JSF2静态资源管理 - 组合,压缩

Question

是否有人知道一种方法来动态组合/缩小所有h:outputStylesheet资源,然后在渲染阶段组合/缩小所有h:outputScript资源？可能需要使用基于组合资源String的键来缓存已压缩/缩小的资源,以避免过度处理.

如果此功能不存在,我想继续处理.有没有人有关于实现这样的事情的最佳方式的想法.我认为Servlet过滤器可以正常工作,但过滤器必须做更多的工作 - 基本上检查整个渲染输出并替换匹配.在呈现阶段实现某些东西似乎会更好地工作,因为所有静态资源都可用而无需解析整个输出.

谢谢你的任何建议!

编辑: 为了表明我并不懒惰,并且会在一些指导下真正解决这个问题,这里有一个存根,它捕获脚本资源名称/库,然后从视图中删除它们.正如您所看到的,我对下一步该做什么有一些疑问......我应该发出http请求并获取要合并的资源,然后将它们组合起来并将它们保存到资源缓存中？

package com.davemaple.jsf.listener;

import java.util.ArrayList;
import java.util.List;

import javax.faces.component.UIComponent;
import javax.faces.component.UIOutput;
import javax.faces.component.UIViewRoot;
import javax.faces.context.FacesContext;
import javax.faces.event.AbortProcessingException;
import javax.faces.event.PhaseEvent;
import javax.faces.event.PhaseId;
import javax.faces.event.PhaseListener;
import javax.faces.event.PreRenderViewEvent;
import javax.faces.event.SystemEvent;
import javax.faces.event.SystemEventListener;

import org.apache.log4j.Logger;

/**
 * A Listener that combines CSS/Javascript Resources
 * 
 * @author David Maple<d@davemaple.com>
 *
 */
public class ResourceComboListener implements PhaseListener, SystemEventListener {

    private static final long serialVersionUID = -8430945481069344353L;
    private static final Logger LOGGER = Logger.getLogger(ResourceComboListener.class);

    @Override
    public PhaseId getPhaseId() {
        return PhaseId.RESTORE_VIEW;
    }

    /*
     * (non-Javadoc)
     * @see javax.faces.event.PhaseListener#beforePhase(javax.faces.event.PhaseEvent)
     */
    public void afterPhase(PhaseEvent event) {
        FacesContext.getCurrentInstance().getViewRoot().subscribeToViewEvent(PreRenderViewEvent.class, this);
    }

    /*
     * (non-Javadoc)
     * @see javax.faces.event.PhaseListener#afterPhase(javax.faces.event.PhaseEvent)
     */
    public void beforePhase(PhaseEvent event) {
        //nothing here
    }

    /*
     * (non-Javadoc)
     * @see javax.faces.event.SystemEventListener#isListenerForSource(java.lang.Object)
     */
    public boolean isListenerForSource(Object source) {
        return (source instanceof UIViewRoot);
    }

    /*
     * (non-Javadoc)
     * @see javax.faces.event.SystemEventListener#processEvent(javax.faces.event.SystemEvent)
     */
    public void processEvent(SystemEvent event) throws AbortProcessingException {
        FacesContext context = FacesContext.getCurrentInstance();
        UIViewRoot viewRoot = context.getViewRoot();
        List<UIComponent> scriptsToRemove = new ArrayList<UIComponent>();

        if (!context.isPostback()) {

            for (UIComponent component : viewRoot.getComponentResources(context, "head")) {
                if (component.getClass().equals(UIOutput.class)) {
                    UIOutput uiOutput = (UIOutput) component;

                    if (uiOutput.getRendererType().equals("javax.faces.resource.Script")) {
                        String library = uiOutput.getAttributes().get("library").toString();
                        String name = uiOutput.getAttributes().get("name").toString();

                        // make https requests to get the resources?
                        // combine then and save to resource cache?
                        // insert new UIOutput script?

