Thymeleaf中的fragments学习

前要：搭建博客项目用到。

1、代码块（片段）表达式语法

th:replace：将代码块片段整个替换使用了th:replace的HTML标签中

• "~{templatename::selector}" Includes the fragment resulting from applying the specified Markup Selector on the template named templatename. Note that selector can be a mere fragment name, so you could specify something as simple as ~{templatename::fragmentname} like in the ~{footer :: copy} above.
• "~{templatename}" Includes the complete template named templatename.
• ~{::selector}" or "~{this::selector}" Inserts a fragment from the same template, matching selector. If not found on the template where the expression appears, the stack of template calls (insertions) is traversed towards the originally processed template (the root), until selector matches at some level. (这里的this一看就明白了嘛，原来是取当前这个html里面的内容)

templatename: 模板名，Thymeleaf会根据模版名解析完整路径：/resources/templates/templatename.html，要注意文件的路径。

fragmentname: 片段名，Thymeleaf通过th:fragment声明定义代码块，即：th:fragment="fragmentname"

selector: 选择器，可以选择html的标签和类等

注："::" 表示取出模板中的代码块片段

2、示例：

2.1、不带参数

templatename.html --> _fragments.html

<!--底部footer-->
<footer th:fragment="footer" class="ui inverted vertical segment m-padded-tb-massive">
    <div class="ui center aligned container">
        <div class="ui inverted divided stackable grid">
            <div class="three wide column">
                <div class="ui inverted link list">
                    <div class="item">
                        <img src="../static/images/wechat.jpg" th:src="@{/images/wechat.jpg}" class="ui rounded image" alt="" style=" 100px">
                    </div>
                </div>
            </div>
            <div class="three wide column">
                <h4 class="ui inverted header m-text-thin m-text-spaced">最新博客</h4>
                <div class="ui inverted link list">
                    <a href="#" class="item">用户故事（User Story）</a>
                    <a href="#" class="item">用户故事（User Story）</a>
                    <a href="#" class="item">用户故事（User Story）</a>
                </div>
            </div>
            <div class="three wide column">
                <h4 class="ui inverted header m-text-thin m-text-spaced">联系我</h4>
                <div class="ui inverted link list">
                    <a href="#" class="item">Email: 1983387472@qq.com</a>
                    <a href="#" class="item">QQ: 1983387472</a>
                </div>
            </div>
            <div class="seven wide column">
                <h4 class="ui inverted header m-text-thin m-text-spaced">Blog</h4>
                <p class="m-text-thin m-text-spaced m-opacity-mini">
                    这是我的个人博客、会分享关于编程、写作、思考相关的任何内容，希望可以给来到这儿的人有所帮助...</p>
            </div>
        </div>
        <div class="ui inverted section divider"></div>
        <p class="m-text-thin m-text-spaced m-opacity-tiny">Copyright © 2016-2020 Fanlumaster Designed by
            Fanlumaster</p>
    </div>
</footer>

使用场景：

<!--底部footer-->
    <footer th:replace="_fragments :: footer" class="ui inverted vertical segment m-padded-tb-massive">
        <div class="ui center aligned container">
            <div class="ui inverted divided stackable grid">
                <div class="three wide column">
                    <div class="ui inverted link list">
                        <div class="item">
                            <img src="../static/images/wechat.jpg" class="ui rounded image" alt="" style=" 100px">
                        </div>
                    </div>
                </div>
                <div class="three wide column">
                    <h4 class="ui inverted header m-text-thin m-text-spaced">最新博客</h4>
                    <div class="ui inverted link list">
                        <a href="#" class="item">用户故事（User Story）</a>
                        <a href="#" class="item">用户故事（User Story）</a>
                        <a href="#" class="item">用户故事（User Story）</a>
                    </div>
                </div>
                <div class="three wide column">
                    <h4 class="ui inverted header m-text-thin m-text-spaced">联系我</h4>
                    <div class="ui inverted link list">
                        <a href="#" class="item">Email: 1983387472@qq.com</a>
                        <a href="#" class="item">QQ: 1983387472</a>
                    </div>
                </div>
                <div class="seven wide column">
                    <h4 class="ui inverted header m-text-thin m-text-spaced">Blog</h4>
                    <p class="m-text-thin m-text-spaced m-opacity-mini">
                        这是我的个人博客、会分享关于编程、写作、思考相关的任何内容，希望可以给来到这儿的人有所帮助...</p>
                </div>
            </div>
            <div class="ui inverted section divider"></div>
            <p class="m-text-thin m-text-spaced m-opacity-tiny">Copyright © 2016-2020 Fanlumaster Designed by
                Fanlumaster</p>
        </div>
    </footer>

