html - 如何为具有动态参数的页面提供面包屑？

Question

我找到了一个用于生成面包屑的 Grails 框架 here .它确实根据 breadcrumbs.xml 文件中的静态定义生成面包屑，其中定义了面包屑的层次结构:

     <map>
        <nav id="homeCrumb" matchController="samplePages" matchAction="homeBreadCrumbPage">
            <!-- levels navigation -->
            <nav id="itemsLevel1Crumb" matchController="samplePages" matchAction="level1BreadCrumbPage">
                <nav id="itemsLevel2Crumb" matchController="samplePages" matchAction="level2BreadCrumbPage">
                    <nav id="itemsLevel3Crumb" matchController="samplePages" matchAction="level3BreadCrumbPage">
                        <nav id="showItemCrumb" matchController="samplePages" matchAction="itemDetailsBreadCrumbPage"/>
                    </nav>
                </nav>
            </nav>
            <nav id="simple1Crumb" matchController="samplePages" matchAction="simpleBreadCrumb"/>
            <nav id="simple2Crumb" matchController="samplePages" matchAction="simpleBreadCrumbWithAttr"/>
            <!-- levels navigation -->
        </nav>
    </map>

此文件由 taglib 评估和打印:

class BreadCrumbTagLib {

    static def log = LogFactory.getLog("grails.app.breadCrumbTag")

    def breadCrumb = { attrs , body ->

            def manager = BreadCrumbManager.getInstance()
            def uri = request.getRequestURI() 
            def context = request.getContextPath() 

            def controller = params.controller
            def action = params.action

            def attrTitle =  attrs.title
            def attrLink = attrs.link

            // if controller and action are missing from params try to get them from request url
            if (!controller && !action && uri && context && uri.indexOf(context) != -1) {
                def uriParams = uri.substring(uri.indexOf(context) + (context.length() + 1), uri.length())
                def uriArray = uriParams.split('/')

                if (uriArray.size() >= 2 ) {
                    controller = uriArray[0]
                    action = uriArray[1]                       
                }
            }

            def crumbs = manager.getBreadCrumbs(controller, action)

            if (crumbs) {
                out << '<div class="breadcrumb"><ul>'
                def size = crumbs.size()
                crumbs.eachWithIndex { crumb, index ->
                    out << '<li>'

                    // override title and link of breadcrumb on current page (i.e. last bread crumb in hierarchy)
                    // if name, link attributes are supplied
                    if (index == size - 1) {
                        if (attrTitle)
                            crumb.title = attrTitle
                        if (attrLink)
                            crumb.link = attrLink
                    }
                    // set title to undefined if not found, associated 
                    // renderer if present can overwrite it
                    if (!crumb.title)
                        crumb.title = "undefined"
                    if (crumb.title && crumb.title.size() > 40)
                        crumb.title = crumb.title.substring(0, 40) + "..."

                    if (crumb.viewController && crumb.viewAction) {
                        def content = g.include(controller:crumb.viewController, action:crumb.viewAction, breadcrumb:crumb, params:params)
                        out << content
                    } else if (crumb.viewTemplate) {
                        def content = g.include(view:crumb.viewTemplate, breadcrumb:crumb, params: params)
                        out << content
                    } else if (crumb.linkToController && crumb.linkToAction && (size - 1 > index)){
                        out << "<a href=\"${g.createLink (controller: crumb.linkToController, action: crumb.linkToAction)}\">${crumb.title}</a>"
                    // if crumb has a link and its not the last vread crumb then show link else
                    // just show the text
                    } else if (crumb.link && (size - 1 > index)){
                        out << "<a href=\"${crumb.link}\">${crumb.title}</a>"
                    } else {
                        out << "${crumb.title}"
                    }
                    out << "</li>"
                    // do not print for last bread crumb
                    if (size - 1 > index)
                        out << "<li>&raquo;</li>"
                }
                out << "</ul></div>"
            }
    }
}  

问题:当我有一个需要一些未修复的参数的结构时。

示例:我在导航的第三级让我们说

A1 / A2 / A3

就我而言 A2应该打开一个类似 user/show/1234 的页面其中 1234 是要显示的用户的 ID。问题是我无法在 breadcrumbs.xml 文件中添加 1234 硬编码，因为此 ID 会根据您要显示的用户而变化。

当中间面包屑链接需要动态参数时，我该如何处理？

Answer 1

再想一想，我意识到最好不要使用 HttpSession。如果您改用 session 范围的服务，则对面包屑代码进行单元测试会更容易。

首先，创建一个 session 范围的服务来维护用户的导航历史。

class NavigationHistoryService {
    static transactional = false
    static scope = "session"

    def history = [:]

    public List push(String controller, String action, Map params) {
        def crumb = [
            action: action, 
            params: params]

        history.controller = crumb

        return history
    }   

在您的 Controller 中注入(inject)服务并使用它来跟踪用户所在的位置。然后将历史记录添加为 Action 模型返回的内容的一部分:

class CompanyController {
    def navigationHistoryService

    def show() {
        navigationHistoryService.push('company', 'show', params)
        ...
        [crumbs: navigationHistoryService.history] 
    }
}

最后，使用 GSP 中的历史记录来呈现面包屑。

<ol class="breadcrumb">
    <li><g:link controller="company" action="${crumbs.company.action}" params="${crumbs.company.params}">SOMETHING</a></li>
</ol>