                        scriptsToRemove.add(component);
                    }


                }
            }

            for (UIComponent component : scriptsToRemove) {
                viewRoot.getComponentResources(context, "head").remove(component);
            }

        }
    }

}

Answer 1

这个答案不包括缩小和压缩.缩小个别CSS/JS资源最好委托构建YUI Compressor Ant任务等脚本.在每个请求上手动执行它太昂贵了.压缩(我假设你的意思是GZIP？)最好委托给你正在使用的servlet容器.手动执行它是过于复杂的.例如,在Tomcat中,compression="on"需要在<Connector>元素中添加属性/conf/server.xml.

这SystemEventListener已经是一个良好的第一步(除了一些PhaseListener不必要的).接下来,您需要实现自定义ResourceHandler和Resource.那部分并非完全无足轻重.如果你想独立于JSF实现,你需要重新发明很多.

首先,在您的工作中SystemEventListener,您希望创建UIOutput表示组合资源的新组件,以便您可以使用它来添加它UIViewRoot#addComponentResource().您需要将其library属性设置为您的自定义资源处理程序可以理解的唯一属性.您需要根据资源的组合(可能是MD5哈希？)将组合资源沿着唯一名称存储在应用程序范围的变量中,然后将此密钥设置为name组件的属性.存储为应用程序范围的变量对服务器和客户端都具有缓存优势.

像这样的东西:

String combinedResourceName = CombinedResourceInfo.createAndPutInCacheIfAbsent(resourceNames);
UIOutput component = new UIOutput();
component.setRendererType(rendererType);
component.getAttributes().put(ATTRIBUTE_RESOURCE_LIBRARY, CombinedResourceHandler.RESOURCE_LIBRARY);
component.getAttributes().put(ATTRIBUTE_RESOURCE_NAME, combinedResourceName + extension);
context.getViewRoot().addComponentResource(context, component, TARGET_HEAD);

然后,在您的自定义ResourceHandler实现中,您需要相应地实现该createResource()方法,以便Resource在库匹配所需值时创建自定义实现:

@Override
public Resource createResource(String resourceName, String libraryName) {
    if (RESOURCE_LIBRARY.equals(libraryName)) {
        return new CombinedResource(resourceName);
    } else {
        return super.createResource(resourceName, libraryName);
    }
}

自定义Resource实现的构造函数应该根据名称获取组合的资源信息:

public CombinedResource(String name) {
    setResourceName(name);
    setLibraryName(CombinedResourceHandler.RESOURCE_LIBRARY);
    setContentType(FacesContext.getCurrentInstance().getExternalContext().getMimeType(name));
    this.info = CombinedResourceInfo.getFromCache(name.split("\\.", 2)[0]);
}

此自定义Resource实现必须提供getRequestPath()返回URI 的正确方法,该URI随后将包含在呈现的<script>或<link>元素中:

@Override
public String getRequestPath() {
    FacesContext context = FacesContext.getCurrentInstance();
    String path = ResourceHandler.RESOURCE_IDENTIFIER + "/" + getResourceName();
    String mapping = getFacesMapping();
    path = isPrefixMapping(mapping) ? (mapping + path) : (path + mapping);
    return context.getExternalContext().getRequestContextPath()
        + path + "?ln=" + CombinedResourceHandler.RESOURCE_LIBRARY;
}

现在,HTML呈现部分应该没问题.它看起来像这样:

<link type="text/css" rel="stylesheet" href="/playground/javax.faces.resource/dd08b105bf94e3a2b6dbbdd3ac7fc3f5.css.xhtml?ln=combined.resource" />
<script type="text/javascript" src="/playground/javax.faces.resource/2886165007ccd8fb65771b75d865f720.js.xhtml?ln=combined.resource"></script>

接下来,您必须拦截浏览器发出的组合资源请求.这是最难的部分.首先,在自定义ResourceHandler实现中,您需要相应地实现该handleResourceRequest()方法:

@Override
public void handleResourceRequest(FacesContext context) throws IOException {
    if (RESOURCE_LIBRARY.equals(context.getExternalContext().getRequestParameterMap().get("ln"))) {
        streamResource(context, new CombinedResource(getCombinedResourceName(context)));
    } else {
        super.handleResourceRequest(context);
    }
}

然后你必须做相应的实现自定义实现的其他方法的大量工作,Resource例如getResponseHeaders()应该返回正确的缓存头,getInputStream()这应该返回InputStream单个组合资源的s,InputStream并且userAgentNeedsUpdate()应该在缓存相关请求时正确响应.