2.2、带参数

<!--导航-->
<nav th:fragment="menu(n)" class="ui inverted attached segment m-padded-tb-mini m-shadow-small">
    <div class="ui container">
        <!--stackable表示可堆叠的-->
        <div class="ui inverted secondary stackable menu">
            <h2 class="ui teal header item">Blog</h2>
            <!--注意，这里图标如果使用mini会导致页面挤压，效果很丑-->
            <a href="#" class="m-item item m-mobile-hide" th:classappend="${n==1}?'active'"><i class="home icon"></i>首页</a>
            <a href="#" class="m-item item m-mobile-hide" th:classappend="${n==2}?'active'"><i class="idea icon"></i>分类</a>
            <a href="#" class="m-item item m-mobile-hide" th:classappend="${n==3}?'active'"><i class="tags icon"></i>标签</a>
            <a href="#" class="m-item item m-mobile-hide" th:classappend="${n==4}?'active'"><i class="clone icon"></i>归档</a>
            <a href="#" class="m-item item m-mobile-hide" th:classappend="${n==5}?'active'"><i class="info icon"></i>关于我</a>
            <div class="m-item right item m-mobile-hide">
                <div class="ui icon inverted transparent input">
                    <input type="text" placeholder="Search....">
                    <i class="search link icon"></i>
                </div>
            </div>
        </div>
    </div>
    <a href="#" class="ui menu toggle black icon button m-right-top m-mobile-show">
        <i class="sidebar icon"></i>
    </a>
</nav>

<!--导航-->
<nav th:replace="_fragments :: menu(1)" class="ui inverted attached segment m-padded-tb-mini m-shadow-small">
    <div class="ui container">
        <!--stackable表示可堆叠的-->
        <div class="ui inverted secondary stackable menu">
            <h2 class="ui teal header item">Blog</h2>
            <!--注意，这里图标如果使用mini会导致页面挤压，效果很丑-->
            <a href="#" class="m-item item m-mobile-hide"><i class="home icon"></i>首页</a>
            <a href="#" class="m-item item m-mobile-hide"><i class="idea icon"></i>分类</a>
            <a href="#" class="m-item item m-mobile-hide"><i class="tags icon"></i>标签</a>
            <a href="#" class="m-item item m-mobile-hide"><i class="clone icon"></i>归档</a>
            <a href="#" class="m-item item m-mobile-hide"><i class="info icon"></i>关于我</a>
            <div class="m-item right item m-mobile-hide">
                <div class="ui icon inverted transparent input">
                    <input type="text" placeholder="Search....">
                    <i class="search link icon"></i>
                </div>
            </div>
        </div>
    </div>
    <a href="#" class="ui menu toggle black icon button m-right-top m-mobile-show">
        <i class="sidebar icon"></i>
    </a>
</nav>

2.3、代码块使用示例

<head th:fragment="head(title)">
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title th:replace="${title}">首页</title>
    <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/semantic-ui@2.2.4/dist/semantic.min.css">
    <link rel="stylesheet" href="../static/css/typo.css" th:href="@{/css/typo.css}">
    <link rel="stylesheet" href="../static/css/animate.css" th:href="@{/css/animate.css}">
    <link rel="stylesheet" href="../static/lib/prism/prism.css" th:href="@{/lib/prism/prism.css}">
    <link rel="stylesheet" href="../static/lib/tocbot/tocbot.css" th:href="@{/lib/tocbot/tocbot.css}">
    <link rel="stylesheet" href="../static/css/me.css" th:href="@{/css/me.css}">
</head>

<head th:replace="_fragments :: head(~{::title})">
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>博客详情</title>
    <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/semantic-ui@2.2.4/dist/semantic.min.css">
    <link rel="stylesheet" href="../static/css/typo.css">
    <link rel="stylesheet" href="../static/css/animate.css">
    <link rel="stylesheet" href="../static/lib/prism/prism.css">
    <link rel="stylesheet" href="../static/lib/tocbot/tocbot.css">
    <link rel="stylesheet" href="../static/css/me.css">
</head>

相当于上面这个再替换之后，title还是博客详情，这样一来，灵活性也就显然地体现了出来。

参考：
https://www.cnblogs.com/itdragon/archive/2018/04/13/8724291.html
https://www.thymeleaf.org/doc/tutorials/3.0/usingthymeleaf.html#fragments (官方文档)