld", new MyCustomHandler(content));
                return new ViewResource() {
                    @Override
                    public URL getURL() {
                        return url;
                    }
                };
            } catch (IOException e) {
                throw new FacesException(e);
            }
        }

        return super.createViewResource(context, resourceName);
    }

    public static Map<String, String> splitQuery(String query) throws UnsupportedEncodingException {
        Map<String, String> params = new LinkedHashMap<>();
        String[] pairs = query.split("&");
        for (String pair : pairs) {
            int idx = pair.indexOf("=");
            params.put(URLDecoder.decode(pair.substring(0, idx), "UTF-8"), URLDecoder.decode(pair.substring(idx + 1), "UTF-8"));
        }
        return params;
    }

    @Override
    public ResourceHandler getWrapped() {
        return wrapped;
    }

    static class MyCustomHandler extends URLStreamHandler {

        private String content;

        public MyCustomHandler(String content) {
            this.content = content;
        }

        @Override
        protected URLConnection openConnection(URL u) throws IOException {
            return new UserURLConnection(u, content);
        }

        private static class UserURLConnection extends URLConnection {

            private String content;

            public UserURLConnection(URL url, String content) {
                super(url);
                this.content = content;
            }

            @Override
            public void connect() throws IOException {
            }

            @Override
            public InputStream getInputStream() throws IOException {
                return new ByteArrayInputStream(content.getBytes("UTF-8"));
            }
        }

    }

}