@Override
public Map<String, String> getResponseHeaders() {
    Map<String, String> responseHeaders = new HashMap<String, String>(3);
    SimpleDateFormat sdf = new SimpleDateFormat(PATTERN_RFC1123_DATE, Locale.US);
    sdf.setTimeZone(TIMEZONE_GMT);
    responseHeaders.put(HEADER_LAST_MODIFIED, sdf.format(new Date(info.getLastModified())));
    responseHeaders.put(HEADER_EXPIRES, sdf.format(new Date(System.currentTimeMillis() + info.getMaxAge())));
    responseHeaders.put(HEADER_ETAG, String.format(FORMAT_ETAG, info.getContentLength(), info.getLastModified()));
    return responseHeaders;
}

@Override
public InputStream getInputStream() throws IOException {
    return new CombinedResourceInputStream(info.getResources());
}

@Override
public boolean userAgentNeedsUpdate(FacesContext context) {
    String ifModifiedSince = context.getExternalContext().getRequestHeaderMap().get(HEADER_IF_MODIFIED_SINCE);

    if (ifModifiedSince != null) {
        SimpleDateFormat sdf = new SimpleDateFormat(PATTERN_RFC1123_DATE, Locale.US);

        try {
            info.reload();
            return info.getLastModified() > sdf.parse(ifModifiedSince).getTime();
        } catch (ParseException ignore) {
            return true;
        }
    }

    return true;
}

我在这里有一个完整的工作概念证明,但是作为SO答案发布的代码太多了.以上只是帮助您朝着正确的方向发展的一部分.我假设缺少的方法/变量/常量声明是自我解释足以编写自己的,否则让我知道.

更新:根据评论,以下是您如何收集资源CombinedResourceInfo:

private synchronized void loadResources(boolean forceReload) {
    if (!forceReload && resources != null) {
        return;
    }

    FacesContext context = FacesContext.getCurrentInstance();
    ResourceHandler handler = context.getApplication().getResourceHandler();
    resources = new LinkedHashSet<Resource>();
    contentLength = 0;
    lastModified = 0;

    for (Entry<String, Set<String>> entry : resourceNames.entrySet()) {
        String libraryName = entry.getKey();

        for (String resourceName : entry.getValue()) {
            Resource resource = handler.createResource(resourceName, libraryName);
            resources.add(resource);

            try {
                URLConnection connection = resource.getURL().openConnection();
                contentLength += connection.getContentLength();
                long lastModified = connection.getLastModified();

                if (lastModified > this.lastModified) {
                    this.lastModified = lastModified;
                }
            } catch (IOException ignore) {
                // Can't and shouldn't handle it here anyway.
            }
        }
    }
}

(上述方法由reload()方法和getter 调用,取决于要设置的属性之一)

以下是这样的CombinedResourceInputStream样子:

final class CombinedResourceInputStream extends InputStream {

    private List<InputStream> streams;
    private Iterator<InputStream> streamIterator;
    private InputStream currentStream;

    public CombinedResourceInputStream(Set<Resource> resources) throws IOException {
        streams = new ArrayList<InputStream>();

        for (Resource resource : resources) {
            streams.add(resource.getInputStream());
        }

        streamIterator = streams.iterator();
        streamIterator.hasNext(); // We assume it to be always true; CombinedResourceInfo won't be created anyway if it's empty.
        currentStream = streamIterator.next();
    }

    @Override
    public int read() throws IOException {
        int read = -1;

        while ((read = currentStream.read()) == -1) {
            if (streamIterator.hasNext()) {
                currentStream = streamIterator.next();
            } else {
                break;
            }
        }

        return read;
    }

    @Override
    public void close() throws IOException {
        IOException caught = null;

        for (InputStream stream : streams) {
            try {
                stream.close();
            } catch (IOException e) {
                if (caught == null) {
                    caught = e; // Don't throw it yet. We have to continue closing all other streams.
                }
            }
        }

        if (caught != null) {
            throw caught;
        }
    }

}

更新2:OmniFaces提供了一个具体且可重复使用的解决方案.有关更多详细信息,另请参见CombinedResourceHandlershowcase页面和API文档.